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The 5 Alpha-Reductase Isozyme Family: A Review of Basic Biology and Their Role in Human Diseases

The 5 Alpha-Reductase Isozyme Family: A Review of Basic Biology and Their Role in Human Diseases Hindawi Publishing Corporation Advances in Urology Volume 2012, Article ID 530121, 18 pages doi:10.1155/2012/530121 Review Article The 5 Alpha-Reductase Isozyme Family: A Review of Basic Biology and Their Role in Human Diseases Faris Azzouni, Alejandro Godoy, Yun Li, and James Mohler Department of Urology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA Correspondence should be addressed to Faris Azzouni, farisazzouni@hotmail.com Received 15 July 2011; Revised 11 September 2011; Accepted 27 September 2011 Academic Editor: Colleen Nelson Copyright © 2012 Faris Azzouni et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Despite the discovery of 5 alpha-reduction as an enzymatic step in steroid metabolism in 1951, and the discovery that dihydrotestosterone is more potent than testosterone in 1968, the significance of 5 alpha-reduced steroids in human diseases was not appreciated until the discovery of 5 alpha-reductase type 2 deficiency in 1974. Affected males are born with ambiguous external genitalia, despite normal internal genitalia. The prostate is hypoplastic, nonpalpable on rectal examination and approximately 1/10th the size of age-matched normal glands. Benign prostate hyperplasia or prostate cancer does not develop in these patients. At puberty, the external genitalia virilize partially, however, secondary sexual hair remains sparse and male pattern baldness and acne develop rarely. Several compounds have been developed to inhibit the 5 alpha-reductase isozymes and they play an important role in the prevention and treatment of many common diseases. This review describes the basic biochemical properties, functions, tissue distribution, chromosomal location, and clinical significance of the 5 alpha-reductase isozyme family. 1. Introduction scrotum), and pubertal growth of facial and body hair. DHT plays an important role in several human diseases, Testosterone (T) is the most abundant androgen in serum. which include acne, hirsutism, male pattern baldness, benign Approximately 97% of T is bound to albumen and sex- prostate hyperplasia (BPH), and prostate cancer (CaP) [3]. hormone binding globulin and the remaining 3% is free The role of DHT was discovered after the description of and biologically active. T is synthesized by the Leydig 5α-R2 deficiency in a group of males from the Dominican cells of the testes under the control of the hypothalamus Republic [4]. DHT has 2–5 times higher binding affinity and anterior pituitary gland. In male fetuses, T stimulates for AR than T, and 10-fold higher potency of inducing AR the differentiation of the Wolffian duct into male internal signaling than T [5], which means that their effects are genitalia (epididymis, vas deferens, and seminal vesicles) different but complementary [6]. and development of libido, enlargement of the vocal cords, Three isozymes of 5α-R are known to exist (5α-R1-3) [7] skeletal muscles, penis, and scrotum and the initiation and two other proteins exhibit 5-alpha reducing capabilities, of spermatogenesis at puberty [1, 2]. T is taken from glycoprotein synaptic 2 (GPSN2), and glycoprotein synaptic circulation to cells through processes that remain poorly 2-like (GPSN2L) proteins. Only one 5 beta-reductase (5β- understood. Intracellular T is converted to dihydrotestos- R) enzyme has been identified. Its products, 5β-isomers, terone (DHT), the preferred ligand for androgen receptor are labeled as epi-product, such as 5β-DHT (epi-DHT) (AR) transactivation, by the enzyme 5 alpha-reductase (5α- [8]. Several compounds have been developed to inhibit the R). Upon ligand binding and transactivation, the DHT- 5α-R enzyme system and they play an important role in AR complex translocates from cytoplasm to nucleus and the prevention and treatment of many common diseases activates the transcription of certain genes (the androgen [9]. This review describes the basic biochemical properties, receptor-regulated genes, ARRG). functions, tissue distribution, chromosomal location, and DHT is important for in utero differentiation and growth of the prostate gland, male external genitalia (penis and clinical significance of this enzyme family. 2 Advances in Urology 2. Background was highest in the primordia of the prostate and external genitalia prior to their virilization, but very low in Wolffian Steroids are a special type of lipid. The backbone of steroids duct structures [27, 28], and from genetic studies on a rare is the compound “gonane”, a 17-carbon molecule composed disorder of male sexual differentiation, originally termed of 4 rings. The three cyclohexane rings are labeled A, B, pseudovaginal perineoscrotal hypospadias and subsequently and C. These 3 rings together are called phenanthrene. Ring referred to as 5α-R deficiency [4]. Analysis of enzyme activity D is a cyclopentane ring. The carbon atoms are numbered in skin samples and of urinary and serum steroids revealed a from 1 to 17. Typically, steroids have a methyl group (– generalized defect in the conversion of T to DHT. CH ) at carbons C-10 and C-13 and an alkyl side chain Studying 5α-R was hampered by the insolubility of the (R) at C-17 (Table 1). Alkanes are saturated hydrocarbons protein, a hurdle which was overcome in 1989. The tech- composed of carbon and hydrogen atoms linked by single nique of expression cloning in Xenopus laevis oocytes bonds. The simplest alkyl group is a methyl group. Steroids was used to isolate a cDNA from rat liver that encoded vary by the configuration of the alkyl side chain, the number 5α-R enzyme, which was used to isolate a human 5α-R of additional methyl groups, and the functional groups by cross-hybridization with a prostate cDNA library. The attached to the steroid nucleus. Carbons number 18 and two expressed proteins had different biochemical properties 19 are attached to carbons number 13 and 10, respectively. and different responses to finasteride. These observations Additional carbon atoms are usually a part of the R side suggested the presence of two 5α-R isozymes that were chain or attached elsewhere to the steroid backbone [22]. confirmed by studies done in patients with 5α-R deficiency. Androgens are derivatives of androstane and contain 19 car- The coding sequence of the gene specifying the rat liver bons and either a keto group (e.g., dehydroepiandrosterone cDNA was isolated and found to be normal in these patients. (DHEA) and androstenedione (ASD)) or a hydroxy group Further genetic studies in these patients identified a different (e.g., T and DHT) at position 17 of the steroid nucleus mutated gene that encoded a 5α-R in normal individuals (Figure 1). with identical biochemical properties to the human prostatic 5α-R. The first cDNA, isolated from rat liver, was named 5α-R1 (SRD5A1) gene, and the second cDNA, which was 3. Historical Overview isolated from human prostate and found defective in 5α-R- Steroid-5-reductases (5α-R and 5β-R) were first discovered, deficient patients, was named 5α-R2 (SRD5A2) gene [29]. More recently, with the development of genome-wide purified, and characterized in rat liver homogenates [23]. These early experiments demonstrated that these enzymes gene expression profile analyses, a third 5α-R (SRD5A3) were capable of irreversibly reducing the delta 4, 5 bond gene was identified. GPSN2 and GPSN2L proteins were 4,5 (double bond between carbons 4 and 5; Δ )ofC-19and identified using sequence searching and NCBI’s BLAST C-21 steroids to 5α-and 5β-stereoisomers. (http://blast.ncbi.nlm.nih.gov/Blast.cgi). All primary species The first androgen isolated was androsterone, a 5α- (from plant, amoeba, yeast, to vertebrate) in Eukaryota reduced androstane, which was isolated by Butenant in 1931 contain all 3 subfamilies [8]. from 25,000 liters of urine from adult men. This steroid was assumed to be the male hormone until 1935 when Ernst 4. Family Members Laquer and his colleagues isolated T from several tons of bull testes. The 5α-R enzyme was characterized initially in the The 5α-R family is composed of 3 subfamilies and 5 members 1950s in rat liver slices based on its ability to convert deoxy- (isozymes) in total. Isozymes are different proteins that per- corticosterone to 5α-reduced metabolites [24]. Tomkins and form the same function: others showed that the enzyme required a reduced pyridine (a) 5α-R1 and 5α-R2, nucleotide cofactor (i.e., NADPH) and could metabolize a variety of steroid substrates [25]. Speculation persisted about (b) 5α-R3, whether a single enzyme or multiple enzymes were involved (c) GPSN2 and GPSN2L proteins. in 5α-reduction of steroids. The 5α-reduction of steroids made them susceptible to further reduction, sulfation, and glucuronidation, modifications that decreased their affinity 5. Functions to bind proteins, made them more hydrophilic and facilitated their excretion. In the 1960s, 5α-reduction was shown to 5.1. 5 Alpha Reduction: (5α-R1-3) [29, 30]. The substrates 4,5 be an irreversible reaction and DHT was found to be a for 5α-reductases are 3-oxo (3-keto), Δ C 19/C21 steroids. more potent androgen than T in prostate bioassays [26]. The The group “3-keto” refers to the oxygen-carbon double bond administration of radiolabeled T to rats resulted in a time- at carbon 3. Delta 4, 5 refers to the double bond between dependent accumulation of DHT in the nuclei of ventral carbon atoms 4 and 5. The reaction involves a stereospecific, prostate cells, which subsequently bound to a specific nuclear irreversible breakage of the double bond between carbons (androgen) receptor. These data indicated that 5α-reduction 4 and 5 (delta 4, 5) with the aid of cofactor NADPH and of T is a crucial step in androgen action and focused the insertion of a hydride anion (H ) to the α face at attention on 5α-R. The central role of 5α-R in mammalian carbon C-5 and a proton to the β face at position C-4. male physiology was obtained from developmental studies Examples of substrates are T, progesterone, androstenedione, of mammalian embryos showing that 5α-reduction activity epi-T, cortisol, aldosterone, and deoxycorticosterone. The Advances in Urology 3 NH R O H H Gonane Finasteride 9 14 F C Dehydroepiandrosterone CF H O NH HO Dutasteride Dehydroepiandrosterone-sulfate H H O O H H HO O Cl OH Testosterone LY 191704 H H CH O 3 OH Dihydrotestosterone Epristeride H H H H HO Figure 1: Structure of various steroids. physiologic role of 5α-reduction of these steroids (other than of the eye, is synthesized in the lens of the eye, and may T) is unknown but probably related to their degradation play a role in the regulation of aqueous humor formation and excretion or to certain physiologic functions. 5α- [32]. 5α-Dihydroaldosterone is a potent antinatriuretic agent dihydroprogesterone (5α-DHP) is a major hormone in the with somewhat different physiologic effects than aldosterone circulation of both normal cycling and pregnant women itself; its formation in the kidney is enhanced by restriction [31]. 5α-dihydrocortisol is present in the aqueous humor of dietary sodium intake, which suggests its importance for 4 Advances in Urology Table 1: Different steroid families. Class Example Number of carbon atoms Steroid backbone Gonane 17 Estranes Estradiol 18 Androstanes Testosterone 19 Pregnanes Progesterone 21 Glucocorticoids Cortisol 21 Mineralocorticoids Aldosterone 21 Cholanes Cholic acid 24 Cholestanes Cholesterol 27 the conservation of sodium [33]: compared to AS-BP. 5α-R3 expression was increased in lung, breast, papillary thyroid, and testicular (seminoma and yolk (Substrate) + (NADPH) + H sac) cancers compared to their benign counterparts. (1) −→ (5α-substrate) + NADP 5.4. Erythropoiesis [36]. 5α-C 19 steroids increase the pro- Uemura et al. used small interfering RNA (siRNA) to knock duction of erythropoietin hormone in the kidneys. 5β-C 19 down the expression of 5α-R3 isozyme in 22RV1 and LNCaP- steroids are important for heme synthesis in the liver. C4-2 CaP cells by transfecting them with several siRNA expression vectors [34]. Subsequently, they studied mRNA 5.5. Regulation of Bile Synthesis [37]. Both 5α-R and 5β-R are expression of 5α-R3 (RT-PCR), cell growth and viability, involved in bile biosynthesis, where they catalyze the conver- and the ratio of DHT/T using liquid chromatography- sion of 7α,12α-dihydroxy-4-cholesten-3-one into 7α,12α- tandem mass spectrometry. Knockdown of 5α-R3 expression dihydroxy- 5α-cholestan-3-one, and 7α,12α-dihydroxy-5β- caused decreased cell growth and viability and DHT/T cholestan-3-one, respectively. Only the 5β-isomer has been ratio. Unpublished work from our group has confirmed shown to be biologically active and is used for bile synthesis. the ability of 5α-R3 to 5α-reduce 3-oxo, delta 4,5 C19 The 5α-isomer is inactive and suggested to be an inhibitory and C21 (T, androstenedione and progesterone) steroids in step in bile biosynthesis regulation in humans. lysates of CHO-K1 cells transfected with 5α-R3 cDNA via an adenovirus vector, CaP cell lines CWR-22 and CWR- 22R, and clinical human samples of androgen-stimulated 5.6. GPSN2 Family [38]. While the functions of the GPSN2 benign prostate (AS-BP), androgen-stimulated (AS-CaP), subfamily are not understood fully, several reports have and castration-recurrent (CR-CaP) CaP. shown that GPSN2 members are involved in the fourth re- action of fatty acid elongation by reducing a fatty chain double bond in mammals. Although the substrate (fatty 5.2. N-Glycosylation of Proteins: (5α-R3). Congenital defi- acid) of GPSN2 members is structurally different from that ciency of 5α-R3 has been linked to a rare, autosomal recessive of the other two 5α-R subfamilies, all three subfamilies of 5α- disorder in which patients are born with mental retardation, R share a similar biochemical ability of reducing a double cerebellar, and ophthalmologic defects [35]. The presumed bond of the substrate. defect involves the reduction of the terminal double bond of polyprenols to dolichols, an important step in protein N-glycosylation. N-linked protein glycosylation involves the 6. Protein Structure and addition of a 14-sugar glycan to select asparagine residues on Gene Location [8, 29, 39] a nascent protein to facilitate proper folding and trafficking of the protein and occurs in the membranes of endoplasmic 5α-R1 and 2 isozymes are NADPH-dependent, membrane- reticula. This disorder is part of the family of congenital associated (microsomal) enzymes, composed of 259 and disorders of glycosylation and was described for the first time 254 amino acids, and have molecular weights of 29.5 and in a family in the United Arab Emirates by Cantagrel et al. 28.4 kilodaltons, respectively. They contain a high content [35]. of hydrophobic amino acids distributed throughout their sequences, which suggests that they are intrinsic membrane 5.3. Potential Biomarker of Malignancy: (5α-R1-3) [14, 20]. proteins deeply embedded in the lipid bilayer. The bulk of published literature indicates that the expression Even though these two isozymes are intrinsic membrane of 5α-R1 increases and 5α-R2 decreases in CaP compared to proteins and catalyze the same reaction, they only share a benign prostate and BPH. Umera et al. confirmed for the limited degree of homology in protein sequence, are located first time increased expression of 5α-R3 at the mRNA level on different chromosomes, and possess distinctive biochem- in CR-CaP. Godoy et al., confirmed this at the protein level. ical properties. The average sequence identity between these A validated monoclonal antibody showed that expression two isozymes within a given species is approximately 47%, of 5α-R3 was increased similarly in AS-CaP and CR-CaP while the sequence identity between the same isozyme Advances in Urology 5 across species is 60% for 5α-R1 and 77% for 5α-R2. They other steroid receptors. The first inhibitors were steroids that are encoded by the 5α-R1 and 5α-R2 genes. These genes mimicked T and, in many cases, were substrates themselves have similar structures, with five coding exons separated (i.e., not true inhibitors). The inhibitors can be broadly by four introns. The positions of the introns are essentially classified into two categories: steroidal and nonsteroidal. The identical in the two genes. However, SRD5A1 is located steroidal class has more inhibitors thus far. on chromosome 5p15 whereas SRD5A2 is on 2p23. Gene The mechanism of 5α-RI is complex but involves the polymorphisms exist for the two genes and are more binding of NADPH to the enzyme followed by the substrate. 4,5 common for 5α-R2. More than 850 and more than 550 single The Δ bond is broken and a hydride anion is transferred nucleotide polymorphisms (SNPs) have been reported for from NADPH directly to the C-5 carbon on the α face 5α-R2 and 5α-R1 genes, respectively [40, 41]. Only a few followed by a proton attacking the C-4 carbon on the β face of these gene polymorphisms affect enzyme activity; some leading to the formation of the product that subsequently + + decrease (e.g., V89L SRD5A2 variant) and others increase leaves the enzyme-NADP complex. NADP departs last and (e.g., A49T SRD5A2 variant) enzyme activity [42]. Molecular the enzyme becomes free for further catalysis cycles. Based on epidemiologic studies are inconclusive as to whether altered this, the mechanism of inhibition of 5α-R isozymes is divided 5α-R2 isozyme activity due to 5α-R2 gene polymorphism into three types [30]: affects CaP risk [43]. A variant of 5α-R1 gene was reported (a) competitive with the cofactor (NADPH) and sub- to increase risk of polycystic ovary syndrome (PCOS) and strate (bi-substrate inhibitors): the inhibitor binds more severe hirsutism in lean women, whereas a variant of the free enzyme, for example, ONO-3805; 5α-R2 gene was associated with decreased risk of PCOS in the same cohort [44]. More than 300 SNPs have been reported (b) competitive with the substrate: the inhibitor binds for 5α-R3 gene; however, their clinical significance remains the enzyme-NADPH complex for example, 4-, 6-, uncertain [45]. 5α-R3 is composed of 318 amino acids and and 10-azasteroids; has only 19% homology with 5α-R1 and 20% homology with (c) uncompetitive with the enzyme-NADP complex: 5α-R2 [39]. 5α-R3 is encoded by SRD5A3, which is located the inhibitor binds the enzyme-NADP complex aft- at 4q12. The genes encoding GPSN2, GPSN2-like, and 5β- er the product leaves, for example, epristeride. R are located at 19p13.12, 4q13.1, and 7q34, respectively. GPSN2 and GPSN2-like proteins are composed of 308 and 8.1. Steroidal 5α-RI (Figure 1). (1) 4-Azasteroids: the 3-oxo, 363 amino acids, respectively. The amino acid sequence 5-alpha steroids with a nitrogen atom at position 4 have been homology for GPSN2 is 15% with 5α-R1, 17% with 5α-R2 the most extensively studied. Examples include finasteride and 11% with 5α-R3. GPSN2-like has 6%, 11%, 6%, and (MK-906), dutasteride (GG745), 4-MA, turosteride, MK- 44% sequence homology with 5α-R1, 5α-R2, 5α-R3, and 386, MK-434, and MK-963. GPSN2, respectively. (a) Finasteride is a synthetic 4-azasteroid and is the first 5α-RI approved for treatment of benign prostatic 7. Biochemical Properties [8, 29] enlargement (BPE) and subsequently male pattern When examined in lysates of transfected cells, 5α-R1 exhibits baldness. Finasteride is a potent (mean inhibitory a broad pH optimum, which ranges between 6.0 and 8.5, concentration [IC ], 69 nM) competitive inhibitor while 5α-R2 shows a narrow acidic pH optimum (pH 5– of 5α-R2 but inhibits less effectively 5α-R1 (IC 5.5). However, there is evidence to suggest that inside intact 360 nM) [47]. Finasteride decreases mean serum level human cells, 5α-R2 isozyme functions optimally at a more of DHT by 71% after 24 weeks of use [48]. Seven-day neutral pH range (6.0–7.0). 5α-R1 has a larger turnover treatment with finasteride (1 or 5 mg daily) has been number, as indicated by its K value and a lower substrate reported to suppress intraprostatic DHT in men with cat affinity for T, K = 1–5 μM. 5α-R2 has a lower turnover m lower urinary tract symptoms (LUTSs) attributed to number (K ) and a higher substrate affinity, as indicated cat BPE by approximately 85% relative to placebo [49], by K = 0.004–1 μM for T. Under optimal conditions, m whereas another study of finasteride 5 mg/d (also in 5α-R2 has a higher 5α-reducing activity than 5α-R1, as men with LUTS attributed to BPE) demonstrated a indicated by its high V /k ratio. Both isozymes contain reductionof68% at 6months [49]. Finasteride was max m an NH -terminal steroid (ligand) binding domain and a 2 shown in vitro to inhibit 5α-R3 at a similar potency to COOH-terminal NADPH binding domain. The apparent 5α-R2 (IC = 17.4 nM, 14.3 nM, resp.) in transfected dissociation constant for NADPH cofactor is similar for HEK-293 cells [21]. both isozymes (3–10 μM). No such comparisons exist for (b) Dutasteride is a synthetic 4-azasteroid with a half-life 5α-R3 except that it appears to be efficient at pH 6.5–6.9 of nearly 5 weeks and is only approved for treatment (unpublished work from our group). of BPH. Dutasteride is a dual 5α-RIsinceitismore effective (more potent) at inhibiting 5α-R1 and 2 than finasteride; IC for inhibiting 5α-R1 is 7 nM 8. 5α-Reductase Inhibitors [9, 30, 46] and 5α-R2 is 6 nM. Dutasteride reduced mean levels Goal of development of 5α-reductase inhibitors (5α-RI) was of serum DHT at 24 weeks better than finasteride to bind to 5α-R with little or no affinity for the androgen or (94.7% versus 70.8% suppression) [50]and caused 6 Advances in Urology a 97% reduction in intraprostatic DHT levels in men or specially a Cl) and a methyl group at position with CaP treated with 5 mg/d for 6–10 weeks [51]. 4. LY 191704 is the most potent (IC = 8 nM). Another trial of dutasteride 3.5 mg/d for 4 months (b) Piperidones lack B and D rings. prior to RP decreased intraprostatic DHT by 99% (c) Quinolinones lack C ring. [52]. The near-maximal suppression of intraprostatic (d) Pyridines lack B and C rings. DHT with dutasteride 3.5–5 mg daily and the report (e) Benzo[c]quinolinones tricyclic compounds de- that dutasteride inhibits 5α-R3 in vitro (IC = rived from 6-azasteroids (no D ring, aromatic 0.33 nM) [21] suggest that the development of a triple ring for the C ring) that have selective but weak 5α-R inhibitor may not be necessary. Table 2 provides inhibitory activity against 5α-R1. a comparison between finasteride and dutasteride. (f) Benzo[c]quinolizinones are tricyclic compounds (c) 4-MA was a potent dual inhibitor of 5α-R1 (IC = derived from 10-azasteroids (no D ring, aroma- 1.7 nM) and 5α-R2 (IC = 1.9 nM). 4-MA had a tic ring for the C ring) that include some very very low affinity for AR and thus was not expected potent, selective inhibitors of 5α-R1. to produce undesirable antiandrogen effects, such as impotence, impaired muscle growth, or gyneco- (Subgroups (b), (c), and (d)) are very weak 5α-R1I. mastia. However, 4-MA was withdrawn from clinical (2) Nonsteroidal aryl acids are tricyclic compounds de- development after it was shown to be an inhibitor rived from androstanecarboxylic acids that differ of 3β-hydroxysteroid dehydrogenase and to cause from their parent compounds in being selective, hepatotoxicity [9]. noncompetitive 5α-R1I. (d) Turosteride, MK-434, and MK-963 inhibit mainly (3) Butanoic acid derivatives contain an aromatic ring 5α-R2. MK-386 is a selective 5α-R1 inhibitor [46]. (generally benzene or indole) that bears a butanoic acid chain and aromatic moieties. Examples include (2) 6-Azasteroids (e.g., GIlS7669X) have a heterocyclic B 4,5 ONO-3805, demonstrated in vitro to be a selective ring (nitrogen atom at position 6) and a Δ bond in the A inhibitor of 5α-R1, and FK143, which inhibits 5α-R1 ring and are potent competitive inhibitors of 5α-R1 and 2 and 5α-R2 equally and noncompetitively. [46]. (3) 10-azasteroids, for example, AS97004, are compet- (4) Polyunsaturated fatty acids, found in vegetable oils, itive 5α-RI with a similar mechanism of action to 6-azas- have been found to inhibit human and rat microso- teroids [9]. mal 5α-R activity. In this group, y-linolenic acid is the (4) Androstanecarboxylic acids, such as epristeride, are most potent compound tested. Since 5α-R isozymes noncompetitive, specific inhibitors for 5α-R2 [30]. are intrinsic membrane proteins, their activity may (5) Other steroidal inhibitors include progesterone esters depend on the unique environment of the lipid such as 4-bromo-17α-(p-fluorobenzoyloxy)-4-pregnene-3, bilayer. Whether and how fatty acids may function as 20-dione [53], 2-azasteroids, 3-azasteroids, 19-nor-10-azas- endogenous regulators of 5α-R remain unknown. teroids, and diazasteroids [9]. (5) Some cations, especially zinc, have been reported to reduce sebum production in vivo and have been used 8.2. Nonsteroidal Inhibitors [9, 30, 46]. Several pharmaceu- to treat acne. In vitro assays have indicated that zinc tical and academic groups have pursued the synthesis of specifically inhibits 5α-R1. This inhibition may be nonsteroidal compounds that inhibit human 5α-reductases mediated both by non-competitive inhibition of T due to the undesired hormonal side effects of steroidal com- binding to 5α-R and by reduced formation of the pounds. Nonsteroidal inhibitors can be classified according NADPH co-factor. to their structure. Most have been derived from azasteroidal (6) Other nonsteroidal inhibitors include epicatechin- inhibitors by removing one or more rings from the aza- 3-gallate and epigallocatechin-3-gallate, which are steroidal structure. Nonsteroidal inhibitors are thought to major constituents of green tea. Also included are act as competitive inhibitors with exception of epristeride 7-hydroxycoumarin derivatives, 2,6-disubstituted 4- analogues, which are noncompetitive inhibitors. The most hydroxy-4-hydroxymethyl biphenyl derivatives, iso- potent and selective inhibitors of human 5α-R1 are found flavonoids, and 3,3-diphenylpentane derivatives [9]. among these classes of compounds and include the follow- ing. 9. Tissue Distribution (1) Benzoquinolines include many subgroups. Numerous reports exist in the literature on the expres- (a) Benzo[f]quinolinones are tricyclic compounds sion pattern of 5α-R1 and 5α-R2inhuman tissue at that are derived from 4-azasteroids by removing various stages of development. The results vary due to the D ring and substituting the C ring with an differences in antibody sensitivity and specificity, mRNA aromatic one. These are selective against 5α- analysis (in situ hybridization versus northern blotting versus R1. The potency against 5α-R1 increases by reverse transcriptase-polymerase chain reaction), protein substituting a halogen atom at position 8 (F, Br, analysis (immunohistochemistry versus western blotting), Advances in Urology 7 Table 2: Comparison between finasteride and dutasteride (referenced in text). Finasteride Dutasteride Family Steroidal 5α-RI (4-azasteroid) Steroidal 5α-RI (4-azasteroid) IC for 5α-R1, 2 and 3 (nM) 360, 69, 17.4 7, 6, 0.33 Male androgenic alopecia FDA-approved clinical uses Benign prostatic enlargement Benign prostatic enlargement 1 mg daily for male androgenic alopecia Clinical dose 0.5 mg daily 5 mg daily for benign prostatic enlargement Half-life (T 1/2) 6–8 hours 5 weeks ↓Serum DHT by 71% ↓Serum DHT by 95% Suppression of DHT ↓Intraprostatic DHT by 85% ↓Intraprostatic DHT by 97–99% tissue preparation, nature of tissue, evaluation of results, not detected in the skin and scalp until the onset of puberty. tissue fixation protocols, and control tissue. In addition, At puberty, only 5α-R1 is reexpressed in the skin and scalp normal, benign, and malignant human tissue specimens are and persists thereafter until 81 years. In the prostate gland, heterogeneous with variable expression of proteins among Lunacek et al. reported that both 5α-R1 and 5α-R2 were specimens from different individuals and within the same detectable at the protein level using IHC until approximately specimen, that is, inter- and intraindividual variability. 1 year of age. After that, they were detectable at the mRNA Therefore, a summary of many studies that discussed the level (RT-PCR) until 6 years of age. Thigpen et al. only tissue distribution of 5α-R1-3 in different human tissues was detected 5α-R2 at the protein level using immunoblotting in tabulated to demonstrate differences in results (Table 3). prostatic tissue from a 7-year-old male. Since the methods used by this group did not detect 5α-R1 protein in the newborn, juvenile, or adult prostatic tissues, and since other 9.1. According to Age groups detected 5α-R1 at the protein level in fetal and adult benign prostatic tissue, 5α-R1 and 5α-R2 appear to 9.1.1. Fetus. Ellsworth and Harris [54] studied 5α-R activity be expressed in the prostate in male fetuses and throughout in fetal scalp, back skin, and prostatic tissues and compared postnatal life. it to 5α-R activity in adult male scalp and prostatic tissues. They studied the conversion of radio-labeled T into DHT in relation to pH and response to selective 5α-R1 and 5α- 9.1.3. Adulthood-Old Age. 5α-R1-3 is ubiquitously expressed R2 inhibitors and calculated the k of T at pH values of [10, 11, 13, 20, 55]. 5α-R1 and 5α-R2 are expressed 7.0 and 5.5. 5α-R1 is expressed in fetal scalp and nongenital differently in liver, genital and nongenital skin, prostate, (back) skin at levels that are 5–50 times less than adult skin. epididymis, seminal vesicle, testis, ovary, uterus, kidney, 5α-R2 is expressed in the fetal prostate at levels similar to exocrine pancreas, and brain (Table 2, Aumuller et al.). Our adult prostate. Thigpen et al. [13] studied 5α-R expression laboratory described the expression of 5α-R3 using IHC in in fetal liver, adrenal, testis, ovary, brain, scalp, chest, and various benign and malignant tissues. 5α-R3 is overexpressed genital skin, using immunoblotting. They detected 5α-R2 particularly in lung adenocarcinoma, testicular seminoma only in fetal genital skin. Lunacek et al. [55] studied the and yolk sac tumors, papillary thyroid cancer, and androgen- expression of 5α-R 1 and 5α-R2 at the mRNA (RT-PCR) and stimulated and castration-recurrent CaP relative to their protein (immunohistochemistry) levels in fetal and postnatal benign counterparts [20]. When contrasting these data with prostatic tissues until 6 years of age. Both 5α-R1 and 5α-R2 the expressed sequence tag (EST) database from NCBI, both proteins were expressed in prostatic epithelial and stromal sets of data suggest a broad pattern of expression for 5α-R1-3 components, at consistent levels throughout all age groups. in human tissues; ESTs for 5α-R1 (271 sequences) have been 5α-R1 is expressed mainly in the epithelium and 5α-R2 is reported from different human tissues, which include lung, expressed mainly in the stroma of the prostate. At the mRNA brain, intestine, skin, prostate, testis, and stomach [56]. ESTs levels, both are detectable throughout the ages studied and for 5α-R2 (39 sequences) have been reported in prostate, both peak in the second trimester. lung, liver, kidney, brain, testis, and skin [57]. ESTs for 5α- R3 (149 sequences) have been reported in kidney, testis, intestine, brain, liver, uterus, pancreas, skin, and prostate 9.1.2. Newborn-Onset of Puberty. In newborns, 5α-R1 is [58]. Tissue distribution of 5α-R3 protein in several human expressed at the protein level in the liver, skin, scalp [13] benign tissues was consistent with the tissue origin of the 5α- and prostate [55]. 5α-R2 is expressed in prostate, seminal R3 EST reported at NCBI [20]. vesicles, epididymis, liver, and to lesser extent in scalp and skin [13]. Hepatic expression of 5α-R1 and 2 is present at the protein level (immunoblotting) throughout postnatal life. At 9.2. According to Organs. (See [10–13, 15–20, 54–61] approximately 1.5 years, the expression of both proteins is (Table 3).) 8 Advances in Urology Table 3: Tissue distribution of 5α-reductase 1–3 according to different authors. Author isozymes Tissue type Materials and methods 5α-R1 5α-R2 Notes studied Nuclear, in epidermis from all sites: (scrotal> axilla> breast> Cytoplasmic, in epidermis from lip> eye lid): all sites: stratum basale (++), stratum stratum spinosum (++), stratum spinosum (++), absent in basale (+), absent in stratum Protein expression (IHC) stratum granulosum and stratum granulosum and stratum using rabbit polyclonal Epidermis: genital corneum, dermal papillae, corneum, inner epithelial RS antibodies against synthetic 5α-R1 more (scrotum) nongenital fibrous and outer epithelial RS (++), matrix cells of hair bulb peptides from C-terminus uniformly spread in Eicheler et al. [10] (Axilla, breast, lip, (++), inner epithelial RS (+), (+), absent in dermal papillae, parts of 5α-R1-2 proteins. skin versus 5α-R2 that 5α-R1-2 eyelid) using a matrix cells of hair bulb (++), fibrous and outer epithelial RS, Antibody sensitivity and is mainly found in semiquantitative scrotal fibroblast (++), basal and basal (+) and glandular (−)cells specificity confirmed by inner epith RS visual scale secretory cells of sebaceous of sebaceous glands, ELISA and WB on FFPE glands (++), secretory and myoepithelial (+) and secretory biopsy or autopsy tissues myoepithelial cells of sweat cells (−) of sweat glands, dermal glands (++), arrector pili adipocytes (+) muscles (+), dermal adipocytes No qualitative differences in (+). No qualitative differences in males and females males and females. Mainly cytoplasmic: Mainly nuclear: Prostate: stroma Prostate: stroma (+), epithelium (+), epithelium (+) (++), specially basal cells Seminal vesicle: stroma (+), Seminal vesicle.: stroma (+), epithelium (+) epithelium (++) Epididymis: stroma (+), Epididymis: stroma (+), epithelium (+) epithelium (+) Testis: Leydig cells (+), Sertoli Testis: spermatogonia (+), Leydig Protein expression (IHC) cells (+) and Sertoli cell (−) using rabbit polyclonal Ovary: stroma (++), theca and Ovary: stroma (+), theca and antibodies against synthetic granulosa cells (−) granulosa cells (+/−) peptides from C-terminus Uterus: endometrium (+), Uterus: endometrium (+), Many tissue types, parts of 5α-R1-2 proteins. myometrium (+) myometrium (+) Aumul ¨ ler et al. [11] using a Antibody sensitivity and Liver: hepatocytes (+/−), bile Liver: hepatocytes (++), bile duct 5α1-2 is ubiquitous 5α-R1-2 semiquantitative specificity confirmed by duct c (+), kupffer cells (++) c(+),kupffer cells (−) visual scale ELISA and WB. Pancreas: exocrine (+), islets of Pancreas: exocrine (+), islets of Tissues from surgical pts Langerhans (−) Langerhans (−) and autopsies, fixed in Kidney: glomerulus (+), PT (−), Kidney: glomerulus (−), PT Bouin’s or formaldehyde DT (++), CD (+) (++), DT (+/−), CD (+) Adrenal: cortex (−), medulla (−) Adrenal: ZG (+), ZF (+/−), ZR Thyroid: thyrocytes (−), C cells (+/−), med (−) (−) Thyroid: thyrocytes (−), C cells Cerebral cortex: pyramidal c (+), (−) glial cells (+/−) Cerebral cortex: pyramidal c Pituitary: prolactin cells (+), (++), glial c (−) others (−) Pituitary: prolactin cells (+), others (−) Advances in Urology 9 Table 3: Continued. Author isozymes Tissue type Materials and methods 5α-R1 5α-R2 Notes studied In balding and nonbalding scalp: Protein expression (IHC) 5α-R2 is expressed in using validated mouse In balding and non-balding infundibula, outer (mainly) and Scalp biopsies from monoclonal antibodies scalp: 5α-R1 is expressed only in Bayne et al. [12] inner epithelial RS of hair bald and non-bald against peptides from sebaceous glands 5α-R1-2 follicles. men N-terminus parts of No expression was detected in No expression was detected in 5α-R1-2 and enzyme hair follicles or in epidermis dermal papillae or in sebaceous activity using H-T glands 5α-R2 protein is expressed in 5α-R1 protein is expressed in prostate, seminal vesicles, liver and chest skin and 5α-R1 epididymis, and liver. mRNA was detected in 5α-R2 mRNA was detected in cerebellum, hypothalamus, pons, prostate, SV, epididymis. and Messenger RNA (NB) and medulla oblongata, skin, and liver. 5α-R2 was detected by WB protein expression (IHC liver 5α-R1 was not detected by only in fetal genital skin (not and WB) using rabbit WB in any fetal tissue. detected in fetal liver, adrenal, 5α-R1 protein was Thigpen et al. [13] Autopsy and surgical polyclonal antibodies 5α-R1 was detected by WB in testis, ovary, scalp, and brain). not detected in any 5α-R1-2 tissue samples against peptides from newborn liver, skin, and 5α-R2 was detected by WB in prostate sample C-terminus parts of scalp.5α-R1 was detected by WB newborn prostate, SV, 5α-R1-2 in all scalp samples from balding epididymis, liver, skin. and scalp. and nonbalding men (except 5α-R2 was not detected by WB in one). It was not detected in any any sample of balding and normal prostate, BPH, or PC nonbalding scalp from one man. sample It was detected in all normal prostate, BPH, and PC samples Protein expression (IHC) using rabbit polyclonal antibodies against peptides from N-terminus of 5α-R1-2 proteins. Antibody specificity Prostate: BPH confirmed with WB on Nuclear in BPH, shifts to Mainly cytoplasmic in all (TURP), ASCaP (RP), na¨ıve, 5α-R1- and 5α-R2- cytoplasm in HGPIN and CaP specimens Immunostaining Thomas et al. [14] CaP metastasis in transfected COS-1 cells and All differences are Immunostaining intensity: intensity: 5α-R1-2 androgen IHC on transfected COS-1 statistically significant Metastasis> CR-CaP> AS-CaP = BPH = Metastasis = CR-CaP> deprivation-treated cells-Evaluated by HGPIN> BPH AS-CaP = HGPIN men (autopsy) measuring percentage of moderate- and high-intensity immunostaining areas in relation to total epithelial, PIN, or tumor area in PE tissues 10 Advances in Urology Table 3: Continued. Author isozymes Tissue type Materials and methods 5α-R1 5α-R2 Notes studied Protein expression (IHC) Mainly nuclear in BPH, nuclear using validated rabbit Staining in and cytoplasmic in CaP (all Mainly cytoplasmic in all polyclonal antibodies, CaP-adjacent benign grades), and in adjacent benign samples (benign and malignant) Prostate: AS-CaP evaluated by visually tissue is not Thomas et al. [14] epithelial tissue Immunostaining Immunostaining intensity: (RP) with Gleason estimating percent of total significanty different 5α-R1-2 intensity: BPH> high grade> moderate score <7, 7, >7 tumor area showing low-, from low- and High grade > moderate grade = grade = low grade = adjacent moderate, and high-grade CaP for low grade > PC-adjacent benign benign tissue high-intensity in relation to either isozyme tissue > BPH Gleason score 5α-R2 mRNA and enzyme Messenger RNA expression 5α-R1 mRNA expression is activity were higher in BPH than (sqRT-PCR) and similar in BPH and AS-CaP. in AS-CaP. Prostate: BPH measurement of 5α-R There was no correlation Soderst ¨ om ¨ et al. [15] Therewas apositivecorrelation (TURP) and AS-CaP enzyme activity at pH 5.5 between enzyme activity at pH 5α-R1-2 between enzyme activity at pH 14 ◦ via RP or RC and 7 using C-T at 37 C (5.5 and 7) and 5α-R1 mRNA 5.5 and expression of 5α-R2 in homogenized frozen expression as expressed on the mRNA as expressed on the basis pulverized prostate tissue basis of β-actin of β-actin ISH showed that 5α-R1 mRNA is ISH showed that 5α-R2 mRNA is BPH and CaP tissue expressed in epithelium > stroma expressed in epithelium > stroma post prostate biopsy Lehle et al. [61] Messenger RNA expression mRNA expression levels by mRNA expression levels by or RP frozen in liquid 5α-R 1-2 (ISH, sqRT-PCR) sqRT-PCR: sqRT-PCR: nitrogen, one human liver> CaP > BPH> Normal liver = BPH > Normal prostate > liver sample prostate CaP Messenger RNA expression 5α-R1 mRNA expressed in BPH tissue (TURP) (ISH, RT-PCR) and epithelium > stroma frozen in liquid measurement of enzyme 5α-R2 mRNA > 5α-R1 mRNA in Habib et al. [16] nitrogen or in 5α-R1 mRNA expressed in activity at pH 5 and 7.5 BPH 5α-R1-2 ice-cold RPMI with epithelium > stroma 3 ◦ using H-T at 37 Cin 5α-R2 enzyme activity  5α-R1 FBS and archival homogenized pulverized enzyme activity in homogenized PE-BPH tissue frozen prostate tissue BPH tissue Mainly nuclear, in normal prostate and BPH tissue (luminal Mainly cytoplasmic (weak), in epithelial > basal) and in stroma normal prostate and BPH tissue Protein expression (IHC) 5α-R1 immunostaining > 5α-R2 (basal > luminal epithelial) and BPH (TURP), using polyclonal rabbit in BPH (in both epithelium and stroma. Bonkhoff et al. [17] AS-CaP (RP), antibodies against peptides stroma). In CaP, 5α-R2 immunostaining 5α-R1-2 CR-CaP (channeling from C-terminus parts of In CaP, 5α-R1 immunostaining became nuclear and cytoplasmic TUR) 5α-R1 and 2, validated by became nuclear and cytoplasmic and more intense in HGPIN and ELISA and WB and more intense in HGPIN and CaP versus adjacent benign CaP versus adjacent benign tissue (specially CR-CaP) tissue (specially CR-CaP) Advances in Urology 11 Table 3: Continued. Author isozymes Tissue type Materials and methods 5α-R1 5α-R2 Notes studied Messenger RNA 5α-R1 mRNA copy numbers> (qRT-PCR), protein (IHC) 5α-R2 mRNA in BPH 5α-R2 mRNA < 5α-R1 mRNA in expression using polyclonal 5α-R1 protein expression is BPH BPH (RC) fixed in rabbit antibodies against Shirakawa et al. [18] intense in epithelium of BPH 5α-R2 protein expression is formaldehyde and peptides from C-terminus 5α-R1-2 (higher than 5α-R2 protein) detected in epithelium and paraffin-embedded parts of 5α-R1 and 2, 5α-R1 enzyme activity at pH 7.5 stroma of BPH (less intense than validated by ELISA and is similar to 5α-R2 enzyme 5α-R1) enzyme activities at pH 5 activity at pH 5.0 3 ◦ and 7.5 using H-T at 37 C 5α-R1 is nuclear and cytoplasmic 5α-R2 is mainly cytoplasmic in in all 3 tissues all 3 tissues Nuclear 5α-R1 staining intensity: Nuclear 5α-R2 staining intensity: Protein expression (by IHC ASBP = AS-CaP = CR-CaP ASBP = AS-CaP> CR-CaP ASBP, AS-CaP and in TMAs that are quantified In all 3 tissues, Cytoplasmic 5α-R1 staining Cytoplasmic 5α-R2 staining CR-CaP (RP or by visual scoring and digital expression of 5α-R1 is intensity: intensity: Titus et al. [19] channeling TURP) image analysis and by WB) consistenty more than ASBP = AS-CaP> CR-CaP ASBP = AS-CaP> CR-CaP 5α-R1-2 tissue that was FFPE and enzyme activity in 5α-R2 (in nucleus) Not detected in stroma in any of Notdetectedinstromainany of or snap frozen in homogenized pulverized but similar in the 3 tissues the 3 tissues liquid nitrogen prostate tissue using cytoplasm In WB, 5α-R1 > 5α-R2 in all 3 In WB, 5α-R2 was undetectable 3 ◦ H-ASD at 37 C tissues in CR-CaP 5α-R1 enzyme activity > 5α-R2 5α-R2 activity > 5α-R1 in ASBP in CR-CaP (3 folds) and AS-CaP 5α-R3 was mainly cytoplasmic Benign tissue immunostaining: Kidney (PT,DT ++), liver (++), 5α-R3 protein Protein expression (IHC) exocrine pancreas (++), skeletal muscle (+), skin (strata basale and expression ↑ in the using validated monoclonal spinosum ++), gastric epithelial cells (+), myometrium (++) cytoplasm of mouse antibody against Malignant tissue: colon adenoCA (++), esophageal adenoCA (++), Godoy et al. [20] Benign and malignant malignant cells versus peptide from N-terminus RCC (++), HCC (++), ovarian mucinous CA (++), stomach 5α-R3 human tissue TMAs benign cells in of 5α-R3 protein and adenoCA (++), testis seminoma and YS tumor (++), thyroid prostate, testis, quantified by visual scoring papillary CA (++), endometrioid CA (++), breast CA (+) thyroid, lung and and digital image analysis ASBP: basal epithelial cells, HGPIN: benign basal and neoplastic breast CA epithelial cells, AS-CaP and CR-CaP: in neoplastic cells (5α-R3 immunostaining intensity: AS-CaP = CR-CaP > ASBP) 5α-R3 expression at the mRNA level is higher than 5α-R1and 2in 5α-R1-3 mRNA expression frontal cortex, heart, colon, stomach, liver, pancreas, lung, BPH, (RT-PCR) and prostate, testis, mammary gland, brain, cervix, ovary, dermis, 20 benign human 5α-R3 is ubiquitous Yamana et al. [21] measurement of 5α-R 1–3 epidermis, total skin, small intestine, spleen, and kidney tissues, CaP, and Dutasteride is a triple 5α-R3 enzyme activity using 5α-R2 mRNA was the most abundant in BPH and muscle breast cancer cell lines 5α-RI in vitro C-labelled ASD and T in Finasteride inhibits 5α-R2 and 5α-R3 with similar potency (IC = intact cells in culture 14.3 nM, 17.4 nM, resp.). Dutasteride is a more potent inhibitor of 5α-R3 than finasteride (IC = 0.33 nM) ELISA: enzyme-linked immunosorbant assay; IHC: immunohistochemistry; WB: western blot; NB: northern blot; FFPE: formalin fixed paraffin embedded; RS: root sheath; RP: radical prostatectomy; sqRT- PCR: semiquantitative reverse transcriptase-polymerase chain reaction; PE: paraffin-embedded; RPMI: Roswell Park Memorial Institute; FBS: fetal bovine serum; PT: proximal tubules; DT: distal tubules; CD: collecting ducts; TURP: transurethral resection of prostate; RC: radical cystectomy; HGPIN: high-grade prostate intraepithelial neoplasia; ISH: in situ hybridization; RCC: renal cell carcinoma; HCC: hepatocellular carcinoma; adenoCA: adenocarcinoma; CA: carcinoma; YS: yolk sac; TMA: tissue microarray. 12 Advances in Urology 10. Clinical Role of 5α-R by the administration of DHT, but is reversed by 3α-an- drostanediol treatment. The biochemical features of this syn- Alterations in the conversion of T into DHT by the enzyme drome include the following: 5α-R are associated with a number of human disorders: (a) high normal to elevated levels of plasma T, 10.1. 5α-R2 Deficiency (Pseudovaginal Perineoscrotal Hypo- (b) low normal to decreased levels of plasma DHT, spadias) [3, 62]. Studies in rabbit, rat, and human fetuses (c) increased T to DHT ratio at baseline and following have shown that 5α-R activity is present in the urogenital hCG stimulation, sinus and external genital anlage prior to prostate and (d) normal metabolic clearance of T and DHT, external genital differentiation. However, 5α-R activity is not present in the Wolffian duct, at the time of epididymal, (e) decreased levels of urinary 5α-reduced metabolites of vas deferens, and seminal vesicle differentiation. Thus, T C19 and C21 steroids, with increased 5β/5α urinary and DHT have selective roles in male sexual differentiation metabolite ratios, during embryogenesis. T mediates Wolffian ductal differenti- (f) decreased plasma and urinary 3α-androstanediol ation, while DHT mediates male external genital and prostate glucuronide, a major metabolite of DHT, differentiation. (g) increased plasma levels of LH and/or FSH. 5α-R2 deficiency is caused by decreased synthesis of DHT due to mutations in the 5α-reductase 2 gene. At Phenotype, development and reproductive function in least 50 mutations have been reported and is autosomal- human females with 5α-R2 deficiency are unaffected. recessive in the majority of patients. 5α-R2 deficiency results in a 46,XY disorder of sexual development (formerly male 10.2. LUTS Attributed to BPE. BPE results in a significant pseudohermaphroditism). Affected males are born with morbidity due to urethral obstruction and secondary detru- normal male internal reproductive structures (epididymis, sor dysfunction. Histological evidence of BPH is found in seminal vesicles, and vasa deferentia); however, their external 50% of males by the age of 50 and 90% of males by genitalia resemble those of females, that is, ambiguous the age of 80 [63]. The development of BPH depends genitalia. These individuals have a small penis that resembles on androgens, and BPH does not occur in men castrated an enlarged clitoris, labioscrotal fusion, and a urogenital prior to puberty [64]. 5α-R isozymes play significant roles sinus in which there are two separate urethral and vaginal in BPH development since DHT is the major androgen openings. The vagina is short and blind ending. The testes in the prostate. Patients with decreased DHT production are either in the labia, or inguinal canals or intra-abdominal. due to 5α-R2 deficiency have a small prostate and BPH The vasa terminate at the blind-ending vaginal pouch. The has not been reported [4]. In castrated dogs, treatment prostate is hypoplastic, nonpalpable on rectal examination with either DHT or T results increased intraprostatic DHT and is found to be rudimentary on transrectal ultrasound and BPH [65]. However, coadministration of T with a and MRI. Prostatic volumes are approximately (1/10)th 5α-R inhibitor decreased DHT formation and prevented of age-matched normal controls. Prostate biopsy reveals BPH [66]. Finasteride and dutasteride have been shown fibrous connective tissue, smooth muscle, and no identifiable to decrease circulating and intraprostatic DHT by 60– epithelial tissue, which suggests atrophic epithelium or lack 90%, and 90–98%, respectively [48–52]. Finasteride and of epithelial differentiation. Plasma PSA is low or unde- dutasteride result in a decrease in prostate size by 20–25% tectable in these patients. Administration of DHT results through prostatic epithelial cell apoptosis and a significant in enlargement of the prostate. Neither BPH nor CaP has improvement in LUTS. Furthermore, they change the natural been reported in these patients. At puberty, these individuals history of the disease by decreasing the risk of acute urinary undergo partial virilization of the external genitalia, although retention by 57–79% and decreasing BPH-related surgery by their secondary sexual hair remains sparse and they develop 48–69% [67, 68]. Although both isozymes are overexpressed less male pattern baldness and acne despite normal sebum in prostate tissues from patients with BPH [15], inhibition production. They undergo an increase in muscle mass, of 5α-R2 activity is the major contributor in the treatment phallic growth, development of male body habitus, and of BPH as the additional inhibition of 5α-R1 activity by deepening of the voice. Their libido is normal and they dutasteride does not appear to be of any further benefit in are capable of erections. Sperm production and fertility BPH treatment [69]. have been reported but depend on testicular location. The mechanism of partial virilization at puberty is through either the androgen receptor binding very high levels of serum T, 10.3. Primary Prevention of CaP [67, 68]. Both finasteride albeit at lower affinity, or the increased expression of skin and dutasteride have been tested in large, prospective, 5α-R1 at puberty, which results in peripheral synthesis of randomized, placebo-controlled, double-blind studies as DHT from T or via the action of 5α-R3 through unknown primary preventive therapies for CaP. The Prostate Cancer mechanisms. 5α-R1 gene is normal in these subjects. No Prevention Trial (PCPT) randomized nearly 19,000 men at genetic deficiencies of the type 1 enzyme have yet been low risk for CaP into a treatment group, given finasteride reported. Inactivation of the 5α-R1geneinmiceadversely at 5 mg/d and a control group, given placebo, who were affected reproduction in females. In addition, mice deficient followed up for 7 years. At the end of the study, participants in 5α-R1 manifest a parturition defect that is not reversed were offered a prostate biopsy. For-cause biopsies were done Advances in Urology 13 Table 4: Comparison between PCPT and REDUCE. PCPT REDUCE Sponsor South West Oncology Group GalxoSmithKline Duration 7 years 4 years Risk of CaP in participants lower higher 18,882 randomized No. of participants 8122 randomized 9060 included in final analysis Age ≥55 years 50–75 years Entry serum PSA ≤3.0 ng/mL 2.5–10 ng/mL Yes (6–12 cores) within 6 months prior to Baseline biopsies No enrollment Study-mandated biopsies Year 7 Years 2 and 4 Study-mandated biopsy cores ≥6 (6 cores in nearly 80%) 10 (83% had at least 1 biopsy) Overall relative risk reduction in CaP 25% 23% versus placebo ↑26% (6.4% in finasteride versus 5.1% in Incidence of Gleason sum ≥7CaP Same (6.7% in dutasteride versus 6.8%: in placebo) placebo), P< 0.05 Same over 4 years (0.9% in dutasteride versus 0.6% ↑91% (2.1% in finasteride versus 1.1% in in placebo); however, in years 3-4, there were 12 GS Incidence of Gleason sum ≥8CaP placebo), P< 0.05 ≥8 CaP in dutasteride group (0.5%) versus 1 in placebo group (<0.1%), P< 0.05 for abnormal DRE and/or PSA > 4.0 ng/mL. PCPT showed American Urological Association and the American Cancer that finasteride was effective at reducing the overall risk of Society issued a “cautious” joint statement that accepted biopsy detectable CaP by nearly 25% and this was due mainly these drugs as an option to prevent CaP provided that to reduction in the risk of low-grade disease (Gleason sum they are used mainly after a thorough discussion of risks <7). The reduction in the risk of CaP was seen across all and benefits. In January 2011, the FDA’s Oncologic Drug subgroups, such as age, race, family history, and baseline Advisory Committee voted against recommending either PSA. Finasteride users also had improved BPH outcomes. dutasteride or finasteride for the specific indication of CaP The benefits of finasteride treatment occurred at the expense risk reduction because of the potential increased risk of high- of a higher rate of diagnosis of moderate- and high-grade grade disease. Table 4 provides a comparison between PCPT CaP (Gleason score ≥7) and more sexual adverse effects. and REDUCE. The Reduction by Dutasteride of Prostate Cancer Events trial (REDUCE) studied the effect of dutasteride versus placebo 10.4. Treatment of CaP in a large group of men at higher risk of CaP than in PCPT who had at least one negative prostate biopsy at (a) Biochemical Failure after Local Therapy with Curative baseline. The study lasted 4 years and participants received Intent [70–73]. Finasteride and dutasteride have been tried, mandatory prostate biopsy at 2 and 4 years. Dutasteride singly and in combination, in patients with biochemical fail- decreased the risk of biopsy detectable CaP by nearly 24% ure after radical prostatectomy or radiotherapy. The most and this reduction in risk was evident across all subgroups common combination was a 5α-RI and a nonsteroidal an- tested. The frequency of diagnosis of moderate- and high- tiandrogen. Finasteride and dutasteride monotherapy de- grade CaP was unchanged over the entire length of the creased serum PSA to variable extent. PSA decrease was more study and beneficial effects were observed on BPH outcomes. frequent and of greater magnitude in patients treated with However, 12 Gleason score 8–10 cancers were detected in an antiandrogen and 5α-RIversus5α-RI alone. However, the dutasteride group at years 3-4 versus only one in the none of these trials studied the impact on disease-specific placebo group and dutasteride treatment was associated with or overall survival and none compared 5α-RI mono- or more sexual adverse effects. The benefit of finasteride or combination therapy against 1st line androgen deprivation dutasteride in reducing the risk of low-grade CaP is clear. treatment in a randomized fashion. Low-grade CaP is unlikely to be lethal and patients may reduce their risk of overtreatment. However, these drugs may induce high-grade CaP, a concern that has prevented (b) CR-CaP. CR-CaP was thought for many years to be FDA approval of finasteride and dutasteride use for CaP androgen-independent or hormone-refractory but CR-CaP prevention. Several secondary analyses of these two trials remains AR-dependent and probably AR-ligand dependent have concluded that these drugs actually reduce the risk in almost all cases [74]. Despite castrate serum levels of of moderate- and high-grade disease but these analyses are T(<50 ng/dL), CR-CaP tissue levels of T and DHT were hypothesis-generating and not definitive. In March 2009, the similar and 80–90% lower compared to their levels in benign 14 Advances in Urology prostatic tissue, respectively [75]. CR-CaP tissue synthesizes and adrenal tumors, congenital adrenal hyperplasia, and testicular androgens (T and DHT) in an intracrine fashion exogenous androgenic hormone administration. Regardless from several substrates such as cholesterol, progesterone, of the cause, overproduction of either T or T precursors adrenal androgens, and androstandione [76–79]. Other phe- leads to exaggerated T action in target tissues such as skin. In nomena intrinsically acquired by CR-CaP tissue in response skin, T is converted to DHT by the enzyme 5α-R, which acts to castration include the continuous expression of AR directly on hair follicles and the sebaceous glands. The most [80], upregulation of the synthesis of enzymes necessary frequent dermatologic manifestations of androgen excess are for steroidogenesis [76], AR hypersensitivity (up to 10,000 hirsutism, acne, and androgenic alopecia [91]. times) to low levels of ligands by alteration of its co-activator Androgen surge can miniaturize hair follicles resulting profile from SRC1 to TIF2 and through its phosphorylation in male androgenic alopecia at puberty and in the scalp by SRC and Ack1 tyrosine kinases [81–83] and AR functional of genetically predisposed individuals. In women, androgen mutations, which broaden ligand specificity in 5–30% of excess plays a role in scalp hair loss; however, this process cases [84]. is different than in men and is referred to as female pattern New second-line hormonal therapeutic agents that have hair loss. Hirsutism is a disorder of excessive growth of shown better performance in CR-CaP compared to the terminal hair in women, in a male-like distribution, which old generation of second-line hormonal therapies are abi- is stimulated by androgen excess [92]. In acne, the pubertal raterone acetate and MDV3100, among others [77, 85]. androgen surge increases the stimulation of sebaceous glands Abiraterone acetate is a potent, selective, and irreversible resulting in increased sebum production and acne formation inhibitor of CYP17A1 enzyme, which is an important in susceptible individuals [93]. enzyme in the intracrine synthesis of testicular androgens. In all androgen-stimulated skin disorders, the activity MDV3100 inhibits ligand binding to the AR and nuclear of 5α-R enzyme system is increased such as in the hair translocation of AR-ligand complex. The clinical response follicles of hirsute women [93], in balding scalps [94], and in to these new drugs is indirect proof that CR-CaP remains acne-prone skin [95]. Inhibition of the 5α-R enzyme system androgen stimulated. 5α-R isozymes are important in the appears to be a target for treatment of androgen-stimulated growth of CR-CaP tissue since they are upregulated in CR- skin disorders, since 5α-R inhibitors may result in fewer side- CaP and may contribute to intracrine synthesis of testicular effects by not blocking the action of T, unlike classical anti- androgens. These enzymes convert progesterone, ASD, and T androgens such as cyproterone acetate or spironolactone. into pregnanldione, androstandione, and DHT, respectively Finasteride and dutasteride reduce scalp DHT levels by [74, 79]. Pregnanldione is further converted via several steps 64% and 51%, respectively [96, 97]. In men with androgenic into androstandiol which is oxidized by 17β-hydroxysteroid alopecia, finasteride and dutasteride significantly increased dehydrogenase 2 and 10 (17β-HSD2 and 10) to DHT (the hair count after a minimum of 6-month treatment [98, 99]. backdoor pathway to DHT synthesis). Androstandione is While finasteride 1 mg daily was superior to 5% topical converted by 17βHSD3 into DHT. minoxidil in inducing hair growth [100], finasteride 5 mg Clinical trials of finasteride [70] and dutasteride [71]as daily was inferior to dutasteride 2.5 mg daily in a phase monotherapy in patients with advanced CaP showed no II study as treatment for male androgenic alopecia [97]. improvement of clinical end points. The presence of 5α-R3 Finasteride and topical minoxidil (but not dutasteride) are in CR-CaP is a potential explanation, until such time that an FDA-approved for male androgenic alopecia. In women inhibitor has been proven effective clinically. Combination with androgenic alopecia, neither finasteride nor dutasteride therapy of 5α-RI with antiandrogen or ketoconazole and is FDA-approved treatment options due to teratogenicity. hydrocortisone was tried in CR-CaP as second or third line Finasteride has been tested in postmenopausal women at the hormonal therapies [86–89]. PSA decreases of variable mag- 1 mg dose without success. However, finasteride was shown nitudes and durations were achieved in more than half to be effective in 4 women with elevated serum T levels [101]. the patients. However, none of the combination trials were Whether finasteride is only effective in women with hair loss designed to test the effect on disease-specific and overall sur- and hyperandrogenism or that higher doses are needed in vival. In a phase II, single arm study of 57 patients with CR- women remains to be tested. A single case report showed CaP, dutasteride added to ketoconazole, and hydrocortisone improvement with dutasteride in a woman who had failed reduced PSA ≥ 50% of baseline value in 56% of patients, to respond to finasteride [102]. responses that lasted for a median of 20 months. Median time 5α-RI also is acceptable therapy for hirsutism. Finasteride to disease progression was 14.5 months that was better than 5 mg/day was superior to placebo and similar to spirono- all prior studies of ketoconazole and hydrocortisone in CR- lactone and flutamide in reducing the severity of hirsutism CaP [89]. [103]; however, in a different study, finasteride was inferior to flutamide as a treatment for hirsutism [104]. Dutasteride 10.5. Androgen-Stimulated Skin Disorders (Acne, Androgenic has not been tested as a treatment for hirsutism. Alopecia and Hirsutism). Hyperandrogenism, or excessive Theroleof5α-RI is unclear for treatment of acne. MK- 386, a selective 5α-R1 inhibitor, decreased sebum DHT levels androgen production, is primarily a disorder of females. Polycystic ovary syndrome (PCOS) is the most common in a dose-dependent fashion [105]. MK-386 was examined cause of female hyperandrogenism with a prevalence of 6% as a treatment for acne in a placebo-controlled trial and to 10% in women of childbearing age [90]. Other causes wasfound to be similartoplacebo andinferiortosys- of hyperandrogenism include androgen-secreting ovarian temic minocycline therapy. Furthermore, MK-386 did not Advances in Urology 15 enhance the therapeutic benefit of minocycline when used in [10] W. Eicheler, M. Dreher, R. Hoffmann, R. Happle, and G. Aumuller, “Immunohistochemical evidence for differential combination [106]. 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The 5 Alpha-Reductase Isozyme Family: A Review of Basic Biology and Their Role in Human Diseases

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Copyright © 2012 Faris Azzouni et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Hindawi Publishing Corporation Advances in Urology Volume 2012, Article ID 530121, 18 pages doi:10.1155/2012/530121 Review Article The 5 Alpha-Reductase Isozyme Family: A Review of Basic Biology and Their Role in Human Diseases Faris Azzouni, Alejandro Godoy, Yun Li, and James Mohler Department of Urology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA Correspondence should be addressed to Faris Azzouni, farisazzouni@hotmail.com Received 15 July 2011; Revised 11 September 2011; Accepted 27 September 2011 Academic Editor: Colleen Nelson Copyright © 2012 Faris Azzouni et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Despite the discovery of 5 alpha-reduction as an enzymatic step in steroid metabolism in 1951, and the discovery that dihydrotestosterone is more potent than testosterone in 1968, the significance of 5 alpha-reduced steroids in human diseases was not appreciated until the discovery of 5 alpha-reductase type 2 deficiency in 1974. Affected males are born with ambiguous external genitalia, despite normal internal genitalia. The prostate is hypoplastic, nonpalpable on rectal examination and approximately 1/10th the size of age-matched normal glands. Benign prostate hyperplasia or prostate cancer does not develop in these patients. At puberty, the external genitalia virilize partially, however, secondary sexual hair remains sparse and male pattern baldness and acne develop rarely. Several compounds have been developed to inhibit the 5 alpha-reductase isozymes and they play an important role in the prevention and treatment of many common diseases. This review describes the basic biochemical properties, functions, tissue distribution, chromosomal location, and clinical significance of the 5 alpha-reductase isozyme family. 1. Introduction scrotum), and pubertal growth of facial and body hair. DHT plays an important role in several human diseases, Testosterone (T) is the most abundant androgen in serum. which include acne, hirsutism, male pattern baldness, benign Approximately 97% of T is bound to albumen and sex- prostate hyperplasia (BPH), and prostate cancer (CaP) [3]. hormone binding globulin and the remaining 3% is free The role of DHT was discovered after the description of and biologically active. T is synthesized by the Leydig 5α-R2 deficiency in a group of males from the Dominican cells of the testes under the control of the hypothalamus Republic [4]. DHT has 2–5 times higher binding affinity and anterior pituitary gland. In male fetuses, T stimulates for AR than T, and 10-fold higher potency of inducing AR the differentiation of the Wolffian duct into male internal signaling than T [5], which means that their effects are genitalia (epididymis, vas deferens, and seminal vesicles) different but complementary [6]. and development of libido, enlargement of the vocal cords, Three isozymes of 5α-R are known to exist (5α-R1-3) [7] skeletal muscles, penis, and scrotum and the initiation and two other proteins exhibit 5-alpha reducing capabilities, of spermatogenesis at puberty [1, 2]. T is taken from glycoprotein synaptic 2 (GPSN2), and glycoprotein synaptic circulation to cells through processes that remain poorly 2-like (GPSN2L) proteins. Only one 5 beta-reductase (5β- understood. Intracellular T is converted to dihydrotestos- R) enzyme has been identified. Its products, 5β-isomers, terone (DHT), the preferred ligand for androgen receptor are labeled as epi-product, such as 5β-DHT (epi-DHT) (AR) transactivation, by the enzyme 5 alpha-reductase (5α- [8]. Several compounds have been developed to inhibit the R). Upon ligand binding and transactivation, the DHT- 5α-R enzyme system and they play an important role in AR complex translocates from cytoplasm to nucleus and the prevention and treatment of many common diseases activates the transcription of certain genes (the androgen [9]. This review describes the basic biochemical properties, receptor-regulated genes, ARRG). functions, tissue distribution, chromosomal location, and DHT is important for in utero differentiation and growth of the prostate gland, male external genitalia (penis and clinical significance of this enzyme family. 2 Advances in Urology 2. Background was highest in the primordia of the prostate and external genitalia prior to their virilization, but very low in Wolffian Steroids are a special type of lipid. The backbone of steroids duct structures [27, 28], and from genetic studies on a rare is the compound “gonane”, a 17-carbon molecule composed disorder of male sexual differentiation, originally termed of 4 rings. The three cyclohexane rings are labeled A, B, pseudovaginal perineoscrotal hypospadias and subsequently and C. These 3 rings together are called phenanthrene. Ring referred to as 5α-R deficiency [4]. Analysis of enzyme activity D is a cyclopentane ring. The carbon atoms are numbered in skin samples and of urinary and serum steroids revealed a from 1 to 17. Typically, steroids have a methyl group (– generalized defect in the conversion of T to DHT. CH ) at carbons C-10 and C-13 and an alkyl side chain Studying 5α-R was hampered by the insolubility of the (R) at C-17 (Table 1). Alkanes are saturated hydrocarbons protein, a hurdle which was overcome in 1989. The tech- composed of carbon and hydrogen atoms linked by single nique of expression cloning in Xenopus laevis oocytes bonds. The simplest alkyl group is a methyl group. Steroids was used to isolate a cDNA from rat liver that encoded vary by the configuration of the alkyl side chain, the number 5α-R enzyme, which was used to isolate a human 5α-R of additional methyl groups, and the functional groups by cross-hybridization with a prostate cDNA library. The attached to the steroid nucleus. Carbons number 18 and two expressed proteins had different biochemical properties 19 are attached to carbons number 13 and 10, respectively. and different responses to finasteride. These observations Additional carbon atoms are usually a part of the R side suggested the presence of two 5α-R isozymes that were chain or attached elsewhere to the steroid backbone [22]. confirmed by studies done in patients with 5α-R deficiency. Androgens are derivatives of androstane and contain 19 car- The coding sequence of the gene specifying the rat liver bons and either a keto group (e.g., dehydroepiandrosterone cDNA was isolated and found to be normal in these patients. (DHEA) and androstenedione (ASD)) or a hydroxy group Further genetic studies in these patients identified a different (e.g., T and DHT) at position 17 of the steroid nucleus mutated gene that encoded a 5α-R in normal individuals (Figure 1). with identical biochemical properties to the human prostatic 5α-R. The first cDNA, isolated from rat liver, was named 5α-R1 (SRD5A1) gene, and the second cDNA, which was 3. Historical Overview isolated from human prostate and found defective in 5α-R- Steroid-5-reductases (5α-R and 5β-R) were first discovered, deficient patients, was named 5α-R2 (SRD5A2) gene [29]. More recently, with the development of genome-wide purified, and characterized in rat liver homogenates [23]. These early experiments demonstrated that these enzymes gene expression profile analyses, a third 5α-R (SRD5A3) were capable of irreversibly reducing the delta 4, 5 bond gene was identified. GPSN2 and GPSN2L proteins were 4,5 (double bond between carbons 4 and 5; Δ )ofC-19and identified using sequence searching and NCBI’s BLAST C-21 steroids to 5α-and 5β-stereoisomers. (http://blast.ncbi.nlm.nih.gov/Blast.cgi). All primary species The first androgen isolated was androsterone, a 5α- (from plant, amoeba, yeast, to vertebrate) in Eukaryota reduced androstane, which was isolated by Butenant in 1931 contain all 3 subfamilies [8]. from 25,000 liters of urine from adult men. This steroid was assumed to be the male hormone until 1935 when Ernst 4. Family Members Laquer and his colleagues isolated T from several tons of bull testes. The 5α-R enzyme was characterized initially in the The 5α-R family is composed of 3 subfamilies and 5 members 1950s in rat liver slices based on its ability to convert deoxy- (isozymes) in total. Isozymes are different proteins that per- corticosterone to 5α-reduced metabolites [24]. Tomkins and form the same function: others showed that the enzyme required a reduced pyridine (a) 5α-R1 and 5α-R2, nucleotide cofactor (i.e., NADPH) and could metabolize a variety of steroid substrates [25]. Speculation persisted about (b) 5α-R3, whether a single enzyme or multiple enzymes were involved (c) GPSN2 and GPSN2L proteins. in 5α-reduction of steroids. The 5α-reduction of steroids made them susceptible to further reduction, sulfation, and glucuronidation, modifications that decreased their affinity 5. Functions to bind proteins, made them more hydrophilic and facilitated their excretion. In the 1960s, 5α-reduction was shown to 5.1. 5 Alpha Reduction: (5α-R1-3) [29, 30]. The substrates 4,5 be an irreversible reaction and DHT was found to be a for 5α-reductases are 3-oxo (3-keto), Δ C 19/C21 steroids. more potent androgen than T in prostate bioassays [26]. The The group “3-keto” refers to the oxygen-carbon double bond administration of radiolabeled T to rats resulted in a time- at carbon 3. Delta 4, 5 refers to the double bond between dependent accumulation of DHT in the nuclei of ventral carbon atoms 4 and 5. The reaction involves a stereospecific, prostate cells, which subsequently bound to a specific nuclear irreversible breakage of the double bond between carbons (androgen) receptor. These data indicated that 5α-reduction 4 and 5 (delta 4, 5) with the aid of cofactor NADPH and of T is a crucial step in androgen action and focused the insertion of a hydride anion (H ) to the α face at attention on 5α-R. The central role of 5α-R in mammalian carbon C-5 and a proton to the β face at position C-4. male physiology was obtained from developmental studies Examples of substrates are T, progesterone, androstenedione, of mammalian embryos showing that 5α-reduction activity epi-T, cortisol, aldosterone, and deoxycorticosterone. The Advances in Urology 3 NH R O H H Gonane Finasteride 9 14 F C Dehydroepiandrosterone CF H O NH HO Dutasteride Dehydroepiandrosterone-sulfate H H O O H H HO O Cl OH Testosterone LY 191704 H H CH O 3 OH Dihydrotestosterone Epristeride H H H H HO Figure 1: Structure of various steroids. physiologic role of 5α-reduction of these steroids (other than of the eye, is synthesized in the lens of the eye, and may T) is unknown but probably related to their degradation play a role in the regulation of aqueous humor formation and excretion or to certain physiologic functions. 5α- [32]. 5α-Dihydroaldosterone is a potent antinatriuretic agent dihydroprogesterone (5α-DHP) is a major hormone in the with somewhat different physiologic effects than aldosterone circulation of both normal cycling and pregnant women itself; its formation in the kidney is enhanced by restriction [31]. 5α-dihydrocortisol is present in the aqueous humor of dietary sodium intake, which suggests its importance for 4 Advances in Urology Table 1: Different steroid families. Class Example Number of carbon atoms Steroid backbone Gonane 17 Estranes Estradiol 18 Androstanes Testosterone 19 Pregnanes Progesterone 21 Glucocorticoids Cortisol 21 Mineralocorticoids Aldosterone 21 Cholanes Cholic acid 24 Cholestanes Cholesterol 27 the conservation of sodium [33]: compared to AS-BP. 5α-R3 expression was increased in lung, breast, papillary thyroid, and testicular (seminoma and yolk (Substrate) + (NADPH) + H sac) cancers compared to their benign counterparts. (1) −→ (5α-substrate) + NADP 5.4. Erythropoiesis [36]. 5α-C 19 steroids increase the pro- Uemura et al. used small interfering RNA (siRNA) to knock duction of erythropoietin hormone in the kidneys. 5β-C 19 down the expression of 5α-R3 isozyme in 22RV1 and LNCaP- steroids are important for heme synthesis in the liver. C4-2 CaP cells by transfecting them with several siRNA expression vectors [34]. Subsequently, they studied mRNA 5.5. Regulation of Bile Synthesis [37]. Both 5α-R and 5β-R are expression of 5α-R3 (RT-PCR), cell growth and viability, involved in bile biosynthesis, where they catalyze the conver- and the ratio of DHT/T using liquid chromatography- sion of 7α,12α-dihydroxy-4-cholesten-3-one into 7α,12α- tandem mass spectrometry. Knockdown of 5α-R3 expression dihydroxy- 5α-cholestan-3-one, and 7α,12α-dihydroxy-5β- caused decreased cell growth and viability and DHT/T cholestan-3-one, respectively. Only the 5β-isomer has been ratio. Unpublished work from our group has confirmed shown to be biologically active and is used for bile synthesis. the ability of 5α-R3 to 5α-reduce 3-oxo, delta 4,5 C19 The 5α-isomer is inactive and suggested to be an inhibitory and C21 (T, androstenedione and progesterone) steroids in step in bile biosynthesis regulation in humans. lysates of CHO-K1 cells transfected with 5α-R3 cDNA via an adenovirus vector, CaP cell lines CWR-22 and CWR- 22R, and clinical human samples of androgen-stimulated 5.6. GPSN2 Family [38]. While the functions of the GPSN2 benign prostate (AS-BP), androgen-stimulated (AS-CaP), subfamily are not understood fully, several reports have and castration-recurrent (CR-CaP) CaP. shown that GPSN2 members are involved in the fourth re- action of fatty acid elongation by reducing a fatty chain double bond in mammals. Although the substrate (fatty 5.2. N-Glycosylation of Proteins: (5α-R3). Congenital defi- acid) of GPSN2 members is structurally different from that ciency of 5α-R3 has been linked to a rare, autosomal recessive of the other two 5α-R subfamilies, all three subfamilies of 5α- disorder in which patients are born with mental retardation, R share a similar biochemical ability of reducing a double cerebellar, and ophthalmologic defects [35]. The presumed bond of the substrate. defect involves the reduction of the terminal double bond of polyprenols to dolichols, an important step in protein N-glycosylation. N-linked protein glycosylation involves the 6. Protein Structure and addition of a 14-sugar glycan to select asparagine residues on Gene Location [8, 29, 39] a nascent protein to facilitate proper folding and trafficking of the protein and occurs in the membranes of endoplasmic 5α-R1 and 2 isozymes are NADPH-dependent, membrane- reticula. This disorder is part of the family of congenital associated (microsomal) enzymes, composed of 259 and disorders of glycosylation and was described for the first time 254 amino acids, and have molecular weights of 29.5 and in a family in the United Arab Emirates by Cantagrel et al. 28.4 kilodaltons, respectively. They contain a high content [35]. of hydrophobic amino acids distributed throughout their sequences, which suggests that they are intrinsic membrane 5.3. Potential Biomarker of Malignancy: (5α-R1-3) [14, 20]. proteins deeply embedded in the lipid bilayer. The bulk of published literature indicates that the expression Even though these two isozymes are intrinsic membrane of 5α-R1 increases and 5α-R2 decreases in CaP compared to proteins and catalyze the same reaction, they only share a benign prostate and BPH. Umera et al. confirmed for the limited degree of homology in protein sequence, are located first time increased expression of 5α-R3 at the mRNA level on different chromosomes, and possess distinctive biochem- in CR-CaP. Godoy et al., confirmed this at the protein level. ical properties. The average sequence identity between these A validated monoclonal antibody showed that expression two isozymes within a given species is approximately 47%, of 5α-R3 was increased similarly in AS-CaP and CR-CaP while the sequence identity between the same isozyme Advances in Urology 5 across species is 60% for 5α-R1 and 77% for 5α-R2. They other steroid receptors. The first inhibitors were steroids that are encoded by the 5α-R1 and 5α-R2 genes. These genes mimicked T and, in many cases, were substrates themselves have similar structures, with five coding exons separated (i.e., not true inhibitors). The inhibitors can be broadly by four introns. The positions of the introns are essentially classified into two categories: steroidal and nonsteroidal. The identical in the two genes. However, SRD5A1 is located steroidal class has more inhibitors thus far. on chromosome 5p15 whereas SRD5A2 is on 2p23. Gene The mechanism of 5α-RI is complex but involves the polymorphisms exist for the two genes and are more binding of NADPH to the enzyme followed by the substrate. 4,5 common for 5α-R2. More than 850 and more than 550 single The Δ bond is broken and a hydride anion is transferred nucleotide polymorphisms (SNPs) have been reported for from NADPH directly to the C-5 carbon on the α face 5α-R2 and 5α-R1 genes, respectively [40, 41]. Only a few followed by a proton attacking the C-4 carbon on the β face of these gene polymorphisms affect enzyme activity; some leading to the formation of the product that subsequently + + decrease (e.g., V89L SRD5A2 variant) and others increase leaves the enzyme-NADP complex. NADP departs last and (e.g., A49T SRD5A2 variant) enzyme activity [42]. Molecular the enzyme becomes free for further catalysis cycles. Based on epidemiologic studies are inconclusive as to whether altered this, the mechanism of inhibition of 5α-R isozymes is divided 5α-R2 isozyme activity due to 5α-R2 gene polymorphism into three types [30]: affects CaP risk [43]. A variant of 5α-R1 gene was reported (a) competitive with the cofactor (NADPH) and sub- to increase risk of polycystic ovary syndrome (PCOS) and strate (bi-substrate inhibitors): the inhibitor binds more severe hirsutism in lean women, whereas a variant of the free enzyme, for example, ONO-3805; 5α-R2 gene was associated with decreased risk of PCOS in the same cohort [44]. More than 300 SNPs have been reported (b) competitive with the substrate: the inhibitor binds for 5α-R3 gene; however, their clinical significance remains the enzyme-NADPH complex for example, 4-, 6-, uncertain [45]. 5α-R3 is composed of 318 amino acids and and 10-azasteroids; has only 19% homology with 5α-R1 and 20% homology with (c) uncompetitive with the enzyme-NADP complex: 5α-R2 [39]. 5α-R3 is encoded by SRD5A3, which is located the inhibitor binds the enzyme-NADP complex aft- at 4q12. The genes encoding GPSN2, GPSN2-like, and 5β- er the product leaves, for example, epristeride. R are located at 19p13.12, 4q13.1, and 7q34, respectively. GPSN2 and GPSN2-like proteins are composed of 308 and 8.1. Steroidal 5α-RI (Figure 1). (1) 4-Azasteroids: the 3-oxo, 363 amino acids, respectively. The amino acid sequence 5-alpha steroids with a nitrogen atom at position 4 have been homology for GPSN2 is 15% with 5α-R1, 17% with 5α-R2 the most extensively studied. Examples include finasteride and 11% with 5α-R3. GPSN2-like has 6%, 11%, 6%, and (MK-906), dutasteride (GG745), 4-MA, turosteride, MK- 44% sequence homology with 5α-R1, 5α-R2, 5α-R3, and 386, MK-434, and MK-963. GPSN2, respectively. (a) Finasteride is a synthetic 4-azasteroid and is the first 5α-RI approved for treatment of benign prostatic 7. Biochemical Properties [8, 29] enlargement (BPE) and subsequently male pattern When examined in lysates of transfected cells, 5α-R1 exhibits baldness. Finasteride is a potent (mean inhibitory a broad pH optimum, which ranges between 6.0 and 8.5, concentration [IC ], 69 nM) competitive inhibitor while 5α-R2 shows a narrow acidic pH optimum (pH 5– of 5α-R2 but inhibits less effectively 5α-R1 (IC 5.5). However, there is evidence to suggest that inside intact 360 nM) [47]. Finasteride decreases mean serum level human cells, 5α-R2 isozyme functions optimally at a more of DHT by 71% after 24 weeks of use [48]. Seven-day neutral pH range (6.0–7.0). 5α-R1 has a larger turnover treatment with finasteride (1 or 5 mg daily) has been number, as indicated by its K value and a lower substrate reported to suppress intraprostatic DHT in men with cat affinity for T, K = 1–5 μM. 5α-R2 has a lower turnover m lower urinary tract symptoms (LUTSs) attributed to number (K ) and a higher substrate affinity, as indicated cat BPE by approximately 85% relative to placebo [49], by K = 0.004–1 μM for T. Under optimal conditions, m whereas another study of finasteride 5 mg/d (also in 5α-R2 has a higher 5α-reducing activity than 5α-R1, as men with LUTS attributed to BPE) demonstrated a indicated by its high V /k ratio. Both isozymes contain reductionof68% at 6months [49]. Finasteride was max m an NH -terminal steroid (ligand) binding domain and a 2 shown in vitro to inhibit 5α-R3 at a similar potency to COOH-terminal NADPH binding domain. The apparent 5α-R2 (IC = 17.4 nM, 14.3 nM, resp.) in transfected dissociation constant for NADPH cofactor is similar for HEK-293 cells [21]. both isozymes (3–10 μM). No such comparisons exist for (b) Dutasteride is a synthetic 4-azasteroid with a half-life 5α-R3 except that it appears to be efficient at pH 6.5–6.9 of nearly 5 weeks and is only approved for treatment (unpublished work from our group). of BPH. Dutasteride is a dual 5α-RIsinceitismore effective (more potent) at inhibiting 5α-R1 and 2 than finasteride; IC for inhibiting 5α-R1 is 7 nM 8. 5α-Reductase Inhibitors [9, 30, 46] and 5α-R2 is 6 nM. Dutasteride reduced mean levels Goal of development of 5α-reductase inhibitors (5α-RI) was of serum DHT at 24 weeks better than finasteride to bind to 5α-R with little or no affinity for the androgen or (94.7% versus 70.8% suppression) [50]and caused 6 Advances in Urology a 97% reduction in intraprostatic DHT levels in men or specially a Cl) and a methyl group at position with CaP treated with 5 mg/d for 6–10 weeks [51]. 4. LY 191704 is the most potent (IC = 8 nM). Another trial of dutasteride 3.5 mg/d for 4 months (b) Piperidones lack B and D rings. prior to RP decreased intraprostatic DHT by 99% (c) Quinolinones lack C ring. [52]. The near-maximal suppression of intraprostatic (d) Pyridines lack B and C rings. DHT with dutasteride 3.5–5 mg daily and the report (e) Benzo[c]quinolinones tricyclic compounds de- that dutasteride inhibits 5α-R3 in vitro (IC = rived from 6-azasteroids (no D ring, aromatic 0.33 nM) [21] suggest that the development of a triple ring for the C ring) that have selective but weak 5α-R inhibitor may not be necessary. Table 2 provides inhibitory activity against 5α-R1. a comparison between finasteride and dutasteride. (f) Benzo[c]quinolizinones are tricyclic compounds (c) 4-MA was a potent dual inhibitor of 5α-R1 (IC = derived from 10-azasteroids (no D ring, aroma- 1.7 nM) and 5α-R2 (IC = 1.9 nM). 4-MA had a tic ring for the C ring) that include some very very low affinity for AR and thus was not expected potent, selective inhibitors of 5α-R1. to produce undesirable antiandrogen effects, such as impotence, impaired muscle growth, or gyneco- (Subgroups (b), (c), and (d)) are very weak 5α-R1I. mastia. However, 4-MA was withdrawn from clinical (2) Nonsteroidal aryl acids are tricyclic compounds de- development after it was shown to be an inhibitor rived from androstanecarboxylic acids that differ of 3β-hydroxysteroid dehydrogenase and to cause from their parent compounds in being selective, hepatotoxicity [9]. noncompetitive 5α-R1I. (d) Turosteride, MK-434, and MK-963 inhibit mainly (3) Butanoic acid derivatives contain an aromatic ring 5α-R2. MK-386 is a selective 5α-R1 inhibitor [46]. (generally benzene or indole) that bears a butanoic acid chain and aromatic moieties. Examples include (2) 6-Azasteroids (e.g., GIlS7669X) have a heterocyclic B 4,5 ONO-3805, demonstrated in vitro to be a selective ring (nitrogen atom at position 6) and a Δ bond in the A inhibitor of 5α-R1, and FK143, which inhibits 5α-R1 ring and are potent competitive inhibitors of 5α-R1 and 2 and 5α-R2 equally and noncompetitively. [46]. (3) 10-azasteroids, for example, AS97004, are compet- (4) Polyunsaturated fatty acids, found in vegetable oils, itive 5α-RI with a similar mechanism of action to 6-azas- have been found to inhibit human and rat microso- teroids [9]. mal 5α-R activity. In this group, y-linolenic acid is the (4) Androstanecarboxylic acids, such as epristeride, are most potent compound tested. Since 5α-R isozymes noncompetitive, specific inhibitors for 5α-R2 [30]. are intrinsic membrane proteins, their activity may (5) Other steroidal inhibitors include progesterone esters depend on the unique environment of the lipid such as 4-bromo-17α-(p-fluorobenzoyloxy)-4-pregnene-3, bilayer. Whether and how fatty acids may function as 20-dione [53], 2-azasteroids, 3-azasteroids, 19-nor-10-azas- endogenous regulators of 5α-R remain unknown. teroids, and diazasteroids [9]. (5) Some cations, especially zinc, have been reported to reduce sebum production in vivo and have been used 8.2. Nonsteroidal Inhibitors [9, 30, 46]. Several pharmaceu- to treat acne. In vitro assays have indicated that zinc tical and academic groups have pursued the synthesis of specifically inhibits 5α-R1. This inhibition may be nonsteroidal compounds that inhibit human 5α-reductases mediated both by non-competitive inhibition of T due to the undesired hormonal side effects of steroidal com- binding to 5α-R and by reduced formation of the pounds. Nonsteroidal inhibitors can be classified according NADPH co-factor. to their structure. Most have been derived from azasteroidal (6) Other nonsteroidal inhibitors include epicatechin- inhibitors by removing one or more rings from the aza- 3-gallate and epigallocatechin-3-gallate, which are steroidal structure. Nonsteroidal inhibitors are thought to major constituents of green tea. Also included are act as competitive inhibitors with exception of epristeride 7-hydroxycoumarin derivatives, 2,6-disubstituted 4- analogues, which are noncompetitive inhibitors. The most hydroxy-4-hydroxymethyl biphenyl derivatives, iso- potent and selective inhibitors of human 5α-R1 are found flavonoids, and 3,3-diphenylpentane derivatives [9]. among these classes of compounds and include the follow- ing. 9. Tissue Distribution (1) Benzoquinolines include many subgroups. Numerous reports exist in the literature on the expres- (a) Benzo[f]quinolinones are tricyclic compounds sion pattern of 5α-R1 and 5α-R2inhuman tissue at that are derived from 4-azasteroids by removing various stages of development. The results vary due to the D ring and substituting the C ring with an differences in antibody sensitivity and specificity, mRNA aromatic one. These are selective against 5α- analysis (in situ hybridization versus northern blotting versus R1. The potency against 5α-R1 increases by reverse transcriptase-polymerase chain reaction), protein substituting a halogen atom at position 8 (F, Br, analysis (immunohistochemistry versus western blotting), Advances in Urology 7 Table 2: Comparison between finasteride and dutasteride (referenced in text). Finasteride Dutasteride Family Steroidal 5α-RI (4-azasteroid) Steroidal 5α-RI (4-azasteroid) IC for 5α-R1, 2 and 3 (nM) 360, 69, 17.4 7, 6, 0.33 Male androgenic alopecia FDA-approved clinical uses Benign prostatic enlargement Benign prostatic enlargement 1 mg daily for male androgenic alopecia Clinical dose 0.5 mg daily 5 mg daily for benign prostatic enlargement Half-life (T 1/2) 6–8 hours 5 weeks ↓Serum DHT by 71% ↓Serum DHT by 95% Suppression of DHT ↓Intraprostatic DHT by 85% ↓Intraprostatic DHT by 97–99% tissue preparation, nature of tissue, evaluation of results, not detected in the skin and scalp until the onset of puberty. tissue fixation protocols, and control tissue. In addition, At puberty, only 5α-R1 is reexpressed in the skin and scalp normal, benign, and malignant human tissue specimens are and persists thereafter until 81 years. In the prostate gland, heterogeneous with variable expression of proteins among Lunacek et al. reported that both 5α-R1 and 5α-R2 were specimens from different individuals and within the same detectable at the protein level using IHC until approximately specimen, that is, inter- and intraindividual variability. 1 year of age. After that, they were detectable at the mRNA Therefore, a summary of many studies that discussed the level (RT-PCR) until 6 years of age. Thigpen et al. only tissue distribution of 5α-R1-3 in different human tissues was detected 5α-R2 at the protein level using immunoblotting in tabulated to demonstrate differences in results (Table 3). prostatic tissue from a 7-year-old male. Since the methods used by this group did not detect 5α-R1 protein in the newborn, juvenile, or adult prostatic tissues, and since other 9.1. According to Age groups detected 5α-R1 at the protein level in fetal and adult benign prostatic tissue, 5α-R1 and 5α-R2 appear to 9.1.1. Fetus. Ellsworth and Harris [54] studied 5α-R activity be expressed in the prostate in male fetuses and throughout in fetal scalp, back skin, and prostatic tissues and compared postnatal life. it to 5α-R activity in adult male scalp and prostatic tissues. They studied the conversion of radio-labeled T into DHT in relation to pH and response to selective 5α-R1 and 5α- 9.1.3. Adulthood-Old Age. 5α-R1-3 is ubiquitously expressed R2 inhibitors and calculated the k of T at pH values of [10, 11, 13, 20, 55]. 5α-R1 and 5α-R2 are expressed 7.0 and 5.5. 5α-R1 is expressed in fetal scalp and nongenital differently in liver, genital and nongenital skin, prostate, (back) skin at levels that are 5–50 times less than adult skin. epididymis, seminal vesicle, testis, ovary, uterus, kidney, 5α-R2 is expressed in the fetal prostate at levels similar to exocrine pancreas, and brain (Table 2, Aumuller et al.). Our adult prostate. Thigpen et al. [13] studied 5α-R expression laboratory described the expression of 5α-R3 using IHC in in fetal liver, adrenal, testis, ovary, brain, scalp, chest, and various benign and malignant tissues. 5α-R3 is overexpressed genital skin, using immunoblotting. They detected 5α-R2 particularly in lung adenocarcinoma, testicular seminoma only in fetal genital skin. Lunacek et al. [55] studied the and yolk sac tumors, papillary thyroid cancer, and androgen- expression of 5α-R 1 and 5α-R2 at the mRNA (RT-PCR) and stimulated and castration-recurrent CaP relative to their protein (immunohistochemistry) levels in fetal and postnatal benign counterparts [20]. When contrasting these data with prostatic tissues until 6 years of age. Both 5α-R1 and 5α-R2 the expressed sequence tag (EST) database from NCBI, both proteins were expressed in prostatic epithelial and stromal sets of data suggest a broad pattern of expression for 5α-R1-3 components, at consistent levels throughout all age groups. in human tissues; ESTs for 5α-R1 (271 sequences) have been 5α-R1 is expressed mainly in the epithelium and 5α-R2 is reported from different human tissues, which include lung, expressed mainly in the stroma of the prostate. At the mRNA brain, intestine, skin, prostate, testis, and stomach [56]. ESTs levels, both are detectable throughout the ages studied and for 5α-R2 (39 sequences) have been reported in prostate, both peak in the second trimester. lung, liver, kidney, brain, testis, and skin [57]. ESTs for 5α- R3 (149 sequences) have been reported in kidney, testis, intestine, brain, liver, uterus, pancreas, skin, and prostate 9.1.2. Newborn-Onset of Puberty. In newborns, 5α-R1 is [58]. Tissue distribution of 5α-R3 protein in several human expressed at the protein level in the liver, skin, scalp [13] benign tissues was consistent with the tissue origin of the 5α- and prostate [55]. 5α-R2 is expressed in prostate, seminal R3 EST reported at NCBI [20]. vesicles, epididymis, liver, and to lesser extent in scalp and skin [13]. Hepatic expression of 5α-R1 and 2 is present at the protein level (immunoblotting) throughout postnatal life. At 9.2. According to Organs. (See [10–13, 15–20, 54–61] approximately 1.5 years, the expression of both proteins is (Table 3).) 8 Advances in Urology Table 3: Tissue distribution of 5α-reductase 1–3 according to different authors. Author isozymes Tissue type Materials and methods 5α-R1 5α-R2 Notes studied Nuclear, in epidermis from all sites: (scrotal> axilla> breast> Cytoplasmic, in epidermis from lip> eye lid): all sites: stratum basale (++), stratum stratum spinosum (++), stratum spinosum (++), absent in basale (+), absent in stratum Protein expression (IHC) stratum granulosum and stratum granulosum and stratum using rabbit polyclonal Epidermis: genital corneum, dermal papillae, corneum, inner epithelial RS antibodies against synthetic 5α-R1 more (scrotum) nongenital fibrous and outer epithelial RS (++), matrix cells of hair bulb peptides from C-terminus uniformly spread in Eicheler et al. [10] (Axilla, breast, lip, (++), inner epithelial RS (+), (+), absent in dermal papillae, parts of 5α-R1-2 proteins. skin versus 5α-R2 that 5α-R1-2 eyelid) using a matrix cells of hair bulb (++), fibrous and outer epithelial RS, Antibody sensitivity and is mainly found in semiquantitative scrotal fibroblast (++), basal and basal (+) and glandular (−)cells specificity confirmed by inner epith RS visual scale secretory cells of sebaceous of sebaceous glands, ELISA and WB on FFPE glands (++), secretory and myoepithelial (+) and secretory biopsy or autopsy tissues myoepithelial cells of sweat cells (−) of sweat glands, dermal glands (++), arrector pili adipocytes (+) muscles (+), dermal adipocytes No qualitative differences in (+). No qualitative differences in males and females males and females. Mainly cytoplasmic: Mainly nuclear: Prostate: stroma Prostate: stroma (+), epithelium (+), epithelium (+) (++), specially basal cells Seminal vesicle: stroma (+), Seminal vesicle.: stroma (+), epithelium (+) epithelium (++) Epididymis: stroma (+), Epididymis: stroma (+), epithelium (+) epithelium (+) Testis: Leydig cells (+), Sertoli Testis: spermatogonia (+), Leydig Protein expression (IHC) cells (+) and Sertoli cell (−) using rabbit polyclonal Ovary: stroma (++), theca and Ovary: stroma (+), theca and antibodies against synthetic granulosa cells (−) granulosa cells (+/−) peptides from C-terminus Uterus: endometrium (+), Uterus: endometrium (+), Many tissue types, parts of 5α-R1-2 proteins. myometrium (+) myometrium (+) Aumul ¨ ler et al. [11] using a Antibody sensitivity and Liver: hepatocytes (+/−), bile Liver: hepatocytes (++), bile duct 5α1-2 is ubiquitous 5α-R1-2 semiquantitative specificity confirmed by duct c (+), kupffer cells (++) c(+),kupffer cells (−) visual scale ELISA and WB. Pancreas: exocrine (+), islets of Pancreas: exocrine (+), islets of Tissues from surgical pts Langerhans (−) Langerhans (−) and autopsies, fixed in Kidney: glomerulus (+), PT (−), Kidney: glomerulus (−), PT Bouin’s or formaldehyde DT (++), CD (+) (++), DT (+/−), CD (+) Adrenal: cortex (−), medulla (−) Adrenal: ZG (+), ZF (+/−), ZR Thyroid: thyrocytes (−), C cells (+/−), med (−) (−) Thyroid: thyrocytes (−), C cells Cerebral cortex: pyramidal c (+), (−) glial cells (+/−) Cerebral cortex: pyramidal c Pituitary: prolactin cells (+), (++), glial c (−) others (−) Pituitary: prolactin cells (+), others (−) Advances in Urology 9 Table 3: Continued. Author isozymes Tissue type Materials and methods 5α-R1 5α-R2 Notes studied In balding and nonbalding scalp: Protein expression (IHC) 5α-R2 is expressed in using validated mouse In balding and non-balding infundibula, outer (mainly) and Scalp biopsies from monoclonal antibodies scalp: 5α-R1 is expressed only in Bayne et al. [12] inner epithelial RS of hair bald and non-bald against peptides from sebaceous glands 5α-R1-2 follicles. men N-terminus parts of No expression was detected in No expression was detected in 5α-R1-2 and enzyme hair follicles or in epidermis dermal papillae or in sebaceous activity using H-T glands 5α-R2 protein is expressed in 5α-R1 protein is expressed in prostate, seminal vesicles, liver and chest skin and 5α-R1 epididymis, and liver. mRNA was detected in 5α-R2 mRNA was detected in cerebellum, hypothalamus, pons, prostate, SV, epididymis. and Messenger RNA (NB) and medulla oblongata, skin, and liver. 5α-R2 was detected by WB protein expression (IHC liver 5α-R1 was not detected by only in fetal genital skin (not and WB) using rabbit WB in any fetal tissue. detected in fetal liver, adrenal, 5α-R1 protein was Thigpen et al. [13] Autopsy and surgical polyclonal antibodies 5α-R1 was detected by WB in testis, ovary, scalp, and brain). not detected in any 5α-R1-2 tissue samples against peptides from newborn liver, skin, and 5α-R2 was detected by WB in prostate sample C-terminus parts of scalp.5α-R1 was detected by WB newborn prostate, SV, 5α-R1-2 in all scalp samples from balding epididymis, liver, skin. and scalp. and nonbalding men (except 5α-R2 was not detected by WB in one). It was not detected in any any sample of balding and normal prostate, BPH, or PC nonbalding scalp from one man. sample It was detected in all normal prostate, BPH, and PC samples Protein expression (IHC) using rabbit polyclonal antibodies against peptides from N-terminus of 5α-R1-2 proteins. Antibody specificity Prostate: BPH confirmed with WB on Nuclear in BPH, shifts to Mainly cytoplasmic in all (TURP), ASCaP (RP), na¨ıve, 5α-R1- and 5α-R2- cytoplasm in HGPIN and CaP specimens Immunostaining Thomas et al. [14] CaP metastasis in transfected COS-1 cells and All differences are Immunostaining intensity: intensity: 5α-R1-2 androgen IHC on transfected COS-1 statistically significant Metastasis> CR-CaP> AS-CaP = BPH = Metastasis = CR-CaP> deprivation-treated cells-Evaluated by HGPIN> BPH AS-CaP = HGPIN men (autopsy) measuring percentage of moderate- and high-intensity immunostaining areas in relation to total epithelial, PIN, or tumor area in PE tissues 10 Advances in Urology Table 3: Continued. Author isozymes Tissue type Materials and methods 5α-R1 5α-R2 Notes studied Protein expression (IHC) Mainly nuclear in BPH, nuclear using validated rabbit Staining in and cytoplasmic in CaP (all Mainly cytoplasmic in all polyclonal antibodies, CaP-adjacent benign grades), and in adjacent benign samples (benign and malignant) Prostate: AS-CaP evaluated by visually tissue is not Thomas et al. [14] epithelial tissue Immunostaining Immunostaining intensity: (RP) with Gleason estimating percent of total significanty different 5α-R1-2 intensity: BPH> high grade> moderate score <7, 7, >7 tumor area showing low-, from low- and High grade > moderate grade = grade = low grade = adjacent moderate, and high-grade CaP for low grade > PC-adjacent benign benign tissue high-intensity in relation to either isozyme tissue > BPH Gleason score 5α-R2 mRNA and enzyme Messenger RNA expression 5α-R1 mRNA expression is activity were higher in BPH than (sqRT-PCR) and similar in BPH and AS-CaP. in AS-CaP. Prostate: BPH measurement of 5α-R There was no correlation Soderst ¨ om ¨ et al. [15] Therewas apositivecorrelation (TURP) and AS-CaP enzyme activity at pH 5.5 between enzyme activity at pH 5α-R1-2 between enzyme activity at pH 14 ◦ via RP or RC and 7 using C-T at 37 C (5.5 and 7) and 5α-R1 mRNA 5.5 and expression of 5α-R2 in homogenized frozen expression as expressed on the mRNA as expressed on the basis pulverized prostate tissue basis of β-actin of β-actin ISH showed that 5α-R1 mRNA is ISH showed that 5α-R2 mRNA is BPH and CaP tissue expressed in epithelium > stroma expressed in epithelium > stroma post prostate biopsy Lehle et al. [61] Messenger RNA expression mRNA expression levels by mRNA expression levels by or RP frozen in liquid 5α-R 1-2 (ISH, sqRT-PCR) sqRT-PCR: sqRT-PCR: nitrogen, one human liver> CaP > BPH> Normal liver = BPH > Normal prostate > liver sample prostate CaP Messenger RNA expression 5α-R1 mRNA expressed in BPH tissue (TURP) (ISH, RT-PCR) and epithelium > stroma frozen in liquid measurement of enzyme 5α-R2 mRNA > 5α-R1 mRNA in Habib et al. [16] nitrogen or in 5α-R1 mRNA expressed in activity at pH 5 and 7.5 BPH 5α-R1-2 ice-cold RPMI with epithelium > stroma 3 ◦ using H-T at 37 Cin 5α-R2 enzyme activity  5α-R1 FBS and archival homogenized pulverized enzyme activity in homogenized PE-BPH tissue frozen prostate tissue BPH tissue Mainly nuclear, in normal prostate and BPH tissue (luminal Mainly cytoplasmic (weak), in epithelial > basal) and in stroma normal prostate and BPH tissue Protein expression (IHC) 5α-R1 immunostaining > 5α-R2 (basal > luminal epithelial) and BPH (TURP), using polyclonal rabbit in BPH (in both epithelium and stroma. Bonkhoff et al. [17] AS-CaP (RP), antibodies against peptides stroma). In CaP, 5α-R2 immunostaining 5α-R1-2 CR-CaP (channeling from C-terminus parts of In CaP, 5α-R1 immunostaining became nuclear and cytoplasmic TUR) 5α-R1 and 2, validated by became nuclear and cytoplasmic and more intense in HGPIN and ELISA and WB and more intense in HGPIN and CaP versus adjacent benign CaP versus adjacent benign tissue (specially CR-CaP) tissue (specially CR-CaP) Advances in Urology 11 Table 3: Continued. Author isozymes Tissue type Materials and methods 5α-R1 5α-R2 Notes studied Messenger RNA 5α-R1 mRNA copy numbers> (qRT-PCR), protein (IHC) 5α-R2 mRNA in BPH 5α-R2 mRNA < 5α-R1 mRNA in expression using polyclonal 5α-R1 protein expression is BPH BPH (RC) fixed in rabbit antibodies against Shirakawa et al. [18] intense in epithelium of BPH 5α-R2 protein expression is formaldehyde and peptides from C-terminus 5α-R1-2 (higher than 5α-R2 protein) detected in epithelium and paraffin-embedded parts of 5α-R1 and 2, 5α-R1 enzyme activity at pH 7.5 stroma of BPH (less intense than validated by ELISA and is similar to 5α-R2 enzyme 5α-R1) enzyme activities at pH 5 activity at pH 5.0 3 ◦ and 7.5 using H-T at 37 C 5α-R1 is nuclear and cytoplasmic 5α-R2 is mainly cytoplasmic in in all 3 tissues all 3 tissues Nuclear 5α-R1 staining intensity: Nuclear 5α-R2 staining intensity: Protein expression (by IHC ASBP = AS-CaP = CR-CaP ASBP = AS-CaP> CR-CaP ASBP, AS-CaP and in TMAs that are quantified In all 3 tissues, Cytoplasmic 5α-R1 staining Cytoplasmic 5α-R2 staining CR-CaP (RP or by visual scoring and digital expression of 5α-R1 is intensity: intensity: Titus et al. [19] channeling TURP) image analysis and by WB) consistenty more than ASBP = AS-CaP> CR-CaP ASBP = AS-CaP> CR-CaP 5α-R1-2 tissue that was FFPE and enzyme activity in 5α-R2 (in nucleus) Not detected in stroma in any of Notdetectedinstromainany of or snap frozen in homogenized pulverized but similar in the 3 tissues the 3 tissues liquid nitrogen prostate tissue using cytoplasm In WB, 5α-R1 > 5α-R2 in all 3 In WB, 5α-R2 was undetectable 3 ◦ H-ASD at 37 C tissues in CR-CaP 5α-R1 enzyme activity > 5α-R2 5α-R2 activity > 5α-R1 in ASBP in CR-CaP (3 folds) and AS-CaP 5α-R3 was mainly cytoplasmic Benign tissue immunostaining: Kidney (PT,DT ++), liver (++), 5α-R3 protein Protein expression (IHC) exocrine pancreas (++), skeletal muscle (+), skin (strata basale and expression ↑ in the using validated monoclonal spinosum ++), gastric epithelial cells (+), myometrium (++) cytoplasm of mouse antibody against Malignant tissue: colon adenoCA (++), esophageal adenoCA (++), Godoy et al. [20] Benign and malignant malignant cells versus peptide from N-terminus RCC (++), HCC (++), ovarian mucinous CA (++), stomach 5α-R3 human tissue TMAs benign cells in of 5α-R3 protein and adenoCA (++), testis seminoma and YS tumor (++), thyroid prostate, testis, quantified by visual scoring papillary CA (++), endometrioid CA (++), breast CA (+) thyroid, lung and and digital image analysis ASBP: basal epithelial cells, HGPIN: benign basal and neoplastic breast CA epithelial cells, AS-CaP and CR-CaP: in neoplastic cells (5α-R3 immunostaining intensity: AS-CaP = CR-CaP > ASBP) 5α-R3 expression at the mRNA level is higher than 5α-R1and 2in 5α-R1-3 mRNA expression frontal cortex, heart, colon, stomach, liver, pancreas, lung, BPH, (RT-PCR) and prostate, testis, mammary gland, brain, cervix, ovary, dermis, 20 benign human 5α-R3 is ubiquitous Yamana et al. [21] measurement of 5α-R 1–3 epidermis, total skin, small intestine, spleen, and kidney tissues, CaP, and Dutasteride is a triple 5α-R3 enzyme activity using 5α-R2 mRNA was the most abundant in BPH and muscle breast cancer cell lines 5α-RI in vitro C-labelled ASD and T in Finasteride inhibits 5α-R2 and 5α-R3 with similar potency (IC = intact cells in culture 14.3 nM, 17.4 nM, resp.). Dutasteride is a more potent inhibitor of 5α-R3 than finasteride (IC = 0.33 nM) ELISA: enzyme-linked immunosorbant assay; IHC: immunohistochemistry; WB: western blot; NB: northern blot; FFPE: formalin fixed paraffin embedded; RS: root sheath; RP: radical prostatectomy; sqRT- PCR: semiquantitative reverse transcriptase-polymerase chain reaction; PE: paraffin-embedded; RPMI: Roswell Park Memorial Institute; FBS: fetal bovine serum; PT: proximal tubules; DT: distal tubules; CD: collecting ducts; TURP: transurethral resection of prostate; RC: radical cystectomy; HGPIN: high-grade prostate intraepithelial neoplasia; ISH: in situ hybridization; RCC: renal cell carcinoma; HCC: hepatocellular carcinoma; adenoCA: adenocarcinoma; CA: carcinoma; YS: yolk sac; TMA: tissue microarray. 12 Advances in Urology 10. Clinical Role of 5α-R by the administration of DHT, but is reversed by 3α-an- drostanediol treatment. The biochemical features of this syn- Alterations in the conversion of T into DHT by the enzyme drome include the following: 5α-R are associated with a number of human disorders: (a) high normal to elevated levels of plasma T, 10.1. 5α-R2 Deficiency (Pseudovaginal Perineoscrotal Hypo- (b) low normal to decreased levels of plasma DHT, spadias) [3, 62]. Studies in rabbit, rat, and human fetuses (c) increased T to DHT ratio at baseline and following have shown that 5α-R activity is present in the urogenital hCG stimulation, sinus and external genital anlage prior to prostate and (d) normal metabolic clearance of T and DHT, external genital differentiation. However, 5α-R activity is not present in the Wolffian duct, at the time of epididymal, (e) decreased levels of urinary 5α-reduced metabolites of vas deferens, and seminal vesicle differentiation. Thus, T C19 and C21 steroids, with increased 5β/5α urinary and DHT have selective roles in male sexual differentiation metabolite ratios, during embryogenesis. T mediates Wolffian ductal differenti- (f) decreased plasma and urinary 3α-androstanediol ation, while DHT mediates male external genital and prostate glucuronide, a major metabolite of DHT, differentiation. (g) increased plasma levels of LH and/or FSH. 5α-R2 deficiency is caused by decreased synthesis of DHT due to mutations in the 5α-reductase 2 gene. At Phenotype, development and reproductive function in least 50 mutations have been reported and is autosomal- human females with 5α-R2 deficiency are unaffected. recessive in the majority of patients. 5α-R2 deficiency results in a 46,XY disorder of sexual development (formerly male 10.2. LUTS Attributed to BPE. BPE results in a significant pseudohermaphroditism). Affected males are born with morbidity due to urethral obstruction and secondary detru- normal male internal reproductive structures (epididymis, sor dysfunction. Histological evidence of BPH is found in seminal vesicles, and vasa deferentia); however, their external 50% of males by the age of 50 and 90% of males by genitalia resemble those of females, that is, ambiguous the age of 80 [63]. The development of BPH depends genitalia. These individuals have a small penis that resembles on androgens, and BPH does not occur in men castrated an enlarged clitoris, labioscrotal fusion, and a urogenital prior to puberty [64]. 5α-R isozymes play significant roles sinus in which there are two separate urethral and vaginal in BPH development since DHT is the major androgen openings. The vagina is short and blind ending. The testes in the prostate. Patients with decreased DHT production are either in the labia, or inguinal canals or intra-abdominal. due to 5α-R2 deficiency have a small prostate and BPH The vasa terminate at the blind-ending vaginal pouch. The has not been reported [4]. In castrated dogs, treatment prostate is hypoplastic, nonpalpable on rectal examination with either DHT or T results increased intraprostatic DHT and is found to be rudimentary on transrectal ultrasound and BPH [65]. However, coadministration of T with a and MRI. Prostatic volumes are approximately (1/10)th 5α-R inhibitor decreased DHT formation and prevented of age-matched normal controls. Prostate biopsy reveals BPH [66]. Finasteride and dutasteride have been shown fibrous connective tissue, smooth muscle, and no identifiable to decrease circulating and intraprostatic DHT by 60– epithelial tissue, which suggests atrophic epithelium or lack 90%, and 90–98%, respectively [48–52]. Finasteride and of epithelial differentiation. Plasma PSA is low or unde- dutasteride result in a decrease in prostate size by 20–25% tectable in these patients. Administration of DHT results through prostatic epithelial cell apoptosis and a significant in enlargement of the prostate. Neither BPH nor CaP has improvement in LUTS. Furthermore, they change the natural been reported in these patients. At puberty, these individuals history of the disease by decreasing the risk of acute urinary undergo partial virilization of the external genitalia, although retention by 57–79% and decreasing BPH-related surgery by their secondary sexual hair remains sparse and they develop 48–69% [67, 68]. Although both isozymes are overexpressed less male pattern baldness and acne despite normal sebum in prostate tissues from patients with BPH [15], inhibition production. They undergo an increase in muscle mass, of 5α-R2 activity is the major contributor in the treatment phallic growth, development of male body habitus, and of BPH as the additional inhibition of 5α-R1 activity by deepening of the voice. Their libido is normal and they dutasteride does not appear to be of any further benefit in are capable of erections. Sperm production and fertility BPH treatment [69]. have been reported but depend on testicular location. The mechanism of partial virilization at puberty is through either the androgen receptor binding very high levels of serum T, 10.3. Primary Prevention of CaP [67, 68]. Both finasteride albeit at lower affinity, or the increased expression of skin and dutasteride have been tested in large, prospective, 5α-R1 at puberty, which results in peripheral synthesis of randomized, placebo-controlled, double-blind studies as DHT from T or via the action of 5α-R3 through unknown primary preventive therapies for CaP. The Prostate Cancer mechanisms. 5α-R1 gene is normal in these subjects. No Prevention Trial (PCPT) randomized nearly 19,000 men at genetic deficiencies of the type 1 enzyme have yet been low risk for CaP into a treatment group, given finasteride reported. Inactivation of the 5α-R1geneinmiceadversely at 5 mg/d and a control group, given placebo, who were affected reproduction in females. In addition, mice deficient followed up for 7 years. At the end of the study, participants in 5α-R1 manifest a parturition defect that is not reversed were offered a prostate biopsy. For-cause biopsies were done Advances in Urology 13 Table 4: Comparison between PCPT and REDUCE. PCPT REDUCE Sponsor South West Oncology Group GalxoSmithKline Duration 7 years 4 years Risk of CaP in participants lower higher 18,882 randomized No. of participants 8122 randomized 9060 included in final analysis Age ≥55 years 50–75 years Entry serum PSA ≤3.0 ng/mL 2.5–10 ng/mL Yes (6–12 cores) within 6 months prior to Baseline biopsies No enrollment Study-mandated biopsies Year 7 Years 2 and 4 Study-mandated biopsy cores ≥6 (6 cores in nearly 80%) 10 (83% had at least 1 biopsy) Overall relative risk reduction in CaP 25% 23% versus placebo ↑26% (6.4% in finasteride versus 5.1% in Incidence of Gleason sum ≥7CaP Same (6.7% in dutasteride versus 6.8%: in placebo) placebo), P< 0.05 Same over 4 years (0.9% in dutasteride versus 0.6% ↑91% (2.1% in finasteride versus 1.1% in in placebo); however, in years 3-4, there were 12 GS Incidence of Gleason sum ≥8CaP placebo), P< 0.05 ≥8 CaP in dutasteride group (0.5%) versus 1 in placebo group (<0.1%), P< 0.05 for abnormal DRE and/or PSA > 4.0 ng/mL. PCPT showed American Urological Association and the American Cancer that finasteride was effective at reducing the overall risk of Society issued a “cautious” joint statement that accepted biopsy detectable CaP by nearly 25% and this was due mainly these drugs as an option to prevent CaP provided that to reduction in the risk of low-grade disease (Gleason sum they are used mainly after a thorough discussion of risks <7). The reduction in the risk of CaP was seen across all and benefits. In January 2011, the FDA’s Oncologic Drug subgroups, such as age, race, family history, and baseline Advisory Committee voted against recommending either PSA. Finasteride users also had improved BPH outcomes. dutasteride or finasteride for the specific indication of CaP The benefits of finasteride treatment occurred at the expense risk reduction because of the potential increased risk of high- of a higher rate of diagnosis of moderate- and high-grade grade disease. Table 4 provides a comparison between PCPT CaP (Gleason score ≥7) and more sexual adverse effects. and REDUCE. The Reduction by Dutasteride of Prostate Cancer Events trial (REDUCE) studied the effect of dutasteride versus placebo 10.4. Treatment of CaP in a large group of men at higher risk of CaP than in PCPT who had at least one negative prostate biopsy at (a) Biochemical Failure after Local Therapy with Curative baseline. The study lasted 4 years and participants received Intent [70–73]. Finasteride and dutasteride have been tried, mandatory prostate biopsy at 2 and 4 years. Dutasteride singly and in combination, in patients with biochemical fail- decreased the risk of biopsy detectable CaP by nearly 24% ure after radical prostatectomy or radiotherapy. The most and this reduction in risk was evident across all subgroups common combination was a 5α-RI and a nonsteroidal an- tested. The frequency of diagnosis of moderate- and high- tiandrogen. Finasteride and dutasteride monotherapy de- grade CaP was unchanged over the entire length of the creased serum PSA to variable extent. PSA decrease was more study and beneficial effects were observed on BPH outcomes. frequent and of greater magnitude in patients treated with However, 12 Gleason score 8–10 cancers were detected in an antiandrogen and 5α-RIversus5α-RI alone. However, the dutasteride group at years 3-4 versus only one in the none of these trials studied the impact on disease-specific placebo group and dutasteride treatment was associated with or overall survival and none compared 5α-RI mono- or more sexual adverse effects. The benefit of finasteride or combination therapy against 1st line androgen deprivation dutasteride in reducing the risk of low-grade CaP is clear. treatment in a randomized fashion. Low-grade CaP is unlikely to be lethal and patients may reduce their risk of overtreatment. However, these drugs may induce high-grade CaP, a concern that has prevented (b) CR-CaP. CR-CaP was thought for many years to be FDA approval of finasteride and dutasteride use for CaP androgen-independent or hormone-refractory but CR-CaP prevention. Several secondary analyses of these two trials remains AR-dependent and probably AR-ligand dependent have concluded that these drugs actually reduce the risk in almost all cases [74]. Despite castrate serum levels of of moderate- and high-grade disease but these analyses are T(<50 ng/dL), CR-CaP tissue levels of T and DHT were hypothesis-generating and not definitive. In March 2009, the similar and 80–90% lower compared to their levels in benign 14 Advances in Urology prostatic tissue, respectively [75]. CR-CaP tissue synthesizes and adrenal tumors, congenital adrenal hyperplasia, and testicular androgens (T and DHT) in an intracrine fashion exogenous androgenic hormone administration. Regardless from several substrates such as cholesterol, progesterone, of the cause, overproduction of either T or T precursors adrenal androgens, and androstandione [76–79]. Other phe- leads to exaggerated T action in target tissues such as skin. In nomena intrinsically acquired by CR-CaP tissue in response skin, T is converted to DHT by the enzyme 5α-R, which acts to castration include the continuous expression of AR directly on hair follicles and the sebaceous glands. The most [80], upregulation of the synthesis of enzymes necessary frequent dermatologic manifestations of androgen excess are for steroidogenesis [76], AR hypersensitivity (up to 10,000 hirsutism, acne, and androgenic alopecia [91]. times) to low levels of ligands by alteration of its co-activator Androgen surge can miniaturize hair follicles resulting profile from SRC1 to TIF2 and through its phosphorylation in male androgenic alopecia at puberty and in the scalp by SRC and Ack1 tyrosine kinases [81–83] and AR functional of genetically predisposed individuals. In women, androgen mutations, which broaden ligand specificity in 5–30% of excess plays a role in scalp hair loss; however, this process cases [84]. is different than in men and is referred to as female pattern New second-line hormonal therapeutic agents that have hair loss. Hirsutism is a disorder of excessive growth of shown better performance in CR-CaP compared to the terminal hair in women, in a male-like distribution, which old generation of second-line hormonal therapies are abi- is stimulated by androgen excess [92]. In acne, the pubertal raterone acetate and MDV3100, among others [77, 85]. androgen surge increases the stimulation of sebaceous glands Abiraterone acetate is a potent, selective, and irreversible resulting in increased sebum production and acne formation inhibitor of CYP17A1 enzyme, which is an important in susceptible individuals [93]. enzyme in the intracrine synthesis of testicular androgens. In all androgen-stimulated skin disorders, the activity MDV3100 inhibits ligand binding to the AR and nuclear of 5α-R enzyme system is increased such as in the hair translocation of AR-ligand complex. The clinical response follicles of hirsute women [93], in balding scalps [94], and in to these new drugs is indirect proof that CR-CaP remains acne-prone skin [95]. Inhibition of the 5α-R enzyme system androgen stimulated. 5α-R isozymes are important in the appears to be a target for treatment of androgen-stimulated growth of CR-CaP tissue since they are upregulated in CR- skin disorders, since 5α-R inhibitors may result in fewer side- CaP and may contribute to intracrine synthesis of testicular effects by not blocking the action of T, unlike classical anti- androgens. These enzymes convert progesterone, ASD, and T androgens such as cyproterone acetate or spironolactone. into pregnanldione, androstandione, and DHT, respectively Finasteride and dutasteride reduce scalp DHT levels by [74, 79]. Pregnanldione is further converted via several steps 64% and 51%, respectively [96, 97]. In men with androgenic into androstandiol which is oxidized by 17β-hydroxysteroid alopecia, finasteride and dutasteride significantly increased dehydrogenase 2 and 10 (17β-HSD2 and 10) to DHT (the hair count after a minimum of 6-month treatment [98, 99]. backdoor pathway to DHT synthesis). Androstandione is While finasteride 1 mg daily was superior to 5% topical converted by 17βHSD3 into DHT. minoxidil in inducing hair growth [100], finasteride 5 mg Clinical trials of finasteride [70] and dutasteride [71]as daily was inferior to dutasteride 2.5 mg daily in a phase monotherapy in patients with advanced CaP showed no II study as treatment for male androgenic alopecia [97]. improvement of clinical end points. The presence of 5α-R3 Finasteride and topical minoxidil (but not dutasteride) are in CR-CaP is a potential explanation, until such time that an FDA-approved for male androgenic alopecia. In women inhibitor has been proven effective clinically. Combination with androgenic alopecia, neither finasteride nor dutasteride therapy of 5α-RI with antiandrogen or ketoconazole and is FDA-approved treatment options due to teratogenicity. hydrocortisone was tried in CR-CaP as second or third line Finasteride has been tested in postmenopausal women at the hormonal therapies [86–89]. PSA decreases of variable mag- 1 mg dose without success. However, finasteride was shown nitudes and durations were achieved in more than half to be effective in 4 women with elevated serum T levels [101]. the patients. However, none of the combination trials were Whether finasteride is only effective in women with hair loss designed to test the effect on disease-specific and overall sur- and hyperandrogenism or that higher doses are needed in vival. In a phase II, single arm study of 57 patients with CR- women remains to be tested. A single case report showed CaP, dutasteride added to ketoconazole, and hydrocortisone improvement with dutasteride in a woman who had failed reduced PSA ≥ 50% of baseline value in 56% of patients, to respond to finasteride [102]. responses that lasted for a median of 20 months. Median time 5α-RI also is acceptable therapy for hirsutism. Finasteride to disease progression was 14.5 months that was better than 5 mg/day was superior to placebo and similar to spirono- all prior studies of ketoconazole and hydrocortisone in CR- lactone and flutamide in reducing the severity of hirsutism CaP [89]. [103]; however, in a different study, finasteride was inferior to flutamide as a treatment for hirsutism [104]. Dutasteride 10.5. Androgen-Stimulated Skin Disorders (Acne, Androgenic has not been tested as a treatment for hirsutism. Alopecia and Hirsutism). Hyperandrogenism, or excessive Theroleof5α-RI is unclear for treatment of acne. MK- 386, a selective 5α-R1 inhibitor, decreased sebum DHT levels androgen production, is primarily a disorder of females. Polycystic ovary syndrome (PCOS) is the most common in a dose-dependent fashion [105]. MK-386 was examined cause of female hyperandrogenism with a prevalence of 6% as a treatment for acne in a placebo-controlled trial and to 10% in women of childbearing age [90]. Other causes wasfound to be similartoplacebo andinferiortosys- of hyperandrogenism include androgen-secreting ovarian temic minocycline therapy. Furthermore, MK-386 did not Advances in Urology 15 enhance the therapeutic benefit of minocycline when used in [10] W. Eicheler, M. Dreher, R. Hoffmann, R. Happle, and G. Aumuller, “Immunohistochemical evidence for differential combination [106]. 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