British Journal of Cancer

Danesh, J

doi: 10.1038/sj.bjc.6690444pmid: 10362097

Eaton, N E; Reeves, G K; Appleby, P N; Key, T J

doi: 10.1038/sj.bjc.6690445pmid: 10362098

This paper presents a quantitative review of the data from eight prospective epidemiological studies, comparing mean serum concentrations of sex hormones in men who subsequently developed prostate cancer with those in men who remained cancer free. The hormones reviewed have been postulated to be involved in the aetiology of prostate cancer: androgens and their metabolites testosterone (T), non-SHBG-bound testosterone (non-SHBG-bound T), di-hydrotestosterone (DHT), androstanediol glucuronide (A-diol-g), androstenedione (A-dione), dehydroepiandrosterone sulphate (DHEAS), sex hormone binding globulin (SHBG), the oestrogens, oestrone and oestradiol, luteinizing hormone (LH) and prolactin. The ratio of the mean hormone concentration in prostate cancer cases to that of controls (and its 95% confidence interval (CI)) was calculated for each study, and the results summarized by calculating the weighted average of the log ratios. No differences in the average concentrations of the hormones were found between prostate cancer cases and controls, with the possible exception of A-diol-g which exhibited a 5% higher mean serum concentration among cases relative to controls (ratio 1.05, 95% CI 1.00–1.11), based on 644 cases and 1048 controls. These data suggest that there are no large differences in circulating hormones between men who subsequently go on to develop prostate cancer and those who remain free of the disease. Further research is needed to substantiate the small difference found in A-diol-g concentrations between prostate cancer cases and controls.

Marschall, Z von; Riecken, E-O; Rosewicz, S

doi: 10.1038/sj.bjc.6690446pmid: 10362099

We have investigated the effects of retinoic acid (RA) on matrix metalloprotease-1 (MMP-1) gene expression in the human pancreatic tumour cell line Dan-G. 13-cis RA results in a time- and dose-dependent increase of MMP-1 protein concentration. These stimulatory effects were paralleled by a time- and dose-dependent increase of MMP-1 mRNA steady-state concentrations. Nuclear run-on analysis revealed that the increase of MMP-1 mRNA was partially due to an increase of MMP-1 gene transcription. In addition, 13-cis RA treatment results in an increase of MMP-1 mRNA stability. These data demonstrate that RA stimulates MMP-1 gene expression in human pancreatic carcinoma cells by transcriptional and post-transcriptional mechanisms.

Herring, C J; Deans, B; Elder, R H; Rafferty, J A; MacKinnon, J; Barzilay, G; Hickson, I D; Hendry, J H; Margison, G P

doi: 10.1038/sj.bjc.6690447pmid: 10362100

Apurinic/apyrimidinic (AP) sites in DNA are potentially lethal and mutagenic. They can arise spontaneously or following DNA damage from reactive oxygen species or alkylating agents, and they constitute a significant product of DNA damage following cellular exposure to ionizing radiation. The major AP endonuclease responsible for initiating the repair of these and other DNA lesions in human cells is HAP1, which also possesses a redox function. We have determined the cellular levels of this enzyme in 11 human tumour and fibroblast cell lines in relation to clonogenic survival following ionizing radiation. Cellular HAP1 levels and surviving fraction at 2 Gy (SF2) varied five- and tenfold respectively. However, no correlation was found between these two parameters following exposure to γ-irradiation at low (1.1 cGy per min) or high (108 cGy per min) dose rates. To examine this further, wild-type and mutant versions of HAP1 were overexpressed, using an inducible HAP1 cDNA expression vector system, in the rat C6 glioma cell line which has low endogenous AP endonuclease activity. Induction of wild-type HAP1 expression caused a > fivefold increase in the capacity of cellular extracts to cleave an oligonucleotide substrate containing a single abasic site, but increased expression did not confer increased resistance to γ-irradiation at high- or low-dose rates, or to the methylating agent methyl methanesulphonate (MMS). Expression in C6 cell lines of mutant forms of HAP1 deleted for either the redox activator or DNA repair functions displayed no apparent titrational or dominant negative effects. These studies suggest that the levels of endogenous AP endonuclease activities in the various cell lines examined are not limiting for efficient repair in cells following exposure to ionizing radiation or MMS. This contrasts with the correlation we have found between HAP1 levels and radiosensitivity in cervix carcinomas (Herring et al (1998) Br J Cancer : 1128–1133), indicating that HAP1 levels in this case assume a critical survival role and hence that established cell lines might not be a suitable model for such studies.

Runnels, J M; Chen, N; Ortel, B; Kato, D; Hasan, T

doi: 10.1038/sj.bjc.6690448pmid: 10362101

Benzoporphyrin derivative monoacid (BPD-MA) photosensitization was examined for its effects on cellular adhesion of a human ovarian cancer cell line, OVCAR 3, to extracellular matrix (ECM) components. Mild BPD-MA photosensitization (~ 85% cell survival) of OVCAR 3 transiently decreased adhesion to collagen IV, fibronectin, laminin and vitronectin to a greater extent than could be attributed to cell death. The loss in adhesiveness was accompanied by a loss of β1 integrin-containing focal adhesion plaques (FAPs), although β1 subunits were still recognized by monoclonal antibody directed against human β1 subunits. In vivo BPD-MA photosensitization decreased OVCAR 3 adhesiveness as well. Photosensitized adhesion was reduced in the presence of sodium azide and enhanced in deuterium oxide, suggesting mediation by singlet oxygen. Co-localization studies of BPD-MA and Rhodamine 123 showed that the photosensitizer was largely mitochondrial, but also exhibited extramitochondrial, intracellullar, diffuse cytosolic fluorescence. Taken together, these data show that intracellular damage mediated by BPD-PDT remote from the FAP site can affect cellular–ECM interactions and result in loss of FAP formation. This may have an impact on long-term effects of photodynamic therapy. The topic merits further investigation.

Takizawa, K; Kamijo, R; Ito, D; Hatori, M; Sumitani, K; Nagumo, M

doi: 10.1038/sj.bjc.6690449pmid: 10362102

Cisplatin (CDDP) and 5-fluorouracil (5-FU) are common anti-tumour agents, and the anti-tumour effect of CDDP and 5-FU are synergistically enhanced by combined treatment. To clarify the mechanisms of this synergism, we examined the effect of CDDP and 5-FU on the expression of cell adhesion molecules involved in recognition of cancer cells by T lymphocytes. When NA cells, a squamous cell carcinoma cell line, were exposed to CDDP and 5-FU for 18 h, the expression of intercellular adhesion molecule-1 (ICAM-1) was synergistically induced, whereas CDDP or 5-FU alone did not induce the expression of ICAM-1, as determined by flow cytometry. Expression of ICAM-2 and ICAM-3, which are recognized by the same counter receptor on T-cells, were not up-regulated by CDDP and 5-FU. RT-PCR analysis showed that the induction of ICAM-1 on NA cells might be due to transcriptional induction of ICAM-1 mRNA. Treatment with genistein, a protein tyrosine kinase (PTK) inhibitor, inhibited the induction of ICAM-1 on NA cells by CDDP and 5-FU, whereas staurosporin, a protein kinase C inhibitor, did not. Although CDDP and 5-FU induced binding at the nuclear factor kappa B (NF-κB) site in the ICAM-1 promoter, pretreatment with genistein did not prevent CDDP and 5-FU-induced binding at the NF-κB site. Moreover, a NF-κB nuclear translocation inhibitor did not inhibit the induction of ICAM-1 expression by treatment with CDDP and 5-FU. The synergistic effect of CDDP and 5-FU was not specific to NA cells, since ICAM-1 was synergistically induced by CDDP and 5-FU on HSC-4 cells, a squamous cell carcinoma cell line. These findings indicate that treatment with CDDP and 5-FU induces ICAM-1 expression by a NF-κB independent regulatory mechanism involving PTK.

Emerich, D F; Snodgrass, P; Dean, R; Agostino, M; Hasler, B; Pink, M; Xiong, H; Kim, B S; Bartus, R T

doi: 10.1038/sj.bjc.6690450pmid: 10362103

CereportTM (RMP-7) is a selective bradykinin B2 receptor agonist which increases the permeability of the ‘blood–brain tumour barrier’ (BBTB) to increase delivery of chemotherapeutic agents to brain tumours. A series of experiments was performed in an RG2 rodent model of glioma to evaluate and refine intravenous (i.v.) parameters to optimize Cereport’s clinical utility. The first experiment demonstrated that while carboplatin levels were increased by twofold when given as a bolus during the Cereport infusion, no increase in carboplatin levels were seen when Cereport and carboplatin were simultaneously co-infused for 15 min. A subsequent experiment established that a major factor responsible for the lack of an effect with the co-infusion paradigm was tachyphylaxis to Cereport during the 15 min infusion, for a progressively diminished response to Cereport occurred over that time frame, as plasma levels of carboplatin were rising. A final experiment adjusted the timing of the Cereport and carboplatin infusions so that higher plasma carboplatin levels were achieved prior to initiating the Cereport infusion. Significant uptake effects were achieved when the carboplatin infusion preceded the Cereport infusion by 10 min (i.e. 5 min overlap in the delivery of the two agents). Collectively, these data provide the first systematic evaluation of dosing parameters involving receptor-mediated changes in BBTB permeability and provide new information regarding the pharmacodynamics and potential clinical use of Cereport.

Erba, E; Bergamaschi, D; Ronzoni, S; Faretta, M; Taverna, S; Bonfanti, M; Catapano, C V; Faircloth, G; Jimeno, J; D’Incalci, M

doi: 10.1038/sj.bjc.6690451pmid: 10362104

Thiocoraline, a new anticancer agent derived from the marine actinomycete Micromonospora marina, was found to induce profound perturbations of the cell cycle. On both LoVo and SW620 human colon cancer cell lines, thiocoraline caused an arrest in G1 phase of the cell cycle and a decrease in the rate of S phase progression towards G2/M phases, as assessed by using bromodeoxyuridine/DNA biparametric flow cytometric analysis. Thiocoraline does not inhibit DNA-topoisomerase II enzymes in vitro, nor does it induce DNA breakage in cells exposed to effective drug concentrations. The cell cycle effects observed after exposure to thiocoraline appear related to the inhibition of DNA replication. By using a primer extension assay it was found that thiocoraline inhibited DNA elongation by DNA polymerase α at concentrations that inhibited cell cycle progression and clonogenicity. These studies indicate that the new anticancer drug thiocoraline probably acts by inhibiting DNA polymerase α activity.

Moorsel, C J A van; Pinedo, H M; Veerman, G; Bergman, A M; Kuiper, C M; Vermorken, J B; van der Vijgh, W J F; Peters, G J

doi: 10.1038/sj.bjc.6690452pmid: 10362105

2′,2′-Difluorodeoxycytidine (gemcitabine, dFdC) and cis-diammine-dichloroplatinum (cisplatin, CDDP) are active agents against ovarian cancer and non-small-cell lung cancer (NSCLC). CDDP acts by formation of platinum (Pt)–DNA adducts; dFdC by dFdCTP incorporation into DNA, subsequently leading to inhibition of exonuclease and DNA repair. Previously, synergism between both compounds was found in several human and murine cancer cell lines when cells were treated with these drugs in a constant ratio. In the present study we used different combinations of both drugs (one drug at its IC25 and the other in a concentration range) in the human ovarian cancer cell line A2780, its CDDP-resistant variant ADDP, its dFdC-resistant variant AG6000 and two NSCLC cell lines, H322 (human) and Lewis lung (LL) (murine). Cells were exposed for 4, 24 and 72 h with a total culture time of 96 h, and possible synergism was evaluated by median drug effect analysis by calculating a combination index (CI; CI < 1 indicates synergism). With CDDP at its IC25, the average CIs calculated at the IC50, IC75 IC90 and IC95 after 4, 24 and 72 h of exposure were < 1 for all cell lines, indicating synergism, except for the CI after 4 h exposure in the LL cell line which showed an additive effect. With dFdC at its IC25, the CIs for the combination with CDDP after 24 h were < 1 in all cell lines, except for the Cls after 4 h exposure in the LL and H322 cell lines which showed an additive effect. At 72 h exposure all Cls were < 1. CDDP did not significantly affect dFdCTP accumulation in all cell lines. CDDP increased dFdC incorporation into both DNA and RNA of the A2780 cell lines 33- and 79-fold (P < 0.01) respectively, and tended to increase the dFdC incorporation into RNA in all cell lines. In the AG6000 and LL cell lines, CDDP and dFdC induced > 25% more DNA strand breaks (DSB) than each drug alone; however, in the other cell lines no effect, or even a decrease in DSB, was observed. dFdC increased the cellular Pt accumulation after 24 h incubation only in the ADDP cell line. However, dFdC did enhance the Pt–DNA adduct formation in the A2780, AG6000, ADDP and LL cell lines (1.6-, 1.4-, 2.9- and 1.6-fold respectively). This increase in Pt–DNA adduct formation seems to be related to the incorporation of dFdC into DNA (r = 0.91). No increase in DNA platination was found in the H322 cell line. dFdC only increased Pt–DNA adduct retention in the A2780 and LL cell lines, but decreased the Pt–DNA adduct retention in the AG6000 cell line. In conclusion, the synergism between dFdC and CDDP appears to be mainly due to an increase in Pt–DNA adduct formation possibly related to changes in DNA due to dFdC incorporation into DNA.

Marchini, S; Cirò, M; Gallinari, F; Geroni, C; Cozzi, P; D’Incalci, M; Broggini, M

doi: 10.1038/sj.bjc.6690453pmid: 10362106

PNU 151807 is a new synthetic α-bromoacryloyl derivative of distamycin A. In the present study we investigated the DNA interaction and the mechanism of action of this compound in parallel with the distamycin alkylating derivative, tallimustine. PNU 151807 possesses a good cytotoxic activity in in vitro growing cancer cells, even superior to that found for tallimustine. By footprinting experiments we found that PNU 151807 and tallimustine interact non-covalently with the same AT-rich DNA regions. However, differently from tallimustine, PNU 151807 failed to produce any DNA alkylation as assessed by Taq stop assay and N3 or N7-adenine alkylation assay in different DNA sequences. PNU 151807, like tallimustine, is able to induce an activation of p53, and consequently of p21 and BAX in a human ovarian cancer cell line (A2780) expressing wild-type p53. However, disruption of p53 function by HPV16-E6 does not significantly modify the cytotoxic activity of the compound. Flow cytometric analysis of cells treated with equitoxic concentrations of PNU 151807 and tallimustine showed a similar induction of accumulation of cells in the G2 phase of the cell cycle but with a different time course. When tested against recombinant proteins, only the compound PNU 151807 (and not tallimustine or distamycin A) is able to abolish the in vitro kinase activity of CDK2–cyclin A, CDK2–cyclin E and cdc2–cyclin B complexes. The results obtained showed that PNU 151807 seems to have a mechanism of action completely different from that of its parent compound tallimustine, possibly involving the inhibition of cyclin-dependent kinases activity, and clearly indicate PNU 151807 as a new non-covalent minor groove binder with cytotoxic activity against cancer cells.