Genes Chromosomes and Cancer

doi: 10.1002/gcc.2870120101pmid: N/A

doi: 10.1002/gcc.2870120116pmid: N/A

Newsham, Irene; Kindler‐Röhrborn, Andrea; Daub, Douglas; Cavenee, Webster

doi: 10.1002/gcc.2870120102pmid: 7534105

Beckwith‐Wiedemann syndrome (BWS) is a congenital overgrowth disorder with a varying spectrum of clinical manifestations including macroglossia, omphalocele, hemihypertrophy, and a predisposition to a subset of embryonal tumors, most frequently Wilms' tumor (WT). A variety of cytogenetic, genetic linkage, and molecular mapping data implicate a gene or genes on chromosome band 11p15.5 in BWS and its related tumors. However, some families with BWS do not show linkage to 11p15, and other alterations have been found in Wilms' tumors as well. One such alteration is loss of heterozygosity (LOH) for chromosome arm 16q. Here we have analyzed a balanced t(11;16)(p15;q13) chromosomal translocation associated with the BWS phenotype and mapped the breakpoint positions for both chromosomes 11 and 16 by using somatic cell hybrids and polymorphic markers. The chromosome 11 breakpoint was found to lie distal to the D11S12 locus, but proximal to TH on 11p15.5, a region shown previously to contain other BWS‐related chromosomal events. The chromosome 16 breakpoint was distal to D16S290 in 16q13, but proximal to loci D16S265, D16S267, and D16S164 in band 16q21. This area encompasses the region of LOH occurring through mitotic recombination in sporadic WT. This raises interesting possibilities for the genetic and epigenetic involvement of both chromosomal regions (11p15 and 16q13) in the pathogenesis of BWS and Wilms' tumor.

van Echten, Jannie; de Jong, Bauke; Sinke, Richard J.; Weghuis, Daniël Olde; Sleijfer, Dirk Th.; Wolter Oosterhuis, J.

doi: 10.1002/gcc.2870120103pmid: 7534118

Two malignant extragonadal germ cell tumors are reported, histologically classified as immature teratomas, having pseudodiploid karyotypes with complex structural rearrangements but lacking isochromosome 12p or other rearrangements involving 12p. The absence of 12p material in structural rearrangements was confirmed by chromosome painting. In the two tumors the following common chromosomal breakpoints were found: 6p21, 6p22, 6q23, and 11q13. Exactly the same chromosomal regions, 6p22::6q23 and 6p21::11q13, were involved in fusions. The two tumors belong to a new entity of extragonadal immature teratomas of adults which may be located in the retroperitoneum and posterior mediastinum and are prone to blood borne metastasis.

Loupart, Marie‐Louise; Adams, Susan; Brammar, William; Armour, John; Walker, Rosemary; Varley, Jennifer

doi: 10.1002/gcc.2870120104pmid: 7534106

In order to characterise the role of chromosome I more fully in breast cancer, polymorphic markers mapping along the length of the whole chromosome were used to assess a panel of 71 tumour‐lymphocyte pairs for allelic imbalance. Complex patterns of alterations were established that are consistent with cytogenetic data in the literature. Deletion mapping of individuals with loss of heterozygosity identified five independent smallest common regions of deletion, two of which are novel. There are also three discrete regions showing a gain in copy number of one homologue. The two arms of the chromosome may be subject to different events; the short arm primarily undergoes interstitial deletions, whereas the long arm is subject to whole arm events (as both gains and losses) as well as regional deletions.

Hoggard, Nigel; Brintnell, Bill; Varley, Jennifer; Howell, Anthony; Weissenbach, Jean

doi: 10.1002/gcc.2870120105pmid: 7534107

We have determined regions of allelic imbalance in human breast cancer cells using highly polymorphic microsatellite markers, which can be rapidly typed by the polymerase chain reaction (PCR) using very small amounts of DNA. It appears that there are several regions of chromosome I which may be the targets of allelic imbalance, including some regions which have been identified previously by different groups. The detail with which we have mapped these regions of imbalance is, however, much greater than has been previously reported, and we have been able to localise these regions to small intervals of the genome. In addition we have identified previously uncharacterised regions of allelic imbalance on chromosome arm 1p, one of which (at 1p22–31) is lost in a high proportion of malignant lesions. We are currently attempting to analyse this latter region in detail in order to identify and characterise the sequence(s) involved. Study of such regions should help us understand some of the mechanisms underlying the development and progression of breast cancer.

Chaganti, Seeta R.; Louie, Diane C.; Chaganti, R. S. K.; Gaidano, Gianluca; Dalla‐Favera, Riccardo

doi: 10.1002/gcc.2870120106pmid: 7534108

We have previously identified deletions of 9p and 9q in a cytogenetic analysis of a large series of non‐Hodgkin's lymphomas (NHLs), which suggested loss of candidate tumor suppressor genes (TSGs). In order to define these deletions at the molecular level, we performed an LOH analysis of a panel of paired normal and tumor DNAs comprising 13 cases of diffuse lymphoma with a large cell component (DLLC) and 18 cases of Burkitt's lymphoma (BL). The loci tested comprised eight polymorphic probes mapped to 9p (D9S33, D9S25, IFNB, IFNA, IFNW, D9S126, D9S3, and D9S19) and seven polymorphic probes mapped to 9q (D9S29, ASS, AKI, ABL, D9S10, D9S7, and D9S14). In this analysis, among cases informative for all loci in each subset, 5/13 (38%) DLLC and 4/18 (22%) BL showed LOH at 9p loci, whereas 5/13 (38%) DLLC and 3/18 (16%) BL showed LOH at 9q loci. Among the 9p loci partial homozygous or heterozygous losses were observed in 20–50% of informative cases of DLLC at D9S25, IFNB, IFNA, IFNW, D9S126, and D9S3, whereas in BL, losses at these loci ranged from 0% to 11%. Among the 9q loci, heterozygous losses were observed in >20% of informative cases of DLLC at D9S7 (23%) and D9S29 (27%), whereas no losses were seen at these two loci in BL. These data demonstrate a high level of molecular deletion in DLLC, but not in BL, suggesting that loss of one or more TSGs on chromosome 9 plays an important role in DLLC development.

Yoshida, Hitoshi; Naoe, Tomoki; Fukutani, Hisashi; Kiyoi, Hitoshi; Kubo, Kazuaki; Ohno, Ryuzo

doi: 10.1002/gcc.2870120107pmid: 7534109

Molecular analysis of the t(15;17) translocation in 70 patients with acute promyelocytic leukemia (APL) confirmed that the breakpoints of chromosome 15 were located in two regions of the promyelocytic leukemia (PML) gene, mainly introns 3 and 6, whereas the breakpoints of chromosome 17 were consistently in intron 2 of the retinoic acid receptor alpha (RARA) gene. To study the reason for the clustering of the breakpoints and the underlying mechanism of the chromosomal translocation, we characterized the joining sequences of der(15) and der(17) by polymerase chain reaction in samples from eight patients with APL. There was no cluster of the breakpoints within the introns, and no consensus sequence‐motif was found around them. One or nine extra nucleotides were inserted into two joining sites. There were identical stretches of one to seven nucleotides between the PML and RARA genes in the majority of the joining sequences. These data provide a potential model of the t(15;17) translocation: random DNA double strand cleavage, modification of DNA ends by enzymes including terminal deoxynucleotidyl transferase, and single strand base‐pairing within identical short stretches. Furthermore, APL develops only when the PML and RARA genes are rearranged within restricted genomic regions and a functional PML‐RARA chimeric product is produced, and this might lead to a clustering of the breakpoints.

Wainwright, Linda J.; Rees, Jonathan L.; Middleton, Peter G.

doi: 10.1002/gcc.2870120108pmid: 7534110

Human telomeres consist of arrays of the sequence TTAGGG up to 15–20 kb in length, which are essential for the maintenance of normal chromosomal stability. It has been suggested that genomic instability observed in tumours may be due to loss of telomere sequences. Somatic cells that are dividing continuously appear to progressively lose telomere sequences, and it would therefore be anticipated that cell type specific differences in mean telomere length may exist within an individual. Previous reports have suggested that mean telomere length may be different in human neoplasia when compared to control. Basal cell carcinomas are epidermal derived tumours and in order therefore to make valid cell type specific comparisons we have measured mean telomere length in 20 basal cell carcinomas as well as in both adjacent epidermis and dermis. Mean telomere length was significantly reduced in epidermis in comparison with dermis, from clinically normal skin immediately adjacent to the tumours (mean difference 2.5 kb). This result is not related to the presence of the tumour as similar results were obtained from skin samples of healthy volunteers. Basal cell carcinomas showed increased mean telomere length in 13/20 samples in comparison with matched epidermis (mean difference 3.1 kb), whereas in 7/20 mean telomere length was reduced (mean difference 2.2 kb). These results showing that mean telomere length varies from cell type to cell type underpin the importance of performing cell type specific controls when assessing changes in tumour telomeres.

Butcher, Mark; Frenck, Robert; Emperor, John; Paderanga, Dorothy; Maybee, David; Olson, Kristin; Shannon, Kevin

doi: 10.1002/gcc.2870120109pmid: 7534111

The observation that juvenile chronic myelogenous leukemia (JCML) and childhood bone marrow monosomy 7 syndrome (Mo 7) are similar in many clinical and epidemiologic respects suggests a shared pathogenic basis and raises the possibility that the bone marrows of patients with JCML might lose chromosome 7 alleles by mechanisms that do not result in detectable cytogenetic deletions. We used a series of polymorphic markers mapped to chromosome 7 to test this hypothesis in 22 children with MPS and MDS, including 19 with JCML. All MPS and MDS samples demonstrated allelic heterozygosity with at least one chromosome 7 marker; 16 were heterozygous with probes from both 7p and 7q. Furthermore, the percentage of patient bone marrow samples heterozygous at each locus tested was similar to the frequency observed in the normal population. Whereas these data demonstrate that submicroscopic loss of large segments of chromosome 7 alleles is uncommon in children with MPS and MDS who do not have Mo 7, they do not exclude small deletions around an uncharacterized tumor‐suppressor locus. Our results suggest that a number of distinct molecular events contribute to leukemogenesis, and we propose a multistep model to explain the similarities and differences between the major subtypes of childhood MPS and MDS.