Putative Tumor Suppressor Gene Loci Research Articles

Tiling resolution array comparative genomic hybridization analysis of a fibrosarcoma of bone

Fibrosarcoma of bone is a rare malignant tumor accounting for less than 5% of all primary malignant bone neoplasms. There is very limited knowledge regarding the molecular genetics of this tumor, and there are no cytogenetic data available. In the present study, a fibrosarcoma deriving from the left iliac bone of a 10-year-old girl was characterized using cytogenetics, fluorescence in situ hybridization (FISH), and whole genome tiling resolution array comparative genomic hybridization (CGH). Cytogenetic and FISH analyses revealed a ring chromosome 6 as the sole acquired aberration, a finding corroborated by array CGH. The ring formation, however, did not result in any gain of genetic material. Nor did the breakpoints in 6p25 and 6q14 seem to affect any known gene loci in such a way that the ring formation could have resulted in the creation of a fusion gene or in the exchange of regulatory sequences. Thus, a reasonable interpretation of the pathogenetic significance of the ring formation would be that it resulted in the loss of one or more putative tumor suppressor gene loci distal to the two breakpoints.

Loss of heterozygosity on the short arm of chromosome 1 in pheochromocytoma and abdominal paraganglioma.

Pheochromocytomas and abdominal paragangliomas are catecholamine-producing tumors that arise from sympathetic paraganglia within and outside the adrenal medulla, respectively. Deletions of the short arm of chromosome 1 have been implicated as important genetic events in their tumorigenesis and suggest a common genetic etiology. The aim of this study was to define further the chromosomal regions on 1p that are involved in the development of these tumor types. We analyzed 46 pheochromocytomas (1 benign, 6 malignant, 9 hereditary) and 7 paragangliomas (3 benign, 4 malignant) from 50 patients for loss of heterozygosity (LOH) on 1p by genotyping 15 microsatellite markers spread over the chromosome arm. Overall, LOH was detected in 33 of 46 pheochromocytomas (72%) and in 6 of 7 (86%) paragangliomas. Three minimal regions of overlapping deletions were identified: one telomeric of D1S1612(1p36.2-pter), one centromeric of D1S429 (1cen-p13), and one in the 18 cM interval defined by D1S2134 andD1S1669 (1p32). The latter region harbors the leukocyte common antigen-related (LAR) gene, which shows altered expression in sporadic rat pheochromocytomas. In conclusion, chromosome 1p may be the site of at least three putative tumor-suppressor gene loci involved in the tumorigenesis of pheochromocytomas and abdominal paragangliomas. Further studies of these regions and of LARas a candidate gene would be valuable.

Sublocalization of putative tumor suppressor gene loci on chromosome arm 14q in neuroblastoma

RFLP and microsatellite analysis with 23 polymorphic markers spanning the entire long arm of chromosome 14 in 108 neuroblastomas showed allelic loss in 19 out of 107 (18%) informative tumors, placing 14q among the most frequently affected chromosomal regions in neuroblastoma. One minimal deletion region could be sublocalized in 17 of 19 cases between markers D14S1 and D14S16, and a second one between markers D14S17 and D14S23 in band 14q32. Furthermore, breakpoints in bands 14q23 and 14q12 were detected. These results suggest the presence of at least two putative tumor suppressor gene loci on chromosome 14. Survival analyses revealed no prognostic impact of allelic loss of 14q in neuroblastoma. Genes Chromosomes Cancer 26:40–46, 1999. © 1999 Wiley-Liss, Inc.

Sublocalization of putative tumor suppressor gene loci on chromosome arm 14q in neuroblastoma

RFLP and microsatellite analysis with 23 polymorphic markers spanning the entire long arm of chromosome 14 in 108 neuroblastomas showed allelic loss in 19 out of 107 (18%) informative tumors, placing 14q among the most frequently affected chromosomal regions in neuroblastoma. One minimal deletion region could be sublocalized in 17 of 19 cases between markers D14S1 and D14S16, and a second one between markers D14S17 and D14S23 in band 14q32. Furthermore, breakpoints in bands 14q23 and 14q12 were detected. These results suggest the presence of at least two putative tumor suppressor gene loci on chromosome 14. Survival analyses revealed no prognostic impact of allelic loss of 14q in neuroblastoma. Genes Chromosomes Cancer 26:40-46, 1999.

Superimposed histologic and genetic mapping of chromosome 9 in progression of human urinary bladder neoplasia: implications for a genetic model of multistep urothelial carcinogenesis and early detection of urinary bladder cancer

The evolution of alterations on chromosome 9, including the putative tumor suppressor genes mapped to the 9p21-22 region (the MTS genes), was studied in relation to the progression of human urinary bladder neoplasia by using whole organ superimposed histologic and genetic mapping in cystectomy specimens and was verified in urinary bladder tumors of various pathogenetic subsets with longterm follow-up. The applicability of chromosome 9 allelic losses as non-invasive markers of urothelial neoplasia was tested on voided urine and/or bladder washings of patients with urinary bladder cancer. Although sequential multiple hits in the MTS locus were documented in the development of intraurothelial precursor lesions, the MTS genes do not seem to represent a major target for p21-23 deletions in bladder cancer. Two additional tumor suppressor genes involved in bladder neoplasia located distally and proximally to the MTS locus within p22-23 and p11-13 regions respectively were identified. Several distinct putative tumor suppressor gene loci within the q12-13, q21-22, and q34 regions were identified on the q arm. In particular, the pericentromeric q12-13 area may contain the critical tumor suppressor gene or genes for the development of early urothelial neoplasia. Allelic losses of chromosome 9 were associated with expansion of the abnormal urothelial clone which frequently involved large areas of urinary bladder mucosa. These losses could be found in a high proportion of urothelial tumors and in voided urine or bladder washing samples of nearly all patients with urinary bladder carcinoma.

A common region of allelic loss on chromosome region 3p25.3-26.3 in nasopharyngeal carcinoma.

Loss of heterozygosity (LOH) of chromosome arm 3p has been commonly observed in carcinomas of various tissues, including those of nasopharyngeal carcinoma (NPC). To determine the frequency and extent of allelic loss in NPC, we investigated 16 loci on chromosome bands 3p21-26 in 24 tumor tissues by microsatellite analysis. LOH on 3p21-26 was found in 16 of 24 (66.7%) tumors. The highest frequency of allelic loss was found in two adjacent loci, D3S1620 (11/22, 50%) and D3S1560 (9/18, 50%). Eight cases showed LOH in one contiguous region and 5 cases in more than one region. Samples 1, 3, 4, 7, 8, 10, 16, 17, 18, 19, and 22 had a contiguous stretch of allelic loss between D3S1297 and D3S1597. The smallest common LOH/deletion region seems likely to lie between D3S1297 (3p26.3-26.2) and D3S1560 (3p25.3). The allelic loss map defined here will facilitate finer mapping of putative tumor suppressor gene loci and positional cloning of such genes, which may play a role in carcinogenesis of NPC.

Utilization of molecular genetics in the differentiation between adrenal cortical adenomas and carcinomas

Distinction between benign adrenal cortical proliferative lesions and adrenal cortical carcinoma has been approached by a combination of histological, immunohistochemical, and macroscopical parameters. Modern imaging studies allow detection of small adrenal cortical lesions that may be incorrectly diagnosed. Differentiation between benign and malignant tumors of the adrenal cortex was attempted by microdissection of nine cases of adrenal cortical hyperplasia, 10 cortical adenomas, and 18 adrenal cortical carcinomas with subsequent polymerase chain reaction (PCR) amplification for loss of heterozygosity (LOH) of five microsatellites of putative tumor suppressor gene loci: p53 gene (17p), the neuroblastoma candidate gene (1p), the p16 gene (9p), the von Hippel Lindau gene (3p), and the retmoblastoma gene (13q). None of the hyperplastic lesions or cortical adenomas showed LOH of any of the gene markers used. Conversely, genetic changes were observed in 61% (11 of 18) of the cases of carcinoma. Forty-four percent of the lesions showed LOH for p53 (7 of 16). LOH of 1p, 3p, and 9p were seen in 22%, 22%, and 26%, respectively. LOH of the retinoblastoma gene was seen in 80% or four of five of the informative cases studied. We conclude that LOH studies may be used to distinguish malignant from nonmalignant adrenal cortical proliferations. Relative infrequency of LOH in 3p may furthermore help to differentiate adrenal lesions from clear cell carcinomas of the kidney.

Comparison of genetic alterations in colonic adenoma and ulcerative colitis-associated dysplasia and carcinoma

Carcinoma is an important complication of ulcerative colitis (UC) and develops from dysplastic precursor lesions. Genetic changes involved in the malignant transformation have not been fully characterized. We studied 19 cases of UC with high-grade dysplasia (HGD) and eight samples of associated carcinoma (CA). Microdissection of normal epithelium, epithelium at the site of chronic inflammation, HGD, and CA was performed. Polymerase chain reaction (PCR) amplification for loss of heterozygosity (LOH) of the following polymorphic microsatellites of putative tumor suppressor gene loci was done: APC (5q), DCC (l8q), p16 (9p), p53 (17p), and 8p12. To compare genetic alterations, 22 typical adenomas of the colon were studied with the markers for APC and p16 gene loci. p ]The results indicated that LOH of p16 and p53 were present in nondysplastic epithelium, HGD, and CA. However, the LOH in nondysplastic epithelium was detected in some associated HGD, but not all. Whereas LOH of p16 was present in 7 of 14 cases of HGD (50%), it was noted in only 1 of 22 adenomas (5.0%). LOH in the APC and DCC gene loci in UC was noted in HGD with associated CA, but LOH of APC was not present either in cases of nondysplastic epithelium or in HGD alone. Conversely, LOH in APC was present in 4 of 19 colonic adenomas. We conclude that LOH of p53 and p16 in nondysplastic epithelium may be associated with chronic reparative processes. These changes may lead to susceptibility to further genetic damage involving the APC and DCC gene loci in the development of dysplasia and progression of CA in UC. The low frequency of LOH in the p16 gene (9p) in adenomas compared with dysplasia in UC combined with infrequent LOH in APC gene loci in cases of pure dysplasia in UC may support this combination of markers as a clinical test for the differentiation of polypoid dysplasia from adenomas in UC.

An allelotype of papillary thyroid cancer.

Although papillary carcinoma accounts for approximately 70% of all thyroid cancers, preliminary studies of allelic loss have thus far not identified any areas of chromosomal deletion. We evaluated 30 papillary thyroid carcinomas for chromosomal loss/allelic imbalance by testing at least 2 microsatellite markers from every autosomal arm. Fifteen of the 30 tumors tested exhibited loss of heterozygosity/allelic imbalance (LOH/AI) at one or more loci. Chromosomal arms with frequent LOH/AI included 4q, 5p, 7p and 11p. An average of 1.1 chromosomal arms displayed LOH/AI in each individual tumor. Therefore, 4q, 5p, 7p and, to a lesser extent, 11p display significant LOH/AI in papillary thyroid cancer, which indicates the presence of putative tumor-suppressor gene loci at these chromosomal arms.

Evidence that wild‐type TP53, and not genes on either chromosome 1 or 11, controls the tumorigenic phenotype of the human fibrosarcoma HT1080

The specific transfer of normal chromosomes via microcell fusion has been instrumental in identifying putative tumor suppressor gene loci in a variety of human cancers. Using this same technique it has been proposed that the tumorigenicity of the human fibrosarcoma cell line HT1080 is controlled by functionally distinct tumor suppressor genes on human chromosomes I and II. To address these results and perhaps further localize the suppressive effect to particular regions on these two chromosomes, we transferred into HT1080 seven different fibroblast-derived human chromosomes containing either intact or discrete portions of chromosome I or II. Interestingly, we found no evidence of genes on these chromosomes that could alter the growth of HT1080 either in vitro or in vivo. Based on these results we were left with the possibility that a gene, or genes, residing on an entirely different chromosome(s) was involved in the tumorigenesis of HT1080. Since TP53 mutation has been documented in a variety of human tumor types, and we found both copies of TP53 to be mutated in HT1080, we were prompted to examine its role by both cDNA transfection and chromosome transfer. Although by cDNA transfection we found that expression of exogenous wild-type TP53 was incompatible with continued proliferation of HT1080 cells in vitro, chromosome 17 transfer studies revealed that a more physiologic expression of exogenous wild-type TP53 could be tolerated in vitro while being completely incompatible with growth in vivo. These studies demonstrate a differential effect of TP53 growth inhibition and clearly show that TP53 tumor suppressing function can be independent from its potent growth suppressing effect in vitro.