Cytogenetic studies, genetic linkage studies of familial melanoma kindreds and allelotyping of sporadic and familial melanomas suggested that genetic changes on the short arm of chromosome 9 near the IFN loci were causally implicated in malignant melanomas. LOH studies with a high density of 9p markers on cell liens and uncultured tumors of various types have recently focused attention on the region of 9p21 between ifna AND d9s171 loci nd because of common homozygous losses centered on a 40kb region in numerous tumor cell lines, including melanomas, the p16 gene (locus name CDKN2, aka MTSI, CDK41) was proposed as a candidate multiple tumor suppressor gene and, more specifically, as the 9p-linked familial malignant melanoma predisposing gene (MLM). Since we do not find frequent CDKN2 mutations in uncultured melanomas and germline mutations have been identified in only a fraction of 9p-linked familial melanoma kindreds, its role as the multiple tumor suppressor gene and as the major 9p21-linked MLM gene is not fully established. Ongoing allelotyping of sporadic melanomas and other tumor types have demonstrated more than one common region of loss in 9p21, suggesting the presence of more than one suppressor gene in this chromosome region. To investigate this complex situation in sporadic and familial melanomas we will pursue two major goals; 1. To clarify the role of p16, we will complete our investigation of the p16 gene in germline transmitted melanomas by following transmission of the mutant germline p16 genes in at least three families and, with our intraprogram colleagues, correlating mutant gene function with penetrance and severity of disease. The natural history of occurrence of specific p16 mutations in sporadic and familial melanomas with serve as a basis for screening and, possible, therapeutic strategies. 2. To identify another 9p21-linked melanoma suppressor gene, we will refine our LOH map 9p21 using primary, uncultured melanoma samples, clone candidate genes from YAC and cosmid contigs, identify the second suppressor gene by analysis in melanoma kindreds and investigate its function, in collaboration with Project 1,2 and 4 investigators. The long range goal is to use our unique collection of malanoma families and cases, in combination with the defined MLM gene mutations, to devise therapeutic strategies, in collaboration with our program leaders and with the jefferson Cancer Center Melanoma Program.
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