CHROMOSOME-9 ALLELE LOSS OCCURS IN BOTH BASAL AND SQUAMOUS-CELL CARCINOMAS OF THE SKIN

Linkage studies of kindreds with the nevoid basal cell carcinoma syndr ome and the high frequency of chromosome 9 allele loss in sporadic bas al cell carcinomas indicate that chromosome 9 may contain tumor suppre ssor genes important in the development of sporadic and familial basal cell carcinomas. The recent mapping of the Ferguson-Smith syndrome, w hich predisposes affected individuals to the development of multiple l esions histologically indistinguishable from squamous cell carcinomas, suggests that tumor suppressor genes on 9q may also be important in t he development of squamous cell neoplasms of the skin. Fifty-four non- melanoma skin cancers (24 basal cell carcinomas, 14 squamous cell carc inomas, and 16 cases of Bowen's disease) were examined for loss of het erozygosity on chromosome 9. Allelic loss at one or more loci on chrom osome 9 was observed in 14 of 24 basal cell carcinomas, four of 14 squ amous cell carcinomas, and three of 16 cases of Bowen's disease. Allel ic deletion of one or more 9q markers was seen in 14 basal cell carcin omas, three squamous cell carcinomas, and three cases of Bowen's disea se. Five basal cell carcinomas had interstitial deletions and in one t he breakpoint mapped within the nevoid basal cell carcinoma syndrome l ocus. 9p loss occurred in three of nine informative squamous cell carc inomas. Allelic deletion of 9p markers was not seen in 19 basal cell c arcinomas and seven cases of Bowen's disease. These findings suggest t hat chromosome 9 contains one or more tumor suppressor genes important in the development of both basal and squamous cell carcinomas of the skin.