Objective: To investigate the role of allele loss on chromosome 9 in the pathogenesis of basal cell carcinoma (BCC) by examining the loss of heterozygosity in sporadic basal cell carcinoma and other cutaneous tumors.
Methods: DNA samples were isolated from the tumors, the matched adjacent normal skin and the blood of patients with sporadic basal cell carcinoma (14), squamous cell carcinoma (25) and Bowen's disease (5) by phenol-chloroform extraction. In our study, we used two microsatellite markers on chromosome 9, one was locus D9S319 (9p21), and the other was D9S299 (9q22.2-22.3). After PCR was performed, the samples were electrophoresed through 5% denatured polyacrylamide gels which were dried and exposed to Fuji XR films.
Results: Loss of heterozygosity with D9S319 (9p21) marker was not observed in the 10 informative cases of sporadic basal cell carcinoma, 19 squamous cell carcinoma and 4 Bowen's disease. Allelic deletion of D9S299 was not seen in the 21 informative cases of squamous cell carcinoma and 4 Bowen's disease. D9S299 (9q22.2-22.3) allele loss occurred in 2 of the 10 informative cases of sporadic basal cell carcinoma, indicating that there might be a susceptible tumor suppressor gene on chromosome 9, and loss of this allele might play an important role in the development of basal cell carcinoma. Inactivation of Drosophila patch (PTCH) (MSSE gene ESS1) in BCC might be necessary, if not sufficient, for BCC carcinogenesis.
Conclusion: Chromosome 9q22.2-22.3 may contain a putative tumor suppressor gene, and the loss of this gene may play an important role in the development of sporadic basal cell carcinoma.