FUNCTIONAL EVIDENCE FOR INVOLVEMENT OF MULTIPLE PUTATIVE TUMOR-SUPPRESSOR GENES ON THE SHORT ARM OF CHROMOSOME-3 IN HUMAN ORAL SQUAMOUS-CELL CARCINOGENESIS

Cytogenetic and restriction fragment length polymorphism (RFLP) analys es have suggested that a putative tumor suppressor genes(s), which may play an important role in the development of human oral squamous cell carcinoma (SCC), is located on the short arm of chromosome 3 (3p). We previously reported that introducing an intact human chromosome 3 int o three different oral SCC tumorigenic cell lines completely suppresse s the tumorigenicity of each cell line with significant decrease in th e in vitro growth rate and morphological changes. To map the tumor sup pressor gene(s) on 3p, we have now examined the tumorigenicity of micr ocell hybrid clones containing various fragments derived from 3p that were introduced by microcell-mediated chromosome transfer. Sixteen hyb rid clones Mare obtained from four successful experiments, and these c lones were classified into two groups: 4 fully tumorigenic clones and 12 suppressed phenotype clones. Analyses of the 3p segments in the ser ies of hybrid clones with the use of RFLP or microsatellite markers re vealed that the 3p21.2-p21.3 or 3p25 regions or both were consistently retained in the 12 clones with suppressed phenotype but not in the 4 tumorigenic clones. The more proximal 3p13 region also was retained in three nontumorigenic clones. The overall results are fairly compatibl e with recent evidence that there are three discrete regions on 3p sho wing frequent allelic losses on oral SCC, and they directly provide fu nctional evidence for the presence of tumor-suppressor genes for oral SCC in these regions. The possibility that three genes, FHIT, VHL, and T beta R-II, recently identified on 3p may be significantly involved in oral SCC development is also discussed. (C) Elsevier Science Inc., 1998.