Genetic analysis of tumorigenesis: XVI. Chromosome changes in azacytidine- and insulin-induced tumorigenesis.

Chromosome changes accompanying differentiation and tumorigenesis in azacytidine- (azaC) and insulin-induced preadipocytes of the Chinese hamster embryo fibroblast cell line CHEF/18 are described. Karyotype analysis of 47 clones, subclones, and tumor-derived cells has shown that trisomy for chromosome 3q (mar 1) is characteristic of azaC preadipocytes but not of insulin preadipocytes. AzaC preadipocytes were consistently tumorigenic as well as trisomic for chromosome 3q, whereas most insulin preadipocytes were nontumorigenic and diploid. Only the few insulin preadipocytes that were tumorigenic were also trisomic for chromosome 3q. Among the tumor-derived cell lines recovered from azaC preadipocytes injected into nude mice, four had no additional chromosome changes except trisomy for 3q, as detected by karyotype analysis. Thus trisomy for 3q may be a sufficient chromosome change to induce tumor-forming ability in these cells. The rearrangements of chromosome 3 seen in this and other work pinpoint the trisomic region between the centromere and 3q5.