Genetic analysis of tumorigenesis: X. Chromosome studies of transformed mutants and tumor-derived CHEF/18 cells.

Chinese hamster embryo fibroblast cell line CHEF/18 is stably diploid, anchorage-dependent, has a high serum requirement, and a does not form tumors in nude mice. The chromosome constitutions of spontaneous and chemically induced anchorage-independent and/or low-serum CHEF/18 mutants and tumors produced in nude mice by some of these mutants are compared. We find a correlation between diploidy and nontumorigenicity among the anchorage-independent mutants but not in the low-serum mutants. One of the four spontaneous and six of the 15 chemically induced anchorage mutants have remained diploid. The remaining 12 mutants are pseudodiploid or aneuploid, and seven of them contain changes in chromosome 1, either a translocation or a deletion involving breakage at the same position (1q11-12). Each of the tumors induced by six mutants has a unique pattern of rearrangements; however five of the six have changes involving chromosome 3. This chromosome was also frequency rearranged in tumor-derived cells previously investigated.