Genetic analysis of tumorigenesis: I. Expression of tumor-forming ability in hamster hybrid cell lines.

Two new fibroblasts cell lines from a male Chinese hamster embryo are described: one tumorigenic in nude mice (CHEF 16-2) and the other not (CHEF 18-1). Both lines have a stable diploid mode and mean of 22 with 10 pairs of homologous autosomes. The cell lines differ unambiguously in cloning ability in methylcellulose, colony morphology, and tumorigenicity; the expression of these traits was examined in a set of 18-1 X 16-2 hybrid clones. The results show initial suppression of tumorigenicity and anchorage independence, followed by growth in the nude mouse of subsets of cells with chromosomes reduced to the diploid range. Further studies are in progress to establish whether ability to grow in methylcellulose and in the nude mouse segregate coordinately at the cellular level, and whether this segregation has an identifiable chromosomal basis.