Growth suppression of hybrids between transformed cells and normal fibroblasts in serum-free medium: correlation with retention of human chromosomes.

Somatic cell hybrids formed by crossing PG19 mouse melanoma cells with mouse embryo fibroblasts have a reduced ability to proliferate in growth factor-unsupplemented serum-free medium relative to the parental melanoma cells. The suppression of growth of the hybrid cells in serum-free medium is attributable to a strict requirement of these cells for polypeptide growth factors (insulin plus platelet-derived growth factor, fibroblast growth factor, or epidermal growth factor). In contrast, the parental melanoma cells are able to grow without exogenously added growth factors. Fifteen hybrids derived from crosses between mouse L cells and normal human skin fibroblasts also have been tested for ability to grow in growth factor-unsupplemented serum-free medium. Depending on which human chromosomes are retained, growth of these hybrids in serum-free medium is also suppressed relative to growth of the L cell parent. There appear to be several genes on different chromosomes that are involved in suppression of serum-free growth of the fibroblast x L cell hybrids. One weak suppressor gene appears to be on the human X chromosome.