Phorbol ester promotes growth and transformation of carcinogen-exposed nonhuman primate cells in vitro

Kidney cells established in vitro from a white-lipped marmoset (106) were exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) alone or in combination with 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Low (0.1 micrograms/ml, 4 times), intermediate (1 microgram/ml) and high (1 microgram/ml, 4 times) doses of MNNG resulted in 100%, 50% and 2.8% of cell survival, respectively. High and low doses of MNNG had no effect on cell transformation. Upon exposure of cells to an intermediate dose of MNNG, 106 cells ecquired immortality and evolved into permanent cell line, 106-1M. However, the cells retained normal morphology and anchorage dependence. Chronic applications of TPA (0.1 micrograms/ml, 13 times) promoted 106-1M cells to morphological transformation and anchorage-independent growth but not to tumorigenicity in nude mice (106-1MT cell line). Chromosome analysis revealed only numerical changes in 106 cells and both numerical and structural aberrations in transformed 106-1MT cells. These changes in marmoset cells usually reflected cell culture instability leading to either senescence or to longer survival of cells in vitro. Chronic treatment with TPA did not result in downregulation of protein kinase C (PKC) in transformed 106-1MT cells. Instead, an additional species of PKC appeared in these cells.