Epidermal growth factor inhibits the synthesis of the nuclear protein cyclin in A431 human carcinoma cells.

The effect of epidermal growth factor (EGF) on the synthesis of the nuclear protein cyclin and its relationship with cell proliferation has been studied in human carcinoma A431 cells. Quantitative two-dimensional gel electrophoretic analysis of [35S]methionine-labeled polypeptides from EGF-treated and untreated A431 cells showed that the synthesis of cyclin (0.07% of total labeled protein) could be decreased to 20% (less than 0.01% of total labeled protein) by EGF at a concentration of 100 ng/ml. A good correlation between the effect of different concentrations of EGF on cyclin synthesis and A431 cell proliferation was found. A431-derived cells resistant to the growth-inhibitory effect of EGF showed no significant changes in cyclin synthesis after EGF treatment. Taken together, these results support the idea that cyclin may be an important protein that is involved in the control of cell proliferation.