Effect of epidermal growth factor on proliferation of human tumor cells in soft agar

The effect of epidermal growth factor (EGF) and fibroblast feeder layers on the proliferation of human tumor cells in soft agar was examined. The addition of EGF to medium supporting growth of tumor cells significantly increased (P less than or equal to 0.02) the number of colonies grown from the cells of 36 to 58 patients (62%) with a variety of neoplasms. The increase in the number of colonies was dependent on the concentration of EGF and was maximal at a concentration of 50 ng EGF/ml. The addition of glucocorticoids did not potentiate the effect of EGF. Lethally irradiated fibroblast feeder layers alone only slightly increased the number of colonies. However, the addition of fibroblasts to cultures significantly increased the mitogenic effect of EGF. The results suggest that a proportion of epithelial-derived tumors retain responsiveness in vitro to physiologic growth regulators such as EGF.