Effects and interactions of epidermal growth factor, insulin, hydrocortisone, and estradiol on the cloning of human tumor cells

We investigated the effects and interactions of epidermal growth factor (EGF), insulin, hydrocortisone, and estradiol on the growth of 18 freshly obtained human tumors in our human tumor stem cell assay (HTSCA) cultured at a reduced serum concentration (8.5 %/ml). All possible combinations of these four supplement factors were added to the assay to determine the ability of each component to enhance colony formation. We found that hydrocortisone was the most effective single supplement in stimulating colony growth in the HTSCA. Supplementation with insulin, estradiol, or both had some growth‐promoting effect but not as great as hydrocortisone. Moreover, the addition of insulin, estradiol, or both often demonstrated a negative interaction with hydrocortisone. EGF supplementation alone; in dual combination with insulin, estradiol, or hydrocortisone; or in combination with estradiol and insulin in the assay did not significantly increase colony formation. However, EGF added to the cultures containing hydrocortisone with insulin and/or estradiol significantly increased colony formation and reversed the negative effect of insulin and estradiol on hydrocortisone activity. Thus, under conditions of our assay, the most effective combination in promoting colony growth contained all four factors.