OBJECTIVETo explore the possibility of use of insulin as a potentiator of 5-Fu to human colon cancer cell lines HCT-8 and HT-29 and study its mechanism.

METHODSMTT assay was used to examine the inhibition rate of cell growth after treatment with 5-Fu and insulin. Cell cycle was determined by flow cytometry.

RESULTSInsulin showed an enhancing effect on the chemotherapeutic response of 5-Fu when insulin was applied at a dose of exceeding 0.8 mU/ml 0 approximately 8 h before 5-Fu. Within the range of from 0.8 mU/ml to 8 mU/ml, a higher concentration of insulin gave a higher proportion of inhibited cells. But when the insulin concentration exceeds 8 mU/ml, the proportion became stable as that of 8 mU/ml. Insulin increased the percentage of S phase cells and decreased the percentage of G(1) phase cells (P < 0.01). The percentage of S phase cells reached a peak when the cells were treated with insulin for 6 hours.

CONCLUSIONInsulin can enhance the anticancer toxicity of 5-Fu to human colon cancer cell lines HCT-8 and HT-29 cells. Insulin increases the percentage of S phase cells, which may be one of the main mechanisms of insulin-induced enhancement of anticancer response of cancer cells to 5-Fu chemotherapy.