Abstract: AIM: To investigate the effects of insulin on drug sensitivity of Etoposide (Vp-16) to MBA-MD-543(human breast cancer cell line) in vitro.METHODS: Insulin was applied directly to the MBA-MD-543 cultured in vitro.The effects of insulin and Vp-16 on the number of viable cell, the total number of cells were assayed by MTT method and cell count.RESULTS: Insulin could induce the cell growth and promote the cell metabolism at the concentration 4.0 -32.0 mU·ml^-1(8 -18 hours).At the condition of same density of cells, the administration of insulin (7.5 mU·ml^-1) before adding Vp-16 in 9-15 h, enhanced the chemocytotoxity of Vp-16 (70.09μg·ml^-1) on human breast cancer cells as indicated by MTT colorimetry.CONCLUSION: Proliferation of human breast cancer cell line can be induced by insulin,and insulin can sensitize MBA-MD-543 to the anticancer activity of Vp-16 in vitro.The key of improving the chemotherapeutic effect is the selection of revulsant occasion and concentration.It is possible to increase the growth and metabolism of cancer cells first so as to enhance the chemosensibility, and then administer chemotherapeutic agents, thus improving their therapeutic effects.

Key words: insulin, Etoposide, human breast cancer cell line, proliferation, chemosensitization