Effect of tetrandrine combined with epirubicin on the growth of human breast carcinoma multidrug resistance cell line.

Multidrug resistance presents a serious problem in cancer chemotherapy. Recent studies have shown that the multidrug resistance of tumor cells can be reversed by tetrandrine by potentiating the cytotoxicity of chemotherapeutic agents. However, whether tetrandrine has such potentiating effect on epirubicin has not been reported. Thus, the combined effect of tetrandrine and epirubicin on the growth of human breast carcinoma multidrug-resistant MCF-7/ADM cells was studied in the present study. It was shown that tetrandrine significantly potentiated the cytotoxicity of epirubicin. To examine the mechanism of the combined effect of tetrandrine and epirubicin on MCF-7/ADM cell growth, cell cycle progression was evaluated by using flow cytometry. The combined use of tetrandrine and epirubicin caused an accumulation of cells at G(2)/M phase, accompanied with a concomitant decrement of cell number at G(0)/G(1) phase. The present study demonstrated for the first time that tetrandrine potentiated the cytotoxcity of epirubicin on MCF-7/ADM cells. Cell cycle arrest at G(2)/M phase may contribute to the combined effect of tetrandrine and epirubicin.