OBJECTIVETo study whether the anti-apoptotic action is reversed by tetrandrine in a combination with vincristine in human breast carcinoma MCF-7 multidrug-resistant cells.

METHODChromatin condensation was observed by co-staining of fluorescent dyes Hoechst 33342 and propidium iodide; and G1 sub-peak was detected by flow cytometry. Apoptotic cells were detected with TUNEL method. Cellular free ca2+ was determined with Fluo-3 staining method.

RESULTTwo types of chromatin condensation were observed after the sensitive and drug-resistant MCF-7 cells were treated with an antitumor drug vincristine 5 mumol.L-1 for 24 h. The number of cell with chromatin condensation was obviously reduced in the drug-resistant cells treated with the same concentration of vincristine, as compared with the sensitive MCF-7 cells. The number of the apoptotic cells was increased by a combination of non-cytotoxic tetrandrine 20 mumol.L-1 and vincristine in both the sensitive and drug-resistant cells, which was confirmed with fluorescent indication and TUNEL method. The increment of introcellular free Ca2+ level in the cells treated with tetrandrine in a combination of vincristine was detected with Fluo-3 staining method.

CONCLUSIONThe anti-apoptotic action of human breast carcinoma MCF-7 cells can be effectively reversed by tetrandrine.