Tanshinone IIA inhibits human breast cancer cells through increased Bax to Bcl-xL ratios

Tanshinone IIA (C19H18O3) was extracted from danshen (Salviae miltiorrhizae radix). It has cytotoxic properties and induces apoptosis in many human cancer cells. The molecular mechanisms are poorly understood, therefore, in the present study, we aimed to elucidate its anticancer activity on human breast cancer MDA-MB-231 cells. The cytotoxic effects of tanshinone IIA on MDA-MB-231 cells were measured by MTT assay. The percentages of cells in different cell cycle phases were determined by flow cytometry. The protein expression of Bax and Bcl-2 was examined using Western blotting. The results showed that tanshinone IIA inhibits the proliferation of MDA-MB-231 cells in a dose- and time-dependent manner. Tanshinone IIA induces apoptosis in a dose-dependent manner and the percentage of cells in sub-G1 phase. It increases the protein expression of Bax but decreases the Bcl-2 expression in MDA-MB-231 cells. Our findings suggest that tanshinone IIA can inhibit the proliferation of MDA-MB-231 cells by active apoptosis. One of the mechanisms may be through upregulating the expression of Bax but down-regulating Bcl-2 expression and then inducing apoptosis. In conclusion, tanshinone IIA has therapeutic potential in breast cancer patients.