Tanshinone IIA (Tan-IIA) is extracted from Danshen and known to inhibit proliferation and induce apoptosis in many cancer cells. We aimed to elucidate its anticancer activity and molecular mechanism in human lung cancer A549 cells. The cytotoxicity of Tan-IIA in A549 cells were measured by the MTT assay. The effects of Tan-IIA on the cell cycle, mitochondrial membrane potential (MMP), calcium and reactive oxygen species (ROS) released in A549 cells were detected by flow cytometry. The protein expressions of p53, Bax, Bcl-2 and β-actin in A549 cells were tested by Western blotting. The proliferative rates of A549 cells were obviously inhibited by Tan-IIA in a dose- and time-dependent manner. The results of FACS showed that the sub-G1 phase was increased when A549 cells were cultured with various concentrations of Tan-IIA (control, 2.5, 5 and 10 µg/ml) for 48 h. Tan-IIA induced the production of ROS, Ca+2 and decreased MMP. The outcome of Western blotting showed that protein expressions of p53 and bax were increased, but proto-oncogene bcl-2 was notably decreased, after culturing with Tan-IIA (5 µg/ml) for 6, 12 and 24 h. Tan-IIA inhibited the proliferation of non-small cell lung cancer A549 cells, possibly by decreasing the MMP and inducing apoptosis due to the induction of a higher ratio of Bax/Bcl-2.

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