Apigenin Enhanced Antitumor Effect of Cisplatin in Lung Cancer via Inhibition of Cancer Stem Cells.

Cancer stem cell theory has been proposed to explain tumor heterogeneity and the carcinogenesis process. Highly tumorigenic lung cancer stem cells develop resistance to cisplatin (CDDP), a common chemotherapy drug. Herein, we attempted to clarify whether apigenin (API) can improve the antitumor efficiency of CDDP in lung cancer using cancer stem cells. Lung cancer stem cells were identified as CD 133 positive cancer cells in non-small cell lung cancer (NSCLC) A549, H1299 cells and CDDP-resistant NSCLC A549R cells. The cytotoxic effect of API was measured in CDDP-treated A549, H1299, and A549R cells. API repressed CD 133 positive cells and enhanced the antitumor effect of CDDP in A549, H1299, and A549R cells. The synergistic antitumor effect of API and CDDP was blocked by addition of the p53 inhibitor Pifithrin-α, and siRNA targeting the gene in A549R cells. Furthermore, API eliminates CDDP-induced CSC via p53, since A549R cells lacking p53 and Pifithrin-α addition derepressed the decrease in CD 133 positive cells after API treatment in CDDP-treated A549 and A549R cells. The findings indicate that API might eliminate cancer stem cells and enhance the antitumor effects of CDDP in NSCLC via p53.