Isovitexin potentiated the antitumor activity of cisplatin by inhibiting the glucose metabolism of lung cancer cells and reduced cisplatin-induced immunotoxicity in mice

The increased resistance and toxicity have become the main causes of chemotherapy failure for treating lung cancer. The combination of chemotherapeutic drugs with other agents has been recognized as a promising strategy to overcome these difficulties. Isovitexin (IVT) is a well-known flavone C-glycoside found in many plants and has attracted wide attention due to its obvious antitumor and antioxidant effects. In this study, we investigated the synergistic effects of IVX and cisplatin (DDP) in non-small cell lung cancer (NSCLC) A549 and H1975 cells. The results showed that the combined treatment with IVT and DDP markedly inhibited proliferation and induced apoptosis of the two NSCLC cells. Using a mouse model of A549 xenograft, IVT potentiated the inhibition of DDP on tumor growth, but reduced DDP-induced hepatotoxicity and nephrotoxicity in mice. Remarkedly, IVT promoted lipopolysaccharide (LPS)- and lectin- stimulated splenocyte proliferation, and enhance cytotoxic T lymphocyte (CTL) and natural killer (NK) cell activities as well as the production of IL-2 and TNF-α. Furthermore, IVT significantly reduced glucose uptake, lactate production, and ATP production, and downregulated the protein expressions of pyruvate kinase M2 (PKM2)-mediated pathway in both A549 and H1975 cells. After the over-expression of PKM2 in the NSCLC cells, the synergistic antitumor effect of IVT and DDP was markedly weakened. Therefore, IVT not only inhibited cell proliferation and glucose metabolism via downregulating the expression of PKM2 to enhance the antitumor activity of DDP against lung cancer cells, and improved DDP-induced immunotoxicity in mice. It also presented a novel strategy to enhance the anti-tumor effect of platinum-based chemotherapy against NSCLC.