Norcantharidin combined with Coix seed oil synergistically induces apoptosis and inhibits hepatocellular carcinoma growth by downregulating regulatory T cells accumulation.

The immune system plays a critical role in exerts effects in the growth and progression of hepatocellular carcinoma (HCC), which needs interacting approaches for effective therapy. In this study, we have found that the Norcantharidin (NCTD) + Coix lacryma-jobi seed oil (CLSO) combination exhibited more potent antitumor effects in an terms of cytotoxicity and apoptotic induction in human HepG2 and HepG2/ADM cells than NCTD or CLSO alone. In vivo, administration of NCTD+CLSO combinations significantly suppressed the formation of tumor in Hepal-1 hepatoma-bearing mice. Furthermore, we found that the in vitro co-cultures of HepG2 or HepG2/ADM cells with PBMCs from healthy donors led to an increase in the number of CD4 (+) CD25 (+) T cells. This increase was down-regulated by the combination effectively. Down-regulation of FoxP3 mRNA and protein expression occurred during the combination in the co-cultures. The amount of Tregs of Hepal-1 hepatoma-bearing mice was significantly decreased in the combination treated group. The combination down-regulated the expression of FoxP3, CTLA-4 and Tregs related cytokine (TGF-β and IL-10) in the serum of tumor bearing mice. Taken together, these results suggest that the most valuable aspect of the NCTD+CLSO combined use improves the anti-tumor activity and regulates tumor infiltrating Tregs.