Novel Combinational Treatment of Cisplatin with Cyclophilin A Inhibitors in Human Heptocellular Carcinomas

The fungal cyclic peptide cyclosporin A (CsA) and fungal macrolide compound sanglifehrin A (SFA) have been developed as immunosuppressive drugs and both bind to cyclophilin A (CypA). CypA has been reported to be upregulated in diverse human cancers including hepatocellular carcinomas (HCC). CypA overexpression induces resistance to hypoxia and chemotherapeutic agents such as cisplatin in cancer cells. In this report, it was shown that CsA or SFA can synergistically increase apoptotic cell death in HCC cells, when combined with cisplatin. The increased cytotoxicity was accompanied by enhanced oxidative stress. The effects of CsA and SFA were due to inhibition of CypA activity. It was also shown that CsA and SFA abrogate cisplatin resistance as well as protection against hypoxia that is provided by CypA overexpression. Importantly, the synergistic effect of CsA or SFA with cisplatin was shown even in p53 defective Hep3B cells. Finally, overexpression of CypA was observed in human HCC tissues. In conclusion, CsA or SFA synergistically enhances cisplatin-induced apoptosis in HCC cells including the p53-defective Hep3B.