(-)-Gossypol enhances epirubicin's anti-tumor effects on hepatocellular carcinoma in vitro via down-regulating X-linked inhibitor of apoptosis protein

Abstract

Objective To investigate mechanism and effect on (-)-gossypol enhancing epirubicin killing hepatocellular carcinoma (HCC) cells. Methods HCC cells (Hep 3B and HuH7) were divided into 8 groups: control, (-)-gossypol, epirubicin, combination, si-control+epirubicin, si-X-linked inhibitor of apoptosis protein (XIAP)+ epirubicin, empty vector+ combination and pEBB-XIAP+ combination groups. Cell viability of each group was detected by CCK-8 assay; Cell apoptosis of each group was detected by flow cytometry and the level of cleavaged PARP, XIAP and eIF4E phosphorylation was detected by Western blot assay. Results Compared with the control group, no major effect was observed on cell viability exposed to (-)-gossypol in 5 μmol/L (P>0.05). Combination of (-)-gossypol and epirubicin significantly enhanced the anti-survival effect on HCC cells (P < 0.05), promoted cells apoptosis, increased the induction of cleavaged PARP, and inhibited XIAP up-regulation and eIF4E phosphorylation induced by epirubicin in HCC cells. Silencing XIAP promoted epirubicin to kill HCC cells and induced PARP cleavaged; Furthermore, XIAP over-expression attenuated epirubicin-induced anti-survival and pro-apoptosis of HCC cells enhanced by (-)-gossypol. Conclusion The combination of (-)-gossypol and epirubicin significantly inhibits HCC cells' survival and promotes cell apoptosis via suppressing epirubicin-induced phosphorylation of eIF4E and up-regulation of XIAP, suggesting that (-)-gossypol holds promise as a sensitizer for epirubicin-based HCC therapy.

Keywords

• epirubicin
• (-)-gossypol
• hepatocellular carcinoma
• xiap
• eif4e