MiR-505 enhances doxorubicin-induced cytotoxicity in hepatocellular carcinoma through repressing the Akt pathway by directly targeting HMGB1

Abstract

Compelling evidence has suggested the relevance of miRNAs in resistance to chemotherapeutic agents in HCC. miR-505 was reported to be downregulated and function as a tumor suppressor in HCC cells by binding to high-mobility group box 1 (HMGB1). Whether miR-505/HMGB1 axis was involved in ADM cytotoxicity in HCC remains to be addressed. The aim of this study was to explore the effect of miR-505/HMGB1 axis on ADM cytotoxicity in HCC cells. MTT, flow cytometry analysis, and caspase-3 activity assays were conducted to assess ADM-induced cytotoxicity. The protein level of phosphorylation of histone H2 AX at Ser139 (γH2AX) was detected to evaluate DNA damage. The effects of miR-505 and HMGB1 on the protein kinase B (Akt) pathway were determined by examining the protein levels of phosphorylated Akt (p-Akt), Akt, phosphorylated glycogen synthase kinase-3β (p-GSK-3β), and GSK-3β. We found that HMGB1 knockdown and miR-505 overexpression exacerbated ADM-induced cell viability inhibition, enhanced ADM-induced apoptosis, and increased caspase-3 activity in ADM-treated HCC cells. However, HMGB1 overexpression reversed the effects of miR-505 on ADM-induced cytotoxicity in HCC cells. HMGB1 knockdown and miR-505 overexpression promoted ADM-induced DNA damage in HCC cells, which was abated by HMGB1 overexpression. On a molecular mechanism level, HMGB1 silencing and miR-505 overexpression inactivated the Akt pathway in HCC cells, while exogenous HMGB1 resisted miR-505-induced Akt pathway inactivation. In conclusion, miR-505 overexpression enhanced ADM-induced cytotoxicity in HCC cells, at least partly by targeting HMGB1 and inactivating the Akt pathway.