Phosphorylation of cofilin-1 by ERK confers HDAC inhibitor resistance in hepatocellular carcinoma cells via decreased ROS-mediated mitochondria injury.

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. Despite the availability of several treatment strategies, resistance to chemotherapeutic agents, which limits the effectiveness of anticancer drugs, is a major problem in cancer therapy. In this study, we used a histone deacetylases inhibitor (HDACi) to establish drug-resistant HCC cells and further analyzed the molecular mechanisms underlying the development of resistance in HCC cells. Compared with the parental cells, HDACi-resistant cells showed high metastatic and pro-survival abilities. Two-dimensional electrophoresis data showed that the cofilin-1 (CFL-1) protein was altered in HDACi-resistant cells and was highly expressed in resistant cells compared with parental cells. The molecular function of CFL-1 is actin depolymerization, and it is involved in tumor metastasis. In this study, we showed that CFL-1 inhibition decreased cell migration and increased cell apoptosis in HDACi-resistant cells. We observed that HDACi induced ROS accumulation in cells and apoptosis via promotion of the CFL-1 interaction with Bax and CFL-1 translocation to the mitochondria, resulting in cytochrome C release. Importantly, phosphorylation of CFL-1 by activated extracellular signal-regulated kinases 1 and 2 (ERK1/2) confers strong protection against HDAC inhibitor-induced cell injury. p-CFL-1 shows a loss of affinity with Bax and will not translocate to mitochondria, stably remaining in the cytoplasm. These results indicate that phosphorylation to inactivate CFL-1 decreased the chemosensitivity to HDAC inhibitors and resulting in drug resistance of HCC cells.