Inhibition of cFLIP overcomes acquired resistance to sorafenib via reducing ER stress-related autophagy in hepatocellular carcinoma

摘要

Treatment with sorafenib remains the first-line therapy for patients with advanced stage hepatocellular carcinoma (HCC), however, it has limited effect due to the acquired resistance of HCC. Elucidating the potential mechanism can assist in developing promising strategies to overcome this resistance. In the present study, a sorafenib-refractory HCC cell was established from the Huh7 parental cell line, which was resistant to sorafenib mediated-cytotoxicity in vitro. The cell inhibition rate and apoptosis of cells were determined by MTT assay and flow cytometry, respectively. Electronic microscopy was used to detect autophagy in cells. The expression levels of endoplasmic reticulum stress (ERS)-related protein, apoptosis-related protein and cFLIP were examined by western blot analysis. Co-immunoprecipitation was used to examine the ubiquitination of cFLIP. It was found that sustained exposure to sorafenib activated ERS in the HCC cells. The ERS inhibitor partly increased sorafenib-induced cell death in these cells. In addition, ERS-induced autophagy was important in resistance to sorafenib, as inhibiting autophagy led to the resistant HCC cells becoming more sensitive to sorafenib. However, ERS-induced apoptosis did not differ between sorafenib-sensitive HCC cells and sorafenib-refractory HCC cells. The knockdown of cFLIP reversed the acquired sorafenib resistance by activating caspase-8 and inhibiting activated ERS in the sorafenib-resistant HCC cells. Mechanistically, a sustained increased in cFLIP was found to be dependent on USP2-induced deubiquitination. In conclusion, cFLIP was identified as a potential target for overcoming the acquired sorafenib resistance in HCC. These effects occurred partially through reducing ERS-related autophagy in HCC.