Purpose: Sorafenib has revolutionized treatment of hepatocellular carcinoma (HCC), but its efficacy is limited by drug resistance. Autophagy is the process by which cellular components are transported to lysosomes for degradation, which promotes energy production and production of macromolecular precursors. Studies have suggested that the cytoprotective function of autophagy may contribute to chemoresistance or targeted drug resistance in cancer cells. We investigated the effects of miR-375 and autophagy-related protein 14, and their interrelationships, on sorafenib efficacy.
Methods: Cell viability was measured using the MTT assay, and apoptosis was evaluated using flow cytometry. Colony formation assay was performed to determine changes in cell number. Real-time PCR and Western blotting were performed to quantify the expression of key genes and proteins. Immunofluorescence and transmission electron microscopy were used to detect autophagy. Dual-luciferase reporter assays were used to verify a direct target.
Results: We characterized the relationship between sorafenib and autophagy. We showed that inhibition of autophagy enhanced sensitivity of HCC to sorafenib and showed that miR-375 was important in this process. Finally, we showed that miR-375 affected sensitivity of HCC cells to sorafenib through regulation of ATG14.
Conclusion: We showed that miR-375 sensitized HCC cells to sorafenib by blocking sorafenib-induced autophagy. We also showed that ATG14 was a direct autophagy-related target of miR-375. These findings indicated that miR-375-ATG14 was important in the development of sorafenib resistance in HCC.
Keywords: autophagy, hepatocellular carcinoma, sorafenib, miR-375, therapy, drug resistance