Role of autophagy in differential sensitivity of hepatocarcinoma cells to sorafenib

AIM: To investigate the role of sorafenib (SFN) in autophagy of hepatocellular carcinoma (HCC). We evaluated how SFN affects autophagy signaling pathway in human HCC cell lines. METHODS: Two different human HCC cell lines, Hep3B and Huh7, were subjected to different concentrations of SFN. Cell viability and onset of apoptosis were determined with colorimetric assay and immunoblotting analysis, respectively. The changes in autophagy-related proteins, including LC3, ULK1, AMPK, and LKB, were determined with immunoblotting analysis in the presence or absence of SFN. To assess autophagic dynamics, autophagic flux was measured with chloroquine, a lysosomal inhibitor. The autophagic responsiveness between different HCC cell lines was compared under the autophagy enhancing conditions. RESULTS: Hep3B cells were significantly more resistant to SFN than Huh7 cells. Immunoblotting analysis revealed a marked increase in SFN-mediated autophagy flux in Huh7 cells, which was, however, absent in Hep3B cells. While both starvation and rapamycin enhanced autophagy in Huh7 cells, only rapamycin increased autophagy in Hep3B cells. Immunoblotting analysis of autophagy initiation proteins showed that SFN substantially increased phosphorylation of AMPK and consequently autophagy in Huh7, but not in Hep3B cells. CONCLUSION: The autophagic responsiveness to SFN is distinct between Hep3B and Huh7 cells. Resistance of Hep3B cells to SFN may be associated with altered autophagy signaling pathways.