الملخص
ObjectiveTo investigate the effects of berbamine hydrochloride on sorafenib resistance in hepatocellular carcinoma cells and the underlying mechanisms. MethodThe sorafenib-resistant cell line SMMC-7721/S was selected by the concentration increment method starting at 1.25 μmol·L-1 sorafenib. Both SMMC-7721 and SMMC-7721/S cells were treated with 0， 2.5， 5， 10， 15， 20 μmol·L-1 sorafenib， and the cell counting kit-8 （CCK-8） assay was employed to determine the half maximal inhibitory concentration （IC50） and calculate the resistance index （RI）. Western blot was conducted to compare the expression of proteins involved in autophagy and phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin （PI3K/Akt/mTOR） signaling pathway between SMMC-7721 and SMMC-7721/S cells. Furthermore， SMMC-7721/S cells were treated with 5 μmol·L-1 berbamine hydrochloride alone or in combination with 2.5， 5， 10 μmol·L-1 sorafenib， and the cell growth was assessed by the CCK-8 assay. In addition， SMMC-7721 and SMMC-7721/S cells were treated with 5 μmol·L-1 berbamine hydrochloride alone or in combination with 5 μmol·L-1 sorafenib， and the cell proliferation was examined by the colony formation assay. The immunofluorescence assays with Microtubule-associated protein 1 light chain 3 （LC3） and LysoTracker as probes were employed to assess the lysosomal acidification in SMMC-7721 cells treated with 5 μmol·L-1 berbamine hydrochloride or 0.1 μmol·L-1 autophagy inhibitor bafilomycin A1 （Baf）. Further， the expression of proteins involved in autophagy and PI3K/Akt/mTOR signaling pathway was determined by Western blot and compared between groups. ResultSorafenib showed the IC50 of 9.56 mol·L-1 （P<0.01） and 7.99 mol·L-1 for SMMC-7721/S and SMMC-7721 cells， respectively， at 24 h. The resistance index （RI） of SMMC-7721/S for sorafenib was 1.20 （P<0.01）， which indicated mild resistance. Compared with SMMC-7721 cells， SMMC-7721/S cells exhibited up-regulated expression of p-mTOR， p-Akt， and LC3Ⅱ， down-regulated expression of p62 protein （P<0.01）， and unchanged Akt protein level. CCK-8 and colony formation assays demonstrated that the combination of berbamine hydrochloride and sorafenib exhibited a synergistic effect （Q>1.15）， with berbamine hydrochloride partially reversing the resistance of liver cancer cells to sorafenib. The immunofluorescence detection of LC3 revealed that berbamine hydrochloride and Baf significantly increased LC3 in SMMC-7721 cells. The detection with LysoTracker as the probe showed that berbamine hydrochloride inhibited the acidity of lysosomes in SMMC-7721 cells （P<0.01）， indicating the suppression of autophagy. Berbamine hydrochloride further enhanced the downregulation of p-mTOR and p-Akt protein levels and did not change the Akt protein level in SMMC-7721 cells exposed to sorafenib. Berbamine hydrochloride inhibited the increase in p-mTOR expression， down-regulated the p-Akt protein level， and did not change the total Akt protein level in the SMMC-7721/S cells exposed to sorafenib. ConclusionBerbamine hydrochloride can ameliorate the resistance of liver cancer cells to sorafenib by inhibiting cellular autophagy and the PI3K/Akt/mTOR signaling pathway.