The role of calcium regulation in the expression of PERK protein induced by sorafenib in hepatoma cells

Aim This study aimed to determine whether calcium signal participates in the sorafenib induced ER stress process and has an impact on the action of sorafenib for the hepatoma. Methods Liver cancer HepG2 cell lines were maintained in DMEM with 10% fetal bovine serum and subcultured in plates or dishes at different densities for the following designed studies. HepG2 cells were basically treated with different doses of sorafenib (5–200 μM) for different time (0–48h) in the present or absent of trans‐Ned‐19 (a NAADP inhibitor, 100μM ) . The intracellular calcium signal was simultaneously recorded by confocal microscopy, and the expression level of PERK and caspase3 protein was detected by westernblot in HepG2 cells. The cell growth and apoptosis in these cells were analyzed by flow cytometry as well. Results Confocal microscopy showed that sorafenib (20–200 μM) induced substantial calcium release in HepG2 cells in a concentration‐dependent manner. Compared with the sorafenib intervention alone, trans‐Ned‐19 significantly attenuated sorafenib‐induced intracellular calcium elevation. Meanwhile, westernbolt assay showed that sorafenib time‐dependently but doses‐independently induced an increment in PERK expression in HepG2 cells. However, in the present of trans‐Ned‐19 was found to significantly enhance this sorafenib‐induced PERK and caspase3 levels, as well as apoptosis rate of HepG2 cells (P<0.05). For further treatment with trans‐Ned‐19 for 24 h, microscopic observation showed that trans‐Ned‐19 significantly inhibited cell growth and caused abnormal cell morphology changes compared with the sorafenib alone group. Conclusion Our preliminary data showed that NAADP‐mediated intracellular calcium release was importantly involved in sorafenib‐induced perk protein expression and cell apoptosis. Blocking NAADP‐mediated calcium channels can significantly enhance the efficacy of sorafenib in the hepatoma cells, suggesting that the combination of NAADP analogues and sorafenib might be a potential strategy in the treatment of liver cancer. Support or Funding Information Support or Funding InformationSupported by NSFC Grants 81360077, 81860654, 30630145, 81172260 and GXNSFC Grants 2015GXNSFDA139022 to Guo Zhang