Effect of regulating TGF-β1/Smad signaling pathway on apoptosis of hepatocellular carcinoma HepG2 cells under endoplasmic reticulum stress

Abstract

Objective: To investigate the effect of TGF-β1/Smad signaling pathway on the apoptosis of HepG2 cells under endoplasmic reticulum stress (ERS). Methods: An ERS model was established firstly. Human hepatocellular carcinoma HepG2 cells were treated with 3 μmol/L tunicamycin (TM) for 24 h to induce ERS. Cells were divided into 6 groups, each with 3 replicate holes, and the experiment was repeated 3 times. The 6 groups included untreated group, TM group (3 μmol/L TM treatment group), TM + NC group(3 μmol/L TM + si-TGF-β1 negative control group), TM + si-TGF-β1 group(3 μmol/L TM + si-TGF-β1 group), TM + pEX-3 group(3 μmol/L TM + plasmid control group), and TM + TGF-β1 pEX-3 group(3 μmol/L TM + TGF-β1 overexpressed plasmid group). HepG2 cells were transfected with TGF-β1 small interfering RNA (TGF-β1 si-RNA) and TGF-β1 overexpressed plasmids (TGF-β1 pEX-3) by Lipofectamine. Twenty-four hours after transfection, RT-qPCR and Western blot were used to detect the expression of TGF-β1 and p-Smad2 in HepG2 cells of each group. CCK-8 and flow cytometry were used to analyze changes in the proliferation inhibition rate and apoptosis rate of HepG2 cells in each group. Results: Compared with the untreated group, the expressions of TGF-β1 and p-Smad2 in TM group were significantly reduced (P＜0.05). Compared with the TM group, the expressions of TGF-β1 and p-Smad2, as well as the cell proliferation inhibition rate and apoptosis rate in TM + si-TGF-β1 group were obviously decreased (P＜ 0.01), while the expressions of TGF-β1 and p-Smad2, cell proliferation inhibition rate and apoptosis rate of TM + TGF-β1 pEX-3 group were significantly increased (P＜0.01). Conclusion: The TGF-β1/Smad signaling pathway was inhibited in hepatocellular carcinoma HepG2 cells under ERS, when this pathway was activated, the apoptosis rate of HepG2 cells under ERS was increased significantly.