Cobalt Chloride Induced Apoptosis by Inhibiting GPC3 Expression via the HIF-1α/c-Myc Axis in HepG2 Cells

Purpose: To investigate the role of glypican-3 (GPC3) in cobalt chloride (CoCl2)-induced cell apoptosis in hepatocellular carcinoma. Methods: HepG2 cells were treated with CoCl2 in the absence or presence of GPC3 plasmid transfection. Cell viability and apoptosis were assessed by MTT assay and flow cytometry, respectively. The expression of GPC3, hypoxia-inducible factor 1 alpha (HIF-1 alpha), c-myc, sp1, poly-ADP-ribose polymerase (PARP) and caspase-3 was determined by real-time PCR, Western blotting, and immunofluorescence after the cells were treated with different concentrations of CoCl2 or siRNA targeting HIF-1 alpha. Results: CoCl2 significantly inhibited the proliferation of HepG2 cells and induced apoptosis. Additionally, the expression of GPC3 mRNA and protein was decreased, and overexpression of GPC3 attenuated the tumour inhibiting effects. Further studies showed that CoCl2 increased the expression of HIF-1 alpha while reducing the expression of sp1 and c-myc; knockdown of HIF-1 alpha elevated the expression of GPC3, sp1, and c-myc. Conclusion: CoCl2 inhibited the growth of HepG2 cells through downregulation of GPC3 expression via the HIF-1 alpha/c-myc axis.