Effect of curcumin on vascular endothelial growth factor in hypoxic HepG2 cells via the insulin-like growth factor 1 receptor signaling pathway

To investigate the anti-angiogenic effect and underlying molecular mechanisms of curcumin on HepG2 cells under hypoxic conditions, insulin-like growth factor 1 receptor (IGF-1R) knockout HepG2 cells were constructed using a clustered regularly interspaced short palindromic repeats/Cas9 genome-editing system. Hypoxic conditions were generated using cobalt chloride (CoCl(2)). An MTT assay was performed to measure the effects of curcumin on cell viability in hypoxia-induced IGF-1R knockout HepG2 cells, while western blot analysis was used to detect the expression of IGF-1R, phosphorylated (p)-protein kinase B (Akt), p-extracellular signal-regulated kinases (Erk)1/2, hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF). The results revealed that CoCl(2) at low concentrations (50 and 100 µM) had no significant inhibitory effects on IGF-1R knockout HepG2 cells. However, with increasing concentrations of CoCl(2) and treatment time, cell viability decreased and was significantly reduced at 150, 200 and 400 µM compared with the control group (P<0.05). The expression of HIF-1α and VEGF were significantly increased when the cells were treated with 150 or 200 µM CoCl(2) compared with the control (P<0.05). With the increase of CoCl(2) concentration or the treatment time, the expression of HIF-1α and VEGF were upregulated gradually. Additionally, curcumin significantly inhibited the expression of p-Akt, p-Erk1/2, HIF-1α and VEGF in hypoxia-induced IGF-1R knockout HepG2 cells. In conclusion, the findings of the present study suggest that curcumin may serve a pivotal role in tumor suppression via the inhibition of IGF-1R-mediated angiogenesis under hypoxic conditions.