Effect of hypoxia on hypoxia inducible factor-1α, insulin-like growth factor I and vascular endothelial growth factor expression in hepatocellular carcinoma HepG2 cells

Hypoxic microenvironments and angiogenesis have been a focus of tumor research in previous years. The aim of the the present study was to create a hypoxic model and observe the effect of hypoxia on the expression of hypoxia inducible factor-1 alpha (HIF-1 alpha), insulin-like growth factor I (IGF-1) and vascular endothelial growth factor expression. The hypoxia model was generated using cobalt chloride (CoCl2) and an MTT assay was used to observe the influence of hypoxia on HepG2 cells. Reverse transcription-polymerase chain reaction, western blotting, ELISA and confocal immunofluorescence microscopy were used to detect the expression of HIF-1 alpha, IGF-1 and VEGF in HepG2 cells, in which hypoxia was induced by various concentrations of CoCl2 and for various incubation times. The cell viability worsened with increasing concentrations of CoCl2. The expression of HIF-1 alpha and IGF-1R was observed in hypoxic HepG2 cells, with the exception of HIF-1 alpha mRNA. The expression of IGF-1R and VEGF mRNA and protein was correlated with the concentration of CoCl2 and the time that hypoxia was induced for. The expression of HIF-1 alpha mRNA and protein was positively correlated with the expression of the VEGF mRNA and protein in a dose- and time-dependent manner under hypoxic conditions. Using immunofluorescence, it was observed that IGF-1R and HIF-1 alpha were secreted from the hypoxic HepG2 cells. It was concluded that hypoxia induces the accumulation of IGF-1R and HIF-1 alpha mRNA and protein, which regulates the expression of VEGF mRNA and protein in hypoxic HepG2 cells.