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

Abstract

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-1α (HIF-1α), 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-1α, 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-1α and IGF-1R was observed in hypoxic HepG2 cells, with the exception of HIF-1α 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-1α 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-1α were secreted from the hypoxic HepG2 cells. It was concluded that hypoxia induces the accumulation of IGF-1R and HIF-1α mRNA and protein, which regulates the expression of VEGF mRNA and protein in hypoxic HepG2 cells.