The Mechanism Of Vascular Endothelial Growth Factor Gene Expression Affected By Transforming Growth Factor-β In HepG2 Cells

Abstract: Hepatocellular carcinoma(HCC) is the common of malignant tumor in our country. Metastasis and recurring of HCC has become the biggest barrier which influences the postoperative long-term survive in patients with HCC. It has considered that Neovascularization was one of the most important mechanism of metastasis of HCC. To study this will be great contribute to solve metastasis and postoperative recurrence.Up to date, the most potent growth factor of endothelium is vascular endothelial growth factor (VEGF), which plays important roles in the regulation of metastasis of malignancy. However, the signal transduction pathways of VEGF and it's function in neovascularization have not been clarified. In addition, transforming growth factor β (TGF-β) also plays important roles in the occurring and progress of tumor because of it's double function. Many studies conformed that TGF-β can stimulate the gene expression of VEGF through Smads or MAPK signaling pathway in vivo or in vitro. But it's signaling remain incompletely understood in HCC. In the progress of tumor hypoxia also play an important roles, what kind of interaction between hypoxia and TGF- P has not been well known.In this report, we cultured the HepG2 cells in vitro and divide them into 6 groups : 1) control group; 2) TGF-β1group; 3) CoCL2 group; 4) TGF-β1+ PD98059 group; 5) TGF-β1+ CoCL₂ group;6) TGF-β1+ CoCL₂ + PD98059 group. The changes of VEGF protein and mRNA were detected by immunohistochemistry and reverse transcriptase chain reaction (RT-PCR).Results: RT-PCR and immunohistochemistry showed that the expression of VEGF mRNA and protein were significantly highter in TGF-β1 group or CoCL₂ group than that of control group. The addition of TGF-β1 with hypoxia results in significantly more VEGF expression than either stimulation alone. Expression of VEGF can be increased by blocking ERK1/2 MAP kinase activation in TGF-P1+ PD98059 group or TGF-β1+ CoCL₂+ PD98059 group.Our findings suggest that Both TGF-β1 and hypoxia can stimulate the VEGF expression and TGF-pi can cooperate with hypoxia to stimulate VEGF expression in HCC. ERK1/2 MAP kinase pathway may affect the hypothesis between TGF-β1 and hypoxia in the progress of VEGF expression.