Radiation Enhances the Invasiveness of Irradiated and Nonirradiated Bystander Hepatoma Cells Through a VEGF-MMP2 Pathway Initiated by p53

Recent evidence has shown that irradiation can promote the invasiveness of hepatocellular carcinoma cells and have an impact on the invasive behavior of nonirradiated surrounding cancer cells, which may enhance overall tumor aggressiveness. However, the role of the TP53 tumor suppressor gene in the invasion of irradiated hepatoma cells and their nonirradiated bystanders remain largely unknown. In the present study, we found that irradiation increased the invasiveness of human hepatoma HepG2 cells, and pretreatment of the cells with SU1498 (an inhibitor of vascular endothelial growth factor receptor 2, VEGFR2) and GM6001 (an inhibitor of matrix metalloproteinases 2, MMP2) demonstrated that radiation-enhanced invasiveness is associated with the interplay between MMP2 and VEGF signaling. In addition, while radiation-induced expression and phosphorylation of p53, inhibition of p53 function with pifithrin-α or transfection of cells with p53 siRNA significantly reduced the activation of both MMP2 and VEGF and r...