Radiation Enhanced Hepatocellular Carcinoma Cell Invasion with Mmp-9 Expression through Pi3k/Akt/Nfκb Signal Transduction Pathway

This study is to investigate the molecular mechanism of radiation enhanced cell invasiveness of hepatocellular carcinoma (HCC) correlating with clinical patients undergoing radiotherapy and subsequently developing metastasis. Three HCC cell lines (HepG2, Hep3B, and Huh7) and normal hepatocyte cell line (CL-48) were irradiated with different doses. The effect of radiation on cell invasiveness was determined using the Boyden chamber assay. Radiation enhanced invasion capability was evident in HCC cells but not in normal hepatocytes. Invasion was observed in gelatin- coated but not fibronectin-coated or type I collagen-coated membranes. Radiation up-regulated matrix metalloproteinase-9 (MMP-9) mRNA level, MMP- 9 protein level, and MMP-9 activity. MMP-9 antisense oligonucleotides inhibited radiation induced MMP-9 expression and thereby significantly inhibited radiation induced HCC invasion. Furthermore, PI3K/Akt chemical inhibitors LY294002 and wortmannin suppressed radiation induced MMP-9 mRNA expression. Transient transfection with dominant negative Akt plasmid also showed that the PI3K/Akt signaling pathway was involved in this radiation induced MMP-9 expression. Moreover, NFκB decoy oligodeoxynucleotide suppressed radiation enhanced MMP-9 promoter activity completely. PI3K/ Akt chemical inhibitors inhibited radiation induced NF κB- driven luciferase promoter activity. Taken together, our results indicated that sublethal dose of radiation could enhance HCC cell invasiveness by MMP-9 expression through the PI3K/Akt/NFκB signal transduction pathway