The role of hgf signalling pathway in the regulation of cellular responses induced by hypoxia and radiation in hepatocellular carcinoma cell lines

Hypoxic microenvironment in liver tissue during hepatocellular carcinogenesis (HCC) activates hepatocyte growth factor (HGF) signaling pathway which is important for the hepatocyte growth and differentiation. In addition to being involved in carcinogenesis, HGF also stimulates resistance to radiotherapy.The induction of HGF/c-Met signalling pathway might be one of the mechanisms in order to develop resistance against hypoxia and radiation in HCC cells. We therefore analysed the putative protective effect of HGF/c-Met signalling pathway from the hypoxic stress and radiation. Hypoxia jars and gamma irradiation were used for hypoxia and irradiation treatment, respectively. We analyzed the survival of HCC cells lines by MTT/LDH viability assays. Alterations of the cell motility were measured by Boyden Chambers. The changes in expression level of c-Met, HIF1 and their targets were evaluated by RT-PCR and Western Blotting.Our results showed that hypoxia or radiation treatment did not alter the viability of HCC cells in short course, but it increased the cellular motility. Intriguingly, HGF addition to system further increased these cellular responses. Before giving radiation to HCC cells, treatment of hypoxia and /or HGF promoted the cellular survival for long term course. HIF activation and its target genes VEGF, EPO and integrins, that are mediating the survival responses, and MT1-MMP and Rlip76 gene expression, which are responsible for the cellular resistancy, were up regulated.These results are showing that the activation of HGF/c-Met signalling pathway up regulates the cellular malignancy regarding with the invasion and metastasis processes. Alterations of the cellular behaviours and gene expression levels, resulted from the stimulation by hypoxia, HGF and radiation, are responsible from the HCC progression and response to therapy. Understanding of these signalling pathways could be helpful in addressing new target molecules and establishing new treatment modalities for the HCC patients.