Screening Of C-Met-mediated Anti-tumor Leading Molecule And Its Blocking Effects On HGF/c-Met Signaling Pathway

Tumor invasion and metastasis are the major causes of death among cancer patients. The mechanisms of tumor metastasis, however, are not fully understood yet. Recent studies have been focused on searching for the key molecules associated with tumor metastasis. This may help to identify the putative therapeutic targets for anti-tumor metastasis and the biological markers for early diagnosis of cancer patients.Tumor metastasis is a complex process, in which many molecules are involved. 1). Upon initiation of tumor metastasis, E-cadherin, Ig super-family members, selectin and integrin are reportedly to be associated with attenuation of cell-cell adhesion, cell drop and enhanced cell-matrix adhesion. 2).HGF/c-Met and transcription factor Ets-1 activate tumor cells to secrete proteinases and their inhibitors which then promote tumor cells hydrolyze extracellular matrix (ECM) and penetrate basal lamina. 3). Tumor cells approach the target organs with the help of move factors and growth factors, among these HGF,EGF, AMF,TGF,IFN-γ,IL-1/3/6 and CD44 all play important roles during the migration and mobility of tumor cells. 4).The angiogenetic factors HGF, VEGF, bFGF, IL-8 and PDGF promote angiogenesis. Tumor cells proliferate and finally form metastases targets. HGF/c-Met signaling pathway was shown to be involved in almost the whole process of tumor metastasis whereas c-Met has been the known target for anti-tumor drug development.The target of this study is c-Met. We first established a HGF-induced MDCK cell (which over-express c-Met receptor) scatter model, with which a small molecular compound library was screened to find some compounds which may block the HGF/c-Met signaling pathway and have the potential for anti-tumor invasion or metastasis. The phage displayed peptide library will then be screened by using c-Met as a bait to find the analogue or native peptides of HGF, which can bind c-Met receptor specifically and abolish the HGF/c-Met signal transduction. In the future, the configuration of these peptides may be modified to comply with anticancer drugs for therapeutic purpose by specifically binding of the c-Met receptor on tumor cells. When we screened the small molecular compound library with the cell scatter model, a small compound named SU5416 was found accidentally. This molecule can inhibit HGF-induced MDCK cell scatter. The same result was observed when HepG2 cells were used. The binding of HGF to c-Met receptor was known to activate C-Met mediated signaling pathway, which can lead to cell scatter, invasion and the proliferation of endothelial cells and hepatocyte. We next examined whether SU5416 affected the HGF-mediated proliferation of endothelial cells and hepatocytes, and the invasion of liver cancer cells. The result showed that SU5416 significantly inhibited HGF-mediated invasion of HepG2 cells. No inhibition was observed for the EGF-mediated tumor cells invasion. We also found that SU5416 can inhibit DNA synthesis of HGF-mediated human ECV304 cells and primary cultured hepatocytes of rat. In contrast, it has no significant inhibitory function on EGF or serum-mediated cell...