| Tumor is the most important disease that threatens the health of human being at present. Colonic cancer is the most common tumor in digestive system, and in our country it has been the second most frequent tumor in the alimentary tract.The prognosis of colonic cancer is still extremely poor in these ten years. The reason is that the chance of cure exists only for a minority of patients with locally limited and surgically resectable tumor. However, parts of patients who are radically treated by surgical curative resection will suffer from an incurable local relapse, distant metastases, and peritoneal carcinosis and 25% from liver metastasis. The overall 5-year survival rate is only 40% after the surgery. Therefore the prognosis of colonic cancer patients is up to the metastasis, and it will extend survival rate of the patients, quality of life and the outcome of therapy through inhibiting the incidence of metastasis.In vivo in the progress of invasion and metastasis of tumor, the relationship between tumor invasion and stromal-derived Hepatocyte growth factor (HGF) have received much attention and HGF can influence the action of cancer cells.Hepatocyte growth factor (HGF) originally identified and cloned as a potent mitogen for hepatocytes. HGF composes of a 69 kD H-chain and a 34 kD L-chain. HGF is a multi-functional molecule that exhibits mitogenic, motogenic, morphogenic, and angiogenic activities. In malignant tumors, HGF plays a role in tumor–stromal interactions that confer invasive, angiogenic, and metastatic potentials through c-Met receptor tyrosine kinase. c-Met, the HGF receptor, is the proto-oncogene and is expressed in a wide variety of carcinoma cells. As the HGF-c-Met receptor system is involved in the malignant behavior of cancer, HGF-c-Met coupling and subsequent activation of c-Met may play a definitive role in invasion and metastasis of cancer. Based on above notions, inhibition of c-Met receptor activation may possibly become a therapeutic strategy in cancer. NK4 is composed of N-terminal 447 amino acids of the H-chain of HGF. This molecule has the ability to bind specifically to the c-Met receptor without inducing any tyrosine phosphorylation of c-Met, resulting in prevention of HGF-mediated activities such as cancer cell proliferation and migration both in vitro and in vivo. As an angiogenesis inhibitor, NK4 not only antagonizes HGF-induced angiogenesis but also abrogates the angiogenesis induced by other angiogenic inducers such as basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF). Considering these two-way inhibitory effects, gene therapy using NK4 seems to be an ideal potential therapy for treatment of patients with cancer. Thereafter, several basic research studies have revealed that the competitive inhibitory effects of NK4 on HGF-c-Met interactions resulted in suppression of malignant behavior in a wide variety of cancer cells including stomach, pancreas, lung, breast, colon, gallbladder, prostate, and ovary.The gene therapy is considered to be the fourth strategies in the treatment of cancer followed surgery, radiotherapy and chemiotherapy. As a gene transferring vector, adenovirus has many virtues and now is widely used in gene therapy for cancer.In our experiments, we firstly construct a non-replicating recombinant adenovirus encoding NK4 gene and term it rvAdCMV/NK4. The replication-deficient adenovirus vectors used in this study are E1a-, partially E1b-, and partially E3 deleted vectors based on the human adenovirus type 5 and belong to the first generation of adenoviral vector. We test recombinant adenoviruses on the human colonic cancer line LS174T in vitro and in vivo.1. Construction and identification of recombinant adenovirus expressing NK4 We first obtained NK4 fragment through PCR from the plasmid containing complete HGF cDNA, then the AdEasy adenoviral vector system was used in this experiment. We constructed recombinant adenovirus expressing NK4 through homologous recombination performed in bacteria and term...
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