| Colorectal cancer is one of the most prevevant cancers in digestive system. Surgical resection, chemotherapy and radiotherapy are the current curative treatment, althouth with not perfect effect due to the liver metastasis. Five-year survival rate after operation is 50～60% in the past 40 years. About 20～40% patients have synchronous hepatic metastasis when diagnosed, and of the patients treated with hepatectomy about 30～50% have a recurrence in the liver. More than 50% of the deaths from colon cancer involved liver metastasis. Despite intense study of the metastatic process, many aspects of its molecular genetic basis remain unclear. Improved understanding of the molecular events underlying metastasis is crucial for development of new methods for early detection and impoving the survival of rate in colorectal cancer.Gene therapy is the insertion of genes into an individual's cells and tissues to treat deseases, such as hereditary disease where deleterious mutant alleles are replaced with functional ones. Although the technology is still in its infancy, it has been used with some success. Scientific breakthroughs continue to move gene therapy toward mainstram medicine. RNAi is an RNA-dependent gene silencing process that is initiated by short double-stranded RNA molecules in a cell's cytoplasm. Nowadays, RNAi technology has been widely used in many hot research areas such as gene function identification, and regulation of post-transcription, improviding new ideas for gene therapy of many diseases.In the first part, we screened differentially expressed gene in colon cancer patients with and without liver metastasis by gene-chip, and verified its expression by real-time PCR. Both gene-chip technology and RT-PCR results showed that RNA binding protein-CUGBP1 is the most differentially expressed gene between these two groups.In the second part, we designed three RNA interference fragment specific to CUGPB1, constructed RNAi-CUGBPl lentivirus vector and pEGFP-N1-3FLAG-CUGBP1 overexpressing vector, and co-transfected these two vectors into 293T cells in order to screen fragment with interference effect. Fluorescent microscopy results showed that the constructed lentivirus vector can transfect 293T cells with high efficency; Western blot results showed that, of the three siRNA inference fragments, target 2 (GATTGAAGAATGCCGGATA) has significant inhibitive effect; moreover, the lentivirus with CUGBP1 siRNA fragment was enveloped.In the last part, human colorectal cells, SW480 and DLD-1 cells, were infected by enveloped lentivirus. qPCR and Western blot results demonstrated thet lentivirus with CUGBP1 interference has apparent inhibitive effects on CUGBP1 expression. Results from MTT assay, colony forming assay, FACS, and invasion experiment revealed that cell proliferation was repressed, capability of invasion and metastasis as well as rate of colony forming reduced.In all, in the present study, we screen significantly elevated expressed CUGBP1 gene in colorectal cancer patients with liver metastasis; siRNA-CUGBPl can inhibit the level of CUGBP1 mRNA and protein in colon cancer cells SW480 and DLD-1; proliferation of SW480 and DLD-1 cells infected by siRNA-CUGBP1 lentivirus was inhibited, the colony forming rate was reduced, and cell cycle was arrested in G1 phase. At the same time, the capability of invasion and metastasis was significantly inhibited...
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