Cytotoxicity of TRAIL on colon cancer cell line SW480

Effect of transfected DPC4 gene on angiogenesis of colon carcinoma

AIM: To study the mechanism of transfected DPC4 gene on angiogenesis.

METHODS: SW620 cells were transfected with PcDNA3.1-DPC4 plasmid by using lipofectamine transfecting technique. Expression of Smad4 in DPC₄⁺-SW620 cells was observed by Western blot. The expression of VEGF protein in the cell supernatant was detected by ELISA, and VEGF mRNA by RT-PCR. The model of nude mice inoculated with DPC₄⁺-SW620 cells was established by injecting into flank subcutaneously. The expression of VEGF protein and the microvessel density of tumor tissue in nude mice were detected by immunohistochemical staining (SP method).

RESULTS: DPC₄⁺-SW620 cells expressing Smad4 were harvested; Smad4 protein showed stronger expression in SW620 cells transfected with PcDNA-DPC4 plasmid than that in not-transfected SW620 cells and SW620 cells transfected with blank plasmid, and the positive signal was localized in cytoplasm and nucleus, mainly in cytoplasm; There were lower expression of VEGF protein and mRNA in DPC₄⁺- SW620 cells than that in SW620 cells and PcDNA-SW620 cells (P < 0.05); The model of nude mice inoculated with colon carcinoma cells was established successfully. The tumors of nude mice inoculated with DPC₄⁺-SW620 cells growed more slowly than that inoculated with SW620 cells and PcDNA-SW620 cells. The volume and mass of tumors in nude mice inoculated with DPC₄⁺-SW620 cells were smaller and lighter than those with SW620 cells and PcDNA- SW620 cells (P < 0.05). The expression of VEGF and the microvessel density in DPC₄⁺-SW620 cells were lower than those in SW620 cells and PcDNA-SW620 cells (P < 0.05).

CONCLUSION: The DPC4 gene can suppress the growth of the tumors in nude mice inoculated with DPC₄⁺-SW620 cells; The inhibitory effect of DPC4 on colon carcinoma may be partly mediated by suppressing angiogenesis of tumor.