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Objective: To study the effect of RhoE on the transcriptional regulation of cd44 and in vivo tumorigenicity of nude mice., Methods: cd44 promoter was amplified from human embryonic kidney HEK293 cells with PCR and insert into Dual-Luciferase Reporter plasmid pGL3-Basic. After confirmed with sequence analysis, the generated recombinant was transfected into SW480 and LoVo cells to monitor their activity. Colon cancer SW480 and LoVo cells were cotransfected with pGL3-CD44 promoter along with pcDNA3. 1-RhoE and pcDNA3. 1 respectively. SW480 and LoVo cells were stably transfected with pcDNA3. 1-RhoE and the control group and were inoculated into nude mice to observe tumor growth. Immunohistochemistry assay was applied to observe the morphology of tumor cells and the expression of CD44 molecules., Results: The cd44 promoter sequence was amplified correctly, Dual-Luciferase Reporter Assay showed that the constructed reporter gene has promoter activity. The expression of cd44 promoter sequence containing reporter gene in pcDNA3. 1-RhoE expression positive LoVo cells was inhibited; HE staining demonstrated that the pcDNA3. 1-RhoE transfected tumor cells was significantly smaller than that in the control group, and consistent size and shape tumor cells were observed but no tumor giant cells, the corresponding volume of the tumor nuclei were also small., Conclusion: RhoE could partially reverse the malignant biological behavior of tumors by inhibiting the transcriptional regulation of cd44 promoter.

Objective: To determine the effect of cell division cycle42 (Cdc42) on the multidrug resistance of oxaliplatin-resistant human colon cancer cells., Methods: The protein expression levels of Cdc42 in oxaliplatin-resistant colon cancer cells and parental cells were examined with Western blot. pDEST26-His-Cdc42 was transfected by lipofectamine 2000 into SW480 and Colo320 cells with low expression of Cdc42. Cdc42 siRNA was transfected by lipofectamine 2000 into SW480/L-OHP and Colo320/L-OHP cells with high expression of Cdc42. The expression of Cdc42 in these cell lines were examined by Western blot and RT-PCR 48 hours after transfection. The sensitivity of colon cancer cells to antitumor drugs was evaluated using CCK-8 assay. The concentration of each drug that caused a 50% reduction in the numbers of cells (IC50) was calculated. The expression of P-gp, MRP1 in SW480/Cdc42 and Colo320/ Cdc42 cells were examined with Western blot., Results: Cdc42 was over-expressed in the SW480/L-OHP and Colo320/L-OHP cell lines. Over-expression of Cdc42 significantly enhanced the resistance of colon cancer cells to multiple antitumor drugs and up-regulated the expression of P-gp and MRP1., Conclusion: Cdc42 enhances the resistance of colon cancer cells to several antitumor drugs. It might become a potential target for reversing multidrug resistance of colon cancer.

Objective: To observe the affect of Small interfering RNA Rac1b (Si-Rac1b) on the malignant biological behaviors of colorectal cancer cell including the proliferation, migration, invasion and apoptosis of the cells., Methods: Mediated by lipofectamine 2000, Si-Rac1b was transfected into colorectal cancer cell line SW1116 (with overexpression of Rac1b). The expression of Rac1b was detected by Western blotting and RT-PCR. The CCK-8 assay was used to analyze the cell proliferation, the Wound-healing assay and invasion assay were respectively applied to analyze the cell migration and invasion, and the Hoechst 33258 was used to evaluate the apoptotic index., Results: Si-Rac1b can knock down the Rac1b but not Rac1 both in the level of mRNA and protein. In addition, Si-Rac1b could singnificantly facilitate the cell proliferation, migration, invasion and control the cell apoptosis., Conclusion: Si-Rac1b could partically reverse the malignant phenotypes of colorectal cancer cell.