Background:Colorectal cancer is one of the commonly seen malignant tumors in digestive system. Most patients with colorectal cancer were diagnosed in advanced stage and the prognosis is poor. Early diagnosis is crucial to improve the overall survival of patient. Currently,molecular markers for diagnosis of colorectal cancer has attracted more and more attention of the investigators. Aims:To investigate the expression and significance of Rab5A in colorectal cancer. Methods:Colorectal cancerous tissue and the paired para-cancer noncancerous tissue of 135 patients who underwent resection for colorectal cancer were collected. Expression of Rab5A mRNA in cancerous tissue,para-cancer noncancerous tissue,colon cancer cell lines HCT116,HT-29,LoVo and SW480 and normal colonic epithelial cell line NCM460 was determined by real-time PCR. Protein expression of Rab5A in cancerous tissue and para-cancer noncancerous tissue of 4 patients was detected by Western blotting. Protein expression of Rab5A in cancerous tissue of 110 patients was detected by immunohistochemistry. Correlations between expression of Rab5A and clinicopathological characteristics and prognosis of colorectal cancer were analyzed. Results:Expression of Rab5A mRNA in cancerous tissue was significantly higher than that in para-cancer noncancerous tissue(P=0. 003). Expression of Rab5A mRNA in colon cancer cell lines HCT116, HT-29,LoVo and SW480 was significantly higher than that in normal colonic epithelial cell line NCM460(P﹤0. 05). Protein expression of Rab5A in cancerous tissue was significantly higher than that in para-cancer noncancerous tissue. In 110 cancerous tissues,51(46. 4%)had low expression of Rab5A and 59(53. 6%)had high expression of Rab5A. Protein expression of Rab5A was significantly correlated with tumor size,serum carcinoembryonic antigen(CEA)level and TNM stage(P =0. 008;P =0. 002;P =0. 010). 3-year survival rate of patients with high Rab5A expression was significantly lower than that of patients with low Rab5A expression(52. 1% vs. 77. 5%,P ﹤0. 05). Rab5A protein expression,serum CEA level and TNM stage were correlated with the prognosis of patients with colorectal cancer( P =0.009;P =0. 006;P =0. 017)and were independent factors for prognosis(P =0. 026;P =0. 032;P=0. 014). Conclusions:Expression of Rab5A correlates with the malignant behavior of colorectal cancer and its high expression indicates a poor prognosis. Rab5A might be used as a predictor for prognosis of colorectal cancer.