Objective:To explore the roles of mammalian target of rapamycin (mTOR) and the activated mTOR (phosphorylated mTOR,p-mTOR) in the development and progression of colorectal cancer,and to discuss the clinical significance.Methods:The expression of mTOR and p-mTOR in 185 colorectal cancer specimens and the corresponding adjacent tissues were evaluated by tissue microarray and immunohistochemistry,and the relationship between the expression and the age,sex,invasion depth(T stage),lymph metastasis,TNM stage and differentiation degree was analyzed.Results:Diffused expression of mTOR and hardly any expression of p-mTOR were found in the adjacent tissues.The expression of mTOR and p-mTOR was obviously stronger in the colorectal cancer tissues compared with that in the adjacent tissues.The over-expression rates of mTOR and p-mTOR in colorectal cancer were 45.9% and 42.2%,respectively.There was no significant correlation of mTOR and p-mTOR over-expression with age,sex(P>0.05); the over-expression of mTOR was correlated with the differentiation degree (P<0.05),but not with the invasion depth (T stage),TNM stage,or lymph metastasis (P>0.05).The correlation of p-mTOR over-expression with the invasion depth (T stage),lymph metastasis and TNM stage was significant (P<0.05),but that with the differentiation degree was not significant (P>0.05).Conclusion:Over-expression of p-mTOR is closely associated with the malignant phenotype of colorectal cancer.It is also indicated that p-mTOR may be involved in the development and progression of colorectal cancer.