mTOR Signaling Combined with Cancer Stem Cell Markers as a Survival Predictor in Stage II Colorectal Cancer

Purpose: Wnt and mammalian target of rapamycin (mTOR) are major molecular signaling pathways associated with the development and progression of tumor, as well as the maintenance and proliferation of cancer stem cells (CSCs), in colorectal cancer (CRC). Identifying patients at risk of poor prognosis is important to determining whether to add adjuvant treatment in stage II CRC and thus improve survival. In the present study, we evaluated the prognostic value of Wnt, mTOR, and CSC markers as survival predictors in stage II CRC. Materials and Methods: We identified 148 cases of stage II CRC and acquired their tumor tissue. Tissue microarrays for immuno-histochemical staining were constructed, and the expressions of CD166, CD44, EphB2, beta-catenin, pS6 were evaluated using immunohistochemical staining. Results: The expressions of CD166 (p=0.045) and pS6 (p=0.045) and co-expression of pS6/CD166 (p=0.005), pS6/CD44 (p=0.042), and pS6/CD44/CD166 (p=0.013) were negatively correlated with cancer-specific survival. Cox proportional hazard analysis showed the combination of CD166/pS6 [hazard ratio, 9.42; 95% confidence interval, 2.36-37.59; p=0.002] to be the most significant predictor related with decreased cancer-specific survival. In addition, co-expression of CD44/CD166 (p=0.017), CD166/beta-catenin (p=0.036), CD44/beta-catenin (1=0.001), and CD44/CD166/beta-caten in (p=0.001) were significant factors associated with liver metastasis. Conclusion: Specific combinations of CSC markers and beta-catenin/mTOR signaling could be a significant predictor of poor survival in stage II CRC.