Prognostic significance of Bcl-xL gene expression in human colorectal cancer

Bcl-xL is a pro-survival member of the Bcl-2 family that plays indispensable roles in regulating cell survival and apoptosis. It is overexpressed in many malignant tumors including colorectal cancer (CRC). However, it is still unclear if Bcl-xL can be used as an independent molecular marker for predicting the prognosis of CRC patients. In this study, reverse transcription-PCR assay was performed to detect the expression of Bcl-xL mRNA in CRC and corresponding non-tumor colon tissues. Immunohistochemistry was performed to detect the immunolocalization of Bcl-xL protein in sixty-eight primary CRC tissue samples. The association between Bcl-xL protein expression and clinicopathological factors of CRC patients was analyzed and the survival was assessed by the Kaplan–Meier method and proportional hazards model. The averaged level of Bcl-xL mRNA expression in CRC tissues (0.85 ± 0.13) was significantly higher than that in non-tumor colon tissues (0.08 ± 0.02). Immunohistochemical staining showed that the Bcl-xL protein was mainly located in the cytoplasm of tumor cells. The level of Bcl-xL protein expression was closely correlated with tumor differentiation (P = 0.002), lymph node metastasis (P = 0.010), venous permeation (P = 0.004), and Dukeʹs classification (P = 0.021). Furthermore, patients with high Bcl-xL expression showed poorer overall survival than those with low Bcl-xL expression (P = 0.016). Univariate and multivariate analysis indicated that the status of Bcl-xL protein expression might be an independent prognostic marker for CRC patients (P = 0.032). Taken together, immunohistochemical assessment of status of Bcl-xL protein may offer a valuable approach for predicting survival after curative surgery for colorectal cancer.