Constitutive activation of Stat3 signaling pathway in human colorectal carcinoma

AIM: Signal transducers and activators of transcription (STATs) are a family of transcription factors activated in response to cytokines and growth factors. Constitutive activation of Stat3 has been observed in a growing number of tumor-derived cell lines, as well as tumor specimens from human cancers. The purpose of this study was to investigate the expression of p-Stat3, activated form of Stat3, and its downstream mediators including cyclin D1 and Bcl-xL in colorectal carcinoma (CRC), and to explore the possible mechanism of Stat3 signaling pathway in the tumorigenesis of colorectal carcinoma. METHODS: Tissue samples from 45 patients of primary colorectal carcinoma were selected for studying Stat3 signaling pathway protein expression. Western blot analysis was used to measure the expression of p-Stat3, cyclin D1, and Bcl-xL proteins in colorectal carcinomas. Furthermore, the expression patterns of these proteins were analyzed for their distribution at the cellular level by immunohistochemical staining of the tissues. RESULTS: Protein levels of p-Stat3, cyclin D1, and Bcl-xL were increased in colorectal carcinomas compared with adjacent normal mucosae (P<0.05). Elevated levels of p-Stat3 were correlated with the nodal metastasis and the stage (P<0.05). Overexpression of cyclin D1 was associated with the nodal metastasis (P<0.05). There was also a significant correlation between the expressions of p-Stat3 and cyclin D1 (r=0.382, P<0.05). CONCLUSION: Constitutive activation of Stat3 may play an important role in the tumorigenesis of colorectal carcinoma, and the detailed mechanism of Stat3 signaling pathway in CRC deserves further investigation.