Abstract: Objective:To examine the expression of the signal transducer and activator of transcription- 5 activation ( phosphory-lated STAT 5, P-STAT 5 ) and apoptosis inhibition factor survivin in colon adenocarcinoma tissues, and to determine the correlation be -tween their expression levels and clinicopathologic factors. Methods:S-P immunohistochemical staining was used to detect the expres-sion of P-STAT5 and survivin among specimens from 116 cases of colon adenocarcinoma and the relationship between expression of these two proteins and various clinicopathologic parameters, including overall survival, were analyzed. Results: The positive expres-sion rate of P-STAT5 was 61.2% among the samples, which were related to the depth of tumor invasion (P = 0.018 ) and clinical stages (tumor-node-metastasis stage, TNM stage) ( P = 0.038 ), but not to age, sex, tumor size, primary site, and differentiation, as well as the incidence of lymph node metastasis and distant metastasis ( P > 0.05). The positive expression rate of survivin was 62.9%. No associa-tions were found between survivin expression and the various clinicopathologic parameters ( P > 0.05). The cases with high expression levels of P-STAT 5 and survivin had high degrees of malignancy and poor prognosis (P = 0.015 and P = 0.025 ). Only the TNM stage was the independent predictor of poor prognosis among the 116 cases of colon adenocarcinoma (P = 0.005 ). P-STAT5 and survivin ex-pression was observed in the cytoplasm of the colon adenocarcinoma cells. There were statistically significant correlations between P-STAT5 and survivin ( r = 0.268, P = 0.004 ). Conclusion:Both P-STAT5 and survivin are overexpressed in colon adenocarcinoma, and this overexpression seems to be an early event in the development of colon adenocarcinoma. The overexpression of P-STAT 5 and survivin plays an important role in tumor development and progression. Moreover, the expression of these two gene products is positive -ly correlated. P-STAT 5 and survivin might share a common molecular pathway. P-STAT5 might contribute to tumorigenesis through the
upregulation of survivin expression, thereby preventing cell apoptosis, and promoting cell transformation. Determination of the level of P-STAT5 expression may be useful in predicting the prognosis of patients with colon adenocarcinoma. The molecular basis of such a re -lationship should be investigated further