Expressional STAT3/STAT5 Ratio is an Independent Prognostic Marker in Colon Carcinoma

Background. Signal transducer and activator of transcription proteins (STATs) are crucial regulators of cell growth and differentiation; however, their specific prognostic impact in human colon cancer has only been studied to limited extent. We aimed to assess the prognostic significance of specific STAT expression patterns in colon carcinoma. Methods. Protein expression patterns of activated STAT1, STAT3, STAT4, and STAT5 in human colon carcinoma tissue and corresponding healthy mucosa (n = 104) were assessed using multiplex bead-based immunoassay technologies. Expression patterns were correlated with clinical and survival data. Immunohistochemistry was performed to assess spatial expression of STAT3 and STAT5. Results. STAT3 was underexpressed whereas STAT4 and STAT5 were overexpressed in colon carcinoma tissue. Primary tumors from patients with distant metastases (M1) displayed significantly increased expression of STAT1 and STAT3 but decreased expression of STAT4 and STAT5. Increased tumor expression of STAT1 or STAT3 was associated with impaired patient survival, whereas increased expression of STAT4 or STAT5 correlated with improved survival. Multivariate analysis identified an increased STAT3/'STAT5 expressional ratio as an adverse prognostic marker in colon cancer patients. Conclusions. The tumor progression-associated transcription factors STAT3, STAT4, and STAT5 are differently expressed in colon carcinoma tissue and colon mucosa. Moreover, the STAT3/'STAT5 expression ratio is an independent prognostic marker in colon cancer patients.