STAT3 expression, molecular features, inflammation patterns, and prognosis in a database of 724 colorectal cancers.

PURPOSE STAT3 is a transcription factor that is constitutively activated in some cancers. It seems to play crucial roles in cell proliferation and survival, angiogenesis, tumor-promoting inflammation, and suppression of antitumor host immune response in the tumor microenvironment. Although the STAT3 signaling pathway is a potential drug target, clinical, pathologic, molecular, or prognostic features of STAT3-activated colorectal cancer remain uncertain. EXPERIMENTAL DESIGN Utilizing a database of 724 colon and rectal cancer cases, we evaluated phosphorylated STAT3 (p-STAT3) expression by immunohistochemistry. The Cox proportional hazards model was used to compute mortality HR, adjusting for clinical, pathologic, and molecular features, including microsatellite instability (MSI), the CpG island methylator phenotype (CIMP), LINE-1 methylation, 18q LOH, TP53 (p53), CTNNB1 (β-catenin), JC virus T-antigen, and KRAS, BRAF, and PIK3CA mutations. RESULTS Among the 724 tumors, 131 (18%) showed high-level p-STAT3 expression (p-STAT3-high), 244 (34%) showed low-level expression (p-STAT3-low), and the remaining 349 (48%) were negative for p-STAT3. p-STAT3 overexpression was associated with significantly higher colorectal cancer-specific mortality [log-rank P = 0.0020; univariate HR (p-STAT3-high vs. p-STAT3-negative): 1.85, 95% CI: 1.30-2.63, P(trend) = 0.0005; multivariate HR: 1.61, 95% CI: 1.11-2.34, P(trend) = 0.015]. p-STAT3 expression was positively associated with peritumoral lymphocytic reaction (multivariate OR: 3.23; 95% CI: 1.89-5.53, P < 0.0001). p-STAT3 expression was not associated with MSI, CIMP, or LINE-1 hypomethylation. CONCLUSIONS STAT3 activation in colorectal cancer is associated with adverse clinical outcome, supporting its potential roles as a prognostic biomarker and a chemoprevention and/or therapeutic target.