p-STAT3 expression in breast cancer correlates negatively with tumor size and HER2 status.

Although some studies have reported the expression and clinical significance of phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in breast cancer tissues, it is still controversial whether p-STAT3 play a role in promoting or suppressing cancer. Here, we used immunohistochemistry analysis to explore expression of p-STAT3 in 407 cases of breast cancer, and analyzed the relationship between p-STAT3 expression and the clinicopathological characteristics and prognosis of breast cancer patients. Positive p-STAT3 expression was seen in 112 cases (27.5%) of breast cancer. p-STAT3 expression was negatively correlated with tumor size, tumor stage and human epidermal growth factor receptor 2 (HER2) status, and the positive rate of p-STAT3 was lowest in HER2-enriched subtype breast cancer (15.3%), while other subtypes were luminal B (23.0%), luminal A (30.2%), and triple-negative breast cancer (TNBC) (37.5%). Logistic regression model multivariate analysis showed that the independent correlation factor of p-STAT3 expression in breast cancer was tumor size (OR = 0.187, 95% CI = 0.042-0.839, P = .029) and HER2 status (OR = 0.392, 95% CI = 0.216-0.710, P = .002). In this study, no clear relationship was observed between patients' prognosis and expression of p-STAT3. Therefore, we suggest that p-STAT3 expression in breast cancer is negatively correlated with tumor size and HER2 status, but appears to have no effect on survival.