Prognostic significance of pSTAT3 expression in feline mammary carcinomas

Feline mammary carcinomas (FMCs) have a highly malignant and metastatic behavior and are associated with a poor prognosis. There is a need to identify new effective therapies for FMC. Signal transducer and activator of transcription 3 (STAT3) is activated in various human and animal tumors. It has been proposed as a potential prognostic marker and therapeutic target in human breast cancer (HBC). Given the similarities between HBC and FMCs, we hypothesized STAT3 expression in FMCs may be prognostically significant. In this study, 60 FMC samples were immunohistochemically evaluated for the expression of total STAT3 (tSTAT3), phosphorylated STAT3 (pSTAT3), and Ki-67. The pSTAT3 and Ki-67 indexes were calculated, and their associations with clinicopathological features, as well as tumor-specific survival (TSS), were investigated. Receiver operating characteristic curves were generated to determine the cutoff values for pSTAT3 and Ki-67 using Youden's index as the criterion. All FMCs positively immunolabeled for tSTAT3 and pSTAT3. Significant associations were observed between the pSTAT3 index and the WHO clinical stage, lymph node metastasis, and lymphovascular invasion. However, no significant associations were established with any other factors. Using the cutoff value to classify the pSTAT3 index, the higher pSTAT3 index (>25.2%) was significantly associated with decreased TSS (P = .00570). No significant associations were established between the Ki-67 index and any of the factors. Also, a significant positive association was observed between the pSTAT3 and Ki-67 indexes (P = .0001). This significant association with TSS underscores the potential role of pSTAT3 as a prognostic marker in FMC.