Overactivation of Signal Transducer and Activator of Transcription 3 in Canine Hepatocellular Carcinoma and Its Prognostic Significance

Phosphorylated signal transducer and activator of transcription 3 (pSTAT3), which is related to anti-apoptosis, cellular proliferation, invasion and migration of tumours, has prognostic significance in malignant tumours in humans as well as in canine melanoma. However, the significance of pSTAT3 in canine liver tissues has not yet been evaluated. This study's objective was to compare its expression in canine normal, non-neoplastic hepatic disease and hepatocellular carcinoma (HCC) tissues by immunohistochemical analysis. Furthermore, the association between pSTAT3 immunostaining and clinicopathological factors was investigated. Overall, 68 canine liver tissues, including 10 normal liver tissues, 30 non-neoplastic hepatic disease tissues and 28 HCC tissues were examined, revealing distinct differences in pSTAT3 immunostaining among the groups. (p < 0.001). Additionally, high pSTAT3 immunostaining was significantly associated with increased tumour size (5 > cm) (p = 0.041), and metastasis (p = 0.046). Furthermore, Kaplan-Meier survival curve analysis revealed a correlation between high pSTAT3 immunostaining and poor disease-free survival (p = 0.013) and overall survival (p = 0.011). These findings suggest that overactivation of STAT3 is associated with poor prognosis in canine HCC. Therefore, pSTAT3 is considered a potential prognostic marker and therapeutic target for canine HCC.