Supplementary Material for: Phosphorylation of STAT3 in Undifferentiated Pleomorphic Sarcoma Is Correlated with a Favorable Prognosis

Objective: The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway plays a role in various biological processes. Phosphorylated STAT3 (p-STAT3) functions as a transcriptional factor, and suppressor of cytokine signaling 3 (SOCS3) is a potential inhibitor of STAT3. Here, we analyzed the status of the JAK-STAT pathway in undifferentiated pleomorphic sarcoma (UPS). Methods: We performed immunohistochemistry in 79 samples of UPS and Western blotting in 10 frozen samples. We also examined alterations in protein expression in the JAK-STAT pathway after the inhibition of phosphorylated Akt (p-Akt) or extracellular signal-regulated kinase (p-Erk) in vitro. Results: Immunohistochemically, p-STAT3 and SOCS3 were positive in 59.7 and 55.8%, respectively. Positivity for p-STAT3 was significantly correlated with a better prognosis (p = 0.0006) and negatively with SOCS3 expression (p = 0.0223). Positivity for SOCS3 was significantly correlated with a worse prognosis (p = 0.0001). Western blotting analysis revealed that p-STAT3 expression was lower in tumor than in normal tissue. In vitro results demonstrated that there was no detectable change in the expression of p-STAT3 regardless of the status of p-Akt or p-Erk. Conclusion: p-STAT3 may be a useful prognostic factor for UPS.