Roles of STAT3 and STAT Family Proteins and Their Signaling Pathways in Thyroid Cancer

Signal transducers and activators of transcription (STAT) proteins, which operate via canonical and non-canonical mechanisms, are critically implicated in thyroid tumorigenesis. This review integrates their multifaceted roles in thyroid cancer. STAT3 acts as a “double-edged sword”: hyperactive STAT3 drives metastasis and BRAF inhibitor resistance in advanced carcinomas, yet paradoxically acts as a tumor suppressor by restraining the Warburg effect via non-canonical mitochondrial localization. Clinically, preserved nuclear STAT3 independently predicts a favorable prognosis and is inversely correlated with TERT promoter mutations, offering a biological modifier for clinical risk stratification. Furthermore, STAT1 regulates differentiation via the IGF2BP2-m⁶A axis, STAT5 drives proliferation upon release from TRβ suppression, and STAT6 confers chemoresistance. While novel direct STAT3 inhibitors (e.g., TTI-101) and rational combinations with immune checkpoint inhibitors or STING agonists show promise in overcoming refractory disease, the intricate dual functionality of STAT family proteins demands rigorous biomarker-guided precision medicine approaches.