STAT3 and neoplasm: Indeed, while CD44 co-stimulation promotes the expression of FoxP3 and supports Treg function via IL-2, IL-10, and TGF-β production (193), FoxP3 has been shown to act as a co-transcription factor with STAT3 in tumor-induced Tregs to promote immunosuppressive IL-10 production (196), suggesting that functional CD44 and STAT3 cooperation is one of the main molecular mechanisms that drives Treg immunosuppressive actions.