USP44 and neoplasm: Furthermore, TGF-β, as The Smad signaling pathway, activates ubiquitin specific peptidase 44 (USP44), which can stabilize Foxp3 protein and eliminate ubiquitination modifications of K3 linked ubiquitin chain connections; the combined expression of USP44 and USP7 stabilizes Foxp3 expression, and the absence of USP44 in Treg cells can promote anti-tumor immunity and impede tumor growth (19).