USP4 and breast carcinoma: Specifically, up‐regulated USP4 potentiated the growth and invasion of colorectal cancer though deubiquitination and stabilization of PRL‐3.19 In addition, USP4 transduced Akt activation to TGF‐β signalling by deubiquitinating and stabilizing TGF‐β type I receptor, thus augmented breast cancer cell invasion and migration.33 These studies demonstrate USP4 as a powerful tumour promoter and an important determinant for canonical oncogenic signalling.