USP4 and gastric cancer: USP4 enhances the Warburg effect and promotes the growth of GC cells by deubiquitinating the M2 isoform of pyruvate kinase (75), regulating levels of phosphatases of regenerating liver-3, and activating the nuclear factor-kappa B (NF-κB) signaling pathway, thereby facilitating GC proliferation and metastasis (76).