USP4 and cancer: Using human lung adenocarcinoma epithelial cell line, A549, Xiao et al. found the tumor-suppressing role of USP4 may result from its negative regulation of NF-κB signaling pathway through targeting K63-linked polyubiquitination of TRAF2 and TRAF6 and inactivate the two proteins, then inhibiting TNFα-induced cancer cell migration [43].