USP4 and cancer: On the other hand, quite a few studies discovered that USP4 exerts suppressive functions in particular types of cancer (Xiao et al., 2012; Hou et al., 2013; Liang et al., 2013, 2019; Li Y. et al., 2016; Yao et al., 2017; Zhong et al., 2018; Lai et al., 2020).