MDM2 and neoplasm: As a transcription factor, p53 exerts tumor-suppressive effects by directly binding to specific DNA sequences to activate or repress the transcription of target genes, such as MDM2 (Barak et al., 1993), p21 (el-Deiry et al., 1993), NOXA (Oda et al., 2000), PUMA (Nakano and Vousden, 2001), and RPS27L (He and Sun, 2007; Li et al., 2007) [for review, see (Fischer, 2017)].