TP53 and neoplasm: Overall, MDM2-p53 antagonists have been shown to activate the p53 pathway, inducing p53-dependent apoptosis and sensitizing tumor cells to cytotoxic and other molecular targeted therapies whilst inducing a reversible cell cycle arrest in normal cells (reviewed by (Van Maerken et al., 2009a); (Vassilev, 2004; Shangary et al., 2008; Korotchkina et al., 2009; Cheok et al., 2011)).