TP53 and cancer: Proteolytically stable peptides havebeen shown to reside longer in the cytosol and thereby reach higherconcentrations, which facilitates successful detection., Thus, the D-peptide PMIγ, a known antagonist of MDM2 thatbinds with a Kd of 52.8 nM, was chosenas a model cargo. MDM2 is an E3 ligasethat regulates p53 levels through ubiquitination and plays a key rolein the inactivation of the apoptotic p53 pathway in many cancer types.−,  By restoring p53 activity, inhibitors of MDM2 and its homologueMDMX are potentially valuable therapeutics for cancer.