Abstract 2472: Small-molecule-induced reactivation of mutant p53 in cancer cells.

Abstract

Abstract The tumour suppressor p53 inhibits tumour growth by induction of cell cycle arrest, apoptosis or senescence. However, p53 mutations occur frequently in human tumours. About one-third of the mutations lower the melting temperature of the protein and cause rapidly unfolds at body temperature. The p53 cancer mutant Y220C is an excellent paradigm for rescuing the function of conformationally unstable p53 mutants because it has a unique surface crevice that can be targeted by small-molecule stabilizers. Through biophysical and cell-based screening, we identified a compound, PK7088, which binds to the Y220C mutant with a dissociation constant of 140 μM. The binding mode of this compound class was determined by X-ray crystallography. In cancer cells carrying the Y220C mutant, PK7088 increased the amount of folded mutant protein with wild-type like conformation, as monitored by immunofluorescence, and restored its transcriptional functions. It induced p53-Y220C-dependent growth inhibition, cell-cycle arrest and apoptosis. This was confirmed by p53 silencing. Most notably, PK7088 increased the expression levels of p21 and the proapoptotic NOXA protein. PK7088 worked synergistically with Nutlin-3 on up-regulating p21 and NOXA expression, whereas Nutlin-3 on its own had no effect, consistent with its mechanism of action. PK7088 also restored non-transcriptional apoptotic functions of p53 by triggering nuclear export of BAX to the mitochondria. These findings provide novel insights into p53 mutant reactivation and may facilitate the development of more potent and selective small-molecule drugs for specific mutant p53 rescue. Citation Format: Xiangrui Liu, Rainer Wilcken, Andreas Joerger, Irina Chuckowree, John Spencer, Alan Fersht. Small-molecule-induced reactivation of mutant p53 in cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2472. doi:10.1158/1538-7445.AM2013-2472