Abstract 829: p53 dimers elicit tumor suppressive activities through an altered metabolic program

Abstract p53 is the most frequently mutated gene in human cancer. As a tetrameric transcription factor, mutation of the p53 Tetramerization Domain (TD) is a mechanism by which cancers abrogate wild-type (WT) p53 function. p53 TD mutations result in a protein that preferentially forms monomers or dimers. Although it is accepted that tetrameric p53 is required for full tumor suppressive activities, the physiological relevance of monomeric and dimeric states of p53 is not well understood. We have established the first in vivo models for hot-spot p53 TD mutants, p53R339P and p53A344D (murine), that result in monomeric and dimeric p53, respectively. These models closely resemble Li-Fraumeni Syndrome (LFS) patients with germline p53 TD alterations and will be used to characterize their physiological activities. p53R339P and p53A344D proteins failed to form tetramers. These mutants were deficient in their transactivation ability for canonical p53 target genes, and unable to induce apoptosis following IR. Both p53 TD mutant mice rescued the p53-dependent embryo lethality caused by genetic deletion of Mdm2, suggesting these are loss-of-function alleles. Monomeric p53 bearing mice succumbed mainly to thymic lymphomas (~60%), with a median survival similar to p53-/- mice (~130 days). Dimeric p53 bearing mice displayed lower incidence of thymic lymphomas (~25%) and longer survival (~180 days). Analyses of the transcriptomes elicited after DNA damage in normal thymus revealed that the p53 signaling pathway is dampened in dimeric p53 thymi. However, under basal conditions, p53 dimers upregulate a lipid metabolic program that is associated with PPAR activation. Further RNA sequencing of common metabolic tissues of the mouse (pancreas, liver, and intestine) revealed that they upregulate lipid-related metabolic programs in p53 dimer samples. This study describes, for the first time, the consequences of altering p53 tetramerization in vivo. Monomer and dimer forms of p53 do not retain most WT p53 features. p53 dimers may exert tumor suppression as seen by extended survival and tumor spectra shift. p53 dimer-specific activities on PPAR signaling and lipid metabolism may explain these phenotypes. These activities are possible therapeutic targets for LFS patients. Citation Format: Jovanka Gencel-Augusto, Xiaoping Su, Guillermina Lozano. p53 dimers elicit tumor suppressive activities through an altered metabolic program [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 829.