SELECTIVE DEGRADATION OF ONCOGENIC p53 MUTANTS THROUGH A DRUG REPURPOSING STRATEGY

COCORDANO, NABILA; BORINI ETICHETTI, CARLA M; LLORENS DE LOS RÍOS, CANDELARIA; AREL ZALAZAR, EVELYN; SORIA, GASTÓN; GIRARDINI, JAVIER

Congreso; REUNIÓN CONJUNTA SAIC SAI&FAIC SAFIS 2022; 2022

The presence of missense mutations in the p53 gene is among the most frequent alterations in human cancer. These mutations lead to the expression of mutant p53 proteins, which can actively collaborate with oncogenic processes. Mutant p53 forms have attracted great interest as therapeutic targets because their elimination could reduce the development of aggressive and metastatic tumors. Targeting mutant p53 would also provide highly selective therapies, since mutations are found exclusively in tumor cells, reducing the possibility of adverse effects. Also, the high mutation frequency of p53 would make this strategy useful in different cancer types. In tumor cells, p53 point mutants show a remarkable increase in stability compared with the wt protein. In order to identify drugs able to induce mutant p53 degradation, we performed a high-throughput screening, using libraries of drugs approved for clinical use in humans against various pathologies. Using In Cell Western Blot, we analyzed the effect of 1760 drugs on the MDA-MB-231 cell line, derived from Triple-Negative breast adenocarcinoma, which endogenously expresses p53R280K mutant. In this way, compounds capable of significantly reducing mutant p53 levels were identified. We further characterized the effect of a selected candidate. We demonstrated that the compound reduced the levels of other p53 point mutants in different cell lines (p < 0,001; n=3). Time course analysis using western blot showed that the drug decreased the half-life of mutant p53 (p < 0,01; n=3), associated with an increase in polyubiquitination. In contrast, wt p53 levels were not affected, suggesting that the effect is selective for cells that express mutant p53. Using wound healing assays we showed that the drug reduced the migration of cancer cells (p < 0,01; n=3), a characteristic trait of metastatic cells promoted by mutant p53. In summary, we identified a compound potentially useful in antitumor strategies based on mutant p53 degradation.