Abstract 4327: Disruption of aggregated oncogenic mutant p53 as a novel therapeutic strategy for gynecologic cancers
Authors: Geneva L. Williams, Jamie L. Padilla, Lane E. Smith, Jun-yong Choe, Doris M. Benbrook, Kimberly K. Leslie
Journal: Cancer Research (2025)

Abstract High grade serous ovarian and endometrial cancers possess TP53 missense mutations that result in loss of the central tumor suppressive functions of wild type p53 (WT p53). In normal unstressed cells, p53 protein is regulated through ubiquitin-tagging and shuttling to the 26S proteasome by the E3 ubiquitin ligase MDM2 (Murine Double Minute 2). In cancer cells with mutant forms of p53, MDM2 is not adequately expressed in such cells to perform its regulatory role, thus leading to mutant p53 aggregates. Understanding mechanisms to target mutant p53 proteins for degradation in cancers has tremendous therapeutic potential. Recent discoveries in p53 refolding agents to reinstate WT p53 functionality for the treatment of gynecologic malignancies have shown promise. Treatment of cancer cells harboring p53 mutations with p53 reactivators HO-3867 and our novel curcumin analogue AKT-100 displayed an upregulated expression of heat shock protein 70 (HSP70) family member genes, as well as the autophagy-inducing co-chaperone BAG3 (Bcl-2-associated athanogene 3) by RNA sequencing analysis. Western blot analysis showed a decrease in p53 protein expression after treatment with the curcumin analogues, while MDM2 levels were unchanged, indicating an alternative mechanism of mutant p53 degradation. We hypothesize that the BAG3-HSP70 interaction varies with different mutations in p53 as well as the various HSP70 family members involved and can be therapeutically normalized to restore WT p53 regulation. Using our cell models of high grade serous ovarian and endometrial cancer, we have determined through co-immunoprecipitation and mass spectrometry that p53 binds HSPA6 and BAG3 upon treatment only with AKT-100 in KLE (p53 R175H) and COV362 (p53 Y220C) cells. Furthermore, co-treatment of curcumin analogue AKT-100 plus HSP inhibitor SHetA2 (sulfur heteroarotinoid A2, NSC 726189) highly increased the expression of BAG3, HSPA1A, HSPA6 and ubiquitination while decreasing mutant p53 expression in KLE cells. Confocal microscopy in KLE cells also displayed a shift of mutant p53 and HSPA6 from nuclear to mostly cytoplasmic upon treatment with AKT-100. Co-treatment with AKT-100 and SHetA2 highly increased HSPA6 expression throughout the cell, while p53 returned to the nucleus to perform normal apoptotic functions based on CyQuant proliferation data. Our data indicates a novel mechanistic insight into therapeutically intervening to re-establish normal p53 levels and regulation to treat women with advanced, mutant p53 gynecologic malignancies. Citation Format: Geneva L. Williams, Jamie L. Padilla, Lane E. Smith, Jun-yong Choe, Doris M. Benbrook, Kimberly K. Leslie. Disruption of aggregated oncogenic mutant p53 as a novel therapeutic strategy for gynecologic cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4327.