Abstract 4885: APR-246 cytotoxic effects are TP53 independent in endometrial cancer cell lines

Abstract

Abstract Background: The majority (80%) of endometrial cancer (EC) related mortality is due to high-grade tumor histology, which harbor high rates of TP53 mutations. APR-246 is a small-molecule drug designed to restore WT p53 signaling in TP53-mutant cancers and has yet to be explored in EC. We aimed to test the cytotoxic potential for APR-246 in EC and its downstream impact. Methods: Using 3 parental EC cell lines with differing TP53 statuses, JHUEM2 (WT), Hec108 (hetero P151H), and Hec1B (R248Q), we generated dose-response curves for APR-246. Cells were treated for 24 hours and viability assessed with CellTiter-Glo after 9 days. To assess for mutation specific effect, we generated dose-response curves using a WT non-targeting control (NTC), CRISPR/Cas9 KO of TP53, and five KO cell lines complemented with 5 common TP53 mutations (R248Q, R248W, R273C, R273H, Y220C). Western blot analysis was performed to assess for p53, p21, PUMA, GADD45, and NOXA using whole-cell lysates, after treatment with 20μM of APR-246 for 24 hours. To further evaluate for a time-dependent effect, 2 representative variants (R248Q and R273C) after 6 and 24 hours of incubation with 50μM APR-246 and 10μM of Nutlin-3. Results: APR-246 demonstrated a negative, dose-dependent effect on cell viability in all EC cell lines. IC50s for JHUEM2, Hec108, and Hec1B were 2.5μM, 4.3μM, and 4.5μM respectively. For NTC, the IC50 was (1.7μM), while TP53-KO (7.5μM) demonstrated similar IC50 values to the variants (6.5-11.9μM). Two variants (Y220C and R248W), had significantly (<0.001 and <0.01 respectively) higher IC50 values (11.9 and 9.1 μM respectively). In Western blot analysis, no p53 downstream signaling via p21, GADD45, PUMA, and NOXA was observed for any variants. Conclusions: Our results demonstrate that APR-246's cytotoxic effects in EC seem to be p53-independent. Potential mechanisms for the anti-neoplastic effects of APR-246 include activity targeting antioxidant pathways demonstrated in other solid tumors and provides an area for further investigation in TP53mut EC. Citation Format: Camilla Yu, Aaron Petty, Roberto Vargas. APR-246 cytotoxic effects are TP53 independent in endometrial cancer cell lines. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4885.