Abstract 4480: Treatment of PTEN/PI3K co-mutated endometrial adenocarcinoma with multitarget small molecule inhibitors

Abstract

Abstract Introduction: The objective of this study is to assess the feasibility and safety of treating endometrial adenocarcinoma (EC) with multitarget inhibitors which orthogonally target known oncogenic kinases and epigenetic regulators. The Molecular Targeted Therapeutics Laboratory has developed nanomolar potent multitarget small molecule chemotypes that inhibit the PI3K/Akt/mTOR pathway, cancer-associated kinases, and epigenetic regulatory proteins such as BRD4 in vitro and in vivo. Methods: Two EC cell lines (AN3-CA, RL95-2) were treated with varying concentrations of triple PI3K/BRD4/CDK4/6/9 inhibitor LCI132 and dual PI3K/CDK4/6/9 inhibitors LCI133 and LCI136 for 48 hours; and cell viability assays were performed with IC50 determination. EC cells were treated with multitarget inhibitors and other indicated inhibitors of PI3K, BET, CDK4/6, and CDK9 for 24 hours; and lysates were prepared accordingly for Western blot (WB) and qRT-PCR analyses. Flow cytometry was conducted for cell cycle and apoptosis assays. Results: In cell-free assays, LCI132 is a nanomolar inhibitor of PI3K/BRD4/CDK4/6/9, LCI133 is a picomolar inhibitor of CDK9, and LCI136 is a nanomolar inhibitor of PI3K and CDK9. LCI133 demonstrated nanomolar potency towards AN3-CA (IC50 248 nM) and RL95-2 (IC50 105 nM). LCI136 demonstrated nanomolar potency towards AN3-CA (IC50 631 nM) and RL95-2 (IC50 728 nM). WB demonstrated 24-hour treatment of FBXW7mut AN3-CA with LCI132 inhibited AKT phosphorylation but an increase in c-MYC protein expression. A corresponding increase in c-Myc gene expression at 24 hours was confirmed on qRT-PCR. In FBXW7wt RL95-2, LCI132 decreased c-Myc protein expression. LCI132 demonstrated dose-dependent G1 arrest, and dose-dependent pre-apoptotic and apoptotic activity. Conclusions: Dual-target inhibitors LCI133 and LCI136 are nanomolar potent in AN3-CA and RL95-2 EC cell lines, suggesting a role of CDK9 inhibition of PTEN/PI3K co-mutated EC. Preliminary studies demonstrate an upregulation of MYC gene and protein expression in FBXW7mut EC but not FBXW7wt, and the role of FBXW7 as a predictive biomarker in treatment of PTEN/PIK3R1 co-mutated EC warrants further investigation. Citation Format: Ritchie Delara, Cody McHale, Dhananjaya Pal, Krishnaiah Maddeboina, R. Wendel Naumann, Erin Crane, Jubilee Brown, Donald Durden. Treatment of PTEN/PI3K co-mutated endometrial adenocarcinoma with multitarget small molecule inhibitors. [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 4480.