Identifying Synthetic Lethality With Novel Cdk2 Small Molecule Inhibitors Via Integration Of Highcontent Microscopy And -Omics Level Platforms.

Abstract CDK4/6 small molecule inhibitors represent a milestone in treating hormone receptor-positive breast cancer. PALOMA (Palbociclib: Ongoing Trials in the Management of Breast Cancer) studies have confirmed prolonged progression-free survival after CDK4/6 inhibitor and anti-estrogen therapy. Notably, disease progression is observed in a subset of patients receiving Palbociclib-Fulvestrant treatment (Turner et al., NEJM 2018). Circulating tumor DNA from PALOMA-3 patients revealed genetic mutations correlating with patient response (O'Leary et al., Cancer Discov, 2018). Compensations in CDK4/6i resistance include circumvention of CDK4/6 substrate regulation, CCNE1/2 amplification (Herrera-Abreu et al., Cancer Res. 2016), and compensatory CDK2 activity. The importance of compensatory CDK2 cancer re-wiring is highlighted by recently reported, highly efficacious CDK2/4/6i (Freeman-Cook et al., in review). Thus, mechanistic understanding of cancer cell and compensatory CDK2 activity is imperative to improve patient outcome. Acute, temporal phenotypes in CDK2-signaling have been observed by live single-cell tracking microscopy in human breast epithelial and ER+ breast cancer cells (Arora & Moser et al., in review). In extending these studies, we utilize first-in-class small molecule inhibitors against CDK2 combined with high content imaging approaches to illuminate cancer cell CDK2 signaling and identify potential synthetic lethality. We report biomarkers parsed in cycling populations as quantifiable phenotypes and identify disengaged control of several processes including S- and G2/M licensing after CDK2i. Combined with internal -omics studies, CDK2i selective molecules support a positive regulatory role of CDK2 on CCNB1-PLK1 signaling before mitotic entry. We combine our high-content techniques with proximity labeling to quantify alternative CDK-Cyclin complex formation following pharmacologic perturbation. We hypothesize that dysregulated CDK-Cyclin complex formation elicits unintended CDK2 kinase activity, revealing potential synthetic lethality with inhibition of centrosome duplication pathways in ER+ breast cancers. Citation Format: Tim Sen Wang, Jon Almaden, Chen Shen, John Lapek, Sherry Niessen, Nichol Miller, Stephen Dann, Todd VanArsdale. Identifying synthetic lethality with novel CDK2 small molecule inhibitors via integration of high-content microscopy and -omics level platforms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1954.