Abstract PR11: Active YAP as a functional marker of drug-tolerant persister cells in EGFR-mutant and ALK fusion-positive NSCLC

Abstract

Abstract Targeted therapies against clinically actionable oncogenic drivers in lung adenocarcinoma have significantly improved survival of cancer patients, but durable responses are limited due to the emergence of drug resistance. Resistance development is often characterized by the retention of a small subpopulation of cancer cells under drug treatment and their evolution from non-/low-proliferative residual disease to an aggressively growing resistant tumor. Most importantly, drug-tolerant persister cells have been identified as a reservoir for a multitude of drug resistance mechanisms and thus, their characterization and the development of rational combinatorial treatment may delay or prevent resistance development and improve treatment outcome for cancer patients. Using a multitude of in vitro models such as cell culture models and patient-derived organoids, we characterized signaling and transcriptional changes in drug-tolerant persisters. We identified YAP nuclear relocalization and its increased transcriptional activity as a key marker of persisters derived from EGFR-mutant and EML4-ALK fusion-positive specimen under third-generation TKI treatment. Image analysis of cells genetically engineered via CRISPR-Cas9 to express endogenously labeled YAP-mNeonGreen validated these results. Moreover, we were able to prove the functional relevance of YAP activation in drug persistence by overexpressing active mutants of YAP that are lacking inhibitory Hippo phosphorylation sites. The latter resulted in increased nuclear levels and transcriptional activity of YAP and mediated significantly reduced cell death under high-dose drug treatment in different cell line models. Using RNA sequencing, we show a clear evolutionary path from drug-sensitive parental cells to drug-tolerant persisters and long-term derived drug-acquired resistant cells. We are currently profiling vulnerabilities of drug-tolerant EGFR-mutant and EML4-ALK fusion persisters using genetic and pharmacologic approaches. In conclusion, YAP activation is a functional marker of EGFR-mutant and EML4-ALK fusion persisters derived under high-dose drug treatment with third-generation TKIs. Targeting YAP activation either on the level of upstream signaling input, its relocalization between cytoplasm and nucleus, or its action as transcriptional coactivator may represent a promising combinatorial treatment approach to limit resistance development and improve patient survival in lung adenocarcinoma. Citation Format: Franziska Haderk, David Allegakoen, Juan Guan, Wei Wu, Trever Bivona. Active YAP as a functional marker of drug-tolerant persister cells in EGFR-mutant and ALK fusion-positive NSCLC [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr PR11.