Abstract 3459: Drug persistence pathways in ovarian cancer identified by single-cell analysis of patient samples and cell line models
Authors: Leshchiner Elizaveta , Panayiotou Richard , Gupta Anay , Zhang Thomas , Neil Kayli , Girnius Nomeda , Henstridge Aylin , Danysh Brian P. , Leshchiner Ignaty , Hill Sarah J. , Parida Laxmi , Matulonis Ursula A. , Brugge Joan S. , Getz Gad 
Published: April 2023

Abstract
Drug resistance and disease recurrence represent a major obstacle in the treatment of high-grade serous ovarian cancer (HGSOC). Here, we performed a comprehensive characterization, at the single-cell level, of residual (persister) cancer cells that survive neoadjuvant treatment in HGSOC and can give rise to future recurrences. We aim to understand the adaptive responses that enable persistence and the key pathways that underlie them to find new targets for combination therapy with the ultimate goal of eradicating all tumor cells. We collected 27 tumor samples (16 pre-treatment and 11 post-neoadjuvant carboplatin/taxol samples, with multi-site sampling per patient) for single-cell RNA sequencing (scRNA-Seq). To complement the patient-derived dataset and model the time course of drug persistence, we performed scRNA-Seq of 13 distinct ovarian cancer cell lines treated with chemotherapy in vitro for a series of time points up to 28 days.
We performed single-cell gene expression and copy number analyses of patient samples, annotated detailed cell types, and detected multiple immune cell populations, the majority of which maintained a highly immunosuppressive program both in untreated and treated samples. Remarkably, we detected a rare population of cancer cells that differed dramatically in their transcriptional program. These cells exhibited high expression of components of motile cilia and the transcription factor FOXJ1, a master regulator of ciliogenesis. We validated the presence of FOXJ1+ cells in patient samples by immunohistochemistry and immunofluorescence. Ciliated cells were enriched in the post-treatment vs. pre-treatment samples, suggesting a possible role in drug persistence. We are now experimentally testing the role of the FOXJ1-driven transcriptional program in mediating drug resistance.
To systematically identify transcriptional programs activated in persister cells, we performed differential expression analysis on pre- vs. post-treatment samples. We identified previously implicated mechanisms of drug resistance, such as the Epithelial-Mesenchymal Transition and the antiapoptotic response driven by MCL1. We additionally detected upregulation of the metallothionein family of genes, which may represent a mechanism of resistance to platinum-based compounds. We detected potentially novel mechanisms representing a stress response signature driven by JUND, an interferon gamma signature, and a pro-stem cell signature characterized by LGR5 expression. Independently, our analysis of the ovarian cancer cell lines treated with taxol in vitro confirmed the JUND transcriptional program as potentially driving ovarian cancer persistence. Our study will help reveal pathways enabling ovarian cancer cells to persist through treatment and, ultimately, could lead to novel approaches for targeting persistence and achieving deeper therapeutic responses.
Citation Format: Elizaveta Leshchiner, Richard Panayiotou, Anay Gupta, Thomas Zhang, Kayli Neil, Nomeda Girnius, Aylin Henstridge, Brian P. Danysh, Ignaty Leshchiner, Sarah J. Hill, Laxmi Parida, Ursula A. Matulonis, Joan S. Brugge, Gad Getz. Drug persistence pathways in ovarian cancer identified by single-cell analysis of patient samples and cell line models [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 3459.