Abstract 1244: Investigating prostate cancer cellular heterogeneity and treatment response at singe-cell level

Abstract Context and Objectives: Androgen deprivation therapy (ADT) is the mainstay for treatment of advanced castration-sensitive prostate cancer (CSPC); yet most patients eventually relapse and progress to lethal castration-resistant prostate cancer (CRPC). Here we aimed at generating single-cell transcriptomic profiles from advanced CSPC samples and ADT-treated patient-derived organoids (PDOs) to dissect cellular dynamics underlying response to androgen deprivation at single-cell resolution. Material and Methods: Nine radical prostatectomy or metastasis resection specimens obtained from treatment-naïve high-grade CSPC patients were collected and processed into single-cell suspensions. Single-cell RNA sequencing (scRNA-seq) was carried out on six specimens meeting necessary quality criteria. In parallel, four PDO lines were established, characterized using whole exome sequencing, IHC and immunofluorescence, and cultured in androgen-deficient conditions to mimic ADT. Viability assay confirmed treatment efficacy before scRNA-seq was performed with a lipid-based multiplexing strategy (MULTI-seq). Results: We generated an atlas encompassing the transcriptomic profiles of more than 20 000 cells originating from rare tissue material. While highlighting patient-specific tumor features and integrating cells from the microenvironment, our single-cell atlas also revealed various epithelial subtypes. This included a subset of intermediate cells, referred to as club/hillock cells, which were previously proposed to play a role in tumor progression. Interestingly, these cells were maintained in PDOs derived from non-metastatic tissues, whereas PDOs derived from metastatic ones were exclusively composed of tumor-like cells. Treated organoids exhibited diverse viability responses and pathway alterations, including changes in the Androgen Response Signature, reflecting their sensitivity to ADT and underscoring their value as clinically relevant in vitro models. Simultaneously, scRNA-seq revealed transcriptional shifts within specific subpopulations of treated PDOs, highlighting significant changes in additional pathways that provide insights into the mechanisms driving the onset of castration resistance. Ongoing analyses aim to determine whether these populations pre-exist in the tumor or if this state is gradually acquired during treatment. Conclusion: PDOs effectively mirror original prostate tumor characteristics and represent functional castration-sensitive models. By leveraging the generated scRNA-seq atlases and transcriptomic shift analyses, we anticipate identifying castration-tolerant cell populations potentially contributing to tumor heterogeneity and relapse. Citation Format: Romuald Parmentier, Julien Roux, Robin Dolgos, Raphaëlle Servant, Kirsten Mertz, Subotic Svetozar, Lukas Bubendorf, Helge Seifert, Cyrill A. Rentsch, Clémentine Le Magnen. Investigating prostate cancer cellular heterogeneity and treatment response at singe-cell level [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1244.