Abstract 639: Evaluation of individual drug response in tumor microenvironment to cisplatin treatment in precision-cut tumor slices of ovarian cancer

Abstract Ovarian cancer is a complex and heterogeneous disease and the major cause of death among women with gynecological cancers. While patients usually respond well to the platinum-based first-line chemotherapy, the disease often becomes increasingly resistant to the treatment. The tumor microenvironment (TME) plays an important role in tumor development and drug resistance. Characterizing the TME of ovarian cancer after drug treatment is essential to identify molecular mechanisms that allow residual tumor cells to survive chemotherapy in ovarian cancer. We have established a preclinical model using precision-cut tumor slices (PCTS) with 250 µm thickness which preserves the TME of solid tumors with their heterogeneous cell composition during cultivation. The tumor morphology, viability and heterogeneity in terms of tumor and stromal cells as well as the immune compartment are preserved within the system. Based on the PCTS model, we also established a method to perform single-cell RNA sequencing (scRNA-seq) of the PCTS after cultivation and drug treatment to characterize the cellular features and dynamic relationships of different cell populations in the TME after drug treatment. Over 20 cell subtypes including different clusters of epithelial cells, immune cells and fibroblasts can be identified in PCTS after cisplatin treatment through the scRNA-seq analysis. This enables further deeper analysis of each cell subgroup in the TME after drug treatment. In response to cisplatin treatment, patients PCTS showed an individual induction of PD-L1 in different cell types. Additionally, multiplex immunofluorescence (mIF) stainings of the PCTS were performed to spatially trace the response of the TME to drug treatment. The mIF staining allows the simultaneous detection of up to 6 different markers on one FFPE tissue section. Images were analyzed using a machine-learning based workflow, which allows the comparison of biomarker expression and immune cell spatial distribution in the PCTS stromal and tumor areas before and after treatment. Combining the PCTS as a preclinical model with scRNA-seq and mIF staining analysis allows us to bridge the cellular characteristics and cellular spatial distribution with treatment response in the TME of solid tumors. It enables the systematic analysis of residual cancer populations after cisplatin treatment within the complex TME and further identification of predictive markers and targets for an individualized combination of chemotherapy with compounds targeting these mechanisms. The individual drug response of patients can be deeply evaluated and efficacious therapies can be further developed. Citation Format: Julia Thiel, Adrian Kneer, Weimeng Yu, Bernd Winkler, Georg Sauer, German Ott, Walter E. Aulitzky, Thomas E. Mürdter, Matthias Schwab, Chunguang Liang, Meng Dong. Evaluation of individual drug response in tumor microenvironment to cisplatin treatment in precision-cut tumor slices of ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 639.