Abstract PR05: Patient-derived tumoroids for exploration of the ovarian cancer stem cell regulation, chemoresistance, and tumor heterogeneity
Authors: Bregenzer Micheal E. , Mehta Pooja , Rao Arvind , McLean Karen , Neamati Nouri , Buckanovich Ronald J. , Mehta Geeta 
Published: September 2020

Abstract
Ovarian cancer is the leading cause of gynecologic malignancy, characterized by a high degree of heterogeneity and relapse leading to poor clinical outcomes. These outcomes are attributed in part to a population of cells termed cancer stem-like cells (CSCs), which are capable of repopulating tumors and are more chemoresistant and tumorigenic. These properties make CSCs a promising target for novel therapies; however, we lack a comprehensive understanding of how they are regulated by the tumor microenvironment. To address this, we have developed a tumoroid culture system wherein patient tumor cells are brought together with controlled ratios of mesenchymal stem cells (MSCs), endothelial cells (ECs), and peripheral blood mononuclear cells (PBMCs) within 384-well hanging drop arrays. This allows for comprehensive analysis of the surrounding cells in the tumor microenvironment and their influence on CSC populations and chemoresistance. The fine control of this culture system over the tumoroid cell composition coupled with the high-throughput nature of 384-well hanging drop also facilitates patient-specific high-throughput analysis of inter- and intrapatient heterogeneity and chemoresistance. Tumoroids were generated from 5 patient samples and characterized using flow cytometry detection of cell type proportions, immunofluorescence evaluation of cell localization, and progressive evaluation of cell localization with fluorescently labeled tumoroids. Patient-derived tumoroids were evaluated by single-cell RNA sequencing. Drug screening was performed on patient-derived tumoroids and control patient-derived spheroids using classic ovarian cancer therapies, carboplatin and paclitaxel, as well as three novel drugs. Additionally, tumor formation assay was performed in immunodeficient mice to compare the rate of tumor formation following injection of tumoroids versus spheroids. Finally, a mathematical model was developed to predict the evolution of cell populations within the tumoroids to facilitate further analysis. Using these methods, we successfully generated and characterized viable tumoroids with primary patient-derived tumor cells, MSCs, ECs, and PBMCs. Within these tumoroids, we observed heterogeneity both between and within patient samples reflective of clinical observations in ovarian cancers. Furthermore, we found increased CSC phenotypes in the tumoroids compared to patient-derived tumor cell-only spheroids. Patient-derived tumoroids also exhibited increased chemoresistance and tumorigenicity compared to spheroids generated with only tumor cells. Through thorough development and characterization of this patient-derived model, we present a novel 3D tumoroid model for comprehensive investigation of CSC regulation, chemoresistance, and heterogeneity in ovarian cancers, with the long-term goal of developing novel CSC targeting therapies and improving clinical outcomes.
This abstract is also being presented as Poster B08.
Citation Format: Micheal E. Bregenzer, Pooja Mehta, Arvind Rao, Karen McLean, Nouri Neamati, Ronald J. Buckanovich, Geeta Mehta. Patient-derived tumoroids for exploration of the ovarian cancer stem cell regulation, chemoresistance, and tumor heterogeneity [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr PR05.