Abstract A011: Epigenetic vulnerabilities in patient-derived colorectal cancer organoids

Abstract

Abstract Colorectal cancer (CRC) is a major cause of cancer-related deaths worldwide. Here, we established human patient-derived colorectal cancer organoid cultures (PDOs) to decipher the patient-specific DNA methylation profile and drug sensitivity towards 5-aza-2’-deoxycytidine, a DNA methyltransferase inhibitor. Organoid lines (n=15) were generated from adjacent normal mucosa and tumor tissue located in different anatomical sites of the colon and rectum. The derived PDOs were characterized on a histopathological level and reproduced the grade and differentiation capacity of their parental tumors. Additional genotypic profiling of PDOs showed a high degree of similarity to the original patient tumors. However, the stability of the DNA methylation landscape of human cancer organoids remains largely unknown. In genome-wide methylation analysis of long-term organoid cultures (up to 6 months in culture), we observed surprisingly stable methylation signatures that recapitulates the patient’s profile whilst demonstrating the vast intertumoral heterogeneity among patients. Strikingly, we identified a tumor-specific methylation signature that consisted of 39 CpG sites, which were unmethylated in normal epithelial cells but highly (91-96%) methylated in all tumor cells analyzed. This signature allows for the estimation of the percentage of tumor content in resected tissues and might represent potent biomarkers for early CRC diagnostics. Notably, it has been demonstrated that PDOs have the potential to predict clinical outcome and response to chemo- and radiation therapy in patients. Herein, drug screening with 5-aza-2’-deoxycytidine revealed heterogeneous responses and a clustering into drug sensitive, median and resistant organoid lines. ATAC- and RNA-seq analyses identified pathways rendering drug sensitivity and resistance. Our findings highlight the utility of PDOs as an advanced model system to study the role of the epigenome, especially DNA methylation, and its impact on tumor burden and vulnerability towards epigenetic modifiers. Citation Format: Loan Tran, Raheleh Sheibani Tezerji, Carlos Uziel Perez Malla, Anna Malzer, Ajna Logo, Katarina Misura, Theresia Mair, Thomas Dillinger, Madeleine Kuroll, Velina Atanasova, Julijan Kabiljo, Helga Schachner, Katharina Wöran, Judith Stift, Helmut Dolznig, Walter Pulverer, Michael Bergmann, Gerda Egger. Epigenetic vulnerabilities in patient-derived colorectal cancer organoids. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Epigenomics; 2022 Oct 6-8; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_2):Abstract nr A011.