LAUSR

Here, we present an approach to study the effects of microenvironmental changes on inter- and intratumoral heterogeneity using colorectal cancer (CRC) patient-derived organoids. We identified relevant paracrine interactions between stromal and tumor cells based on the expression of ligand-receptor pairs in single cell-RNAseq data of 12 colorectal cancer patients. Physiological relevance was tested by adding CRC stroma-derived ligands to patient-derived organoids. A systematic screening of different conditions was enabled by multiplexed mass cytometry and scRNAseq analysis. We also aimed to model the effects of a changing extracellular matrix composition, by supplementing the laminin/collagen IV rich environment with other known ECM proteins such as collagen I to identify the impact of a changing substrate on cell plasticity. We found that ECM parameters as well as niche specific paracrine factors affect proliferation, differentiation, and developmental trajectories of colorectal cancer patient-derived organoids. We hypothesize that supplementing patient-derived organoids in vitro with physiologically relevant factors and substrates may expand the phenotypic space in which organoid cells differentiate, resulting in a more versatile preclinical model system.Our data provide insights into non-genetic sources of inter- and intratumoral heterogeneity resulting in differential drug responses. Additionally, they can serve as guidelines to improve existing patient-derived colorectal cancer models and provide a feasible approach to address common limitations in organoid culture. Citation Format: Jennifer von Schlichting, Stefan Peidli, Markus Morkel, Nils Blüthgen, Leona Simon. Modeling the effects of niche specific microenvironmental changes on patient-derived organoids. [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 4644.