Abstract PO024: Organoids with modified tumor microenvironment architecture induces phenotypic changes in metastatic colorectal cancer

Introduction: It is now well understood that interactions between tumor cells, microenvironment-specific stromal cells, and extracellular matrix (ECM) are essential for tumor growth and significantly affect drug response. The tumor microenvironment (TME) is not easily modeled in previously developed two-dimensional (2D) in vitro techniques; therefore, the consideration of new methods for visualization and manipulation has been investigated. Conventional 2D techniques are advantageous for their high-throughput capabilities and low cost; however, they lack the potential to mimic the complexity of the TME and are relatively limited in studying cancer metastasis and drug resistance mechanisms. Additionally, in vivo animal models are expensive and inefficient, influencing the use of three-dimensional (3D) culture systems, such as spheroids, organoids, or microfluidics, to study the TME effect on cancer progression and chemotherapy response. 3D culture systems have also proven useful in studying cancer stem cells (CSC) due to its ability to maintain ECM density, hypoxia, and low nutrients. Our innovative organoid approach uses advanced biofabrication methods that mimic in vivo conditions in order to create a microenvironment similar to that of a colorectal tumor that has metastasized to the liver. We describe the utilization of our tumor organoid platform to analyze the interactions between an HSC cell line of the liver and metastatic CRC cell lines. In this study, we expose cancer cells to various HSC-produced ECM densities using TGF-β and determine macroscopic characteristics of the collagen remodeling and its effect on embedded cells. The overall goal of this research is to determine how structural/mechanical changes in the tumor microenvironment, specifically the ECM, impact tumor cell phenotype. Methods: We embedded a metastatic human colorectal cancer cell spheroid into an organoid consisting of an HSC cell line and collagen type 1. We activated the HSCs with TGF-s causing excessive deposition and remodeling of collagen. The remodeled TME that resulted from TGF-s-mediated activation was confirmed. IHC staining of the stromal and cancerous cells was used to determine the phenotypic changes of each cell line. Results: Our results showed that in a remodeled collaged environment created by the activated HSCs, reduced tumor proliferative, mesenchymal phenotype, and induced epithelial phenotype. Our results also revealed that the dense environment preserved the CSC population in the HCT-116 cells after 7 days in culture. Conclusions: Our CRC organoid platform enables us to study the interactions between tumor cells and the controllable surrounding ECM. We are able to identify changes in a low plasticity cell line, HCT-116, when changes in the ECM architecture occur that result in differing chemotherapy resistance and sensitivities. This system will allow us to begin investigating the effect ECM density has on tumor samples directly from patients to help better understand the underlying mechanisms of chemoresistance through precision medicine. Citation Format: Anthony Dominijanni, Shay Soker. Organoids with modified tumor microenvironment architecture induces phenotypic changes in metastatic colorectal cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr PO024.