Abstract 636: Coculture model for investigating cellular interactions between colorectal tumor organoids and cancer-associated fibroblasts

Abstract The tumor microenvironment (TME) is well recognized for its role in tumor progression, chemoresistance, and recurrence. The TME consists of various components, such as extracellular matrix (ECM), chemical and mechanical cues, as well as stromal cells and their interactions. As the most abundant cells in tumor stroma, cancer-associated fibroblasts (CAFs) have drawn a lot of attention. It has been reported that CAFs not only directly interact with cancer cells via surface proteins and cytokines, but also influence their behaviors by remodeling the ECM. However, due to their heterogenous characteristics and diverse functions, the influence of tumor-CAF interactions on drug response is not fully understood. Here, we present a coculture model for investigating CAF effects on patient-derived colorectal tumor organoids (CTOs) growth, differentiation, and drug response. It consists of normal colon fibroblasts, CCD18-Co, or patient-derived CAFs seeded with CTOs in a mixed hydrogel containing 90% basement membrane extract (BME) and 10% collagen type I. Media conditions were optimized (1: 1 mix of CTO culture media plus reduced media excluding growth factors and inhibitors) to achieve similar organoid sizes in the monoculture and coculture conditions at the onset of drug testing. To support higher throughput investigations, our workflow incorporates a liquid handler for automated CTO seeding, media and drug exchange, and an automated microscope with a robotic arm for multi-plate imaging. Briefly, single cell CTOs and fibroblasts were seeded at a 1: 1 ratio (3000 total cells/well) in 96-well plates. After 4 days in culture, anti-cancer drugs were administrated in reduced media to the samples. Brightfield images were acquired on days 0, 3, and 5 after drug administration. The collected images were analyzed with a neural network (NN) to dynamically monitor the growth and viability of individual organoids. The CellTiter-Glo assay was performed on day 5 to quantify the total CTO cell viability. The normalized drug response (NDR) was calculated from the NN processed images to determine the drug response. An immunostaining panel, which includes protein markers such as CK20, Ki67, α-SMA, Vimentin, and FAP, was used to evaluate the fibroblast phenotypes and CTO differentiation. Additionally, the cultures were subjected to fluorescent lifetime imaging microscopy (FLIM), a label-free imaging technique, to measure the metabolic adaptations of each cell population. Preliminary studies revealed a CAF-dependent increase in CTO growth and glycolytic signatures in the co-culture setting; however, minimal effects on drug response to common chemotherapy agents such as 5-fluorouracil and irinotecan were observed. In the future, we will use this integrated pipeline as a screening method to identify new treatment strategies aimed at targeting the stromal microenvironment in colorectal cancer. Citation Format: Yuyuan Zhou, Yu-Kai Huang, Emma J. Fong, Elizabeth Elton, Erin McManus, Brandon Choi, Seungil Kim, Shannon M. Mumenthaler. Coculture model for investigating cellular interactions between colorectal tumor organoids and cancer-associated fibroblasts 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 (6Suppl): Abstract nr 636.