Abstract 4567: Transcriptomic analysis of a 3D engineered cancer model recapitulating stage-dependent heterogeneity in colorectal PDX tumors
Authors: Tian Yuan , Hassani Iman , Anbiah Benjamin , Ahmed Bulbul , Van Der Pol William , Lefkowitz Elliot J. , Kuhlers Peyton C. , Habbit Nicole L. , Heslin Martin J. , Lipke Elizabeth A. , Greene Michael W. 
Published: April 2023

Abstract
Colorectal cancer (CRC) is the third-most leading cause of cancer-related deaths in the United States. To advance the understanding of CRC tumor progression, models which mimic the tumor microenvironment (TME) and have translatable study outcomes are urgently needed. CRC patient-derived xenografts (PDXs) are promising tools for their ability to recapitulate tumor heterogeneity and key patient tumor characteristics, such as molecular characteristics. However, as in vivo models, CRC PDXs are costly and low-throughput, which leads to a need for equivalent in vitro models. To address this need, we previously established an in vitro model using a tissue engineering toolset with CRC PDX cells. However, it is unclear whether tissue engineering has the capacity to maintain patient- and/or cancer stage-specific tumor heterogeneity. To address this gap, we employed three PDX tumor lines, originated from stage II, III-B, and IV CRC tumors, in the formation of 3D engineered CRC PDX (3D-eCRC-PDX) tissues and performed an in-depth comparison between the 3D-eCRC-PDX tissues and the original CRC-PDX tumors. To form the tissues, CRC-PDX tumors were expanded in vivo and dissociated. The isolated cells were encapsulated within poly(ethylene glycol)-fibrinogen hydrogels and remained viable and proliferative post encapsulation over the course of 29 days in culture. To gain molecular insight into the maintenance of PDX line stage heterogeneity, we performed a transcriptomic analysis using RNA seq to determine the extent to which there were similarities and differences between the CRC-PDX tumors and the 3D-eCRC-PDX tissues. We observed the greatest correspondence in overlapping differentially expressed human genes, gene ontology, and Hallmark gene set enrichment between the 3D-eCRC-PDX tissues and CRC-PDX tumors in the stage II PDX line, while the least correspondence was observed in the stage IV PDX line. The Hallmark gene set enrichment from murine mapped RNA seq transcripts was PDX line-specific which suggested that the stromal component of the 3D-eCRC-PDX tissues was maintained in a PDX line-dependent manner. Consistent with our transcriptomic analysis, we observed that tumor cell subpopulations, including human proliferative (B2M+Ki67+) and CK20+ cells, remained constant for up to 15 days in culture even though the number of cells in the 3D-eCRC-PDX tissues from all three CRC stages increased over time. Yet, tumor cell subpopulation differences in the stage IV 3D-eCRC-PDX tissues were observed starting at 22 days in culture. Overall, our results demonstrate a strong correlation between our in vitro 3D-eCRC-PDX models and the originating in vivo CRC-PDX tumors, providing evidence that these engineered tissues may be capable of mimicking patient- and/or cancer stage-specific heterogeneity.
Citation Format: Yuan Tian, Iman Hassani, Benjamin Anbiah, Bulbul Ahmed, William Van Der Pol, Elliot J. Lefkowitz, Peyton C. Kuhlers, Nicole L. Habbit, Martin J. Heslin, Elizabeth A. Lipke, Michael W. Greene. Transcriptomic analysis of a 3D engineered cancer model recapitulating stage-dependent heterogeneity in colorectal PDX tumors. [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 4567.