Recapitulating Patient-to-Patient Colorectal Cancer Tumor Heterogeneity  Using Patient-Derived Xenograft Cells in an Engineered Tissue Model
Establishing in vitro cancer models that more closely recapitulate patient tumor microenvironmental heterogeneity, including variations in stromal cells and mechanical properties that influence colorectal cancer (CRC) progression, is crucial for advancing  CRC research. This study evaluated the ability of 3D engineered CRC-PDX (3D-eCRC-PDX) tissues to recapitulate the heterogeneity found between patient-derived xenograft (PDX) tumors from three CRC patients (stage II, III-B, and IV). To form the 3D-eCRC-PDX tissues, CRC-PDX tumor cells were encapsulated in PEG-fibrinogen hydrogels and maintained for 29 days in vitro. 3D-eCRC-PDX tissues recapitulated key patient-specific tumor characteristics. During long-term culture, 3D-eCRC-PDX tissues mimicked the patient-specific growth rates of the originating CRC-PDX tumors. Importantly, tumor cellular subpopulations, including the ratio of human cancer cells to mouse stromal cells and the ratios of proliferative human cancer cells and CK20+ cells were maintained in 3D-eCRC-PDX tissues, unlike in 2D cell culture.  Differences in mechanical stiffness between the originating CRC-PDX tumors were also recapitulated by the 3D-eCRC-PDX tissues. Principle component analysis of transcriptomic data clustered 3D-eCRC-PDX tissues and CRC-PDX tumors together by patient, indicating similar gene expression profiles.  These findings highlight the potential of 3D-eCRC-PDX tissues as a promising tool for CRC research, capable of maintaining patient-specific tumor microenvironment heterogeneity. Overall design: mRNA profiles of 3D engineered CRC tissues cultured for 15 days and the corresponding in vivo PDX subcutaneous tumor grown in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NOD-SCID) mice.