Orthotopic CRC organoid transplantation in mice: A novel model for the study and treatment of peritoneal carcinomatosis [TIL scRNA-Seq]

Metastasized colorectal cancer (CRC) is associated with a poor prognosis and rapid disease progression. Besides hepatic metastasis, peritoneal carcinomatosis is the major cause of death in UICC stage IV CRC patients. Insights into differential site-specific reconstitution of tumor cells and the corresponding tumor microenvironment are still missing. Here, we analysed the transcriptome of single cells derived from murine multivisceral CRC and gave insight into the inter-metastatic cellular heterogeneity regarding tumor epithelium, stroma and immune cells. Interestingly, we found an intercellular site-specific network of cancer associated fibroblasts and tumor epithelium during peritoneal metastasis as well as an autologous feed-forward loop in cancer stem cells. We furthermore deciphered a metastatic dysfunctional adaptive immunity by a loss of B cell dependent antigen presentation and consecutive effector cell exhaustion. Consequently, we demonstrate the high human-mimicking potential of this murine metastatic CRC model and provide a valid tool for future site-specific preclinical drug testing. Overall design: scRNA-Seq from tumor-infiltrating lymphocytes (TIL) from organoid-derived primary tumor (PT), peritoneal carcinomatisis (PC) and liver metastasis (LM) CRC murine models