A Novel Balloon Procedure for Generating Physiologically and Clinically Relevant Orthotopic Colorectal Cancer Mouse Model 2259578

Abstract Introduction The tumor microenvironment (TME) plays a crucial role in influencing therapeutic interventions in colorectal cancer (CRC). Current CRC mouse models, like cecal-wall injection, develop tumors from the outer cecal wall instead of natural colon mucosa, thereby failing to mimic human CRC development and differing in tumor immune profiling. Methods Here, we present a non-surgical balloon procedure that induces localized mucosal abrasion to enable tumor cell adhesion, resulting in physiologically relevant tumors originating from the mucosal lining, like human CRC. Human scRNA sequencing data were used to analyze immune profiling in CRC patients. MSI-like and MSS-like tumors were generated using MC38 and CT26 cell lines in syngeneic mouse. Treatment was initiated 6 days after tumor cell inoculation. Results This method achieved high tumor success rates (70-100%) with minimal mortality and reduced invasiveness in both immunocompromised and immunocompetent mice. Interestingly, these tumors exhibited human CRC immune profiles, displaying immunosuppressive “cold” microenvironments in MSS-like tumors and immunogenic “hot” microenvironments in MSI-H-like models. Furthermore, these models faithfully recapitulate human therapeutic responses: a combination of 5-FU and anti-PD1 enhances anti-tumor immunity in MSS-like tumors by reducing immunosuppression, while anti-PD1 monotherapy restores cytotoxic T-cell function in MSI-H-like tumors. Conclusion This balloon procedure provides a highly reproducible and accessible platform for generating orthotopic CRC models that recapitulate human tumor physiology, the native immune TME, and therapeutic responsiveness, offering a valuable tool for translational research. Funding Source n/a Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)