A surgical orthotopic xenograft approach with immune response for colorectal cancer research

The high morbidity and mortality of colorectal cancer (CRC) is a major challenge in clinical practice. Although a series of alternative research models of CRC have been developed, appropriate orthotopic animal models that reproduce the specific clinical response as well as pathophysiological immune features of CRC are still lacking. In the current study, we constructed a CRC orthotopic xenograft model by implanting the tumor tubes at the colorectum of mice and monitored the model development using bioluminescence imaging. This model successfully recapitulates the clinical chemotherapy efficacy, including reduced total flux, tumor weight, and the expression of Ki67 after treatment of the first-line chemotherapy regime of CRC (FOLFOX: oxaliplatin and 5-fluorouracil/calcium folinate). The model also reproduced the immunosuppressive effect of FOLFOX, indicated by decreased infiltration of macrophages and increased Treg cells in tumor. Additionally, the orthotopic xenograft approach may be applied in immunodeficient NCG/NSG mice for constructing patient-derived xenografts, and being used in clinical precision medicine and drug evaluation. We believe the current model is a successful surgical orthotopic xenograft approach for cancer research and deserves to be popularized, which will provide a convenient and efficient platform for in-depth mechanism exploration of CRC and preclinical drug evaluation.