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Murine orthotopic model for the assessment of chemoradiotherapeutic interventions in rectal cancer

A murine orthotopic model for the study of colon cancer has been described earlier. However, for the study of rectal cancer, three issues remain: (i) the relative sensitivity of the implanted tumors to ionizing radiation (IR); (ii) the location of the tumor for the delivery of external beam IR; and (iii) the assessment of a given modality over time before necropsy. In this protocol, we have modified an orthotopic model for colon cancer described earlier for the specific assessment of chemoradiation in rectal cancer by (i) cecal transplantation of tumors with a known response to IR; (ii) securing the tumor to the lateral abdominal wall with a permanent suture for the administration of IR; and (iii) transfection of cells with luciferase before tumor implantation for the assessment of the chemoradiotherapeutic interventions over time by bioluminescence imaging before the end on the study. This technique allows targeted delivery of IR in an intraperitoneal tumor. Imaging throughout the course of the treatment is possible such that the timing of chemoradiation can be determined and permits comparison between groups before the end of the treatment. This model represents a modified technique that allows the assessment of chemoradiotherapeutic interventions in rectal cancer.