Endoscopic ultrasound-guided inoculation of transmissible venereal tumor in the colon: A large animal model for colon neoplasia

Background: To develop and evaluate the feasibility of emerging interventions, animal models with accurate anatomical environment are required. Objectives: We aimed to establish a clinically relevant colorectal tumor model with canine transmissible venereal tumor (CTVT) utilizing endoscopic ultrasound (EUS) imaging guidance. Design: Survival study using a canine model. Setting: Endoscopic animal research laboratory at a tertiary cancer center. Materials and Methods: This study involved five canines. Interventions: A colorectal tumor model was established and evaluated in five canines under cyclosporine immune suppression. Under endoscopic imaging guidance, saline was injected into the submucosal layer forming a bleb. Subsequently, CTVT was inoculated into the bleb under EUS guidance. Endoscopy was the primary method of assessing tumor growth. Tumors developed in 60-130 days. Upon detection of lesions > 1 cm, the animals were euthanized and the tumors were harvested for histopathological characterization. Main outcome measurements: Success rate of tumor growth. The presence or absence of vasculature inside tumors. Results: Colorectal tumor successfully developed in three out of the five animals (60%). Among the ones with tumor growth, average inoculated CTVT volume, incubation time, and tumor size was 1.8 cc, 65.7 days, and 2.0 cm, respectively. The two animals without tumor growth were observed for > 100 days. In all the tumors, vascular structure was characterized with CD31 imunohistochemical stain. Limitations: Small number of animals. Conclusion: We succeeded in creating a new colorectal tumor canine model with CTVT utilizing EUS.