Abstract 119: A non-surgical method for developing a pre-clinical orthotopic mouse model for colorectal cancer

Abstract Recapitulating physiologically relevant tumor microenvironment is important yet a significant challenge in modeling colorectal cancer (CRC) for basic and translational studies. Among the different methods, using the cecal-wall injection technique is the most common way to create animal models of colorectal cancer (CRC). However, this approach requires complex surgery, and its unnatural placement creates a significant obstacle for developing treatments. Here, we report a non-surgical procedure for establishing orthotopic CRC mouse models, reflecting the appropriate tumor microenvironment to better model the disease development and facilitate translational studies including drug identification and validation. In this procedure, anesthesia is induced in overnight fasted study immunocompetent or immunodeficient mice while placed on a thermostat-controlled heating blanket. A specialized catheter is inserted and distended into the mouse colon to gently block the colon and ensure the localization for tumor development. Hereafter, the colonic epithelium is treated with proteases and mechanical abrasion to cause mild disruption. Following the local gut inflammation, the targeted colon region is incubated with tumor cells, leading to the adhesion of tumor cells to the colonic epithelium. Based on the animal background and the cell line used, the tumor developed within 3-4 weeks. The stages of tumor development at different time points were successfully confirmed using hematoxylin and eosin stain. Tumor microenvironment data revealed a significant increase in the immune cell infiltration specifically CD4+ T-cells and tumor-associated macrophages in the non-surgical procedure as compared to the cecal-wall injection. Furthermore, a significant increase in the PD-1 expression of the CD8+ T-cells in the cecal-wall injection as compared to the non-surgical procedure, suggests that the precise location of the tumor site may exert a substantial influence on pre-clinical therapeutic outcomes of immune-checkpoint inhibitors, thereby potentially hampering the clinical efficacy of drug treatments. Additional adaptations of this procedure may include: i) tumor development in different mouse strains, ii) local delivery of adeno-Cre in transgenic mice for CRC, and iii) delivering tumor organoids and patient-derived xenografts in immuno-deficient mice. Overall, our non-surgical procedure overcomes the technical difficulties of surgery and offers several advantages like ease of handling, cost-effectiveness, pain-free with nearly no procedure-associated mortality and adaptability to several strains. In conclusion, this procedure provides novel and promising alternative to conventional surgical orthotopic CRC mouse models for therapeutic interventions. Citation Format: Naresh Singh, Samantha Sharma, Kevin Van Der Jeught, Zhuolong Zhou, Xinna Zhang, Xiongbin Lu. A non-surgical method for developing a pre-clinical orthotopic mouse model for colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 119.