Abstract 29: Characterization of a murine intestinal cancer homograft model for therapeutic evaluation

Abstract

Abstract Introduction: Intestinal cancers are one of the most lethal malignancies and are responsible for a mass of cancer-related deaths. The discovery of new drugs and therapeutic strategies is underway, and to complement this, the development of superior animal models is required for preclinical studies. Genetically engineered mouse models (GEMMs) mimic de novo human tumor growth within an intact tumor microenvironment and are potent immunocompetent models for studying pathogenesis and immuno-oncology of intestinal cancers. GEMMs with dysfunctional DNA mismatch repair (MMR) genes, like MHL1 and MSH2, manifest intestinal tumors related to microsatellite instability (MSI). However, the low incidence and distinct latency among individuals hamper the application of these GEMMs in preclinical research. In this study, a murine intestinal cancer homograft from GEMMs with MMR deficiency is established to enroll larger cohorts of mice for preclinical studies. Methods: MMR-deficient GEMMs were generated by knockout of Mlh1 gene with a CRISPR-Cas9 system. Intestinal cancer development was investigated in 16 GEMMs. The developed tumor in the intestine of GEMM was isolated by surgery and inoculated into C57BL/6 mice subcutaneously to establish a murine homograft model. The tumor homograft was passaged and expanded in vivo, and stable tumor growth was established over consecutive passages. Histopathological studies were conducted for both the original and passaged tumors. Genomic mutations and gene expression were analyzed by whole exome sequencing and RNA-sequencing, and tumor-infiltrating lymphocytes (TILs) were analyzed by flow cytometry. Therapeutic efficacy of chemotherapies and immune checkpoint inhibitors were evaluated in vivo for tumor growth inhibition. Results: The intestinal tumors or lesions were observed in two of the sixteen Mlh1-KO mice with an incidence of 12.5%. A murine homograft model of small bowel adenocarcinoma was successfully established using the tumor located in jejunum of a Mlh1-KO mouse. This model was stably passaged in vivo with semblable pathological features as the original lesion in Mlh1-KO mice. The various degrees of TILs and response to treatments revealed the potential of this model for in vivo investigation of immune response. Conclusion: Our murine intestinal cancer homograft model presented rapid and stable subcutaneous growth in immunocompetent mice, providing an efficient approach for intestinal cancer researchers and a superior preclinical model for new drug discovery. Citation Format: Jinxi Wang, Leilei Chen, Likun Zhang, Jingqian Zhu, Ludovic Bourre, Jingjing Wang. Characterization of a murine intestinal cancer homograft model for therapeutic evaluation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 29.