Development and Characterization of a Genetic Mouse Model of KRAS Mutated Colorectal Cancer

Abstract

Patients with KRAS mutated colorectal cancer (CRC) represent a cohort with unmet medical needs, with limited options of FDA-approved therapies. Representing 40–45% of all CRC patients, they are considered ineligible to receive anti-EGFR monoclonal antibodies that have added a significant therapeutic benefit for KRAS wild type CRC patients. Although several mouse models of CRC have been developed during the past decade, one genetically resembling the KRAS mutated CRC is yet to be established. In this study C57 BL/6 mice with truncated adenomatous polyposis coli (APC) floxed allele was crossed with heterozygous KRAS floxed outbred mice to generate an APCf/f KRAS+/f mouse colony. In another set of breeding, APC floxed mice were crossed with CDX2-Cre-ERT2 mice and selected for APCf/f CDX2-Cre-ERT2 after the second round of inbreeding. The final model of the disease was generated by the cross of the two parental colonies and viable APC f/f KRAS +/f CDX2-Cre-ERT2 (KPC: APC) were genotyped and characterized. The model animals were tamoxifen (TAM) induced to generate tumors. Micro-positron emission tomography (PET) scan was used to detect and measure tumor volume and standard uptake value (SUV). Hematoxylin and eosin (H&E) staining was performed to establish neoplasm and immunohistochemistry (IHC) was performed to determine histological similarities with human FFPE biopsies. The MSI/microsatellite stable (MSS) status was determined. Finally, the tumors were extensively characterized at the molecular level to establish similarities with human CRC tumors. The model KPC: APC animals are conditional mutants that developed colonic tumors upon induction with tamoxifen in a dose-dependent manner. The tumors were confirmed to be malignant within four weeks of induction by H&E staining and higher radioactive [18F] fluoro-2-deoxyglucose (FDG) uptake (SUV) in micro-PET scan. Furthermore, the tumors histologically and molecularly resembled human colorectal carcinoma. Post tumor generation, the KPC: APC animals died of cachexia and rectal bleeding. Implications: This model is an excellent preclinical platform to molecularly characterize the KRAS mutated colorectal tumors and discern appropriate therapeutic strategies to improve disease management and overall survival.

Management of Cancer Cachexia: Attempting to Develop New Pharmacological Agents for New Effective Therapeutic Options

“…Thus, the KPP genotype appears to be more robust for research on CC compared with the KPC model. Further examples of potentially useful GEM for research on CC are the KL model (KRAS G12D/+ ; LKB1 f/f ), recently used to study the metabolic profile of advanced non-small cell lung cancer (NSCLC) (152), and the lately developed KPC:APC model (APC f/f ; KRAS +/f ; CDX2-Cre-ER T2 ), which aims to recapitulate features of human colorectal carcinoma (CRC) with mutated KRAS and leads to development of CC (153).…”

An enteroendocrine-microbial axis in the large intestine controls host metabolism

“…The targeting vector was generated by PCR using the BAC clone RP23–191l4 as a template. These Neurog3 fl/fl mice were mated with animals containing the CDX2 Cre-ERT2 transgene and available from Jackson (JAX Strain #035169) 49 . Traits present in strain #035169, other than CDX2 Cre-ERT2 ( Kras G12D and Apc fl ), were bred out of the colony to derive Neurog3 fl/fl , CDX2Cre-ERT2 mice.…”

From Chaos to Opportunity: Decoding Cancer Heterogeneity for Enhanced Treatment Strategies

“…Employing this approach permits researchers to functionally assess the oncogenic properties and resistance to therapeutic interventions of genetic and genomic alterations identified in human tumors. Illustrative instances include the induction of oncogenic KRAS activity in colorectal and lung cancers [ 108 ], the amplification of HER2 in breast cancer [ 109 ], and the targeted inactivation of p53 across various cancer types [ 110 , 111 , 112 ]. It is noteworthy that the advancement of the Cre-Lox strategy and CRISPR/Cas9 methodologies has significantly hastened the progression of murine models of human malignancies [ 113 , 114 ].…”

“…However, one of the challenges encountered in reproducing non-human models is precisely the extent of genetic heterogeneity. To elucidate further, murine tumors display a diminished degree of genetic heterogeneity (primary vs. metastatic tumors) due to the absence of environmental mutagens and the controlled living environments of the mice utilized in these investigations, which also exhibit genetic similarity [ 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 ].…”