Mouse models in colon cancer, inferences, and implications

Experimental toolkit to study the oncogenic role of WNT signaling in colorectal cancer

Colorectal cancer (CRC) is linked to the WNT/β-catenin signaling as its primary driver. Aberrant activation of WNT/β-catenin signaling is closely correlated with increased incidence, malignancy, poorer prognosis, and even higher cancer-related death. Research over the years has postulated various experimental models that have facilitated an understanding of the complex mechanisms underlying WNT signaling in CRC. In the present review, we have comprehensively summarized the in vitro, in vivo, patient-derived, and computational models used to study the role of WNT signaling in CRC. We discuss the use of CRC cell lines and organoids in capturing the molecular intricacies of WNT signaling and implementing xenograft and genetically engineered mouse models to mimic the tumor microenvironment. Patient-derived models, including xenografts and organoids, provide valuable insights into personalized medicine approaches. Additionally, we elaborated on the role of computational models in simulating WNT signaling dynamics and predicting therapeutic outcomes. By evaluating the advantages and limitations of each model, this review highlights the critical contributions of these systems to our understanding of WNT signaling in CRC. We emphasize the need to integrate diverse model systems to enhance translational research and clinical applications, which is the primary goal of this review.

Recent advances in the development and application of colorectal cancer mouse models

Colorectal cancer (CRC) remains a significant global health challenge, necessitating the development of reliable preclinical models to advance mechanistic understanding and therapeutic innovation. This review comprehensively examines the diverse spectrum of rodent models employed in CRC research, focusing on their unique characteristics, applications, and translational relevance. We systematically evaluate conventional models, including carcinogen-induced models and genetically engineered mouse models (GEMMs), which have been instrumental in elucidating tumorigenic pathways and genetic drivers. Furthermore, we highlight the emergence of patient-derived xenografts (PDX) as a transformative tool for recapitulating tumor heterogeneity and predicting clinical responses. The review also explores metastatic models, which are critical for studying advanced disease, and spontaneous models that mimic natural tumor progression. Additionally, we discuss the growing utility of composite animal models, which integrate multiple methodologies to better reflect the complexity of human CRC. By comparing the strengths and limitations of each model system, this review provides a framework for selecting appropriate models based on specific research objectives. Collectively, these preclinical platforms have significantly advanced our understanding of CRC biology and continue to drive the development of targeted therapies and personalized treatment strategies.

Mouse colorectal cancer organoids: Lessons from syngeneic and orthotopic transplantation systems

Colorectal cancer (CRC) organoids provide more accurate and tissue-relevant models compared to conventional two-dimensional cultured cell cultures. Mouse CRC organoids, in particular, offer unique advantages over their human counterparts, as they can be transplanted into immunocompetent mice. These syngeneic transplantation models create a robust system for studying cancer biology in the immunocompetent tumor microenvironment (TME). This article discusses the development and applications of these organoid systems, emphasizing their capacity to faithfully recapitulate in vivo tumor progression, metastasis, and the immune landscape.

Integrin α3β1 Is Not Required for Onset of Dysplasia in Genetic Model of Colon Cancer but Promotes Motility of Colon Cancer Cells

BACKGROUND/OBJECTIVES

The progression of colorectal cancer through clinically and histopathologically well-defined stages is driven by specific mutations that activate oncogenes or inactivate tumor-suppressor genes. In addition, pre-cancerous/cancer cells respond to cues from the tissue microenvironment that support tumorigenesis and progression, many of which are transmitted through integrin receptors for the extracellular matrix. Integrin α3β1 has pro-tumorigenic/pro-metastatic roles in many cancers, but it also has suppressive roles in some cancers or at specific stages of progression, indicating that its potential value as a therapeutic target cannot be extrapolated across cancer types or stages. In this study, we investigated roles for α3β1 in colorectal cancer using cellular and genetic models that represent different stages.

METHODS

We generated mice with colon-specific α3 knockout in a tamoxifen-inducible model of KRAS-mutated colorectal cancer to assess the effects of α3β1 ablation on early dysplasia. We also used siRNA to suppress α3β1 in human colorectal cancer cells, then assessed effects on motility and invasion in vitro.

RESULTS

Genetic deletion of α3β1 in the colon did not alter dysplasia in mice predisposed to KRAS-mutated colorectal cancer, and it was accompanied by an increase in the colocalization of α6 integrin with laminin-332 (a matrix ligand for both integrins), suggesting functional compensation. However, suppression of α3β1 caused an approximately 40% to 60% reduction in the motility/invasion of human colorectal cancer cells.

CONCLUSIONS

Our findings that α3β1 is not required for pre-cancerous dysplasia but promotes colorectal cancer cell motility/invasion indicate an important role for pro-migratory functions of this integrin at later stages of progression when cells invade from the primary tumor, suggesting that strategies to target α3β1 in colorectal cancer should be aimed at distinct stages of disease progression.

Human-specific elimination of epithelial Siglec-XII suppresses the risk of inflammation-driven colorectal cancers

Carcinomas are common in humans but rare among closely related "great apes." Plausible explanations, including human-specific genomic alterations affecting the biology of sialic acids, are proposed, but causality remains unproven. Here, an integrated evolutionary genetics-phenome-transcriptome approach studied the role of SIGLEC12 gene (encoding Siglec-XII) in epithelial transformation and cancer. Exogenous expression of the protein in cell lines and genetically engineered mice recapitulated approximately 30% of the human population in whom the protein is expressed in a form that cannot bind ligand because of a fixed, homozygous, human-universal missense mutation. Siglec-XII-null cells/mice recapitulated the remaining approximately 70% of the human population in whom an additional polymorphic frameshift mutation eliminates the entire protein. Siglec-XII expression drove several pro-oncogenic phenotypes in cell lines and increased tumor burden in mice challenged with chemical carcinogen and inflammation. Transcriptomic studies yielded a 29-gene signature of Siglec-XII-positive disease and when used as a computational tool for navigating human data sets, pinpointed with surprising precision that SIGLEC12 expression (model) recapitulates a very specific type of colorectal carcinomas (disease) that is associated with mismatch-repair defects and inflammation, disproportionately affects European Americans, and carries a favorable prognosis. They revealed a hitherto-unknown evolutionary genetic mechanism for an ethnic/environmental predisposition of carcinogenesis.

Interactions between diet and gut microbiota in cancer

Dietary patterns and specific dietary components, in concert with the gut microbiota, can jointly shape susceptibility, resistance and therapeutic response to cancer. Which diet-microbial interactions contribute to or mitigate carcinogenesis and how they work are important questions in this growing field. Here we interpret studies of diet-microbial interactions to assess dietary determinants of intestinal colonization by opportunistic and oncogenic bacteria. We explore how diet-induced expansion of specific gut bacteria might drive colonic epithelial tumorigenesis or create immuno-permissive tumour milieus and introduce recent findings that provide insight into these processes. Additionally, we describe available preclinical models that are widely used to study diet, microbiome and cancer interactions. Given the rising clinical interest in dietary modulations in cancer treatment, we highlight promising clinical trials that describe the effects of different dietary alterations on the microbiome and cancer outcomes.

Understanding the complexity of p53 in a new era of tumor suppression

p53 was discovered 45 years ago as an SV40 large T antigen binding protein, coded by the most frequently mutated TP53 gene in human cancers. As a transcription factor, p53 is tightly regulated by a rich network of post-translational modifications to execute its diverse functions in tumor suppression. Although early studies established p53-mediated cell-cycle arrest, apoptosis, and senescence as the classic barriers in cancer development, a growing number of new functions of p53 have been discovered and the scope of p53-mediated anti-tumor activity is largely expanded. Here, we review the complexity of different layers of p53 regulation, and the recent advance of the p53 pathway in metabolism, ferroptosis, immunity, and others that contribute to tumor suppression. We also discuss the challenge regarding how to activate p53 function specifically effective in inhibiting tumor growth without harming normal homeostasis for cancer therapy.

MT1-MMP and TIMP-2 are first expressed in the colon glands after a single dose of azoxymethane (AOM)

Tissue inhibitor of metalloproteinase-2 (TIMP-2) and membrane-type 1-matrix metalloproteinase (MT1-MMP) are always expressed during the cancer process. The aim was to identify which regions of the colon mucosa MT1-MMP and TIMP-2 begin to express themselves, as well as to establish their expression in relation to cell proliferation and mucin production. After intraperitoneal injection of 15 mg/kg of azoxymethane (AOM) at 4, 12, and 20 weeks, histological sections of the middle segment of the rat colon mucosa were evaluated by immunohistochemistry for cell proliferation and expression of MT1-MMP and TIMP-2 and histochemistry for mucin. As a result, a single dose of AOM initially increased the intensity of MT1-MMP and TIMP-2 expression in the conjunctive cells and glands, concurrently with alterations in the distribution of the mucin produced in the gland of the large intestine mucosa and cell proliferation. As a result, at 4 and 12 weeks, a single dose of AOM initially stimulated the expression of MT1-MMP and TIMP-2 in the conjunctive cells and glands with greater intensity. Changes in the cell proliferation and distribution of the mucin produced in the large intestine mucosa gland were observed. We conclude that MT1-MMP and TIMP-2 were first and strongly expressed in all cells of the colon glands, concurrently with an increase in cell proliferation and a diffuse dispersion of mucin, indicating the onset of the dysplasia process following a single dosage of AOM.

Colorectal ALOX15 as a host factor determinant of EPA and DHA effects on colorectal carcinogenesis

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), omega-3 polyunsaturated fatty acids (ω-3 PUFAs) derived from fish oil, are widely used as dietary supplements and FDA-approved treatments for hypertriglyceridemia. However, studies investigating the effects of EPA and DHA on colorectal carcinogenesis (CRC) have yielded conflicting results. The factors that determine these discrepant results remain unknown. Resolvins, oxidative metabolites of EPA and DHA, inhibit key pro-tumorigenic cytokine and chemokine signaling of colorectal cancer (e.g., IL-6, IL-1β, and CCL2). 15-lipoxygenase-1 (ALOX15), a critical enzyme for resolvin generation is commonly lost during human CRC. Whether ALOX15 expression, as a host factor, modulates the effects of EPA and DHA on CRC remains unknown. Therefore, we evaluated the effects of ALOX15 transgenic expression in colonic epithelial cells on resolvin generation by EPA and DHA and CRC in mouse models representative of human CRC. Our results revealed that 1) EPA and DHA effects on CRC were diverse, ranging from suppressive to promotive, and these effects were occasionally altered by the formulations of EPA and DHA (free fatty acid, ethyl ester, triglyceride); 2) EPA and DHA uniformly suppressed CRC in the presence of intestinal ALOX15 transgenic expression, which induced the production of resolvins, decreased colonic CCL3-5 and CXCL-5 expression and tumor associated macrophages while increasing CD8 T cell abundance in tumor microenvironment; and 3) RvD5, the predominant resolvin produced by ALOX15, inhibited macrophage generation of pro-tumorigenic cytokines. These findings demonstrate the significance of intestinal ALOX15 expression as a host factor in determining the effects of EPA and DHA on CRC.

Significance

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are widely used as dietary supplements and FDA-approved treatments for hypertriglyceridemia. Studies of EPA and DHA effects on colorectal carcinogenesis (CRC) have revealed inconsistencies; factors determining the direction of their impact on CRC have remained unidentified. Our data show that EPA and DHA effects on CRC were divergent and occasionally influenced by their formulations. More importantly, intestinal 15-lipoxgenase-1 (ALOX15) expression modulated EPA and DHA effects on CRC, leading to their consistent suppression of CRC. ALOX15 promoted EPA and DHA oxidative metabolism to generate resolvins, which inhibited key pro-tumorigenic inflammatory cytokines and chemokines, including IL-6. IL-1β, and CCL2. ALOX15 is therefore an important host factor in determining EPA and DHA effects on CRC.

Colorectal cancer murine models: Initiation to metastasis

Despite significant advancements in prevention and treatment, colorectal cancer (CRC) remains the third leading cause of cancer-related deaths. Animal models, including xenografts, syngeneic, and genetically engineered, have emerged as indispensable tools in cancer research. These models offer a valuable platform to address critical questions regarding molecular pathogenesis and test therapeutic interventions before moving on to clinical trials. Advancements in CRC animal models have also facilitated the advent of personalized and precision medicine. Patient-derived xenografts and genetically engineered mice that mirror features of human tumors allow for tailoring treatments to specific CRC subtypes, improving treatment outcomes and quality of life. To overcome the limitations of individual model systems, recent studies have employed a multi-modal approach, combining different animal models, 3D organoids, and in vitro studies. This integrative approach provides a comprehensive understanding of CRC biology, including the tumor microenvironment and therapeutic responses, driving the development of more effective and personalized therapeutic interventions. This review discusses the animal models used for CRC research, including recent advancements and limitations of these animal models.

Integrin-linked kinase expression in myeloid cells promotes colon tumorigenesis

Colorectal cancer (CRC) is one of the most common forms of cancer worldwide and treatment options for advanced CRC, which has a low 5-year survival rate, remain limited. Integrin-linked kinase (ILK), a multifunctional, scaffolding, pseudo-kinase regulating many integrin-mediated cellular processes, is highly expressed in many cancers. However, the role of ILK in cancer progression is yet to be fully understood. We have previously uncovered a pro-inflammatory role for myeloid-specific ILK in dextran sodium sulfate (DSS)-induced colitis. To establish a correlation between chronic intestinal inflammation and colorectal cancer (CRC), we investigated the role of myeloid-ILK in mouse models of CRC. When myeloid-ILK deficient mice along with the WT control mice were subjected to colitis-associated and APCmin/+-driven CRC, tumour burden was reduced by myeloid-ILK deficiency in both models. The tumour-promoting phenotype of macrophages, M2 polarization, in vitro was impaired by the ILK deficiency and the number of M2-specific marker CD206-expressing tumour-associated macrophages (TAMs) in vivo were significantly diminished in myeloid-ILK deficient mice. Myeloid-ILK deficient mice showed enhanced tumour infiltration of CD8+ T cells and reduced tumour infiltration of FOXP3+ T cells in colitis-associated and APCmin/+-driven CRC, respectively, with an overall elevated CD8+/FOXP3+ ratio suggesting an anti-tumour immune phenotypes. In patient CRC tissue microarrays we observed elevated ILK+ myeloid (ILK+ CD11b+) cells in tumour sections compared to adjacent normal tissues, suggesting a conserved role for myeloid-ILK in CRC development in both human and animal models. This study identifies myeloid-specific ILK expression as novel driver of CRC, which could be targeted as a potential therapeutic option for advanced disease.