Multiple intestinal neoplasia caused by a mutation in the murine homolog of the APC gene

A comprehensive review of animal models for cancer cachexia: Implications for translational research

Cancer cachexia is a multifactorial syndrome characterized by progressive weight loss and a disease process that nutritional support cannot reverse. Although progress has been made in preclinical research, there is still a long way to go in translating research findings into clinical practice. One of the main reasons for this is that existing preclinical models do not fully replicate the conditions seen in clinical patients. Therefore, it is important to understand the characteristics of existing preclinical models of cancer cachexia and pay close attention to the latest developments in preclinical models. The main models of cancer cachexia used in current research are allogeneic and xenograft models, genetically engineered mouse models, chemotherapy drug-induced models, Chinese medicine spleen deficiency models, zebrafish and Drosophila models, and cellular models. This review aims to revisit and summarize the commonly used animal models of cancer cachexia by evaluating existing preclinical models, to provide tools and support for translational medicine research.

Rodent models of tumours of the central nervous system

Modelling of human diseases is an essential component of biomedical research, to understand their pathogenesis and ultimately, develop therapeutic approaches. Here, we will describe models of tumours of the central nervous system, with focus on intrinsic CNS tumours. Model systems for brain tumours were established as early as the 1920s, using chemical carcinogenesis, and a systematic analysis of different carcinogens, with a more refined histological analysis followed in the 1950s and 1960s. Alternative approaches at the time used retroviral carcinogenesis, allowing a more topical, organ-centred delivery. Most of the neoplasms arising from this approach were high-grade gliomas. Whilst these experimental approaches did not directly demonstrate a cell of origin, the localisation and growth pattern of the tumours already pointed to an origin in the neurogenic zones of the brain. In the 1980s, expression of oncogenes in transgenic models allowed a more targeted approach by expressing the transgene under tissue-specific promoters, whilst the constitutive inactivation of tumour suppressor genes ('knock out')-often resulted in embryonic lethality. This limitation was elegantly solved by engineering the Cre-lox system, allowing for a promoter-specific, and often also time-controlled gene inactivation. More recently, the use of the CRISPR Cas9 technology has significantly increased experimental flexibility of gene expression or gene inactivation and thus added increased value of rodent models for the study of pathogenesis and establishing preclinical models.

A Ctnnb1 enhancer transcriptionally regulates Wnt signaling dosage to balance homeostasis and tumorigenesis of intestinal epithelia

The β-catenin-dependent canonical Wnt signaling is pivotal in organ development, tissue homeostasis, and cancer. Here, we identified an upstream enhancer of Ctnnb1 - the coding gene for β-catenin, named ieCtnnb1 (intestinal enhancer of Ctnnb1), which is crucial for intestinal homeostasis. ieCtnnb1 is predominantly active in the base of small intestinal crypts and throughout the epithelia of large intestine. Knockout of ieCtnnb1 led to a reduction in Ctnnb1 transcription, compromising the canonical Wnt signaling in intestinal crypts. Single-cell sequencing revealed that ieCtnnb1 knockout altered epithelial compositions and potentially compromised functions of small intestinal crypts. While deletion of ieCtnnb1 hampered epithelial turnovers in physiologic conditions, it prevented occurrence and progression of Wnt/β-catenin-driven colorectal cancers. Human ieCTNNB1 drove reporter gene expression in a pattern highly similar to mouse ieCtnnb1. ieCTNNB1 contains a single-nucleotide polymorphism associated with CTNNB1 expression levels in human gastrointestinal epithelia. The enhancer activity of ieCTNNB1 in colorectal cancer tissues was stronger than that in adjacent normal tissues. HNF4α and phosphorylated CREB1 were identified as key trans-factors binding to ieCTNNB1 and regulating CTNNB1 transcription. Together, these findings unveil an enhancer-dependent mechanism controlling the dosage of Wnt signaling and homeostasis in intestinal epithelia.

Food antigens suppress small intestinal tumorigenesis

Food components suppressing small intestinal tumorigenesis are not well-defined partly because of the rarity of this tumor type compared to colorectal tumors. Using Apcmin/+ mice, a mouse model for intestinal tumorigenesis, and antigen-free diet, we report here that food antigens serve this function in the small intestine. By depleting Peyer's patches (PPs), immune inductive sites in the small intestine, we found that PPs have a role in the suppression of small intestinal tumors and are important for the induction of small intestinal T cells by food antigens. On the follicle-associated epithelium (FAE) of PPs, microfold (M) cells pass food antigens from lumen to the dendritic cells to induce T cells. Single-cell RNA-seq (scRNA-seq) analysis of immune cells in PPs revealed a significant impact of food antigens on the induction of the PP T cells and the antigen presentation capacity of dendritic cells. These data demonstrate the role of food antigens in the suppression of small intestinal tumorigenesis by PP-mediated immune cell induction.

Plasma-Derived Extracellular Vesicles and Non-Extracellular Vesicle Components from APCMin/+ Mice Promote Pro-Tumorigenic Activities and Activate Human Colonic Fibroblasts via the NF-κB Signaling Pathway

Colorectal cancer (CRC) is the third most prevalent cancer worldwide. Current studies have demonstrated that tumor-derived extracellular vesicles (EVs) from different cancer cell types modulate the fibroblast microenvironment to contribute to cancer development and progression. Here, we isolated and characterized circulating large EVs (LEVs), small EVs (SEVs) and non-EV entities released in the plasma from wild-type (WT) mice and the APCMin/+ CRC mice model. Our results showed that human colon fibroblasts exposed from APC-EVs, but not from WT-EVs, exhibited the phenotypes of cancer-associated fibroblasts (CAFs) through EV-mediated NF-κB pathway activation. Cytokine array analysis on secreted proteins revealed elevated levels of inflammatory cytokine implicated in cancer growth and metastasis. Finally, non-activated cells co-cultured with supernatant from fibroblasts treated with APC-EVs showed increased mRNA expressions of CAFs markers, the ECM, inflammatory cytokines, as well as the expression of genes controlled by NF-κB. Altogether, our work suggests that EVs and non-EV components from APCMin/+ mice are endowed with pro-tumorigenic activities and promoted inflammation and a CAF-like state by triggering NF-κB signaling in fibroblasts to support CRC growth and progression. These findings provide insight into the interaction between plasma-derived EVs and human cells and can be used to design new CRC diagnosis and prognosis tools.

Enhanced ApcMin/+ adenoma formation after epithelial CUL4B deletion by recruitment of myeloid-derived suppressor cells

Colorectal cancer (CRC) stands as a prevalent malignancy globally. A pivotal event in CRC pathogenesis involves the loss-of-function mutation in the APC gene, leading to the formation of benign polyps. Despite the well-established role of APC, the contribution of CUL4B to CRC initiation in the pre-tumorous stage remains poorly understood. In this investigation, we generated a murine model by crossing ApcMin/+ mice with Cul4bΔIEC mice to achieve specific deletion of Cul4b in the gut epithelium against an ApcMin/+ background. By employing histological methods, RNA-sequencing (RNA-seq), and flow cytometry, we assessed alterations and characterized the immune microenvironment. Our results unveiled that CUL4B deficiency in gut epithelium expedited ApcMin/+ adenoma formation. Notably, CUL4B in adenomas restrained the accumulation of tumor-infiltrating myeloid-derived suppressor cells (MDSCs). In vivo inhibition of MDSCs significantly delayed the growth of CUL4B deleted ApcMin/+ adenomas. Furthermore, the addition of MDSCs to in vitro cultured ApcMin/+; Cul4bΔIEC adenoma organoids mitigated their alterations. Mechanistically, CUL4B directly interacted with the promoter of Csf3, the gene encoding granulocyte-colony stimulating factor (G-CSF) by coordinating with PRC2. Inhibiting CUL4B epigenetically activated the expression of G-CSF, promoting the recruitment of MDSCs. These findings offer novel insights into the tumor suppressor-like roles of CUL4B in regulating ApcMin/+ adenomas, suggesting a potential therapeutic strategy for CRC initiation and progression in the context of activated Wnt signaling.

Wnt/β-catenin signaling pathway in carcinogenesis and cancer therapy

The Wnt/β-catenin signaling pathway plays a crucial role in various physiological processes, encompassing development, tissue homeostasis, and cell proliferation. Under normal physiological conditions, the Wnt/β-catenin signaling pathway is meticulously regulated. However, aberrant activation of this pathway and downstream target genes can occur due to mutations in key components of the Wnt/β-catenin pathway, epigenetic modifications, and crosstalk with other signaling pathways. Consequently, these dysregulations contribute significantly to tumor initiation and progression. Therapies targeting the Wnt/β-catenin signaling transduction have exhibited promising prospects and potential for tumor treatment. An increasing number of medications targeting this pathway are continuously being developed and validated. This comprehensive review aims to summarize the latest advances in our understanding of the role played by the Wnt/β-catenin signaling pathway in carcinogenesis and targeted therapy, providing valuable insights into acknowledging current opportunities and challenges associated with targeting this signaling pathway in cancer research and treatment.

Combined effects of radiation and simulated microgravity on intestinal tumorigenesis in C3B6F1 ApcMin/+ mice

Explorations of the Moon and Mars are planned as future manned space missions, during which humans will be exposed to both radiation and microgravity. We do not, however, know the health effects for such combined exposures. In a ground-based experiment, we evaluated the combined effects of radiation and simulated microgravity on tumorigenesis by performing X-irradiation and tail suspension in C3B6F1 ApcMin/+ mice, a well-established model for intestinal tumorigenesis. Mice were irradiated at 2 weeks of age and underwent tail suspension for 3 or 11 weeks using a special device that avoids damage to the tail. The tail suspension treatment significantly reduced the thymus weight after 3 weeks but not 11 weeks, suggesting a transient stress response. The combination of irradiation and tail suspension significantly increased the number of small intestinal tumors less than 2 mm in diameter as compared with either treatment alone. The combined treatment also increased the fraction of malignant tumors among all small intestinal tumors as compared with the radiation-only treatment. Thus, the C3B6F1 ApcMin/+ mouse is a useful model for assessing cancer risk in a simulated space environment, in which simulated microgravity accelerates tumor progression when combined with radiation exposure.

DHX9 maintains epithelial homeostasis by restraining R-loop-mediated genomic instability in intestinal stem cells

Epithelial barrier dysfunction and crypt destruction are hallmarks of inflammatory bowel disease (IBD). Intestinal stem cells (ISCs) residing in the crypts play a crucial role in the continuous self-renewal and rapid recovery of intestinal epithelial cells (IECs). However, how ISCs are dysregulated in IBD remains poorly understood. Here, we observe reduced DHX9 protein levels in IBD patients, and mice with conditional DHX9 depletion in the intestinal epithelium (Dhx9ΔIEC) exhibit an increased susceptibility to experimental colitis. Notably, Dhx9ΔIEC mice display a significant reduction in the numbers of ISCs and Paneth cells. Further investigation using ISC-specific or Paneth cell-specific Dhx9-deficient mice demonstrates the involvement of ISC-expressed DHX9 in maintaining epithelial homeostasis. Mechanistically, DHX9 deficiency leads to abnormal R-loop accumulation, resulting in genomic instability and the cGAS-STING-mediated inflammatory response, which together impair ISC function and contribute to the pathogenesis of IBD. Collectively, our findings highlight R-loop-mediated genomic instability in ISCs as a risk factor in IBD.

Advances in Making Cancer Mouse Models More Accessible and Informative through Non-Germline Genetic Engineering

Genetically engineered mouse models (GEMMs) allow for modeling of spontaneous tumorigenesis within its native microenvironment in mice and have provided invaluable insights into mechanisms of tumorigenesis and therapeutic strategies to treat human disease. However, as their generation requires germline manipulation and extensive animal breeding that is time-, labor-, and cost-intensive, traditional GEMMs are not accessible to most researchers, and fail to model the full breadth of cancer-associated genetic alterations and therapeutic targets. Recent advances in genome-editing technologies and their implementation in somatic tissues of mice have ushered in a new class of mouse models: non-germline GEMMs (nGEMMs). nGEMM approaches can be leveraged to generate somatic tumors de novo harboring virtually any individual or group of genetic alterations found in human cancer in a mouse through simple procedures that do not require breeding, greatly increasing the accessibility and speed and scale on which GEMMs can be produced. Here we describe the technologies and delivery systems used to create nGEMMs and highlight new biological insights derived from these models that have rapidly informed functional cancer genomics, precision medicine, and immune oncology.

Cancer-on-a-chip model shows that the adenomatous polyposis coli mutation impairs T cell engagement and killing of cancer spheroids

Evaluating the ability of cytotoxic T lymphocytes (CTLs) to eliminate tumor cells is crucial, for instance, to predict the efficiency of cell therapy in personalized medicine. However, the destruction of a tumor by CTLs involves CTL migration in the extra-tumoral environment, accumulation on the tumor, antigen recognition, and cooperation in killing the cancer cells. Therefore, identifying the limiting steps in this complex process requires spatio-temporal measurements of different cellular events over long periods. Here, we use a cancer-on-a-chip platform to evaluate the impact of adenomatous polyposis coli (APC) mutation on CTL migration and cytotoxicity against 3D tumor spheroids. The APC mutated CTLs are found to have a reduced ability to destroy tumor spheroids compared with control cells, even though APC mutants migrate in the extra-tumoral space and accumulate on the spheroids as efficiently as control cells. Once in contact with the tumor however, mutated CTLs display reduced engagement with the cancer cells, as measured by a metric that distinguishes different modes of CTL migration. Realigning the CTL trajectories around localized killing cascades reveals that all CTLs transition to high engagement in the 2 h preceding the cascades, which confirms that the low engagement is the cause of reduced cytotoxicity. Beyond the study of APC mutations, this platform offers a robust way to compare cytotoxic cell efficiency of even closely related cell types, by relying on a multiscale cytometry approach to disentangle complex interactions and to identify the steps that limit the tumor destruction.

BAMLET administration via drinking water inhibits intestinal tumor development and promotes long-term health

Though new targeted therapies for colorectal cancer, which progresses from local intestinal tumors to metastatic disease, are being developed, tumor specificity remains an important problem, and side effects a major concern. Here, we show that the protein-fatty acid complex BAMLET (bovine alpha-lactalbumin made lethal to tumor cells) can act as a peroral treatment for colorectal cancer. ApcMin/+ mice, which carry mutations relevant to hereditary and sporadic human colorectal cancer, that received BAMLET in the drinking water showed long-term protection against tumor development and decreased expression of tumor growth-, migration-, metastasis- and angiogenesis-related genes. BAMLET treatment via drinking water inhibited the Wnt/β-catenin and PD-1 signaling pathways and prolonged survival without evidence of toxicity. Systemic disease in the lungs, livers, spleens, and kidneys, which accompanied tumor progression, was inhibited by BAMLET treatment. The metabolic response to BAMLET included carbohydrate and lipid metabolism, which were inhibited in tumor prone ApcMin/+ mice and weakly regulated in C57BL/6 mice, suggesting potential health benefits of peroral BAMLET administration in addition to the potent antitumor effects. Together, these findings suggest that BAMLET administration in the drinking water maintains antitumor pressure by removing emergent cancer cells and reprogramming gene expression in intestinal and extra-intestinal tissues.

Orthotopic MC-38 Allograft as a Robust Preclinical Model of Colorectal Carcinoma

Colorectal cancer (CRC) is a significant global health concern, requiring effective preclinical models for studying its development and testing therapies. Mouse models have been used, including spontaneous tumors, carcinogen exposure, and tumor cell implantation as xenografts or at orthotopic sites. Here, we describe an orthotopic preclinical model of CRC, which provides a valuable tool for studying tumor growth and the tumor microenvironment, offering a more accurate representation of human CRC compared to xenograft models.

The mechanism of intestinal stem cells differentiation after ischemia-reperfusion injury in a rat model

PURPOSE

Notch and Wnt/β-catenin signaling are responsible for regulation of intestinal stem cells (ISCs) proliferation and differentiation. The purpose of the study was to evaluate Wnt/β-catenin and Notch signaling roles in regulation of ISC differentiation following ischemia-reperfusion (IR) injury in a rat.

METHODS

Rats were assigned into two groups: Sham rats underwent laparotomy without vascular intervention and IR rats underwent occlusion of SMA and portal vein for 20 min followed by 48 h of reperfusion. Wnt/β-catenin and Notch-related gene expression were determined using Real-Time PCR. Enterocyte proliferation, differentiation and Wnt-related proteins were determined by immunohistochemistry.

RESULTS

IR rats demonstrated a significant decrease in β-catenin gene expression, a decrease in cyclin D1 and β-catenin positive cells in jejunum and ileum compared to Sham rats. IR rats demonstrated a significant increase in Notch-related gene expression in jejunum and ileum compared to Sham rats. The number of secretory cells was higher mainly in the jejunum and number of absorptive cells was significantly lower in jejunum and lower in ileum in IR rats compared to Sham rats.

CONCLUSIONS

Intestinal stem-cell differentiation is toward secretory cells 48 h after IR injury; however, Wnt/β-catenin pathway inhibition and Notch-related gene expression stimulation suggest crosstalk between pathways.

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.

STAT2 Controls Colorectal Tumorigenesis and Resistance to Anti-Cancer Drugs

Colorectal cancer (CRC) is a significant socioeconomic burden in modern society and is accountable for millions of premature deaths each year. The role of signal transducer and activator of transcription 2 (STAT2)-dependent signaling in this context is not yet fully understood, and no therapies targeting this pathway are currently being pursued. We investigated the role of STAT2 in CRC using experimental mouse models coupled with RNA-sequencing (RNA-Seq) data and functional assays with anti-cancer agents in three-dimensional tumoroids. Stat2-/- mice showed greater resistance to the development of CRC in both inflammation-driven and inflammation-independent experimental CRC models. In ex vivo studies, tumoroids derived from Stat2-/- mice with the multiple intestinal neoplasia (Min) mutant allele of the adenomatous polyposis coli (Apc) locus exhibited delayed growth, were overall smaller and more differentiated as compared with tumoroids from ApcMin/+ wildtype (WT) mice. Notably, tumoroids from ApcMin/+ Stat2-/- mice were more susceptible to anti-cancer agents inducing cell death by different mechanisms. Our findings clearly indicated that STAT2 promotes CRC and suggested that interventions targeting STAT2-dependent signals might become an attractive therapeutic option for patients with CRC.

DNASE1L3 enhances antitumor immunity and suppresses tumor progression in colon cancer

DNASE1L3, an enzyme highly expressed in DCs, is functionally important for regulating autoimmune responses to self-DNA and chromatin. Deficiency of DNASE1L3 leads to development of autoimmune diseases in both humans and mice. However, despite the well-established causal relationship between DNASE1L3 and immunity, little is known about the involvement of DNASE1L3 in regulation of antitumor immunity, the foundation of modern antitumor immunotherapy. In this study, we identify DNASE1L3 as a potentially new regulator of antitumor immunity and a tumor suppressor in colon cancer. In humans, DNASE1L3 is downregulated in tumor-infiltrating DCs, and this downregulation is associated with poor patient prognosis and reduced tumor immune cell infiltration in many cancer types. In mice, Dnase1l3 deficiency in the tumor microenvironment enhances tumor formation and growth in several colon cancer models. Notably, the increased tumor formation and growth in Dnase1l3-deficient mice are associated with impaired antitumor immunity, as evidenced by a substantial reduction of cytotoxic T cells and a unique subset of DCs. Consistently, Dnase1l3-deficient DCs directly modulate cytotoxic T cells in vitro. To our knowledge, our study unveils a previously unknown link between DNASE1L3 and antitumor immunity and further suggests that restoration of DNASE1L3 activity may represent a potential therapeutic approach for anticancer therapy.

Methionine restriction-induced sulfur deficiency impairs antitumour immunity partially through gut microbiota

Restriction of methionine (MR), a sulfur-containing essential amino acid, has been reported to repress cancer growth and improve therapeutic responses in several preclinical settings. However, how MR impacts cancer progression in the context of the intact immune system is unknown. Here we report that while inhibiting cancer growth in immunocompromised mice, MR reduces T cell abundance, exacerbates tumour growth and impairs tumour response to immunotherapy in immunocompetent male and female mice. Mechanistically, MR reduces microbial production of hydrogen sulfide, which is critical for immune cell survival/activation. Dietary supplementation of a hydrogen sulfide donor or a precursor, or methionine, stimulates antitumour immunity and suppresses tumour progression. Our findings reveal an unexpected negative interaction between MR, sulfur deficiency and antitumour immunity and further uncover a vital role of gut microbiota in mediating this interaction. Our study suggests that any possible anticancer benefits of MR require careful consideration of both the microbiota and the immune system.

Platelet status in cancer cachexia progression in ApcMin/+ mice

Cachexia, a complex wasting syndrome, significantly affects the quality of life and treatment options for cancer patients. Studies have reported a strong correlation between high platelet count and decreased survival in cachectic individuals. Therefore, this study aimed to investigate the immunopathogenesis of cancer cachexia using the ApcMin/+ mouse model of spontaneous colorectal cancer. The research focused on identifying cellular elements in the blood at different stages of cancer cachexia, assessing inflammatory markers and fibrogenic factors in the skeletal muscle, and studying the behavioral and metabolic phenotype of ApcMin/+ mice at the pre-cachectic and severely cachectic stages. Platelet measurements were also obtained from other animal models of cancer cachexia - Lewis Lung Carcinoma and Colon 26 adenocarcinoma. Our study revealed that platelet number is elevated prior to cachexia development in ApcMin/+ mice and can become activated during its progression. We also observed increased expression of TGFβ2, TGFβ3, and SMAD3 in the skeletal muscle of pre-cachectic ApcMin/+ mice. In severely cachectic mice, we observed an increase in Ly6g, CD206, and IL-10 mRNA. Meanwhile, IL-1β gene expression was elevated in the pre-cachectic stage. Our behavioral and metabolic phenotyping results indicate that pre-cachectic ApcMin/+ mice exhibit decreased physical activity. Additionally, we found an increase in anemia at pre-cachectic and severely cachectic stages. These findings highlight the altered platelet status during early and late stages of cachexia and provide a basis for further investigation of platelets in the field of cancer cachexia.

Metabolic profiling stratifies colorectal cancer and reveals adenosylhomocysteinase as a therapeutic target

The genomic landscape of colorectal cancer (CRC) is shaped by inactivating mutations in tumour suppressors such as APC, and oncogenic mutations such as mutant KRAS. Here we used genetically engineered mouse models, and multimodal mass spectrometry-based metabolomics to study the impact of common genetic drivers of CRC on the metabolic landscape of the intestine. We show that untargeted metabolic profiling can be applied to stratify intestinal tissues according to underlying genetic alterations, and use mass spectrometry imaging to identify tumour, stromal and normal adjacent tissues. By identifying ions that drive variation between normal and transformed tissues, we found dysregulation of the methionine cycle to be a hallmark of APC-deficient CRC. Loss of Apc in the mouse intestine was found to be sufficient to drive expression of one of its enzymes, adenosylhomocysteinase (AHCY), which was also found to be transcriptionally upregulated in human CRC. Targeting of AHCY function impaired growth of APC-deficient organoids in vitro, and prevented the characteristic hyperproliferative/crypt progenitor phenotype driven by acute deletion of Apc in vivo, even in the context of mutant Kras. Finally, pharmacological inhibition of AHCY reduced intestinal tumour burden in ApcMin/+ mice indicating its potential as a metabolic drug target in CRC.

What the BTBR/J mouse has taught us about diabetes and diabetic complications

Human and mouse genetics have delivered numerous diabetogenic loci, but it is mainly through the use of animal models that the pathophysiological basis for their contribution to diabetes has been investigated. More than 20 years ago, we serendipidously identified a mouse strain that could serve as a model of obesity-prone type 2 diabetes, the BTBR (Black and Tan Brachyury) mouse (BTBR T+ Itpr3tf/J, 2018) carrying the Lepob mutation. We went on to discover that the BTBR-Lepob mouse is an excellent model of diabetic nephropathy and is now widely used by nephrologists in academia and the pharmaceutical industry. In this review, we describe the motivation for developing this animal model, the many genes identified and the insights about diabetes and diabetes complications derived from >100 studies conducted in this remarkable animal model.

Formyl peptide receptor-1 (FPR1) represses intestinal oncogenesis

Formyl peptide receptor-1 (FPR1) is a pattern recognition receptor that is mostly expressed by myeloid cells. In patients with colorectal cancer (CRC), a loss-of-function polymorphism (rs867228) in the gene coding for FPR1 has been associated with reduced responses to chemotherapy or chemoradiotherapy. Moreover, rs867228 is associated with accelerated esophageal and colorectal carcinogenesis. Here, we show that dendritic cells from Fpr1-/- mice exhibit reduced migration in response to chemotherapy-treated CRC cells. Moreover, Fpr1-/- mice are particularly susceptible to chronic ulcerative colitis and colorectal oncogenesis induced by the mutagen azoxymethane followed by oral dextran sodium sulfate, a detergent that induces colitis. These experiments were performed after initial co-housing of Fpr1-/- mice and wild-type controls, precluding major Fpr1-driven differences in the microbiota. Pharmacological inhibition of Fpr1 by cyclosporin H also tended to increase intestinal oncogenesis in mice bearing the ApcMin mutation, and this effect was reversed by the anti-inflammatory drug sulindac. We conclude that defective FPR1 signaling favors intestinal tumorigenesis through the modulation of the innate inflammatory/immune response.

Azithromycin induces read-through of the nonsense Apc allele and prevents intestinal tumorigenesis in C3B6F1 ApcMin/+ mice

Therapeutic strategies that promote read-through of a mutant gene have proved effective for certain non-neoplastic diseases. However, the efficacy of this approach is unproven regarding neoplastic diseases with germline nonsense mutations, including familial adenomatous polyposis. Here we examined the cancer-preventive efficacy of the macrolide antibiotic azithromycin, with a reported read-through effect, on intestinal tumorigenesis in C3B6F1 Apc^Min/+ mice harboring a nonsense Apc mutation resulting in a truncated Apc protein. Mice were given drinking water lacking azithromycin or containing 0.0125-0.2 mg/mL azithromycin from 3 weeks of age. The small intestine and cecum were analyzed for pathological changes and alterations of intestinal flora. Azithromycin suppressed the number of tumors and the proportion of adenocarcinomas, with the most effective drinking-water concentration being 0.0125 mg/mL. Furthermore, azithromycin recovered the cellular level of full-length Apc, resulting in downregulation of β-catenin and cyclin D1. Conversely, the effect of azithromycin on the diversity of the intestinal microbiota depended on the drinking-water concentration. These results suggest that the balance between azithromycin-mediate read-through of mutant Apc mRNA and antibacterial effects influences intestinal tumorigenesis. Thus, azithromycin is a potential anticancer agent for familial adenomatous polyposis patients harboring nonsense mutations.

Interstitial deletion of the Apc locus in β-catenin-overexpressing cells is a signature of radiation-induced intestinal tumors in C3B6F1 ApcMin/+ mice†

Recent studies have identified interstitial deletions in the cancer genome as a radiation-related mutational signature, although most of them do not fall on cancer driver genes. Pioneering studies in the field have indicated the presence of loss of heterozygosity (LOH) spanning Apc in a subset of sporadic and radiation-induced intestinal tumors of ApcMin/+ mice, albeit with a substantial subset in which LOH was not detected; whether copy number losses accompany such LOH has also been unclear. Herein, we analyzed intestinal tumors of C3B6F1 ApcMin/+ mice that were either left untreated or irradiated with 2 Gy of γ-rays. We observed intratumor mosaicism with respect to the nuclear/cytoplasmic accumulation of immunohistochemically detectable β-catenin, which is a hallmark of Apc+ allele loss. An immunoguided laser microdissection approach enabled the detection of LOH involving the Apc+ allele in β-catenin-overexpressing cells; in contrast, the LOH was not observed in the non-overexpressing cells. With this improvement, LOH involving Apc+ was detected in all 22 tumors analyzed, in contrast to what has been reported previously. The use of a formalin-free fixative facilitated the LOH and microarray-based DNA copy number analyses, enabling the classification of the aberrations as nondisjunction/mitotic recombination type or interstitial deletion type. Of note, the latter was observed only in radiation-induced tumors (nonirradiated, 0 of 8; irradiated, 11 of 14). Thus, an analysis considering intratumor heterogeneity identifies interstitial deletion involving the Apc+ allele as a causative radiation-related event in intestinal tumors of ApcMin/+ mice, providing an accurate approach for attributing individual tumors to radiation exposure.

Biomarkers of Response to Low-Dose Aspirin in Familial Adenomatous Polyposis Patients

BACKGROUND

The results of Aspirin prevention of colorectal adenomas in patients with familial adenomatous polyposis (FAP) are controversial.

METHODS

We conducted a biomarker-based clinical study in eight FAP patients treated with enteric-coated low-dose Aspirin (100 mg daily for three months) to explore whether the drug targets mainly platelet cyclooxygenase (COX)-1 or affects extraplatelet cellular sources expressing COX-isozymes and/or off-target effects in colorectal adenomas.

RESULTS

In FAP patients, low-dose Aspirin-acetylated platelet COX-1 at Serine529 (>70%) was associated with an almost complete inhibition of platelet thromboxane (TX) B₂ generation ex vivo (serum TXB₂). However, enhanced residual urinary 11-dehydro-TXB₂ and urinary PGEM, primary metabolites of TXA₂ and prostaglandin (PG)E₂, respectively, were detected in association with incomplete acetylation of COX-1 in normal colorectal biopsies and adenomas. Proteomics of adenomas showed that Aspirin significantly modulated only eight proteins. The upregulation of vimentin and downregulation of HBB (hemoglobin subunit beta) distinguished two groups with high vs. low residual 11-dehydro-TXB₂ levels, possibly identifying the nonresponders and responders to Aspirin.

CONCLUSIONS

Although low-dose Aspirin appropriately inhibited the platelet, persistently high systemic TXA₂ and PGE₂ biosynthesis were found, plausibly for a marginal inhibitory effect on prostanoid biosynthesis in the colorectum. Novel chemotherapeutic strategies in FAP can involve blocking the effects of TXA₂ and PGE₂ signaling with receptor antagonists.

Krüppel-like Factors 4 and 5 in Colorectal Tumorigenesis

Krüppel-like factors (KLFs) are transcription factors regulating various biological processes such as proliferation, differentiation, migration, invasion, and homeostasis. Importantly, they participate in disease development and progression. KLFs are expressed in multiple tissues, and their role is tissue- and context-dependent. KLF4 and KLF5 are two fascinating members of this family that regulate crucial stages of cellular identity from embryogenesis through differentiation and, finally, during tumorigenesis. They maintain homeostasis of various tissues and regulate inflammation, response to injury, regeneration, and development and progression of multiple cancers such as colorectal, breast, ovarian, pancreatic, lung, and prostate, to name a few. Recent studies broaden our understanding of their function and demonstrate their opposing roles in regulating gene expression, cellular function, and tumorigenesis. This review will focus on the roles KLF4 and KLF5 play in colorectal cancer. Understanding the context-dependent functions of KLF4 and KLF5 and the mechanisms through which they exert their effects will be extremely helpful in developing targeted cancer therapy.

The adenomatous polyposis coli protein 30 years on

Mutations in the gene encoding the Adenomatous polyposis coli protein (APC) were discovered as driver mutations in colorectal cancers almost 30 years ago. Since then, the importance of APC in normal tissue homeostasis has been confirmed in a plethora of other (model) organisms spanning a large evolutionary space. APC is a multifunctional protein, with roles as a key scaffold protein in complexes involved in diverse signalling pathways, most prominently the Wnt signalling pathway. APC is also a cytoskeletal regulator with direct and indirect links to and impacts on all three major cytoskeletal networks. Correspondingly, a wide range of APC binding partners have been identified. Mutations in APC are extremely strongly associated with colorectal cancers, particularly those that result in the production of truncated proteins and the loss of significant regions from the remaining protein. Understanding the complement of its role in health and disease requires knowing the relationship between and regulation of its diverse functions and interactions. This in turn requires understanding its structural and biochemical features. Here we set out to provide a brief overview of the roles and function of APC and then explore its conservation and structure using the extensive sequence data, which is now available, and spans a broad range of taxonomy. This revealed conservation of APC across taxonomy and new relationships between different APC protein families.

Tellu - an object-detector algorithm for automatic classification of intestinal organoids

Intestinal epithelial organoids recapitulate many of the in vivo features of the intestinal epithelium, thus representing excellent research models. Morphology of the organoids based on light-microscopy images is used as a proxy to assess the biological state of the intestinal epithelium. Currently, organoid classification is manual and, therefore, subjective and time consuming, hampering large-scale quantitative analyses. Here, we describe Tellu, an object-detector algorithm trained to classify cultured intestinal organoids. Tellu was trained by manual annotation of >20,000 intestinal organoids to identify cystic non-budding organoids, early organoids, late organoids and spheroids. Tellu can also be used to quantify the relative organoid size, and can classify intestinal organoids into these four subclasses with accuracy comparable to that of trained scientists but is significantly faster and without bias. Tellu is provided as an open, user-friendly online tool to benefit the increasing number of investigations using organoids through fast and unbiased organoid morphology and size analysis.

USP7 inactivation suppresses APC-mutant intestinal hyperproliferation and tumor development

Adenomatous polyposis coli (APC) mutation is the hallmark of colorectal cancer (CRC), resulting in constitutive WNT activation. Despite decades of research, targeting WNT signaling in cancer remains challenging due to its on-target toxicity. We have previously shown that the deubiquitinating enzyme USP7 is a tumor-specific WNT activator in APC-truncated cells by deubiquitinating and stabilizing β-catenin, but its role in gut tumorigenesis is unknown. Here, we show in vivo that deletion of Usp7 in Apc-truncated mice inhibits crypt hyperproliferation and intestinal tumor development. Loss of Usp7 prolongs the survival of the sporadic intestinal tumor model. Genetic deletion, but not pharmacological inhibition, of Usp7 in Apc+/- intestine induces colitis and enteritis. USP7 inhibitor treatment suppresses growth of patient-derived cancer organoids carrying APC truncations in vitro and in xenografts. Our findings provide direct evidence that USP7 inhibition may offer a safe and efficacious tumor-specific therapy for both sporadic and germline APC-mutated CRC.

Lentiviral in situ targeting of stem cells in unperturbed intestinal epithelium

BACKGROUND

Methods for the long-term in situ transduction of the unperturbed murine intestinal epithelium have not been developed in past research. Such a method could speed up functional studies and screens to identify genetic factors influencing intestinal epithelium biology. Here, we developed an efficient method achieving this long-sought goal.

RESULTS

We used ultrasound-guided microinjections to transduce the embryonic endoderm at day 8 (E8.0) in utero. The injection procedure can be completed in 20 min and had a 100% survival rate. By injecting a small volume (0.1-0.2 μl) of concentrated virus, single shRNA constructs as well as lentiviral libraries can successfully be transduced. The new method stably and reproducibly targets adult intestinal epithelium, as well as other endoderm-derived organs such as the lungs, pancreas, liver, stomach, and bladder. Postnatal analysis of young adult mice indicates that single transduced cells at E8.0 gave rise to crypt fields that were comprised of 20-30 neighbouring crypts per crypt-field at 90 days after birth. Lentiviral targeting of ApcMin/+ mutant and wildtype mice revealed that heterozygous loss of Apc function suppresses the developmental normal growth pattern of intestinal crypt fields. This suppression of crypt field sizes did not involve a reduction of the crypt number per field, indicating that heterozygous Apc loss impaired the growth of individual crypts within the fields. Lentiviral-mediated shRNA knockdown of p53 led to an approximately 20% increase of individual crypts per field in both Apc+/+ and ApcMin/+ mice, associating with an increase in crypt size in ApcMin/+ mice but a slight reduction in crypt size in Apc+/+ mice. Overall, p53 knockdown rescued the reduction in crypt field size in Apc-mutant mice but had no effect on crypt field size in wildtype mice.

CONCLUSIONS

This study develops a novel technique enabling robust and reproducible in vivo targeting of intestinal stem cells in situ in the unperturbed intestinal epithelium across different regions of the intestine. In vivo somatic gene editing and genetic screening of lentiviral libraries has the potential to speed up discoveries and mechanistic understanding of genetic pathways controlling the biology of the intestinal epithelium during development and postnatal life. The here developed method enables such approaches.

The Barretos Cancer Hospital Animal Facility: Implementation and Results of a Dedicated Platform for Preclinical Oncology Models

The Barretos Cancer Hospital Animal Facility (BCHAF) is a unique facility in Brazil exclusively dedicated to working with animal models for cancer research. In this article, we briefly present our modern facility and the main experiments performed, focusing on mutant strains of mice (PTCH-knockout and ApcMin mice), xenograft models, and patient-derived xenografts (PDXs). Our results show the progress and challenges in establishing these models and the need for having an appropriate representation of our cancer population to better understand tumor biology and to identify cancer biomarkers, which could be putatively targeted, allowing for personalized therapy.

The specific deletion of cyclooxygenase-1 in megakaryocytes/platelets reduces intestinal polyposis in ApcMin/+ mice

Clinical and experimental evidence sustain the role of cyclooxygenase (COX)-1 in intestinal tumorigenesis. However, the cell type expressing the enzyme involved and molecular mechanism(s) have not been clarified yet. We aimed to elucidate the role of platelet COX-1 (the target of low-dose aspirin in humans) in intestinal tumorigenesis of ApcMin/+ mice, considered a clinically relevant model. To realize this objective, we generated an ApcMin/+ mouse with a specific deletion of Ptgs1(COX-1 gene name) in megakaryocytes/platelets (ApcMin/+;pPtgs1-/-mice) characterized by profound inhibition of thromboxane(TX)A2 biosynthesis ex vivo (serum TXB2; by 99%) and in vivo [urinary 2,3-dinor-TXB2(TXM), by 79%]. ApcMin/+ mice with the deletion of platelet COX-1 showed a significantly reduced number (67%) and size (32%) of tumors in the small intestine. The intestinal adenomas of these mice had decreased proliferative index associated with reduced COX-2 expression and systemic prostaglandin(PG)E2 biosynthesis (urinary PGEM) vs. ApcMin/+mice. Extravasated platelets were detected in the intestine of ApcMin/+mice. Thus, we explored their contribution to COX-2 induction in fibroblasts, considered the primary polyp cell type expressing the protein. In the coculture of human platelets and myofibroblasts, platelet-derived TXA2 was involved in the induction of COX-2-dependent PGE2 in myofibroblasts since it was prevented by the selective inhibition of platelet COX-1 by aspirin or by a specific antagonist of TXA2 receptors. In conclusion, our results support the platelet hypothesis of intestinal tumorigenesis and provide experimental evidence that selective inhibition of platelet COX-1 can mitigate early events of intestinal tumorigenesis by restraining COX-2 induction.

MCC is a centrosomal protein that relocalizes to non-centrosomal apical sites during intestinal cell differentiation

The gene mutated in colorectal cancer (MCC) encodes a coiled-coil protein implicated, as its name suggests, in the pathogenesis of hereditary human colon cancer. To date, however, the contributions of MCC to intestinal homeostasis and disease remain unclear. Here, we examine the subcellular localization of MCC, both at the mRNA and protein levels, in the adult intestinal epithelium. Our findings reveal that Mcc transcripts are restricted to proliferating crypt cells, including Lgr5+ stem cells, where the Mcc protein is distinctly associated with the centrosome. Upon intestinal cellular differentiation, Mcc is redeployed to the apical domain of polarized villus cells where non-centrosomal microtubule organizing centers (ncMTOCs) are positioned. Using intestinal organoids, we show that the shuttling of the Mcc protein depends on phosphorylation by casein kinases 1δ and ε, which are critical modulators of WNT signaling. Together, our findings support a role for MCC in establishing and maintaining the cellular architecture of the intestinal epithelium as a component of both the centrosome and ncMTOC.

Clone wars: From molecules to cell competition in intestinal stem cell homeostasis and disease

The small intestine is among the fastest self-renewing tissues in adult mammals. This rapid turnover is fueled by the intestinal stem cells residing in the intestinal crypt. Wnt signaling plays a pivotal role in regulating intestinal stem cell renewal and differentiation, and the dysregulation of this pathway leads to cancer formation. Several studies demonstrate that intestinal stem cells follow neutral drift dynamics, as they divide symmetrically to generate other equipotent stem cells. Competition for niche space and extrinsic signals in the intestinal crypt is the governing mechanism that regulates stemness versus cell differentiation, but the underlying molecular mechanisms are still poorly understood, and it is not yet clear how this process changes during disease. In this review, we highlight the mechanisms that regulate stem cell homeostasis in the small intestine, focusing on Wnt signaling and its regulation by RNF43 and ZNRF3, key inhibitors of the Wnt pathway. Furthermore, we summarize the evidence supporting the current model of intestinal stem cell regulation, highlighting the principles of neutral drift at the basis of intestinal stem cell homeostasis. Finally, we discuss recent studies showing how cancer cells bypass this mechanism to gain a competitive advantage against neighboring normal cells.

Stem cells in the gut rapidly renew themselves through processes that cancer cells co-opt to trigger tumor development. Gabriele Colozza from the Institute of Molecular Biotechnology in Vienna, Austria, and colleagues review how a network of critical molecular signals and competition for limited space help to regulate the dynamics of stem cells in the intestines. The correct balance between self-renewal and differentiation is tightly controlled by the so-called Wnt signaling pathway and its inhibitors. Competition between dividing cells in the intestinal crypts, the locations between finger-like protrusions in the gut where stem cells are found, provides another protective mechanism against runaway stem cell growth. However, intestinal cancer cells, thanks to their activating mutations, bypass these safeguards to gain a survival advantage. Drugs that target these ‘super-competitive’ behaviors could therefore help combat tumor proliferation.

Long Noncoding RNA MIR4435-2HG Suppresses Colorectal Cancer Initiation and Progression By Reprogramming Neutrophils

MIR4435-2HG, also known as LINC00978, has previously been described as an oncogenic long noncoding RNA (lncRNA). However, we show here that Mir4435-2hg depletion promoted colorectal tumorigenesis and progression in in vivo models of colitis-associated colorectal cancer, spontaneous intestinal adenomatous polyposis, and subcutaneous tumors. Alteration of MIR4435-2HG in colorectal cancer cells did not change the potential for cell proliferation, migration, or invasion in vitro. RNAscope assays showed that most MIR4435-2HG was located in the tumor stroma, which caused high expression of MIR4435-2HG in colorectal cancer tumor tissue. Transcriptome analysis of colorectal cancer tissues from wild-type and Mir4435-2hg-deficient mice revealed Mir4435-2hg as a tumor suppressor gene that regulated the immune microenvironment. Loss of Mir4435-2hg led to a decline in neutrophils and elevation of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC). In tissue-specific Mir4435-2hg knockout mice, we confirmed that Mir4435-2hg depletion in neutrophils, but not in intestinal epithelial cells, promoted colorectal cancer progression. Mechanistically, Mir4435-2hg depletion enhanced the immunosuppressive ability of PMN-MDSCs by disturbing their fatty acid metabolism. These findings suggest that MIR4435-2HG is a tumor-suppressing lncRNA whose deficiency could increase tumor-infiltrating PMN-MDSCs and enhance the immunosuppressive potential of PMN-MDSCs to promote colorectal cancer development. This provides a theoretical basis for further illustrating the pathogenesis of colorectal cancer and a potential antitumor immunotherapy target.

Complement downregulation promotes an inflammatory signature that renders colorectal cancer susceptible to immunotherapy

BACKGROUND AND AIMS

The role of inflammatory immune responses in colorectal cancer (CRC) development and response to therapy is a matter of intense debate. While inflammation is a known driver of CRC, inflammatory immune infiltrates are a positive prognostic factor in CRC and predispose to response to immune checkpoint blockade (ICB) therapy. Unfortunately, over 85% of CRC cases are primarily unresponsive to ICB due to the absence of an immune infiltrate, and even the cases that show an initial immune infiltration can become refractory to ICB. The identification of therapy supportive immune responses in the field has been partially hindered by the sparsity of suitable mouse models to recapitulate the human disease. In this study, we aimed to understand how the dysregulation of the complement anaphylatoxin C3a receptor (C3aR), observed in subsets of patients with CRC, affects the immune responses, the development of CRC, and response to ICB therapy.

METHODS

We use a comprehensive approach encompassing analysis of publicly available human CRC datasets, inflammation-driven and newly generated spontaneous mouse models of CRC, and multiplatform high-dimensional analysis of immune responses using microbiota sequencing, RNA sequencing, and mass cytometry.

RESULTS

We found that patients' regulation of the complement C3aR is associated with epigenetic modifications. Specifically, downregulation of C3ar1 in human CRC promotes a tumor microenvironment characterized by the accumulation of innate and adaptive immune cells that support antitumor immunity. In addition, in vivo studies in our newly generated mouse model revealed that the lack of C3a in the colon activates a microbiota-mediated proinflammatory program which promotes the development of tumors with an immune signature that renders them responsive to the ICB therapy.

CONCLUSIONS

Our findings reveal that C3aR may act as a previously unrecognized checkpoint to enhance antitumor immunity in CRC. C3aR can thus be exploited to overcome ICB resistance in a larger group of patients with CRC.

TROP2 Represents a Negative Prognostic Factor in Colorectal Adenocarcinoma and Its Expression Is Associated with Features of Epithelial-Mesenchymal Transition and Invasiveness

Trophoblastic cell surface antigen 2 (TROP2) is a membrane glycoprotein overexpressed in many solid tumors with a poor prognosis, including intestinal neoplasms. In our study, we show that TROP2 is expressed in preneoplastic lesions, and its expression is maintained in most colorectal cancers (CRC). High TROP2 positivity correlated with lymph node metastases and poor tumor differentiation and was a negative prognostic factor. To investigate the role of TROP2 in intestinal tumors, we analyzed two mouse models with conditional disruption of the adenomatous polyposis coli (Apc) tumor-suppressor gene, human adenocarcinoma samples, patient-derived organoids, and TROP2-deficient tumor cells. We found that Trop2 is produced early after Apc inactivation and its expression is associated with the transcription of genes involved in epithelial-mesenchymal transition, the regulation of migration, invasiveness, and extracellular matrix remodeling. A functionally similar group of genes was also enriched in TROP2-positive cells from human CRC samples. To decipher the driving mechanism of TROP2 expression, we analyzed its promoter. In human cells, this promoter was activated by β-catenin and additionally by the Yes1-associated transcriptional regulator (YAP). The regulation of TROP2 expression by active YAP was verified by YAP knockdown in CRC cells. Our results suggest a possible link between aberrantly activated Wnt/β-catenin signaling, YAP, and TROP2 expression.

Characterization of an intelectin-1 (Itln1) knockout mouse model

Intelectins are carbohydrate-binding proteins implicated in innate immunity and highly conserved across chordate evolution, including both ascidians and humans. Human intelectin-1 (ITLN1) is highly abundant within the intestinal mucosa and binds microbial but not host glycans. Genome-wide association studies identified SNPs in ITLN1 that are linked to susceptibility for Crohn's disease. Moreover, ITLN1 has been implicated in the pathophysiology of obesity and associated metabolic disease. To gain insight on biological activities of human ITLN1 in vivo, we developed a C57BL/6 mouse model genetically targeting the gene encoding the functional mouse ortholog. In wild-type C57BL/6 mice, both mRNA and protein analysis showed high expression of Itln1 in the small intestine, but manifold lower levels in colon and other extraintestinal tissues. Whereas intestinal expression of human ITLN1 localizes to goblet cells, our data confirm that mouse Itln1 is expressed in Paneth cells. Compared to wild-type littermate controls, mice homozygous for the Itln1 hypomorphic trapping allele had reduced expression levels of Itln1 expression (~10,000-fold). The knockout mice exhibited increased susceptibility in an acute model of experimentally induced colitis with 2% w/v dextran sulfate sodium (DSS). In a model of chronic colitis using a lower dose of DSS (1.5% w/v), which enabled a detailed view of disease activity across a protracted period, no differences were observed in body weight, fecal texture, hemoccult scores, food/water intake, or colon length at necropsy, but there was a statistically significant genotype over time effect for the combined fecal scores of disease activity. In model of diet-induced obesity, using two western-style diets, which varied in amounts of sugar (as sucrose) and saturated fat (as lard), mice with Itln1 expression ablated showed no increased susceptibility, in terms of weight gain, food intake, plasma markers of obesity compared to wildtype littermates. While the mouse genetic knockout model for Itln1 holds promise for elucidating physiological function(s) for mammalian intelectins, results reported here suggest that Itln1, a Paneth cell product in C57BL/6 mice, likely plays a minor role in the pathophysiology of chemically induced colitis or diet-induced obesity.

Stem Cell Models for Breast and Colon Cancer: Experimental Approach for Drug Discovery

The progression of the early stages of female breast and colon cancer to metastatic disease represents a major cause of mortality in women. Multi-drug chemotherapy and/or pathway selective targeted therapy are notable for their off-target effects and are associated with spontaneous and/or acquired chemotherapy resistance and the emergence of premalignant chemo-resistant cancer-initiating stem cells. The stem cell populations are responsible for the evolution of therapy-resistant metastatic disease. These limitations emphasize an unmet need to develop reliable drug-resistant cancer stem cell models as novel experimental approaches for therapeutic alternatives in drug discovery platforms. Drug-resistant stem cell models for breast and colon cancer subtypes exhibit progressive growth in the presence of cytotoxic chemo-endocrine therapeutics. The resistant cells exhibit upregulated expressions of stem cell-selective cellular and molecular markers. Dietary phytochemicals, nutritional herbs and their constituent bioactive compounds have documented growth inhibitory efficacy for cancer stem cells. The mechanistic leads for the stem cell-targeted efficacy of naturally occurring agents validates the present experimental approaches for new drug discovery as therapeutic alternatives for therapy-resistant breast and colon cancer. The present review provides a systematic discussion of published evidence on (i) conventional/targeted therapy for breast and colon cancer, (ii) cellular and molecular characterization of stem cell models and (iii) validation of the stem cell models as an experimental approach for novel drug discovery of therapeutic alternatives for therapy-resistant cancers.

The transcription factor Cdx2 regulates inflammasome activity through expression of the NLRP3 suppressor TRIM31 to maintain intestinal homeostasis

The intestine-specific transcription factor Cdx2 is essential for intestinal homeostasis and has been implicated in the pathogenesis of disorders including inflammatory bowel disease. However, the mechanism by which Cdx2 influences intestinal disease is not clear. Here, we present evidence supporting a novel Cdx2–TRIM31–NLRP3 (NLR family, pyrin domain containing 3) signaling pathway, which may represent a mechanistic means by which Cdx2 impacts intestinal inflammation. We found that conditional loss of Cdx function resulted in an increase in proinflammatory cytokines, including tumor necrosis factor alpha, interleukin (IL)-1β, and IL-6, in the mouse colon. We further show that TRIM31, which encodes a suppressor of NLRP3 (a central component of the NLRP3 inflammasome complex) is a novel Cdx2 target gene and is attenuated in the colon of Cdx conditional mutants. Consistent with this, we found that attenuation of TRIM31 in Cdx mutant intestine occurs concomitant with elevated levels of NLRP3 and an increase in inflammasome products. We demonstrate that specific inhibition of NLRP3 activity significantly reduced IL-1β and IL-6 levels and extended the life span of Cdx conditional mutants, reflecting the therapeutic potential of targeting NLRP3. Tumor necrosis factor-alpha levels were also induced independent of NLRP3, potentially via elevated activity of the proinflammatory NF-κB signaling pathway in Cdx mutants. Finally, in silico analysis of ulcerative colitis patients revealed attenuation of CDX2 and TRIM31 expression coincident with enhanced expression of proinflammatory cytokines. We conclude that the novel Cdx2–TRIM31–NLRP3 signaling pathway promotes proinflammatory cytokine expression, and its inhibition may have therapeutic potential in human intestinal diseases.

Elp3-mediated codon-dependent translation promotes mTORC2 activation and regulates macrophage polarization

Macrophage polarization is a process whereby macrophages acquire distinct effector states (M1 or M2) to carry out multiple and sometimes opposite functions. We show here that translational reprogramming occurs during macrophage polarization and that this relies on the Elongator complex subunit Elp3, an enzyme that modifies the wobble uridine base U34 in cytosolic tRNAs. Elp3 expression is downregulated by classical M1‐activating signals in myeloid cells, where it limits the production of pro‐inflammatory cytokines via FoxO1 phosphorylation, and attenuates experimental colitis in mice. In contrast, alternative M2‐activating signals upregulate Elp3 expression through a PI3K‐ and STAT6‐dependent signaling pathway. The metabolic reprogramming linked to M2 macrophage polarization relies on Elp3 and the translation of multiple candidates, including the mitochondrial ribosome large subunit proteins Mrpl3, Mrpl13, and Mrpl47. By promoting translation of its activator Ric8b in a codon‐dependent manner, Elp3 also regulates mTORC2 activation. Elp3 expression in myeloid cells further promotes Wnt‐driven tumor initiation in the intestine by maintaining a pool of tumor‐associated macrophages exhibiting M2 features. Collectively, our data establish a functional link between tRNA modifications, mTORC2 activation, and macrophage polarization.

Golden Syrian Hamster Models for Cancer Research

The golden Syrian hamster (Mesocricetus auratus) has long been a valuable rodent model of human diseases, especially infectious and metabolic diseases. Hamsters have also been valuable models of several chemically induced cancers such as the DMBA-induced oral cheek pouch cancer model. Recently, with the application of CRISPR/Cas9 genetic engineering technology, hamsters can now be gene targeted as readily as mouse models. This review describes the phenotypes of three gene-targeted knockout (KO) hamster cancer models, TP53, KCNQ1, and IL2RG. Notably, these hamster models demonstrate cancer phenotypes not observed in mouse KOs. In some cases, the cancers that arise in the KO hamster are similar to cancers that arise in humans, in contrast with KO mice that do not develop the cancers. An example is the development of aggressive acute myelogenous leukemia (AML) in TP53 KO hamsters. The review also presents a discussion of the relative strengths and weaknesses of mouse cancer models and hamster cancer models and argues that there are no perfect rodent models of cancer and that the genetically engineered hamster cancer models can complement mouse models and expand the suite of animal cancer models available for the development of new cancer therapies.

Circadian regulation of digestive and metabolic tissues

The circadian clock is a self-sustained molecular timekeeper that drives 24-h (circadian) rhythms in animals. The clock governs important aspects of behavior and physiology including wake/sleep activity cycles that regulate the activity of metabolic and digestive systems. Light/dark cycles (photoperiod) and cycles in the time of feeding synchronize the circadian clock to the surrounding environment, providing an anticipatory benefit that promotes digestive health. The availability of animal models targeting the genetic components of the circadian clock has made it possible to investigate the circadian clock's role in cellular functions. Circadian clock genes have been shown to regulate the physiological function of hepatocytes, gastrointestinal cells, and adipocytes; disruption of the circadian clock leads to the exacerbation of liver diseases and liver cancer, inflammatory bowel disease and colorectal cancer, and obesity. Previous findings provide strong evidence that the circadian clock plays an integral role in digestive/metabolic disease pathogenesis, hence, the circadian clock is a necessary component in metabolic and digestive health and homeostasis. Circadian rhythms and circadian clock function provide an opportunity to improve the prevention and treatment of digestive and metabolic diseases by aligning digestive system tissue with the 24-h day.

Synthetic Essentiality of Tryptophan 2,3-Dioxygenase 2 in APC-Mutated Colorectal Cancer

Inactivation of adenomatous polyposis coli (APC) is common across many cancer types and serves as a critical initiating event in most sporadic colorectal cancers. APC deficiency activates WNT signaling, which remains an elusive target for cancer therapy, prompting us to apply the synthetic essentiality framework to identify druggable vulnerabilities for APC-deficient cancers. Tryptophan 2,3-dioxygenase 2 (TDO2) was identified as a synthetic essential effector of APC-deficient colorectal cancer. Mechanistically, APC deficiency results in the TCF4/β-catenin-mediated upregulation of TDO2 gene transcription. TDO2 in turn activates the Kyn-AhR pathway, which increases glycolysis to drive anabolic cancer cell growth and CXCL5 secretion to recruit macrophages into the tumor microenvironment. Therapeutically, APC-deficient colorectal cancer models were susceptible to TDO2 depletion or pharmacologic inhibition, which impaired cancer cell proliferation and enhanced antitumor immune profiles. Thus, APC deficiency activates a TCF4-TDO2-AhR-CXCL5 circuit that affects multiple cancer hallmarks via autonomous and nonautonomous mechanisms and illuminates a genotype-specific vulnerability in colorectal cancer.

SIGNIFICANCE

This study identifies critical effectors in the maintenance of APC-deficient colorectal cancer and demonstrates the relationship between APC/WNT pathway and kynurenine pathway signaling. It further determines the tumor-associated macrophage biology in APC-deficient colorectal cancer, informing genotype-specific therapeutic targets and the use of TDO2 inhibitors. This article is highlighted in the In This Issue feature, p. 1599.

Stem Cell Models for Cancer Therapy

Metastatic progression of female breast and colon cancer represents a major cause of mortality in women. Spontaneous/acquired resistance to conventional and targeted chemo-endocrine therapy is associated with the emergence of drug-resistant tumor-initiating cancer stem cell populations. The cancer-initiating premalignant stem cells exhibit activation of select cancer cell signaling pathways and undergo epithelial-mesenchymal transition, leading to the evolution of a metastatic phenotype. The development of reliable cancer stem cell models provides valuable experimental approaches to identify novel testable therapeutic alternatives for therapy-resistant cancer. Drug-resistant stem cell models for molecular subtypes of clinical breast cancer and for genetically predisposed colon cancer are developed by selecting epithelial cells that survive in the presence of cytostatic concentrations of relevant therapeutic agents. These putative stem cells are characterized by the expression status of select cellular and molecular stem cell markers. The stem cell models are utilized as experimental approaches to examine the stem-cell-targeted growth inhibitory efficacy of naturally occurring dietary phytochemicals. The present review provides a systematic discussion on (i) conceptual and experimental aspects relevant to the chemo-endocrine therapy of breast and colon cancer, (ii) molecular/cellular aspects of cancer stem cells and (iii) potential stem-cell-targeting lead compounds as testable alternatives against the progression of therapy-resistant breast and colon cancer.

Intestinal FXR Activation via Transgenic Chimera or Chemical Agonism Prevents Colitis-Associated and Genetically-Induced Colon Cancer

Simple Summary

Disruption of Bile Acids (BA) regulation with increased BA concentration and modulation or their detergent pro-inflammatory activity has been linked to colorectal cancer (CRC). Farnesoid X Receptor (FXR) is the master regulator of BA homeostasis; FXR is a nuclear receptor that transcriptionally modulates their synthesis, transport and metabolism. In this study, we demonstrated that intestinal FXR activation prevented both inflammation- and genetically-driven colorectal tumorigenesis by modulating BA pool size and composition. This could open new avenues for the therapeutic management of intestinal inflammation and tumorigenesis.

Abstract

The Farnesoid X Receptor (FXR) is the master regulator of Bile Acids (BA) homeostasis orchestrating their synthesis, transport and metabolism. Disruption of BA regulation has been linked to gut-liver axis diseases such as colorectal cancer (CRC). In this study, firstly we examined the role of constitutive activation of intestinal FXR in CRC; then we pre-clinically investigated the therapeutic potential of a diet enriched with a synthetic FXR agonist in two models of CRC (chemically-induced and genetic models). We demonstrated that mice with intestinal constitutive FXR activation are protected from AOM/DSS-induced CRC with a significant reduction of tumor number compared to controls. Furthermore, we evaluated the role of chemical FXR agonism in a DSS model of colitis in wild type (WT) and FXR^null mice. WT mice administered with the FXR activating diet showed less morphological alterations and decreased inflammatory infiltrates compared to controls. The FXR activating diet also protected WT mice from AOM/DSS-induced CRC by reducing tumors’ number and size. Finally, we proved that the FXR activating diet prevented spontaneous CRC in APC^Min/+ mice via an FXR-dependent modulation of BA homeostasis. Our results demonstrate that intestinal FXR activation prevented both inflammation- and genetically-driven colorectal tumorigenesis by modulating BA pool size and composition. This could open new avenues for the therapeutic management of intestinal inflammation and tumorigenesis.

Hypothalamic-pituitary-adrenal axis activation and glucocorticoid-responsive gene expression in skeletal muscle and liver of Apc mice

BACKGROUND

Cancer patients at advanced stages experience a severe depletion of skeletal muscle compartment together with a decrease in muscle function, known as cancer cachexia. Cachexia contributes to reducing quality of life, treatment efficiency, and lifespan of cancer patients. However, the systemic nature of the syndrome is poorly documented. Here, we hypothesize that glucocorticoids would be important systemic mediators of cancer cachexia.

METHODS

To explore the role of glucocorticoids during cancer cachexia, biomolecular analyses were performed on several tissues (adrenal glands, blood, hypothalamus, liver, and skeletal muscle) collected from Apc^Min/+ male mice, a mouse model of intestine and colon cancer, aged of 13 and 23 weeks, and compared with wild type age-matched C57BL/6J littermates.

RESULTS

Twenty-three-week-old Apc mice recapitulated important features of cancer cachexia including body weight loss (-16%, P < 0.0001), muscle atrophy (gastrocnemius muscle: -53%, P < 0.0001), and weakness (-50% in tibialis anterior muscle force, P < 0.0001), increased expression of atrogens (7-fold increase in MuRF1 transcript level, P < 0.0001) and down-regulation of Akt-mTOR pathway (3.3-fold increase in 4EBP1 protein content, P < 0.0001), together with a marked transcriptional rewiring of hepatic metabolism toward an increased expression of gluconeogenic genes (Pcx: +90%, Pck1: +85%), and decreased expression of glycolytic (Slc2a2: -40%, Gk: -30%, Pklr: -60%), ketogenic (Hmgcs2: -55%, Bdh1: -80%), lipolytic/fatty oxidation (Lipe: -50%, Mgll: -60%, Cpt2: -60%, Hadh: -30%), and lipogenic (Acly: -30%, Acacb: -70%, Fasn: -45%) genes. The hypothalamic pituitary-adrenal axis was activated, as evidenced by the increase in the transcript levels of genes encoding corticotropin-releasing hormone in the hypothalamus (2-fold increase, P < 0.01), adrenocorticotropic hormone receptor (3.4-fold increase, P < 0.001), and steroid biosynthesis enzymes (Cyp21a1, P < 0.0001, and Cyp11b1, P < 0.01) in the adrenal glands, as well as by the increase in corticosterone level in the serum (+73%, P < 0.05), skeletal muscle (+17%, P < 0.001), and liver (+24%, P < 0.05) of cachectic 23-week-old Apc mice. A comparative transcriptional analysis with dexamethasone-treated C57BL/6J mice indicated that the activation of the hypothalamic-pituitary-adrenal axis in 23-week-old Apc^Min/+ mice was significantly associated with the transcription of glucocorticoid-responsive genes in skeletal muscle (P < 0.05) and liver (P < 0.001). The transcriptional regulation of glucocorticoid-responsive genes was also observed in the gastrocnemius muscle of Lewis lung carcinoma tumour-bearing mice and in KPC mice (tibialis anterior muscle and liver).

CONCLUSIONS

These findings highlight the role of the hypothalamic-pituitary-adrenal-glucocorticoid pathway in the transcriptional regulation of skeletal muscle catabolism and hepatic metabolism during cancer cachexia. They also provide the paradigm for the design of new therapeutic strategies.

Intracellular complement C5a/C5aR1 stabilizes β-catenin to promote colorectal tumorigenesis

Complement is operative in not only the extracellular but also the intracellular milieu. However, little is known about the role of complement activation inside tumor cells. Here, we report that intracellular C5 is cleaved by cathepsin D (CTSD) to produce C5a in lysosomes and endosomes of colonic cancer cells. After stimulation by C5a, intracellular C5aR1 assembles a complex with KCTD5/cullin3/Roc-1 and β-catenin to promote the switch of polyubiquitination of β-catenin from K48 to K63, which enhances β-catenin stability. Genetic loss or pharmacological blockade of C5aR1 dramatically impedes colorectal tumorigenesis at least by destabilizing β-catenin. In human colorectal cancer specimens, high levels of C5aR1, C5a, and CTSD are closely correlated with elevated β-catenin levels and a poor prognosis. Importantly, intracellular C5a/C5aR1-mediated β-catenin stabilization is also observed ubiquitously in other cell types. Collectively, we identify a machinery for β-catenin activation and provide a potential target for tumor prevention and treatment.

AP4 suppresses DNA damage, chromosomal instability and senescence via inducing MDC1/Mediator of DNA damage Checkpoint 1 and repressing MIR22HG/miR-22-3p

Background

AP4 (TFAP4) encodes a basic helix-loop-helix leucine zipper (bHLH-LZ) transcription factor and is a direct target gene of the oncogenic transcription factor c-MYC. Here, we set out to determine the relevance of AP4 in human colorectal cancer (CRC) cells.

Methods

A CRISPR/Cas9 approach was employed to generate AP4-deficient CRC cell lines with inducible expression of c-MYC. Colony formation, β-gal staining, immunofluorescence, comet and homologous recombination (HR) assays and RNA-Seq analysis were used to determine the effects of AP4 inactivation. qPCR and qChIP analyses was performed to validate differentially expressed AP4 targets. Expression data from CRC cohorts was subjected to bioinformatics analyses. Immunohistochemistry was used to evaluate AP4 targets in vivo. Ap4-deficient APC^min/+ mice were analyzed to determine conservation. Immunofluorescence, chromosome and micronuclei enumeration, MTT and colony formation assays were used to determine the effects of AP4 inactivation and target gene regulation on chromosomal instability (CIN) and drug sensitivity.

Results

Inactivation of AP4 in CRC cell lines resulted in increased spontaneous and c-MYC-induced DNA damage, chromosomal instability (CIN) and cellular senescence. AP4-deficient cells displayed increased expression of the long non-coding RNA MIR22HG, which encodes miR-22-3p and was directly repressed by AP4. Furthermore, Mediator of DNA damage Checkpoint 1 (MDC1), a central component of the DNA damage response and a known target of miR-22-3p, displayed decreased expression in AP4-deficient cells. Accordingly, MDC1 was directly induced by AP4 and indirectly by AP4-mediated repression of miR-22-3p. Adenomas and organoids from Ap4-deficient APC^min/+ mice displayed conservation of these regulations. Inhibition of miR-22-3p or ectopic MDC1 expression reversed the increased senescence, DNA damage, CIN and defective HR observed in AP4-deficient CRC cells. AP4-deficiency also sensitized CRC cells to 5-FU treatment, whereas ectopic AP4 conferred resistance to 5-FU in a miR-22-3p and MDC1-dependent manner.

Conclusions

In summary, AP4, miR-22-3p and MDC1 form a conserved and coherent, regulatory feed-forward loop to promote DNA repair, which suppresses DNA damage, senescence and CIN, and contributes to 5-FU resistance. These findings explain how elevated AP4 expression contributes to development and chemo-resistance of colorectal cancer after c-MYC activation.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01581-1.