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Chronic inflammation of the large intestine is associated with an increased risk of developing colorectal cancer (CRC), the second most common cause of cancer-related deaths worldwide. Necroptosis has emerged as a form of lytic programmed cell death that, distinct from apoptosis, triggers an inflammatory response. Dysregulation of necroptosis has been linked to multiple chronic inflammatory diseases, including inflammatory bowel disease and cancer. Here, we used murine models of acute colitis, colitis-associated CRC, sporadic CRC, and spontaneous intestinal tumorigenesis to investigate the role of necroptosis in these gastrointestinal pathologies. In the Dextran Sodium Sulfate-induced acute colitis model, in some experiments, mice lacking the terminal necroptosis effector protein, MLKL, or its activator RIPK3, exhibited greater weight loss compared to wild-type mice, consistent with some earlier reports. However, the magnitude of weight loss and accompanying inflammatory pathology upon Mlkl deletion varied substantially between independent repeats. Such variation provides a possible explanation for conflicting literature reports. Furthermore, contrary to earlier reports, we observed that genetic deletion of MLKL had no impact on colon cancer development using several mouse models. Collectively, these data do not support an obligate role for necroptosis in inflammation or cancer within the gastrointestinal tract.

Gastrointestinal epithelial cells provide a selective barrier that segregates the host immune system from luminal microorganisms, thereby contributing directly to the regulation of homeostasis. We have shown that from early embryonic development Bcl-G, a Bcl-2 protein family member with unknown function, was highly expressed in gastrointestinal epithelial cells. While Bcl-G was dispensable for normal growth and development in mice, the loss of Bcl-G resulted in accelerated progression of colitis-associated cancer. A label-free quantitative proteomics approach revealed that Bcl-G may contribute to the stability of a mucin network, which when disrupted, is linked to colon tumorigenesis. Consistent with this, we observed a significant reduction in Bcl-G expression in human colorectal tumors. Our study identifies an unappreciated role for Bcl-G in colon cancer.

Simple Summary Colorectal cancer is the second leading cause of cancer-related death worldwide. The immune system plays a key role in controlling tumour onset and development. However, our immune system is complex and includes many different cell types which differently impact colorectal cancer outcomes. In this study, we investigated the function of the specialised type 2 innate lymphoid cells (ILC2) in colorectal cancer development and progression. We found that ILC2 infiltrate colorectal tumours and their presence was associated with reduced tumour burden in mice. In patients, this infiltration correlated with improved overall survival. Collectively, our work reveals that ILC2s are beneficial to colorectal cancer outcomes. Abstract Chronic inflammation of the gastrointestinal (GI) tract contributes to colorectal cancer (CRC) progression. While the role of adaptive T cells in CRC is now well established, the role of innate immune cells, specifically innate lymphoid cells (ILCs), is not well understood. To define the role of ILCs in CRC we employed complementary heterotopic and chemically-induced CRC mouse models. We discovered that ILCs were abundant in CRC tumours and contributed to anti-tumour immunity. We focused on ILC2 and showed that ILC2-deficient mice developed a higher tumour burden compared with littermate wild-type controls. We generated an ILC2 gene signature and using machine learning models revealed that CRC patients with a high intratumor ILC2 gene signature had a favourable clinical prognosis. Collectively, our results highlight a critical role for ILC2 in CRC, suggesting a potential new avenue to improve clinical outcomes through ILC2-agonist based therapeutic approaches.

Anti-microbial signaling pathways are normally triggered by innate immune receptors when detecting pathogenic microbes to provide protective immunity. Here we show that the inflammasome sensor Nlrp1 aggravates DSS-induced experimental mouse colitis by limiting beneficial, butyrate-producing Clostridiales in the gut. The colitis-protective effects of Nlrp1 deficiency are thus reversed by vancomycin treatment, but recapitulated with butyrate supplementation in wild-type mice. Moreover, an activating mutation in Nlrp1a increases IL-18 and IFNγ production, and decreases colonic butyrate to exacerbate colitis. We also show that, in patients with ulcerative colitis, increased NLRP1 in inflamed regions of the colon is associated with increased IFN-γ. In this context, NLRP1, IL-18 or IFN-γ expression negatively correlates with the abundance of Clostridiales in human rectal mucosal biopsies. Our data identify the NLRP1 inflammasome to be a key negative regulator of protective, butyrate-producing commensals, which therefore promotes inflammatory bowel disease.

About 5% to 10% of human gastric tumors harbor oncogenic mutations in the KRAS pathway, but their presence alone is often insufficient for inducing gastric tumorigenesis, suggesting a requirement for additional mutagenic events or microenvironmental stimuli, including inflammation. Assessing the contribution of such events in preclinical mouse models requires Cre recombinase–mediated conditional gene expression in stem or progenitor cells of normal and transformed gastric epithelium. We therefore constructed a bacterial artificial chromosome containing transgene (Tg), comprising the regulatory elements of the trefoil factor 1 (Tff1) gene and the tamoxifen-inducible Cre recombinase (CreERT2)–coding sequence. The resulting Tg(Tff1-CreERT2) mice were crossed with mice harboring conditional oncogenic mutations in Kras or Braf. The administration of tamoxifen to the resulting adult Tg(Tff1-CreERT2);KrasLSL-G12D/+ and Tg(Tff1-CreERT2);BrafLSL-V600E/+ mice resulted in gastric metaplasia, inflammation, and adenoma development, characterized by excessive STAT3 activity. To assess the contribution of STAT3 to the spontaneously developing gastric adenomas in gp130F/F mice, which carry a knockin mutation in the Il6 signal transducer (Il6st), we generated Tg(Tff1-CreERT2);Stat3fl/fl;gp130F/F mice that also harbor a conditional Stat3 knockout allele and found that tamoxifen administration conferred a significant reduction in their tumor burden. Conversely, excessive Kras activity in Tg(Tff1-CreERT2);KrasLSL-G12D/+;gp130F/F mice promoted more extensive gastric inflammation, metaplastic transformation, and tumorigenesis than observed in Tg(Tff1-CreERT2);KrasLSL-G12D/+ mice. Collectively, our findings demonstrate that advanced gastric tumorigenesis requires oncogenic KRAS or BRAF in concert with aberrant STAT3 activation in epithelial precursor cells of the glandular stomach, providing a new conditional model of gastric cancer in which to investigate candidate therapeutic targets and treatment strategies. Cancer Res; 76(8); 2277–87. ©2016 AACR.

The gastrointestinal tract is a unique organ system that provides an epithelial barrier between our underlying immune system and luminal pathogens. Disruption of gastrointestinal homeostasis, as a result of impaired barrier function, is associated with numerous pathologies including inflammatory bowel disease and colorectal cancer. In parallel to the clinical development of endoscopy technologies to monitor and diagnose these pathologies in humans, advanced mouse colonoscopy techniques are being developed. When these technologies are coupled with model systems of human disease, which are essential to our understanding of the pathophysiology of gastrointestinal diseases, the requirement for euthanasia of multiple cohorts of mice is eliminated. Here we highlight the suitability of white light endoscopy to monitor the progression of colitis in mice. We further outline the experimental power of combined standard endoscopy with confocal microendoscopy, which permits visualization of fluorescent markers in a single animal in real-time. Together, these technologies will enhance our understanding of the interplay between components of the gastrointestinal microenvironment and their role in disease., Highlights • Monitoring of mucosal damage using white light endoscopy • Monitoring of the epithelial barrier using confocal endomicroscopy • Monitoring of the vasculature architecture using confocal endomicroscopy

Inflammasomes are key regulators of innate immunity in chronic inflammatory disorders and autoimmune diseases, but their role in inflammation-associated tumorigenesis remains ill-defined. Here we reveal a protumorigenic role in gastric cancer for the key inflammasome adaptor apoptosis-related speck-like protein containing a CARD (ASC) and its effector cytokine IL18. Genetic ablation of ASC in the gp130F/F spontaneous mouse model of intestinal-type gastric cancer suppressed tumorigenesis by augmenting caspase-8-like apoptosis in the gastric epithelium, independently from effects on myeloid cells and mucosal inflammation. This phenotype was characterized by reduced activation of caspase-1 and NF-κB activation and reduced expression of mature IL18, but not IL1β, in gastric tumors. Genetic ablation of IL18 in the same model also suppressed gastric tumorigenesis, whereas blockade of IL1β and IL1α activity upon genetic ablation of the IL1 receptor had no effect. The specific protumorigenic role for IL18 was associated with high IL18 gene expression in the gastric tumor epithelium compared with IL1β, which was preferentially expressed in immune cells. Supporting an epithelial-specific role for IL18, we found it to be highly secreted from human gastric cancer cell lines. Moreover, IL18 blockade either by a neutralizing anti-IL18 antibody or by CRISPR/Cas9-driven deletion of ASC augmented apoptosis in human gastric cancer cells. In clinical specimens of human gastric cancer tumors, we observed a significant positive correlation between elevated mature IL18 protein and ASC mRNA levels. Collectively, our findings reveal the ASC/IL18 signaling axis as a candidate therapeutic target in gastric cancer. Significance: Inflammasome activation that elevates IL18 helps drive gastric cancer by protecting cancer cells against apoptosis, with potential implications for new therapeutic strategies in this setting. Cancer Res; 78(5); 1293–307. ©2017 AACR.

International audience; Aberrant activation of the SRC family kinase hematopoietic cell kinase (HCK) triggers hematological malignancies as a tumor cell-intrinsic oncogene. Here we find that high HCK levels correlate with reduced survival of colorectal cancer patients. Likewise, increased Hck activity in mice promotes the growth of endogenous colonic malignancies and of human colorectal cancer cell xenografts. Furthermore, tumor-associated macrophages of the corresponding tumors show a pronounced alternatively activated endotype, which occurs independently of mature lymphocytes or of Stat6-dependent Th2 cytokine signaling. Accordingly, pharmacological inhibition or genetic reduction of Hck activity suppresses alternative activation of tumor-associated macrophages and the growth of colon cancer xenografts. Thus, Hck may serve as a promising therapeutic target for solid malignancies.

Animal models of inflammatory bowel disease (IBD) and colorectal cancer (CRC) have provided significant insight into the cell intrinsic and extrinsic mechanisms that contribute to the onset and progression of intestinal diseases. The identification of new molecules that promote these pathologies has led to a flurry of activity focused on the development of potential new therapies to inhibit their function. As a result, various pre-clinical mouse models with an intact immune system and stromal microenvironment are now heavily used. Here we describe three experimental protocols to test the efficacy of new therapeutics in pre-clinical models of (1) acute mucosal damage, (2) chronic colitis and/or colitis-associated colon cancer, and (3) sporadic colorectal cancer. We also outline procedures for serial endoscopic examination that can be used to document the therapeutic response of an individual tumor and to monitor the health of individual mice. These protocols provide complementary experimental platforms to test the effectiveness of therapeutic compounds shown to be well tolerated by mice.

SummaryAmong the cytokines linked to inflammation-associated cancer, interleukin (IL)-6 drives many of the cancer “hallmarks” through downstream activation of the gp130/STAT3 signaling pathway. However, we show that the related cytokine IL-11 has a stronger correlation with elevated STAT3 activation in human gastrointestinal cancers. Using genetic mouse models, we reveal that IL-11 has a more prominent role compared to IL-6 during the progression of sporadic and inflammation-associated colon and gastric cancers. Accordingly, in these models and in human tumor cell line xenograft models, pharmacologic inhibition of IL-11 signaling alleviated STAT3 activation, suppressed tumor cell proliferation, and reduced the invasive capacity and growth of tumors. Our results identify IL-11 signaling as a potential therapeutic target for the treatment of gastrointestinal cancers.

Colorectal cancer is the second most commonly diagnosed cancer worldwide, and may develop sporadically or due to chronic colitis. Macrophages are a major component of the colorectal tumour microenvironment and may be broadly classified as classically-activated (CAM) ‘inflammatory’ or alternatively-activated (AAM) ‘pro-angiogenic’ macrophages. Hematopoietic Cell Kinase (Hck) is a myeloid-specific Src family kinase involved in alternative macrophage polarisation, which correlates with a poor prognosis in human colorectal cancer. To investigate the role of Hck in colorectal tumourigenesis, Hck mutant mice that express a constitutively active form of Hck (HckCA) were subjected to models of sporadic and colitis-associated colorectal cancer. In both models, HckCA mice demonstrated increased tumour size and multiplicity compared to wild-type animals. FACS analysis of tumour immune-cell infiltrates did not reveal a difference in the number of tumour-associated macrophages (TAMs) between genotypes; however, CD206+ alternatively-activated TAMs were significantly greater in HckCA mice compared to wild-type. Furthermore, qPCR analysis highlighted a significant increase in genes associated with alternative-macrophage activation in HckCA TAMs. To confirm the role of macrophages in HckCA-driven tumourigenesis, wild-type mice were reconstituted with HckCA bone-marrow, and subjected to sporadic or colitis-associated colon cancer induction, after which we observed an increased tumour burden and an AAM phenotype compared to wild-type bone-marrow recipients. Finally, we have shown that the inhibition of Hck using a small molecule inhibitor reduces alternative macrophage polarisation. Collectively, our results suggest that excessive Hck activation enhances colorectal tumourigenesis by facilitating alternative macrophage polarisation, which may be alleviated through the therapeutic targeting of this kinase.