Identification of a genetic locus controlling bacteria-driven colitis and associated cancer through effects on innate inflammation

The ceramide synthase (CERS/LASS) family: Functions involved in cancer progression

INTRODUCTION

Ceramide synthases (CERSes) are also known longevity assurance (LASS) genes. CERSes play important roles in the regulation of cancer progression. The CERS family is expressed in a variety of human tumours and is involved in tumorigenesis. They are closely associated with the progression of liver, breast, cervical, ovarian, colorectal, head and neck squamous cell, gastric, lung, prostate, oesophageal, pancreatic and blood cancers. CERSes play diverse and important roles in the regulation of cell survival, proliferation, apoptosis, migration, invasion, and drug resistance. The differential expression of CERSes in tumour and nontumour cells and survival analysis of cancer patients suggest that some CERSes could be used as potential prognostic markers. They are also important potential targets for cancer therapy.

METHODS

In this review, we summarize the available evidence on the inhibitory or promotive roles of CERSes in the progression of many cancers. Furthermore, we summarize the identified upstream and downstream molecular mechanisms that may regulate the function of CERSes in cancer settings.

Evaluation of C-reactive protein and fibrinogen in comparison to CEA and CA72-4 as diagnostic biomarkers for colorectal cancer

Carcinoembryonic antigen (CEA) and carbohydrate antigen 72-4 (CA72-4) are commonly used markers for colorectal cancer (CRC) in clinical applications. However, low positivity rate and sensitivity limits their clinical effectiveness. In this study, we explored the potential of C-reactive protein (CRP) and fibrinogen to improve the diagnostic efficiency of traditional biomarkers of CRC. The concentrations of CRP and fibrinogen in plasma were significantly higher in CRC patients compared with benign or healthy controls. The area under the ROC curves (AUCs) showed that the diagnostic efficacy of CRP and fibrinogen was 0.745 (95% CI: 0.712-0.779) and 0.699 (95% CI: 0.663-0.734), respectively. AUC increased to 0.750 (95% CI: 0.716-0.784) when CRP and fibrinogen were combined. It also further improved to 0.889 (95% CI: 0.866-0.913) when CRP and fibrinogen were integrated with CEA and CA72-4. Moreover, this combination increased the maximum area under AUC to 0.857 (95% CI: 0.830-0.883), which effective differentiated CRC from benign disease. Overall, this study found that CRP and fibrinogen were highly expressed in the plasma of CRC patients, suggesting their potential to improve the diagnostic efficiency of traditional biomarkers of CRC.

A hierarchy of cell death pathways confers layered resistance to shigellosis in mice

Bacteria of the genus Shigella cause shigellosis, a severe gastrointestinal disease driven by bacterial colonization of colonic intestinal epithelial cells. Vertebrates have evolved programmed cell death pathways that sense invasive enteric pathogens and eliminate their intracellular niche. Previously we reported that genetic removal of one such pathway, the NAIP-NLRC4 inflammasome, is sufficient to convert mice from resistant to susceptible to oral Shigella flexneri challenge (Mitchell et al., 2020). Here, we investigate the protective role of additional cell death pathways during oral mouse Shigella infection. We find that the Caspase-11 inflammasome, which senses Shigella LPS, restricts Shigella colonization of the intestinal epithelium in the absence of NAIP-NLRC4. However, this protection is limited when Shigella expresses OspC3, an effector that antagonizes Caspase-11 activity. TNFα, a cytokine that activates Caspase-8-dependent apoptosis, also provides potent protection from Shigella colonization of the intestinal epithelium when mice lack both NAIP-NLRC4 and Caspase-11. The combined genetic removal of Caspases-1, -11, and -8 renders mice hyper-susceptible to oral Shigella infection. Our findings uncover a layered hierarchy of cell death pathways that limit the ability of an invasive gastrointestinal pathogen to cause disease.

“Just one word, plastic!”: Controversies and caveats in innate lymphoid cell plasticity

Innate lymphoid cells (ILCs) are frontline immune effectors involved in the early stages of host defense and maintenance of tissue homeostasis, particularly at mucosal surfaces such as the intestine, lung, and skin. Canonical ILCs are described as tissue-resident cells that populate peripheral tissues early in life and respond appropriately based on environmental exposure and their anatomical niche and tissue microenvironment. Intriguingly, there are accumulating reports of ILC “plasticity” that note the existence of non-canonical ILCs that exhibit distinct patterns of master transcription factor expression and cytokine production profiles in response to tissue inflammation. Yet this concept of ILC-plasticity is controversial due to several confounding caveats that include, among others, the independent large-scale recruitment of new ILC subsets from distal sites and the local, in situ, differentiation of uncommitted resident precursors. Nevertheless, the ability of ILCs to acquire unique characteristics and adapt to local environmental cues is an attractive paradigm because it would enable the rapid adaptation of innate responses to a wider array of pathogens even in the absence of pre-existing ‘prototypical’ ILC responder subsets. Despite the impressive recent progress in understanding ILC biology, the true contribution of ILC plasticity to tissue homeostasis and disease and how it is regulated remains obscure. Here, we detail current methodologies used to study ILC plasticity in mice and review the mechanisms that drive and regulate functional ILC plasticity in response to polarizing signals in their microenvironment and different cytokine milieus. Finally, we discuss the physiological relevance of ILC plasticity and its implications for potential therapeutics and treatments.

Ceramide-mediated gut dysbiosis enhances cholesterol esterification and promotes colorectal tumorigenesis in mice

Colorectal cancer (CRC) severely threatens human health and life span. An effective therapeutic strategy has not been established because we do not clearly know its pathogenesis. Here, we report that ceramide and sterol O-acyltransferase 1 (SOAT1) have roles in both spontaneous and chemical-induced intestinal cancers. We first found that miRNA-148a deficiency dramatically increased mouse gut dysbiosis through upregulating ceramide synthase 5 (Cers5) expression, which promoted ceramide synthesis afterward. The newly generated ceramide further promoted both azoxymethane/dextran sodium sulfate–induced (AOM/DSS-induced) and Apc^Min/+ spontaneous intestinal tumorigenesis via increasing mouse gut dysbiosis. Meanwhile, increased level of ceramide correlated with the significant enhancements of both β-catenin activity and colorectal tumorigenesis in a TLR4-dependent fashion. Next, we found a direct binding of β-catenin to SOAT1 promoter to activate transcriptional expression of SOAT1, which further induced cholesterol esterification and colorectal tumorigenesis. In human patients with CRC, the same CERS5/TLR4/β-catenin/SOAT1 axis was also found to be dysregulated. Finally, the SOAT1 inhibitor (avasimibe) showed significant levels of therapeutic effects on both AOM/DSS-induced and Apc^Min/+ spontaneous intestinal cancer. Our study clarified that ceramide promoted CRC development through increasing gut dysbiosis, further resulting in the increase of cholesterol esterification in a SOAT1-dependent way. Treatment with avasimibe to specifically decrease cholesterol esterification could be considered as a clinical strategy for effective CRC therapy in a future study.

Genetic and environmental factors shape the host response to Helicobacter hepaticus: insights into IBD pathogenesis

Pathobionts are members of the gut microbiota with the capacity to cause disease when there is malfunctioning intestinal homeostasis. These organisms are thought to be major contributors to the pathogenesis of inflammatory bowel disease (IBD), a group of chronic inflammatory disorders driven by dysregulated responses towards the microbiota. Over two decades have passed since the discovery of Helicobacter hepaticus, a mouse pathobiont which causes colitis in the context of immune deficiency. During this time, we have developed a detailed understanding of the cellular players and cytokine networks which drive H. hepaticus immunopathology. However, we are just beginning to understand the microbial factors that enable H. hepaticus to interact with the host and influence colonic health and disease. Here we review key H. hepaticus-host interactions, their relevance to other exemplar pathobionts and how when maladapted they drive colitis. Further understanding of these pathways may offer new therapeutic approaches for IBD.

IL-10 Receptor Neutralization-Induced Colitis in Mice: A Comprehensive Guide

Interleukin-10 (IL-10) and its receptor (IL-10R) have been foremost targets to understand inflammatory bowel disease (IBD) pathogenesis. For the past several decades, IL-10-deficient (Il10^-/- ) mice were considered one of the best models to study immune-mediated colitis. Several physiologic limitations with this model, e.g., delayed and varied disease onset, have hindered investigators in testing new clinical therapies for IBD. In this article, we provide comprehensive guidance for using anti-IL-10R monoclonal antibody (αIL-10R mAb) neutralization as a superior alternative model to study IBD. This article describes the feasibility of using αIL-10R mAb to induce chronic colitis (within 4 weeks), perform time-dependent mechanistic studies, and assess the efficacy of IBD therapeutics. This article also delineates protocols for in-house assays to critically assess colitis and associated inflammatory parameters. Overall, we underscore αIL-10R mAb neutralization as a relevant immune-mediated murine colitis model to study human Crohn's disease. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Induction of chronic colitis in mice via αIL-10R mAb neutralization Basic Protocol 2: Biochemical evaluation of αIL-10R mAb neutralization-induced chronic colitis Support Protocol 1: Stool analysis and scoring Support Protocol 2: Swiss roll method.

Extracellular Granzyme A Promotes Colorectal Cancer Development by Enhancing Gut Inflammation

If not properly regulated, the inflammatory immune response can promote carcinogenesis, as evident in colorectal cancer (CRC). Aiming to gain mechanistic insight into the link between inflammation and CRC, we perform transcriptomics analysis of human CRC, identifying a strong correlation between expression of the serine protease granzyme A (GzmA) and inflammation. In a dextran sodium sulfate and azoxymethane (DSS/AOM) mouse model, deficiency and pharmacological inhibition of extracellular GzmA both attenuate gut inflammation and prevent CRC development, including the initial steps of cell transformation and epithelial-to-mesenchymal transition. Mechanistically, extracellular GzmA induces NF-κB-dependent IL-6 production in macrophages, which in turn promotes STAT3 activation in cultured CRC cells. Accordingly, colon tissues from DSS/AOM-treated, GzmA-deficient animals present reduced levels of pSTAT3. By identifying GzmA as a proinflammatory protease that promotes CRC development, these findings provide information on mechanisms that link immune cell infiltration to cancer progression and present GzmA as a therapeutic target for CRC.

The role of innate lymphoid cells in selected disease states - cancer formation, metabolic disorder and inflammation

Innate lymphoid cells (ILCs) are a recently described group of immune cells that can regulate homeostasis and protect mammalian organisms, including humans, from infections and diseases. Considering this, ILC research is still ongoing to better understand the biology of these cells and their roles in the human body. ILCs are a multifunctional group of immune cells, making it important for the medical community to be familiar with the latest research about the ILC families and their functions in selected disease states, such as cancer formation, metabolic disorders and inflammation. By discovering the roles of ILC populations and their participation in many disorders, we can improve disease diagnostics and patient healthcare.

ADP-heptose: a bacterial PAMP detected by the host sensor ALPK1

The innate immune response constitutes the first line of defense against pathogens. It involves the recognition of pathogen-associated molecular patterns (PAMPs) by pathogen recognition receptors (PRRs), the production of inflammatory cytokines and the recruitment of immune cells to infection sites. Recently, ADP-heptose, a soluble intermediate of the lipopolysaccharide biosynthetic pathway in Gram-negative bacteria, has been identified by several research groups as a PAMP. Here, we recapitulate the evidence that led to this identification and discuss the controversy over the immunogenic properties of heptose 1,7-bisphosphate (HBP), another bacterial heptose previously defined as an activator of innate immunity. Then, we describe the mechanism of ADP-heptose sensing by alpha-protein kinase 1 (ALPK1) and its downstream signaling pathway that involves the proteins TIFA and TRAF6 and induces the activation of NF-κB and the secretion of inflammatory cytokines. Finally, we discuss possible delivery mechanisms of ADP-heptose in cells during infection, and propose new lines of thinking to further explore the roles of the ADP-heptose/ALPK1/TIFA axis in infections and its potential implication in the control of intestinal homeostasis.

Citrobacter rodentium induces rapid and unique metabolic and inflammatory responses in mice suffering from severe disease

The mouse pathogen Citrobacter rodentium is used to model infections with enterohaemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC). Pathogenesis is commonly modelled in mice developing mild disease (e.g., C57BL/6). However, little is known about host responses in mice exhibiting severe colitis (e.g., C3H/HeN), which arguably provide a more clinically relevant model for human paediatric enteric infection. Infection of C3H/HeN mice with C. rodentium results in rapid colonic colonisation, coinciding with induction of key inflammatory signatures and colonic crypt hyperplasia. Infection also induces dramatic changes to bioenergetics in intestinal epithelial cells, with transition from oxidative phosphorylation (OXPHOS) to aerobic glycolysis and higher abundance of SGLT4, LDHA, and MCT4. Concomitantly, mitochondrial proteins involved in the TCA cycle and OXPHOS were in lower abundance. Similar to observations in C57BL/6 mice, we detected simultaneous activation of cholesterol biogenesis, import, and efflux. Distinctly, however, the pattern recognition receptors NLRP3 and ALPK1 were specifically induced in C3H/HeN. Using cell‐based assays revealed that C. rodentium activates the ALPK1/TIFA axis, which is dependent on the ADP‐heptose biosynthesis pathway but independent of the Type III secretion system. This study reveals for the first time the unfolding intestinal epithelial cells' responses during severe infectious colitis, which resemble EPEC human infections.

Coordination of Immune-Stroma Crosstalk by IL-6 Family Cytokines

Stromal cells are a subject of rapidly growing immunological interest based on their ability to influence virtually all aspects of innate and adaptive immunity. Present in every bodily tissue, stromal cells complement the functions of classical immune cells by sensing pathogens and tissue damage, coordinating leukocyte recruitment and function, and promoting immune response resolution and tissue repair. These diverse roles come with a price: like classical immune cells, inappropriate stromal cell behavior can lead to various forms of pathology, including inflammatory disease, tissue fibrosis, and cancer. An important immunological function of stromal cells is to act as information relays, responding to leukocyte-derived signals and instructing leukocyte behavior in kind. In this regard, several members of the interleukin-6 (IL-6) cytokine family, including IL-6, IL-11, oncostatin M (OSM), and leukemia inhibitory factor (LIF), have gained recognition as factors that mediate crosstalk between stromal and immune cells, with diverse roles in numerous inflammatory and homeostatic processes. This review summarizes our current understanding of how IL-6 family cytokines control stromal-immune crosstalk in health and disease, and how these interactions can be leveraged for clinical benefit.

Analysis of Cdcs1 colitogenic effects in the hematopoietic compartment reveals distinct microbiome interaction and a new subcongenic interval active in T cells

Disease activity in Interleukin-10-deficient (Il10^-/-) mice, a model for IBD, depends on genetic background and microbiome composition. B6.129P2/JZtm-Il10^tm1Cgn (B6-Il10^-/-) mice are partially resistant to colitis, whereas mice carrying the Cdcs1^C3Bir haplotype on chromosome 3, B6.Cg-Il10^tm1CgnMMU3(D3Mit11-D3Mit348)/JZtm (BC-R3-Il10^-/-), are susceptible. This study was performed to clarify Cdcs1 and candidate gene effects on the colitogenic potential of hematopoietic cells using bone marrow (BM) and T-cell transfer models. Acute and chronic graft versus host reaction was excluded by high-density genotyping, in vitro and in vivo approaches. BM-chimeras were created with animals housed in two barriers (I and II) with distinct microbiota composition as identified by sequencing. BM-chimeras of all groups developed comparable moderate-to-severe colitis in Barrier I, however, in Barrier II only recipients of BC-R3-Il10^-/- BM. Subsequent adoptive T cell transfers pointed to a new subcongenic interval within Cdcs1 affecting their colitogenic potential. Transfers excluded Larp7 and Alpk1 but highlighted Ifi44 as potential candidate genes. In this model-system, colitis development after cell transfer heavily depends on microbiome, though Cdcs1 acts mainly independently in hematopoietic cells. A new subcongenic interval, provisionally named Cdcs1.4, modifies colitogenic T cell function. Within this locus, Ifi44 represents an important candidate gene for colitis expression.

Alpha kinase 1 controls intestinal inflammation by suppressing the IL-12/Th1 axis

Inflammatory bowel disease (IBD) are heterogenous disorders of the gastrointestinal tract caused by a spectrum of genetic and environmental factors. In mice, overlapping regions of chromosome 3 have been associated with susceptibility to IBD-like pathology, including a locus called Hiccs. However, the specific gene that controls disease susceptibility remains unknown. Here we identify a Hiccs locus gene, Alpk1 (encoding alpha kinase 1), as a potent regulator of intestinal inflammation. In response to infection with the commensal pathobiont Helicobacter hepaticus (Hh), Alpk1-deficient mice display exacerbated interleukin (IL)-12/IL-23 dependent colitis characterized by an enhanced Th1/interferon(IFN)-γ response. Alpk1 controls intestinal immunity via the hematopoietic system and is highly expressed by mononuclear phagocytes. In response to Hh, Alpk1-/- macrophages produce abnormally high amounts of IL-12, but not IL-23. This study demonstrates that Alpk1 promotes intestinal homoeostasis by regulating the balance of type 1/type 17 immunity following microbial challenge.

ALPK1: a pattern recognition receptor for bacterial ADP-heptose

A commentary on “Alpha-kinase 1 is a cytosolic innate immune receptor for bacterial ADP-heptose”.

Interleukin-22 drives nitric oxide-dependent DNA damage and dysplasia in a murine model of colitis-associated cancer

The risk of colon cancer is increased in patients with Crohn's disease and ulcerative colitis. Inflammation-induced DNA damage could be an important link between inflammation and cancer, although the pathways that link inflammation and DNA damage are incompletely defined. RAG2-deficient mice infected with Helicobacter hepaticus (Hh) develop colitis that progresses to lower bowel cancer. This process depends on nitric oxide (NO), a molecule with known mutagenic potential. We have previously hypothesized that production of NO by macrophages could be essential for Hh-driven carcinogenesis, however, whether Hh infection induces DNA damage in this model and whether this depends on NO has not been determined. Here we demonstrate that Hh infection of RAG2-deficient mice rapidly induces expression of iNOS and the development of DNA double-stranded breaks (DSBs) specifically in proliferating crypt epithelial cells. Generation of DSBs depended on iNOS activity, and further, induction of iNOS, the generation of DSBs, and the subsequent development of dysplasia were inhibited by depletion of the Hh-induced cytokine IL-22. These results demonstrate a strong association between Hh-induced DNA damage and the development of dysplasia, and further suggest that IL-22-dependent induction of iNOS within crypt epithelial cells rather than macrophages is a driving force in this process.

miR-148a inhibits colitis and colitis-associated tumorigenesis in mice

miR-148a has been shown to regulate inflammation, immunity and the growth of certain tumors, but its roles in colitis and colorectal tumorigenesis remain largely undetermined. Here we found miR-148a-deficient mice to be more susceptible to colitis and colitis-associated tumorigenesis. Both were associated with increased nuclear factor κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) signaling. Bone marrow- and non-bone marrow-derived miR-148a contributed to colitis and colitis-associated tumorigenesis. miR-148a loss of heterozygosity exacerbated Apc^min/+ colon and small intestinal spontaneous tumor development. Restoring miR-148a expression prevented both spontaneous and carcinogen-induced colon tumor development. miR-148a was downregulated in human inflammatory bowel disease (IBD) and colorectal cancer patient tissues. This correlated with a high degree of miR-148a promoter methylation mediated by a complex comprised of P65 and DNA methyltransferase 3 alpha (DNMT3A). miR-148a directly targets several well-accepted upstream regulators of NF-κB and STAT3 signaling, including GP130, IKKα, IKKβ, IL1R1 and TNFR2, which leads to decreased NF-κB and STAT3 activation in macrophages and colon tissues. Our findings reveal that miR-148a is an indirect tumor suppressor that modulates colitis and colitis-associated tumorigenesis by suppressing the expression of signaling by NF-κB and STAT3 and their pro-inflammatory consequences.

Loss of β-arrestin-2 and Activation of CXCR2 Correlate with Lymph Node Metastasis in Non-small Cell Lung Cancer

Background: Although β-arrestin-2 (β-arr2) and CXCR2 have been shown to affect various malignant tumors, their exact roles in lung cancer remain unclear. We investigated expression of β-arr2 and CXCR2 in patients with non-small cell lung cancer (NSCLC) and their correlation with lymph node metastasis and prognosis.

Methods: We reviewed medical records of 136 patients with NSCLC who underwent surgical resection, and assessed their specimens immunohistochemically for expression of β-arr2 and CXCR2 in primary tumors and metastatic lymph nodes (MLNs), respectively.

Results: High β-arr2 expression was seen in 63 specimens (46.3%), and was significantly associated with male patients (P=0.011), squamous cell carcinoma (P=0.003), and lymph node metastasis (P<0.001). High CXCR2 expression was seen in 62 specimens (45.6%), and was significantly correlated only with lymph node metastasis (P<0.001). Expression of β-arr2 was significantly lower at MLNs than at primary lesions (Z=-2.315; P=0.021; Wilcoxon signed-rank), whereas CXCR2 expression was significantly higher in MLNs than in primary lesions (Z=-3.712; P<0.001; Wilcoxon signed-rank). No relationship was seen between β-arr2 and CXCR2 expression in primary lesions (r=-0.065, P=0.548; Spearman rank coefficient), but they were inversely related in MLNs (r=-0.263, P=0.012). Kaplan-Meier survival curve was shown that low β-arr2 and high CXCR2 expressions was associated with poor survival (log-rank: χ²=5.926, P=0.015).

Conclusions: β-arr2 may promote lymph node metastasis in NSCLC by modulating CXCR2 activation.

Innate lymphoid cells in intestinal immunity and inflammation

Innate lymphoid cells (ILCs) are a new and distinct family of innate immune cells that play an important role in immunity and inflammation. In this review, we focus on the role of ILCs in mucosal tissues, especially in the gut, in health and disease. ILCs support intestinal homeostasis by protecting the intestine from pathogens, contributing to the development of gut lymphoid tissue, and helping to repair injuries. By cooperating with epithelial cells and other innate and adaptive immune cells, ILCs participate in the control of pathogens and tolerance of commensal bacteria. The development and maintenance of ILCs are influenced by nutrients and metabolites sourced from diet and/or gut bacteria. ILCs have been shown to be involved in host metabolism and to participate in various diseases of the intestine including infectious and chronic inflammatory diseases, and cancer. Thus, the elucidation of ILC biology provides an exciting potential for development of novel therapeutic means to modulate immune responses in various disease settings.

Colitis-associated colon cancer: Is it in your genes?

Colitis-associated colorectal cancer (CA-CRC) is the cause of death in 10%-15% of inflammatory bowel disease (IBD) patients. CA-CRC results from the accumulation of mutations in intestinal epithelial cells and progresses through a well-characterized inflammation to dysplasia to carcinoma sequence. Quantitative estimates of overall CA-CRC risks are highly variable ranging from 2% to 40% depending on IBD severity, duration and location, with IBD duration being the most significant risk factor associated with CA-CRC development. Recently, studies have identified IBD patients with similar patterns of colonic inflammation, but that differ with respect to CA-CRC development, suggesting a role for additional non-inflammatory risk factors in CA-CRC development. One suggestion is that select IBD patients carry polymorphisms in various low penetrance disease susceptibility genes, which pre-dispose them to CA-CRC development, although these loci have proven difficult to identify in human genome-wide association studies. Mouse models of CA-CRC have provided a viable alternative for the discovery, validation and study of individual genes in CA-CRC pathology. In this review, we summarize the current CA-CRC literature with a strong focus on genetic pre-disposition and highlight an emerging role for mouse models in the search for CA-CRC risk alleles.

Microbes and inflammation in colorectal cancer

Over the past decade, there has been a renaissance in research on physiologic interactions between humans and their resident microbiota, the vast numbers of bacteria, fungi, and viruses that live within and on the body. The burgeoning interest in what constitutes the human microbiome has also focused on the contribution of microbes to carcinogenesis. Given the microbiomes of malignancies arising at mucosal sites, the microbiota may prove as influential as stromal cells and immune cells in the tumor microenvironment. Herein, we focus on the interconnections of microbes and inflammation in colorectal carcinogenesis.

Cytokines, IBD, and colitis-associated cancer

Inflammatory bowel diseases (IBDs) are debilitating conditions that result in intestinal damage due to chronic inflammation. In addition, the perpetual state of inflammation predisposes individuals to the development of colitis-associated cancer. Because of the immense immune cell infiltration into colon, cytokines produced by immune cells are major players in the initiation and progression of IBD and colitis-associated cancer. In this review, we will explore the functions of many key cytokines and their roles in IBD and colitis-associated cancer, as well as their influences on the immune system and stromal cells. Finally, we will briefly discuss current therapies and current clinical trials targeting cytokines in IBD.

Immune diseases caused by mutations in kinases and components of the ubiquitin system

The signaling networks that control the immune system are coordinated by a myriad of interconnecting phosphorylation and ubiquitylation events. This review provides an overview of mutations in human genes encoding these proteins that give rise to immune diseases. Analysis of the biological effects of these mutations has revealed the true physiological roles of particular signaling networks and promises to revolutionize the treatment of these diseases.

Interleukin-23 is sufficient to induce rapid de novo gut tumorigenesis, independent of carcinogens, through activation of innate lymphoid cells

Chronic inflammation has been associated with increased risk for developing gastrointestinal cancer. Interleukin-23 (IL-23) receptor signaling has been correlated with inflammatory bowel disease pathogenesis, as well as promotion of tumor growth. However, little is known about the relative potential for IL-23-directed causality in gut tumorigenesis. We report that IL-23 transgene expression was sufficient to induce rapid (3-4 weeks) de novo development of intestinal adenomas with 100% incidence. Initiation of tumorigenesis was independent of exogenous carcinogens, Helicobacter colonization, or pre-existing tumor-suppressor gene mutations. Tumorigenesis was mediated by Thy1(+)IL-23R(+) innate lymphoid cells (ILC3), in part, through IL-17 responses as tumor development was inhibited in RAG(-/-) × IL-17(-/-) double knockout mice. Remarkably, IL-23 initiation of tumorigenesis by resident ILCs consistently occurred before recruitment of conspicuous inflammatory infiltrates. Our results reveal an explicit role for IL-23-mediated initiation of gut tumorigenesis and implicate a key role for IL-23R(+) ILC3 in the absence of overt cellular infiltrate recruitment.

MyD88 adaptor-like (Mal) regulates intestinal homeostasis and colitis-associated colorectal cancer in mice

Toll-like receptors (TLRs) play a central role in the recognition and response to microbial pathogens and in the maintenance and function of the epithelial barrier integrity in the gut. The protein MyD88 adaptor-like (Mal/TIRAP) serves as a bridge between TLR2/TLR4- and MyD88-mediated signaling to orchestrate downstream inflammatory responses. Whereas MyD88 has an essential function in the maintenance of intestinal homeostasis, a role for Mal in this context is less well described. Colitis was induced in wild-type (WT) and Mal-deficient (Mal(-/-)) mice by administration of dextran sodium sulfate (DSS). Colitis-associated cancer was induced by DSS and azoxymethane (AOM) treatment. Chimeric mice were generated by total body gamma irradiation followed by transplantation of bone marrow cells. In the DSS model of colon epithelial injury, Mal(-/-) mice developed increased inflammation and severity of colitis relative to WT mice. Mal(-/-) mice demonstrated the presence of inflammatory cell infiltrates, increased crypt proliferation, and presence of neoformations. Furthermore, in the AOM/DSS model, Mal(-/-) mice had greater incidence of tumors. Mal(-/-) and WT bone marrow chimeras demonstrated that nonhematopoietic cell expression of Mal had an important protective role in the control of intestinal inflammation and inflammation-associated cancer. Mal is essential for the maintenance of intestinal homeostasis and expression of Mal in nonhematopoietic cells prevents chronic intestinal inflammation that may predispose to colon neoplasia.

The Collaborative Cross as a resource for modeling human disease: CC011/Unc, a new mouse model for spontaneous colitis

Inflammatory bowel disease (IBD) is an immune-mediated condition driven by improper responses to intestinal microflora in the context of environmental and genetic background. GWAS in humans have identified many loci associated with IBD, but animal models are valuable for dissecting the underlying molecular mechanisms, characterizing environmental and genetic contributions and developing treatments. Mouse models rely on interventions such as chemical treatment or introduction of an infectious agent to induce disease. Here, we describe a new model for IBD in which the disease develops spontaneously in 20-week-old mice in the absence of known murine pathogens. The model is part of the Collaborative Cross and came to our attention due to a high incidence of rectal prolapse in an incompletely inbred line. Necropsies revealed a profound proliferative colitis with variable degrees of ulceration and vasculitis, splenomegaly and enlarged mesenteric lymph nodes with no discernible anomalies of other organ systems. Phenotypic characterization of the CC011/Unc mice with homozygosity ranging from 94.1 to 99.8% suggested that the trait was fixed and acted recessively in crosses to the colitis-resistant C57BL/6J inbred strain. Using a QTL approach, we identified four loci, Ccc1, Ccc2, Ccc3 and Ccc4 on chromosomes 12, 14, 1 and 8 that collectively explain 27.7% of the phenotypic variation. Surprisingly, we also found that minute levels of residual heterozygosity in CC011/Unc have significant impact on the phenotype. This work demonstrates the utility of the CC as a source of models of human disease that arises through new combinations of alleles at susceptibility loci.

The gut microbiota in mouse models of inflammatory bowel disease

The intestine and the intestinal immune system have evolved through a symbiotic homeostasis under which a highly diverse microbial flora is maintained in the gastrointestinal tract while pathogenic bacteria are recognized and eliminated. Disruption of the balance between the immune system and the gut microbiota results in the development of multiple pathologies in humans. Inflammatory bowel diseases (IBD) have been associated with alterations in the composition of intestinal flora but whether these changes are causal or result of inflammation is still under dispute. Various chemical and genetic models of IBD have been developed and utilized to elucidate the complex relationship between intestinal epithelium, immune system and the gut microbiota. In this review we describe some of the most commonly used mouse models of colitis and Crohn's disease (CD) and summarize the current knowledge of how changes in microbiota composition may affect intestinal disease pathogenesis. The pursuit of gut-microbiota interactions will no doubt continue to provide invaluable insight into the complex biology of IBD.

Expression of toll-like receptors on human rectal adenocarcinoma cells

The innate immune system uses Toll-like receptors (TLR) to detect the presence of pathogen patterns thus allowing for rapid host defense responses. Stimulation of TLR results in inflammatory response and regulatory cytokine production affecting acquired immunity. The aim of the study was an evaluation of TLR2 and TLR4 expression on the surface of human colon cancer cells in primary culture with or without autologous peripheral blood mononuclear cells. Surgical specimens of colon cancer were processed to obtain cancer cells. Cancer cells separation was conducted first by mechanical tissue disintegration and than by gradient centrifugation to obtain 95 % cell confluence. By staining the isolated cells the pathologist determined them as adenocarcinoma. Colon cancer cells were then co-cultured in 24 h culture alone or together with autologous lymphocytes. Reverse-transcription polymerase chain reaction was performed for detection of TLR2 and TLR4 mRNA in colon cancer and normal colon epithelial cells using commercially available primers. Resting as well as phytohemagglutinin or lipopolysaccharide (LPS) stimulated cells were tested. Receptor proteins on cancer cells were examined by immunohistochemistry. TLR4 mRNA was detected in cancer cells. Autologous lymphocytes do not exert any effect on these receptors expression. TLR4 mRNA expression was not observed in normal colon epithelial cells. TLR2 mRNA was present on LPS stimulated cancer cells as well as on resting and stimulated lymphocytes. Expression of TLR2 and TLR4 receptor proteins on colon cancer cells were confirmed by immunohistochemistry. TLR4 may be responsible for uncontrolled tumor growth under LPS stimulation in human colon environment.

Characterization of dextran sodium sulfate-induced inflammation and colonic tumorigenesis in Smad3(-/-) mice with dysregulated TGFβ

There are few mouse models that adequately mimic large bowel cancer in humans or the gastrointestinal inflammation which frequently precedes it. Dextran sodium sulphate (DSS)-induces colitis in many animal models and has been used in combination with the carcinogen azoxymethane (AOM) to induce cancer in mice. Smad3^−/− mice are deficient in the transforming growth factor beta (TGFβ) signaling molecule, SMAD3, resulting in dysregulation of the cellular pathway most commonly affected in human colorectal cancer, and develop inflammation-associated colon cancer. Previous studies have shown a requirement for a bacterial trigger for the colitis and colon cancer phenotype in Smad3^−/− mice. Studies presented here in Smad3^−/− mice detail disease induction with DSS, without the use of AOM, and show a) Smad3^−/− mice develop a spectrum of lesions ranging from acute and chronic colitis, crypt herniation, repair, dysplasia, adenomatous polyps, disseminated peritoneal adenomucinosis, adenocarcinoma, mucinous adenocarcinoma (MAC) and squamous metaplasia; b) the colon lesions have variable galactin-3 (Mac2) staining c) increased DSS concentration and duration of exposure leads to increased severity of colonic lesions; d) heterozygosity of SMAD3 does not confer increased susceptibility to DSS-induced disease and e) disease is partially controlled by the presence of T and B cells as Smad3^−/−Rag2^−/− double knock out (DKO) mice develop a more severe disease phenotype. DSS-induced disease in Smad3^−/− mice may be a useful animal model to study not only inflammation-driven MAC but other human diseases such as colitis cystica profunda (CCP) and pseudomyxomatous peritonei (PMP).

The microbiome and cancer

Microbiota and host form a complex 'super-organism' in which symbiotic relationships confer benefits to the host in many key aspects of life. However, defects in the regulatory circuits of the host that control bacterial sensing and homeostasis, or alterations of the microbiome, through environmental changes (infection, diet or lifestyle), may disturb this symbiotic relationship and promote disease. Increasing evidence indicates a key role for the bacterial microbiota in carcinogenesis. In this Opinion article, we discuss links between the bacterial microbiota and cancer, with a particular focus on immune responses, dysbiosis, genotoxicity, metabolism and strategies to target the microbiome for cancer prevention.

Innate lymphoid cells in the defense against infections

Barrier surfaces are under constant attack by potentially dangerous microbes. Interestingly, mucosal tissues contain a large number of innate lymphocytes now collectively referred to as innate lymphoid cells (ILCs). Different groups of ILCs are being distinguished, each of which produce an array of cytokines strikingly resembling the profile of the various T helper cell effector subsets. Over the last couple of years, evidence has been emerging that the various ILC subsets play important roles in immune defense against mucosal infections. In this review, I will introduce the various groups of ILCs and then focus on their roles for immunity to mucosal infections.

Mapping colitis susceptibility in mouse models: distal chromosome 3 contains major loci related to Cdcs1

Inflammatory bowel disease (IBD) summarizes a group of chronic intestinal disorders with Crohn's disease and ulcerative colitis being most prominent. Though much effort is put into identification of causative factors, its etiology is still not understood. Risk factors for disease development include genetic predisposition and environmental triggers. Crucial for identification and analysis of relevant factors are mouse models. Experimental IBD in mice occurs spontaneously or is induced by chemicals, cell transfer, pathogens, or genetic mutation. These models were utilized for analyzing genetic contribution to disease and genotype-environmental interactions. In these studies, a variety of modifier loci were identified, thereby demonstrating the complexity of disease. A major contribution of distal chromosome 3 was independently replicated in several studies. The first colitogenic QTL in this region was detected using the IL-10-deficient mouse model and called cytokine deficiency-induced colitis susceptibility (Cdcs)1. This quantitative trait locus contains at least three subintervals with independent genetic factors. This locus or defined subintervals were replicated in at least seven studies, using models based on dysregulation of innate or adaptive immunity or pathogen control. In this review we illustrate the various models used for genetic mapping of susceptibility to experimental IBD and display Cdcs1-related loci as well as the mechanism of their contribution identified so far.

How microRNAs influence both hereditary and inflammatory-mediated colon cancers

MicroRNAs have emerged as important post-translational regulators of gene expression and are involved in several physiological and pathological states including the pathogenesis of human colon cancers. In regards to tumor development, microRNAs can act as oncogenes or tumor suppressors. Two hereditary predispositions (i.e., Lynch syndrome and familial adenomatous polyposis) contribute to the development of colon cancer. In addition, individuals who suffer from inflammatory bowel diseases such as Crohn's disease or ulcerative colitis have a higher risk of developing colon cancer. Here, we discuss the occurrence of the deregulated expression of microRNAs in colon cancer that arise as a result of hereditary predisposition and inflammatory bowel disease.

Interleukin-11 is the dominant IL-6 family cytokine during gastrointestinal tumorigenesis and can be targeted therapeutically

Among 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.

Chemical and cytokine features of innate immunity characterize serum and tissue profiles in inflammatory bowel disease

Inflammatory bowel disease (IBD) arises from inappropriate activation of the mucosal immune system resulting in a state of chronic inflammation with causal links to colon cancer. Helicobacter hepaticus-infected Rag2(-/-) mice emulate many aspects of human IBD, and our recent work using this experimental model highlights the importance of neutrophils in the pathology of colitis. To define molecular mechanisms linking colitis to the identity of disease biomarkers, we performed a translational comparison of protein expression and protein damage products in tissues of mice and human IBD patients. Analysis in inflamed mouse colons identified the neutrophil- and macrophage-derived damage products 3-chlorotyrosine (Cl-Tyr) and 3-nitrotyrosine, both of which increased with disease duration. Analysis also revealed higher Cl-Tyr levels in colon relative to serum in patients with ulcerative colitis and Crohn disease. The DNA chlorination damage product, 5-chloro-2'-deoxycytidine, was quantified in diseased human colon samples and found to be present at levels similar to those in inflamed mouse colons. Multivariate analysis of these markers, together with serum proteins and cytokines, revealed a general signature of activated innate immunity in human IBD. Signatures in ulcerative colitis sera were strongly suggestive of neutrophil activity, and those in Crohn disease and mouse sera were suggestive of both macrophage and neutrophil activity. These data point to innate immunity as a major determinant of serum and tissue profiles and provide insight into IBD disease processes.

Innate lymphoid cells sustain colon cancer through production of interleukin-22 in a mouse model

Patients with inflammatory bowel disease (IBD) have an increased risk of colon cancer. However, the immune cells and cytokines that mediate the transition from intestinal inflammation to cancer are poorly understood. We show that bacteria-induced colon cancer is accompanied by differential accumulation of IL-17(+)IL-22(+) colonic innate lymphoid cells (cILCs), which are phenotypically distinct from LTi and NK-22 cells, and that their depletion in mice with dysplastic inflammation blocks the development of invasive colon cancer. Analysis of the functional role of distinct Type 17 cytokines shows that although blockade of IL-17 inhibits some parameters of intestinal inflammation, reduction in dysplasia and colorectal cancer (CRC) requires neutralization of IL-22 indicating a unique role for IL-22 in the maintenance of cancer in this model. Mechanistic analyses showed that IL-22 selectively acts on epithelial cells to induce Stat3 phosphorylation and proliferation. Importantly, we could detect IL-22(+)CD3(+) and IL-22(+)CD3(−) cells in human CRC. Our results describe a new activity of IL-22 in the colon as a nonredundant mediator of the inflammatory cascade required for perpetuation of CRC, highlighting the IL-22 axis as a novel therapeutic target in colon cancer.

The new prophylactic strategy for colon cancer in inflammatory bowel disease by modulating microbiota

It is well understood that intestinal microbiota play an important role in the pathogenesis of inflammatory bowel disease (IBD). In addition, IBD patients are well known to have a higher risk of developing colon cancer due to chronic inflammation. Recent evidence suggests that manipulation of microbiota improves the clinical outcome of patients with IBD and may reduce onset of colon cancer without obvious toxicity. This review summarizes the current experimental and clinical knowledge about the role of intestinal microbiota in IBD and colon cancer, and the nutraceutical therapy for colon cancer.

Hcp and VgrG1 are secreted components of the Helicobacter hepaticus type VI secretion system and VgrG1 increases the bacterial colitogenic potential

The enterohepatic Epsilonproteobacterium Helicobacter hepaticus persistently colonizes the intestine of mice and causes chronic inflammatory symptoms in susceptible mouse strains. The bacterial factors causing intestinal inflammation are poorly characterized. A large genomic pathogenicity island, HHGI1, which encodes components of a type VI secretion system (T6SS), was previously shown to contribute to the colitogenic potential of H. hepaticus. We have now characterized the T6SS components Hcp, VgrG1, VgrG2 and VgrG3, encoded on HHGI1, including the potential impact of the T6SS on intestinal inflammation in a mouse T-cell transfer model. The H. hepaticus T6SS components were expressed during the infection and secreted in a T6SS-dependent manner, when the bacteria were cultured either in the presence or in the absence of mouse intestinal epithelial cells. Mutants deficient in VgrG1 displayed a significantly lower colitogenic potential in T-cell-transferred C57BL/6 Rag2(-/-) mice, despite an unaltered ability to colonize mice persistently. Intestinal microbiota analyses demonstrated only minor changes in mice infected with wild-typeH. hepaticus as compared with mice infected with VgrG1-deficient isogenic bacteria. In addition, competitive assays between both wild-type and T6SS-deficient H. hepaticus, and between wild-type H. hepaticus and Campylobacter jejuni or Enterobacteriaceae species did not show an effect of the T6SS on interbacterial competitiveness. Therefore, we suggest that microbiota alterations did not play a major role in the changes of pro-inflammatory potential mediated by the T6SS. Cellular innate pro-inflammatory responses were increased by the secreted T6SS proteins VgrG1 and VgrG2. We therefore concluded that the type VI secretion component VgrG1 can modulate and specifically exacerbate the innate pro-inflammatory effect of the chronic H. hepaticus infection.

Inflammation and colorectal cancer: colitis-associated neoplasia

Connection between inflammation and cancer is a rapidly developing field. Epidemiological data suggests that inflammation along with distinct arms of host immune system plays a very important role in the development and progression of many different cancers. Inflammatory bowel disease (IBD) is an important risk factor for the development of colon cancer, namely, colitis-associated cancer (CAC). The molecular mechanisms by which inflammation promotes cancer development are still being uncovered and may differ between CAC and other forms of colorectal cancer. Recent work has shed light on the role of distinct immune cells, cytokines, and other immune mediators in virtually all of the steps of colonic tumorigenesis, including tumor initiation and promotion as well as progression and metastasis. The close proximity of colonic tumors to the myriad of intestinal microbes, as well as instrumental role of microbiota in IBD, introduces microbes as new players capable of triggering inflammation and possibly promoting tumorigenesis. Various mechanisms of CAC tumorigenesis as well as new possible hints for the future approaches for prevention and therapy are discussed in this review.

IL-1β mediates chronic intestinal inflammation by promoting the accumulation of IL-17A secreting innate lymphoid cells and CD4(+) Th17 cells

Although very high levels of interleukin (IL)-1β are present in the intestines of patients suffering from inflammatory bowel diseases (IBD), little is known about the contribution of IL-1β to intestinal pathology. Here, we used two complementary models of chronic intestinal inflammation to address the role of IL-1β in driving innate and adaptive pathology in the intestine. We show that IL-1β promotes innate immune pathology in Helicobacter hepaticus-triggered intestinal inflammation by augmenting the recruitment of granulocytes and the accumulation and activation of innate lymphoid cells (ILCs). Using a T cell transfer colitis model, we demonstrate a key role for T cell-specific IL-1 receptor (IL-1R) signals in the accumulation and survival of pathogenic CD4(+) T cells in the colon. Furthermore, we show that IL-1β promotes Th17 responses from CD4(+) T cells and ILCs in the intestine, and we describe synergistic interactions between IL-1β and IL-23 signals that sustain innate and adaptive inflammatory responses in the gut. These data identify multiple mechanisms through which IL-1β promotes intestinal pathology and suggest that targeting IL-1β may represent a useful therapeutic approach in IBD.