NOD1 and NOD2 Genetic Variants in Association with Risk of Gastric Cancer and Its Precursors in a Chinese Population

Nucleotide-binding oligomerization domain 1 (NOD1) regulates microglial activation in pseudorabies virus infection

The primary cause of viral encephalitis (VE) is invasion of the central nervous system (CNS) by the virus, which leads to neuroinflammation and poses a significant threat to global public health. Microglia, as CNS-resident macrophages, play a crucial role in neuroinflammation and are often identified as the preferred target for the prevention or treatment of VE. In this study, we used pseudorabies virus (PRV)-induced VE in mice and pigs as a model to investigate the regulation of microglial responses during viral encephalitis and explored the mechanism of microglial activation. Cellular experiments revealed that microglial activation was accompanied by cell migration, characteristic morphological changes, phagocytosis, inflammatory cytokine production, and antigen presentation. Transcriptome analysis revealed that genes related to inflammation in PRV-infected BV2 cells were significantly enriched. The expression of the NOD1 gene in BV2 cells was significantly increased during PRV infection, after which NOD1 in BV2 cells was silenced by siRNA and overexpressed via a plasmid. NOD1 was found to be involved in the secretion of cytokines in BV2 cells by regulating the MAPK/NF-κB signalling pathway. Mouse and pig experiments have shown that NOD1 is involved in the secretion of cytokines by microglia by regulating the MAPK/NF-κB signalling pathway during PRV infection.

NOD2 inhibits the proliferation of esophageal adenocarcinoma cells through autophagy

AIM

To study the regulatory mechanism of NOD2 in the inhibition of esophageal adenocarcinoma cell proliferation.

METHODS

Cell experiments: after confirming the decrease in NOD2 expression in esophageal adenocarcinoma, we overexpressed NOD2 in esophageal adenocarcinoma cells via lentivirus, compared and verified the changes in esophageal adenocarcinoma cell proliferation before and after NOD2 overexpression, and compared the overexpression group with the control group by mRNA sequencing to identify pathways that may affect cell proliferation. Then, the autophagy level of multiple groups were assessed, and the results were verified by rescue experiments. In vivo experiments: we administered esophageal adenocarcinoma cells to nude mice to form tumors under their skin and then injected the tumors with NOD2 overexpression lentivirus and negative control lentivirus. After a period of time, the growth curve of the tumor was generated, and the tumor was removed to generate sections. Ki67 was labeled with immunohistochemistry to verify cell proliferation, and the protein was extracted from the tissue to detect the molecular indices of the corresponding pathway.

RESULTS

Upregulation of NOD2 expression inhibited the proliferation of esophageal adenocarcinoma cells. Upregulation of NOD2 expression increased the autophagy level of esophageal adenocarcinoma cells via ATG16L1. After ATG16L1 was inhibited, NOD2 had no significant effect on autophagy and proliferation of esophageal adenocarcinoma cells. Enhanced autophagy in esophageal adenocarcinoma cell lines inhibited cell proliferation. In vivo, the upregulation of NOD2 expression improved the autophagy level of tumor tissue and inhibited cells proliferation.

CONCLUSION

NOD2 can activate autophagy in esophageal adenocarcinoma cells through the ATG16L1 pathway and inhibit cell proliferation.

Construction of a Prognosis Model of the Pyroptosis-Related Gene in Multiple Myeloma and Screening of Core Genes

Pyroptosis is an important factor affecting the proliferation, invasion, and metastasis of tumor cells. However, in multiple myeloma (MM), there are few studies on whether the occurrence of pyroptosis is related to the occurrence and prognosis of the disease. Based on the Gene Expression Omnibus and Cancer Genome Atlas database search dataset, this study identified pyroptosis-related genes with a specific prognosis, constructed and verified the prediction model by stepwise Cox regression analysis and time receiver operating characteristic curve analysis, and predicted specific functions by single-sample gene set enrichment analysis and the Kyoto Encyclopedia of Genes and Genomes. Dataset analysis identified key genes, which were used to construct a risk scoring system for the prognosis of MM. The entire test set and external verification set verified the results. The expression levels of related genes in the clinical samples were detected using fluorescence quantitative PCR. A prognostic gene model based on six pyroptosis-related genes (CYCS, NLRP9, AIM2, NOD2, CHMP3, and GSDME) was constructed. The model has an excellent prognostic ability and can be popularized in the external validation set. The predictive prognostic nomogram integrating clinical information can effectively evaluate the risk score of each patient and predict their survival. After sample validation, our study found three potential key pyroptosis-related genes in multiple myeloma. GSDME, NOD2, and CHMP3 were significantly different between MM and healthy subjects, suggesting that they are pyroptosis-related protective genes. This study shows that the key pyroptosis-related gene in the model can be used as a marker for predicting the prognosis of myeloma, which may provide a basis for clinical individualized stratification therapy.

An Overview of Autophagy in Helicobacter pylori Infection and Related Gastric Cancer

Helicobacter pylori (H. pylori) infection is considered a class I carcinogen in the pathogenesis of gastric cancer. In recent years, the interaction relationship between H. pylori infection and autophagy has attracted increasing attention. Most investigators believe that the pathogenesis of gastric cancer is closely related to the formation of an autophagosome-mediated downstream signaling pathway by H. pylori infection-induced cells. Autophagy is involved in H. pylori infection and affects the occurrence and development of gastric cancer. In this paper, the possible mechanism by which H. pylori infection affects autophagy and the progression of related gastric cancer signaling pathways are reviewed.

Therapeutic Interventions Targeting Innate Immune Receptors: A Balancing Act

The innate immune system is an organism's first line of defense against an onslaught of internal and external threats. The downstream adaptive immune system has been a popular target for therapeutic intervention, while there is a relative paucity of therapeutics targeting the innate immune system. However, the innate immune system plays a critical role in many human diseases, such as microbial infection, cancer, and autoimmunity, highlighting the need for ongoing therapeutic research. In this review, we discuss the major innate immune pathways and detail the molecular strategies underpinning successful therapeutics targeting each pathway as well as previous and ongoing efforts. We will also discuss any recent discoveries that could inform the development of novel therapeutic strategies. As our understanding of the innate immune system continues to develop, we envision that therapies harnessing the power of the innate immune system will become the mainstay of treatment for a wide variety of human diseases.

New insights into genetic characteristics between multiple myeloma and COVID-19: An integrative bioinformatics analysis of gene expression omnibus microarray and the cancer genome atlas data

Background

Multiple myeloma (MM) is a hematological malignancy. Coronavirus disease 2019 (COVID‐19) infection correlates with MM features. This study aimed to identify MM prognostic biomarkers with potential association with COVID‐19.

Methods

Differentially expressed genes (DEGs) in five MM data sets (GSE47552, GSE16558, GSE13591, GSE6477, and GSE39754) with the same expression trends were screened out. Functional enrichment analysis and the protein‐protein interaction network were performed for all DEGs. Prognosis‐associated DEGs were screened using the stepwise Cox regression analysis in the cancer genome atlas (TCGA) MMRF‐CoMMpass cohort and the GSE24080 data set. Prognosis‐associated DEGs associated with COVID‐19 infection in the GSE164805 data set were also identified.

Results

A total of 98 DEGs with the same expression trends in five data sets were identified, and 83 DEGs were included in the protein‐protein interaction network. Cox regression analysis identified 16 DEGs were associated with MM prognosis in the TCGA cohort, and only the cytochrome c oxidase subunit 6C (COX6C) gene (HR = 1.717, 95% CI 1.231–2.428, p = .002) and the nucleotide‐binding oligomerization domain containing 2 (NOD2) gene (HR = 0.882, 95% CI 0.798–0.975, p = .014) were independent factors related to MM prognosis in the GSE24080 data set. Both of them were downregulated in patients with mild COVID‐19 infection compared with controls but were upregulated in patients with severe COVID‐19 compared with patients with mild illness.

Conclusions

The NOD2 and COX6C genes might be used as prognostic biomarkers in MM. The two genes might be associated with the development of COVID‐19 infection.

Association of CYP2C19, TNF-α, NOD1, NOD2, and PPARγ polymorphisms with peptic ulcer disease enhanced by Helicobacter pylori infection

OBJECTIVES

To assess the correlation between a number of genetic variations of CYP2C19, TNF-α, NOD1, NOD2, and PPARγ genes with the severity of Helicobacter pylori (H. pylori) infections and peptic ulcers (PU).

METHODS

A retrospective cross-sectional design was used in this study. Formalin-fixed paraffin-embedded (FFPE) tissue was used to extract genomic DNA that was collected from Jordanian patients who visited endoscopy clinics between 2014 to 2018 at the King Abdullah University Hospital (KAUH), Irbid, Jordan. Genotyping of the studied single nucleotide polymorphisms (SNPs) were applied using the sequencing protocol. Results:  A total of 251 patients (mean age: 42.12 ± 16.09 years) and healthy controls (mean age: 52.76 ± 19.45 years) were enrolled in this study. This study showed no significant association between patients and the studied polymorphisms except for rs2075820 of the NOD1 (p=0.0046). It is hypothesized that the heterozygous genotype (TC); 44.8% in patients versus 61.3% in controls has a decreased risk of peptic ulcers (OR:  0.49). The alleles frequency association was insignificant in all studied SNPs with a p-value more than 0.05.

CONCLUSION

This study provided evidence regarding the association of the rs2075820 with H. pylori infections. The other studied SNPs were not statistically significant.

NOD1 rs2075820 (p.E266K) polymorphism is associated with gastric cancer among individuals infected with cagPAI-positive H. pylori

Background

Helicobacter pylori is detected by pathogen recognition receptors including toll-like receptors (TLR) and nucleotide-binding oligomerization domain (NOD)-like receptors, eliciting an innate immune response against this bacteria. The aim of this study was to assess if polymorphisms of TLR2, TLR4, TLR5, NOD1 and NOD2 genes are associated with gastric cancer, in particular in individuals infected with H. pylori.

Results

A case-control study of 297 gastric cancer patients and 300 controls was performed to assess the association of 17 polymorphisms. Analyses performed under the allele model did not find association with gastric cancer. However, NOD1 rs2075820 (p.E266K) showed association with intestinal-type gastric cancer among H. pylori infected subjects (OR = 2.69, 95% CI 1.41–5.13, p = 0.0026). The association was not statistically significant in diffuse-type gastric cancer cases (OR = 1.26, 95% CI 0.63–2.52, p = 0.51). When the analyses were performed in patients carrying H. pylori strains harboring the cag pathogenicity island (cagPAI), we noticed significant association with NOD1 rs2075820 (OR = 4.90, 95% CI 1.80–3.36, p = 0.0019), in particular for intestinal-type gastric cancer cases (OR = 7.16, 95% CI 2.40–21.33, p = 4.1 × 10^− 4) but not among diffuse-type gastric cancer cases (OR = 3.39, 95% CI 1.13–0.10, p = 0.03).

Conclusions

NOD1 rs2075820 increases the risk of intestinal-type gastric cancer among individuals infected with H. pylori, particularly in those harboring the cagPAI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-021-00336-4.

Cell death as part of innate immunity: Cause or consequence?

Regulated or programmed cell death plays a critical role in the development and tissue organization and function. In addition, it is intrinsically connected with immunity and host defence. An increasing cellular and molecular findings cause a change in the concept of cell death, revealing an expanding network of regulated cell death modalities and their biochemical programmes. Likewise, recent evidences demonstrate the interconnection between cell death pathways and how they are involved in different immune mechanisms. This work provides an overview of the main cell death programmes and their implication in innate immunity not only as an immunogenic/inflammatory process, but also as an active defence strategy during immune response and at the same time as a regulatory mechanism.

A small sustained increase in NOD1 abundance promotes ligand-independent inflammatory and oncogene transcriptional responses

Small, genetically determined differences in transcription [expression quantitative trait loci (eQTLs)] are implicated in complex diseases through unknown molecular mechanisms. Here, we showed that a small, persistent increase in the abundance of the innate pathogen sensor NOD1 precipitated large changes in the transcriptional state of monocytes. A ~1.2- to 1.3-fold increase in NOD1 protein abundance resulting from loss of regulation by the microRNA cluster miR-15b/16 lowered the threshold for ligand-induced activation of the transcription factor NF-κB and the MAPK p38. An additional sustained increase in NOD1 abundance to 1.5-fold over basal amounts bypassed this low ligand concentration requirement, resulting in robust ligand-independent induction of proinflammatory genes and oncogenes. These findings reveal that tight regulation of NOD1 abundance prevents this sensor from exceeding a physiological switching checkpoint that promotes persistent inflammation and oncogene expression. Furthermore, our data provide insight into how a quantitatively small change in protein abundance can produce marked changes in cell state that can serve as the initiator of disease.

The Role of Host Genetic Polymorphisms in Helicobacter pylori Mediated Disease Outcome

The clinical outcome of infection with the chronic gastric pathogen Helicobacter pylori is not the same for all individuals and also differs in different ethnic groups. Infection occurs in early life (<3 years of age), and while all infected persons mount an immune response and develop gastritis, the majority of individuals are asymptomatic. However, up to 10-15% develop duodenal ulceration, up to 1% develop gastric cancer (GC) and up to 0.1% can develop gastric mucosa-associated lymphoid tissue (MALT) lymphoma. The initial immune response fails to clear infection and H. pylori can persist for decades. H. pylori has been classified as a group one carcinogen by the WHO. Interestingly, development of duodenal ulceration protects against GC. Factors that determine the outcome of infection include the genotype of the infecting strains and the environment. Host genetic polymorphisms have also been identified as factors that play a role in mediating the clinical outcome of infection. Several studies present compelling evidence that polymorphisms in genes involved in the immune response such as pro and anti-inflammatory cytokines and pathogen recognition receptors (PRRs) play a role in modulating disease outcome. However, as the number of studies grows emerging confounding factors are small sample size and lack of appropriate controls, lack of consideration of environmental and bacterial factors and ethnicity of the population. This chapter is a review of current evidence that host genetic polymorphisms play a role in mediating persistent H. pylori infection and the consequences of the subsequent inflammatory response.

NOD-like receptors: major players (and targets) in the interface between innate immunity and cancer

Innate immunity comprises several inflammation-related modulatory pathways which receive signals from an array of membrane-bound and cytoplasmic pattern recognition receptors (PRRs). The NLRs (NACHT (NAIP (neuronal apoptosis inhibitor protein), C2TA (MHC class 2 transcription activator), HET-E (incompatibility locus protein from Podospora anserina) and TP1 (telomerase-associated protein) and Leucine-Rich Repeat (LRR) domain containing proteins) relate to a large family of cytosolic innate receptors, involved in detection of intracellular pathogens and endogenous byproducts of tissue injury. These receptors may recognize pathogen-associated molecular patterns (PAMPs) and/or danger-associated molecular patterns (DAMPs), activating host responses against pathogen infection and cellular stress. NLR-driven downstream signals trigger a number of signaling circuitries, which may either initiate the formation of inflammasomes and/or activate nuclear factor κB (NF-κB), stress kinases, interferon response factors (IRFs), inflammatory caspases and autophagy. Disruption of those signals may lead to a number of pro-inflammatory conditions, eventually promoting the onset of human malignancies. In this review, we describe the structures and functions of the most well-defined NLR proteins and highlight their association and biological impact on a diverse number of cancers.

Genetic Polymorphisms in Inflammatory and Other Regulators in Gastric Cancer: Risks and Clinical Consequences

Helicobacter pylori infection is associated with the development of a chronic inflammatory response, which may induce peptic ulcers, gastric cancer (GC), and mucosa-associated lymphoid tissue (MALT) lymphoma. Chronic H. pylori infection promotes the genetic instability of gastric epithelial cells and interferes with the DNA repair systems in host cells. Colonization of the stomach with H. pylori is an important cause of non-cardia GC and gastric MALT lymphoma. The reduction of GC development in patients who underwent anti-H. pylori eradication schemes has also been well described. Individual susceptibility to GC development depends on the host's genetic predisposition, H. pylori virulence factors, environmental conditions, and geographical determinants. Biological determinants are urgently sought to predict the clinical course of infection in individuals with confirmed H. pylori infection. Possible candidates for such biomarkers include genetic aberrations such as single-nucleotide polymorphisms (SNPs) found in various cytokines/growth factors (e.g., IL-1β, IL-2, IL-6, IL-8, IL-10, IL-13, IL-17A/B, IFN-γ, TNF, TGF-β) and their receptors (IL-RN, TGFR), innate immunity receptors (TLR2, TLR4, CD14, NOD1, NOD2), enzymes involved in signal transduction cascades (PLCE1, PKLR, PRKAA1) as well as glycoproteins (MUC1, PSCA), and DNA repair enzymes (ERCC2, XRCC1, XRCC3). Bacterial determinants related to GC development include infection with CagA-positive (particularly with a high number of EPIYA-C phosphorylation motifs) and VacA-positive isolates (in particular s1/m1 allele strains). The combined genotyping of bacterial and host determinants suggests that the accumulation of polymorphisms favoring host and bacterial features increases the risk for precancerous and cancerous lesions in patients.

Nucleotide-binding oligomerization domain 1 and Helicobacter pylori infection: A review

Nucleotide-binding oligomerization domain 1 (NOD1) is an intracellular innate immune sensor for small molecules derived from bacterial cell components. NOD1 activation by its ligands leads to robust production of pro-inflammatory cytokines and chemokines by innate immune cells, thereby mediating mucosal host defense systems against microbes. Chronic gastric infection due to Helicobacter pylori (H. pylori) causes various upper gastrointestinal diseases, including atrophic gastritis, peptic ulcers, and gastric cancer. It is now generally accepted that detection of H. pylori by NOD1 expressed in gastric epithelial cells plays an indispensable role in mucosal host defense systems against this organism. Recent studies have revealed the molecular mechanism by which NOD1 activation caused by H. pylori infection is involved in the development of chronic gastritis and gastric cancer. In this review, we have discussed and summarized how sensing of H. pylori by NOD1 mediates the prevention of chronic gastritis and gastric cancer.

Association between receptor interacting serine/threonine kinase 2 polymorphisms and gastric cancer susceptibility

The present study aimed to investigate whether single nucleotide polymorphisms in receptor interacting serine/threonine kinase 2 (RIPK2), which encodes a component of the nucleotide binding oligomerization domain containing 2-RIP2 pathway, may compromise the innate immune response to Helicobacter pylori infection, leading to increased susceptibility to gastric cancer in the Japanese population. The present case control study investigated the associations between RIPK2 single nucleotide polymorphisms and gastric mucosal inflammation, atrophy and cancer susceptibility in 528 patients with gastric cancer and 697 patients without gastric malignancies on upper gastro-duodenal endoscopy. Overall, the RIPK2 rs16900627 minor allele was significantly associated with the susceptibility to gastric cancer [OR, 1.37; 95% confidence interval (CI), 1.06-1.77; P=0.016], particularly of the intestinal type (OR, 1.53; 95% CI, 1.13-2.07; P=0.0062). It was also significantly associated with gastric mucosal atrophy (OR, 1.83; 95% CI, 1.14-2.93; P=0.011). When assessing the severity of chronic gastritis using the updated Sydney system, the activity and inflammation scores, as well as atrophy and metaplasia scores, were significantly higher in rs16900627 minor allele carriers compared with wild-type homozygotes. In patients younger than 60 years old, the pepsinogen I/II ratio was significantly lower in rs16900627 minor allele carriers compared with wild-type homozygotes (P=0.037). The rs16900627 minor allele is associated with the severity of gastric mucosal inflammation and the development of gastric mucosal atrophy. Carriers of this allele may have an increased risk for the development of gastric cancer, particularly of the intestinal type.

NOD2 maybe a biomarker for the survival of kidney cancer patients

Background

Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) may play an important role in the outcome of kidney cancer patients. To explore the relationship between NOD2 and the prognosis of kidney cancer patients, a databank-based reanalysis was conducted.

Materials and Methods

Data related to kidney cancer patients at least with survival information, was obtained mainly from The Cancer Genome Atlas (TCGA). Some clinical data, not available online, was collected by personal email to the author. Then, we reanalyzed all the data in order to make a conclusion about the relationship between NOD2 gene and the prognosis of kidney cancer patients.

Results

A total of 1953 samples with NOD2 information from four databanks of The Cancer Genome Atlas (TCGA) were enrolled in this study. The results of KIPAN showed the Kaplan-Meier curve for risk groups, concordance index, and p-value of the log-rank testing equality of survival curves ( Concordance Index = 56.57, Log−Rank Equal Curves p=0.0009006, R^2 = 0.036/0.953, Risk Groups Hazard Ratio = 1.61 (conf. int. 1.21 ~ 2.13), p = 0.001005) , while a box plot across risk groups, including the p-value testing for difference using t-test (or f-test for more than two groups) was shown. There was a statistical significance for the p value of the result (p < 0.01 ). The similar results could be seen in KIRC and the fourth data (including 468 samples).

Conclusions

The status of NOD2 gene maybe a biomarker for the survival of kidney cancer patients.

NOD1CARD Might Be Using Multiple Interfaces for RIP2-Mediated CARD-CARD Interaction: Insights from Molecular Dynamics Simulation

The nucleotide-binding and oligomerization domain (NOD)-containing protein 1 (NOD1) plays the pivotal role in host-pathogen interface of innate immunity and triggers immune signalling pathways for the maturation and release of pro-inflammatory cytokines. Upon the recognition of iE-DAP, NOD1 self-oligomerizes in an ATP-dependent fashion and interacts with adaptor molecule receptor-interacting protein 2 (RIP2) for the propagation of innate immune signalling and initiation of pro-inflammatory immune responses. This interaction (mediated by NOD1 and RIP2) helps in transmitting the downstream signals for the activation of NF-κB signalling pathway, and has been arbitrated by respective caspase-recruitment domains (CARDs). The so-called CARD-CARD interaction still remained contradictory due to inconsistent results. Henceforth, to understand the mode and the nature of the interaction, structural bioinformatics approaches were employed. MD simulation of modelled 1:1 heterodimeric complexes revealed that the type-Ia interface of NOD1^CARD and the type-Ib interface of RIP2^CARD might be the suitable interfaces for the said interaction. Moreover, we perceived three dynamically stable heterotrimeric complexes with an NOD1:RIP2 ratio of 1:2 (two numbers) and 2:1. Out of which, in the first trimeric complex, a type-I NOD1-RIP2 heterodimer was found interacting with an RIP2^CARD using their type-IIa and IIIa interfaces. However, in the second and third heterotrimer, we observed type-I homodimers of NOD1 and RIP2 CARDs were interacting individually with RIP2^CARD and NOD1^CARD (in type-II and type-III interface), respectively. Overall, this study provides structural and dynamic insights into the NOD1-RIP2 oligomer formation, which will be crucial in understanding the molecular basis of NOD1-mediated CARD-CARD interaction in higher and lower eukaryotes.

Additive interactions between PRKAA1 polymorphisms and Helicobacter pylori CagA infection associated with gastric cancer risk in Koreans

Although several studies reported genetic polymorphisms in protein kinase AMP‐activated alpha 1 catalytic subunit (PRKAA1) and their associations with gastric cancer risk, few have evaluated associations between Helicobacter pylori infection and PRKAA1 gene‐environment interactions. Here, we evaluated the effects of interactions between H. pylori infection and PRKAA1 polymorphisms on gastric cancer risk in Koreans. In this hospital‐based case–control study, PRKAA1 genotypes were analyzed and H. pylori infection and CagA status were examined using a serologic method in 846 pairs of gastric cancer patients and controls matched for age and sex. H. pylori seropositivity was associated with a 1.43‐fold [95% confidence interval: 1.12–1.81] increase in the risk of gastric cancer, and CagA low‐positive titers during H. pylori infection increased the risk by 1.85‐fold (95% confidence interval, 1.38–2.48). Significant positive interaction between the PRKAA1 rs13361707 genotype and H. pylori infection was verified on an additive scale [relative excess risk due to interaction, 0.55; 95% confidence interval, 0.05–1.04; P = 0.030], and the gene‐environment interaction between PRKAA1 rs13361707 and CagA status was also statistically significant (relative excess risk due to interaction, 0.50; 95% confidence interval, 0.30–0.70; P < 0.001). Our results indicated that H. pylori infection, CagA status, and PRKAA1 polymorphisms were risk factors for gastric cancer in Koreans, and that the combination of two of these factors rather than their independent effects synergistically increased the risk.

NOD2 mutations and colorectal cancer - Where do we stand?

Due to the overwhelming burden of colorectal cancer (CRC), great effort has been placed on identifying genetic mutations that contribute to disease development and progression. One of the most studied polymorphisms that could potentially increase susceptibility to CRC involves the nucleotide-binding and oligomerization-domain containing 2 (NOD2) gene. There is growing evidence that the biological activity of NOD2 is far greater than previously thought and a link with intestinal microbiota and mucosal immunity is increasingly sought after. In fact, microbial composition may be an important contributor not only to inflammatory bowel diseases (IBD) but also to CRC. Recent studies have showed that deficient NOD2 function confers a communicable risk of colitis and CRC. Despite the evidence from experimental models, population-based studies that tried to link certain NOD2 polymorphisms and an increase in CRC risk have been described as conflicting. Significant geographic discrepancies in the frequency of such polymorphisms and different interpretations of the results may have limited the conclusions of those studies. Since being first associated to IBD and CRC, our understanding of the role of this gene has come a long way, and it is tempting to postulate that it may contribute to identify individuals with susceptible genetic background that may benefit from early CRC screening programs or in predicting response to current therapeutic tools. The aim of this review is to clarify the status quo of NOD2 mutations as genetic risk factors to chronic inflammation and ultimately to CRC. The use of NOD2 as a predictor of certain phenotypic characteristics of the disease will be analyzed as well.

Cdx2 Expression and Intestinal Metaplasia Induced by H. pylori Infection of Gastric Cells Is Regulated by NOD1-Mediated Innate Immune Responses

Chronic infection with the bacterial Helicobacter pylori is a major cause of gastric and duodenal ulcer disease, gastric mucosal atrophy, and cancer. H. pylori-induced expression of the intestinal epithelial-specific transcription factor caudal-related homeobox 2 (Cdx2) contributes to intestinal metaplasia, a precursor event to gastric cancer. Given a role for the bacterial pattern recognition molecule nucleotide-binding oligomerization domain 1 (NOD1) in the innate immune response to bacterial infection, we investigated mechanisms used by NOD1 to regulate H. pylori infection and its propensity towards the development of intestinal metaplasia. We found that Cdx2 was induced by H. pylori infection in both normal and neoplastic gastric epithelial cells in a manner that was inversely related to NOD1 signaling. Mechanistic investigations revealed that Cdx2 induction relied upon activation of NF-κB but was suppressed by NOD1-mediated activation of TRAF3, a negative regulator of NF-κB. In vivo, prolonged infection of NOD1-deficient mice with H. pylori led to increased Cdx2 expression and intestinal metaplasia. Furthermore, gastric epithelial cells from these mice exhibited increased nuclear expression of the NF-κB p65 subunit and decreased expression of TRAF3. Overall, our findings illuminated a role for NOD1 signaling in attenuating H. pylori-induced Cdx2 expression in gastric epithelial cells, suggesting a rationale to augment NOD1 signaling in H. pylori-infected patients to limit their risks of accumulating precancerous gastric lesions.