Helicobacter and gastric cancer disease mechanisms: host response and disease susceptibility

Human genomics of the humoral immune response against polyomaviruses

Human polyomaviruses are widespread in humans and can cause severe disease in immunocompromised individuals. To identify human genetic determinants of the humoral immune response against polyomaviruses, we performed genome-wide association studies and meta-analyses of qualitative and quantitative immunoglobulin G responses against BK polyomavirus (BKPyV), JC polyomavirus (JCPyV), Merkel cellpolyomavirus (MCPyV), WU polyomavirus (WUPyV), and human polyomavirus 6 (HPyV6) in 15,660 individuals of European ancestry from three independent studies. We observed significant associations for all tested viruses: JCPyV, HPyV6, and MCPyV associated with human leukocyte antigen class II variation, BKPyV and JCPyV with variants in FUT2, responsible for secretor status, MCPyV with variants in STING1, involved in interferon induction, and WUPyV with a functional variant in MUC1, previously associated with risk for gastric cancer. These results provide insights into the genetic control of a family of very prevalent human viruses, highlighting genes and pathways that play a modulating role in human humoral immunity.

Autophagy in Helicobacter pylori Infection and Related Gastric Cancer

BACKGROUND

Autophagy, a degradation pathway in which cytoplasmic content is engulfed and degraded by lysosomal hydrolases, plays a pivotal role in infection and inflammation. Given that defects in autophagy lead to increased susceptibility to infection, we investigated the role of autophagy in Helicobacter pylori-related gastric cancer (GC).

MATERIALS AND METHODS

Gene expression of 84 molecules was examined through quantitative real-time PCR in gastric epithelial cells (AGS) and macrophages (THP-1) upon exposure to H. pylori GC026 (GC) and 26695 (gastritis). Further, ATG16L1 rs2241880, IRGM rs13361189, and IRGM rs4958847, polymorphisms that have been investigated in relation to H. pylori infection or GC in Caucasians, were detected by MALDI-TOF mass spectrometry in 304 ethnic Chinese (86 noncardia GC cases/218 functional dyspepsia controls).

RESULTS

Gene expression analyses showed twenty-eight molecules involved in vesicle nucleation, elongation, and maturation to be significantly down-regulated in H. pylori GC026-challenged AGS cells. Further, core autophagy proteins and autophagy regulators were differentially expressed in H. pylori-challenged THP-1-derived macrophages. Analyses of the selected polymorphisms showed that ATG16L1 rs2241880 increased the risk of GC (OR: 2.38, 95% CI: 1.34-4.24) and H. pylori infection (OR: 1.49, 95% CI: 1.02-2.16) while IRGM rs4958847 decreased GC risk (OR: 0.26, 95% CI: 0.09-0.74) in ethnic Chinese, these effect sizes being especially strong in H. pylori-infected individuals (ATG16L1 rs2241880 and IRGM rs13361189).

CONCLUSIONS

Our findings indicate that highly virulent H. pylori strains markedly modulate autophagy in the host cell. Further, for the first time, autophagy polymorphisms were associated with GC in Chinese, a high GC-risk population.

Pattern-recognition receptors and gastric cancer

Chronic inflammation has been associated with an increased risk of several human malignancies, a classic example being gastric adenocarcinoma (GC). Development of GC is known to result from infection of the gastric mucosa by Helicobacter pylori, which initially induces acute inflammation and, in a subset of patients, progresses over time to chronic inflammation, gastric atrophy, intestinal metaplasia, dysplasia, and finally intestinal-type GC. Germ-line encoded receptors known as pattern-recognition receptors (PRRs) are critical for generating mature pro-inflammatory cytokines that are crucial for both Th1 and Th2 responses. Given that H. pylori is initially targeted by PRRs, it is conceivable that dysfunction within genes of this arm of the immune system could modulate the host response against H. pylori infection, and subsequently influence the emergence of GC. Current evidence suggests that Toll-like receptors (TLRs) (TLR2, TLR3, TLR4, TLR5, and TLR9), nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) (NOD1, NOD2, and NLRP3), a C-type lectin receptor (DC-SIGN), and retinoic acid-inducible gene (RIG)-I-like receptors (RIG-I and MDA-5), are involved in both the recognition of H. pylori and gastric carcinogenesis. In addition, polymorphisms in genes involved in the TLR (TLR1, TLR2, TLR4, TLR5, TLR9, and CD14) and NLR (NOD1, NOD2, NLRP3, NLRP12, NLRX1, CASP1, ASC, and CARD8) signaling pathways have been shown to modulate the risk of H. pylori infection, gastric precancerous lesions, and/or GC. Further, the modulation of PRRs has been suggested to suppress H. pylori-induced inflammation and enhance GC cell apoptosis, highlighting their potential relevance in GC therapeutics. In this review, we present current advances in our understanding of the role of the TLR and NLR signaling pathways in the pathogenesis of GC, address the involvement of other recently identified PRRs in GC, and discuss the potential implications of PRRs in GC immunotherapy.

The role of TLR2, TLR4 and CD14 genetic polymorphisms in gastric carcinogenesis: a case-control study and meta-analysis

Background

In addition to Helicobacter pylori infection, host genetic factors contribute to gastric cancer (GC). Recognition of H. pylori is known to involve Toll-like receptors (TLR), which subsequently leads to activation of NF-κB. Thus, the overall aim of this study was to estimate for the first time the pooled effect size of polymorphisms in TLR2, TLR4 and CD14 on GC development through a meta-analysis.

Methods

A case-control study comprising 284 ethnic Chinese individuals (70 non-cardia GC cases and 214 functional dyspepsia controls) was conducted for the genotyping of TLR2 -196 to -174del, CD14 -260 C/T and TLR4 rs11536889 using PCR, RT-PCR and mass spectrometry. Case-control studies of TLR2, TLR4 and CD14 polymorphisms and GC were searched up to June 2012. Pooled odds ratios and 95% confidence intervals were obtained by means of the random effects model.

Results

In our ethnic Chinese case-control study, the TLR4 rs11536889 C allele increased the risk of GC (OR: 1.89, 95%CI: 1.23–2.92) while the CD14 -260 T allele was protective (OR: 0.62, 95%CI: 0.42–0.91). TLR2 -196 to -174 increased the risk of GC only in H. pylori-infected individuals (OR: 3.10, 95%CI: 1.27–7.60). In the meta-analysis, TLR4 Asp299Gly showed borderline results in the general analysis (pooled OR: 1.58, 95%CI: 0.98–2.60), nevertheless, stratified analysis by ethnicity showed that the mutant allele was a definitive risk factor for GC in Western populations (pooled OR: 1.87, 95%CI: 1.31–2.65). There was a potential association between the TLR2 -196 to -174 deletion allele and GC in Japanese (pooled OR: 1.18, 95%CI: 0.96–1.45). TLR4 Thr399Ile did not provide significant results.

Conclusions

TLR4 rs11536889 and CD14 -260 C/T are associated with non-cardia GC in Chinese. Based on our meta-analysis, the TLR signalling pathway is involved in gastric carcinogenesis, TLR4 Asp299Gly and TLR2 -196 to -174del showing associations with GC in an ethnic-specific manner.

Synthesis and antimicrobial activity of novel substituted ethyl 2-(quinolin-4-yl)-propanoates

Substituted 4-hydroxyquinolines were synthesized from anilines and diethyl 2-(ethoxymethylene)malonate by the Gould-Jacobs reaction via cyclization of the intermediate anilinomethylenemalonate followed by hydrolysis and decarboxylation. The 4-hydroxyquinolines reacted with phosphorous oxychloride to form 4-chloroquinolines, which reacted on heating with diethyl sodiomethylmalonate in DMF to yield moderate yields of substituted ethyl 2-(quinolin-4-yl)propanoates, many of which showed potent antimicrobial activity against Helicobacter pylori.

A novel compound from celery seed with a bactericidal effect against Helicobacter pylori

Objectives

The aim was to purify and characterise an antimicrobial component from celery (Apium graveolens) seeds, which have been used for centuries as a herbal medicine with reported antibacterial effects.

Methods

A crude alcoholic extract of celery seeds was fractionated by organic solvent extractions, column chromatography and HPLC. Fractions were assayed for antimicrobial activity against the gastric pathogen Helicobacter pylori and other bacteria. The purified antibacterial component was characterised via MS and NMR. Preliminary investigation of its mechanism of action included morphological studies, incorporation of macromolecular precursors, membrane integrity and two-dimensional protein electrophoresis.

Key findings

The purified component, termed ‘compound with anti-Helicobacter activity’ (CAH), had potent bactericidal effects against H. pylori; the minimum inhibitory concentration and minimum bactericidal concentration were 3.15 μg/ml and 6.25–12.5 μg/ml, respectively. CAH (Mr = 384.23; empirical formula C24H32O4) had specific inhibitory effects on H. pylori and was not active against Campylobacter jejuni or Escherichia coli. MS and NMR data were consistent with a dimeric phthalide structure. The results appeared to rule out mechanisms that operated solely by loss of membrane integrity or inhibition of protein or nucleic acid synthesis.

Conclusions

CAH may be suitable for further investigation as a potent agent for treating H. pylori infections.

Carcinogenesis of Helicobacter pylori

Helicobacter infection is the leading cause of gastric cancer worldwide. Infection with this ubiquitous bacterium incites a chronic active immune response that persists for the life of the host, in the absence of antibiotic-induced eradication. It is the combination of bacterial factors, environmental insults, and the host immune response that drives the initiation and progression of mucosal atrophy, metaplasia, and dysplasia toward gastric cancer. Although it may seem intuitively obvious that removing the offending organism would negate the cancer risk, this approach is neither feasible (half of the world harbors this infection) nor is it straightforward. Most patients are infected in childhood, and present with various degrees of mucosal damage before any therapy. This review outlines the histologic progression of human Helicobacter infection from the early stages of inflammation through the development of metaplasia, dysplasia, and, finally, cancer. The effects of dietary and bacterial eradication therapy on disease progression and lesion reversibility are reviewed within the context of population studies and compared between study designs and populations tested. Eradication studies in the mouse model of infection prevents the formation of gastric cancer, and allows regression of established lesions, providing a useful model to study interaction between bacterium, environment, and host, without the difficulties inherent in human population studies. Recent advances in identifying the bone marrow-derived stem cell as the cell of origin of Helicobacter-induced gastric cancer in the murine model are discussed and interpreted in the context of human disease, and implications for future treatment are discussed.

Role of bacterial strain diversity of Helicobacter pylori in gastric carcinogenesis induced by N-methyl-N-nitrosourea in Mongolian gerbils

AIM

Helicobacter pylori is known to enhance gastric carcinogenesis induced by chemical carcinogens. We previously demonstrated that infection with H. pylori strain SS1 did not enhance such carcinogenesis in C57BL/6 mice. Whether this result was due to the bacterial strain SS1 or to the experimental host, C57BL/6 mice, should be addressed. Therefore, we examined whether H. pylori strains introduced to the same host (Mongolian gerbils) differed in carcinogenicity.

MATERIALS AND METHODS

H. pylori TN2GF4 strain (CagA(+), VacA(+)) and SS1 strain (CagA functionally(-), VacA(-)) were infected to Mongolian gerbils (n = 126). In the first experiment (induction of gastritis), histologic change in gastric mucosa of gerbils infected by H. pylori (TN2GF4, SS1, vehicle) without N-methyl-N-nitrosourea (MNU) at 1 month or 6 months was assessed. In the second experiment (experimental carcinogenesis), H. pylori (TN2GF4, SS1, vehicle) was inoculated to the gerbils after administration of MNU for 10 weeks, and the number of cancers and histopathologic changes at week 54 were assessed.

RESULTS

In the first experiment, activity and inflammation in the TN2GF4 group were significantly greater than in the SS1 group at 1 month, while no significant difference was noted at 6 months. On the other hand, intestinal metaplasia and atrophy were significantly greater with TN2GF4 than with SS1 at 6 months but not at 1 month. In studies on experimental carcinogenesis, microscopically, 47.8% (11/23), 26% (7/26), and 0% (0/26), of animals had gastric adenocarcinoma in the MNU + TN2GF4 group, MNU + SS1 group, and MNU alone group, respectively.

CONCLUSION

Both H. pylori strains, TN2GF4 and SS1, promoted carcinogenesis in Mongolian gerbils. The severity of gastritis and destruction and restoration of gastric mucosa may be related to gastric carcinogenesis. That the SS1 strain significantly accelerated carcinogenesis only in Mongolian gerbils and not in C57BL/6 mice suggests the crucial role of host factors in carcinogenesis by H. pylori infection.

The inflammatory and immune response to Helicobacter pylori infection

Lifelong Helicobacter pylori infection and its associated gastric inflammation underlie peptic ulceration and gastric carcinogenesis. The immune and inflammatory responses to H. pylori are doubly responsible: gastric inflammation is the main mediator of pathology, and the immune and inflammatory response is ineffective, allowing lifelong bacterial persistence. However, despite inducing gastric inflammation, most infections do not cause disease, and bacterial, host and environmental factors determine individual disease risk. Although H. pylori avoids many innate immune receptors, specific virulence factors (including those encoded on the cag pathogenicity island) stimulate innate immunity to increase gastric inflammation and increase disease risk. An acquired T helper 1 response upregulates local immune effectors. The extent to which environmental factors (including parasite infection), host factors and H. pylori itself influence T-helper differentiation and regulatory T-cell responses remains controversial. Finally, effective vaccines have still not been developed: a better understanding of the immune response to H. pylori may help.

Stem cells and cancer

The cell of origin of cancer has been a strongly debated topic through out the history of cancer research. This review provides a historic framework and a synopsis of how the theories of cancer initiation and progression evolved from early times to the present day. We present the concept of a cancer stem cell, and review for you the literature supporting the existence of cancer stem cells in addition to a brief discussion on our own work supporting a bone marrow-derived source for the cancer stem cell, as well as cells of the cancer stroma.

Gastric helicobacter infection induces a Th2 phenotype but does not elevate serum cholesterol in mice lacking inducible nitric oxide synthase

Persistent Helicobacter felis infection in (C57BL/6 x 129SvEv)F1 mice induces chronic gastritis. Expression of inducible nitric oxide synthase (iNOS) is upregulated in response to Helicobacter infection. In this study, 20 10-week-old iNOS-/- mice and 20 wild-type [(C57BL/6 x 129SvEv)F1] mice were infected with H. felis by oral gavage and were assessed histologically and serologically at 32 weeks postinfection. Equal numbers of uninfected controls were sham inoculated. The mice were scored for severity of gastric inflammation, hyperplasia, glandular atrophy, and mucous metaplasia in the corpus and for the level of helicobacter colonization. The immunoglobulin G1 (IgG1), IgG2a, and IgG2c antibody responses to H. felis were determined. As a secondary measure, serum cholesterol levels were assessed. iNOS-/- mice have a propensity for increased serum cholesterol, and although controversial, several human epidemiologic studies have demonstrated an association between Helicobacter infection and several risk factors for cardiovascular disease, including elevated serum cholesterol. Nevertheless, no differences in serum cholesterol levels were observed between the H. felis-infected and -uninfected iNOS-/- mice in this study. The uninfected animals had minimal to no gastric pathology. The gastric pathology scores for the infected animals were reduced significantly in the iNOS-deficient mice relative to those for the wild-type mice (all P <0.01). Helicobacter-infected iNOS-/- mice had chronic lymphoid infiltration and negligible to mild glandular atrophy and mucous metaplasia in the fundic mucosa, while H. felis-infected wild-type mice had severe atrophic and metaplastic mucosal changes. The atrophic gastritis in the infected wild-type mice, particularly the female mice, was also accompanied by greater granulocytic infiltration, antral hyperplasia, and diminished antral colonization, unlike that in the infected iNOS-/- mice. iNOS-/- mice developed significantly lower Th1-associated IgG2c antibody responses to H. felis (P <0.0003); the Th2-associated IgG1 responses were similar (P=0.09), suggesting a greater effect of the iNOS defect on Th1 responses. H. felis colonization was significantly greater in the iNOS-deficient mice. These findings are indicative of an impaired Th1 component of the H. felis-induced inflammatory response when the influence of iNOS is removed.

Concentrations of α- and β-defensins in gastric juice of patients with various gastroduodenal diseases

AIM: To determine the concentration of α- and β-defensins in gastric juice of patients with various gastroduodenal diseases.

METHODS: Concentrations of human neutrophil peptides (HNPs) 1-3, the major forms of α-defensins, and human β-defensin (HBD)-1 and HBD-2 were measured by radioimmunoassay in plasma and gastric juice of 84 subjects, consisting of 54 Helicobacter pylori-infected and 30 uninfected subjects. They included 33 patients with chronic gastritis (CG), 12 with gastric ulcer (GU), 11 with duodenal ulcer (DU), 11 with benign gastric polyp (BGP) and 16 with normal mucosa (N group) on upper endoscopy. Plasma pepsinogen I and II levels, biomarkers for gastric mucosal inflammation and atrophy, were also measured.

RESULTS: Gastric juice HNPs 1-3 levels in patients with CG, GU and BGP were significantly higher than those in patients with DU and N. Gastric juice HBD-2 concentrations in patients with CG and GU were significantly higher than those in the N group, but were significantly lower in DU patients than in GU patients. Gastric juice HBD-1 levels and plasma levels of these peptides were similar in the patient groups. Concentrations of gastric juice HNPs 1-3 and HBD-2 of in H pylori-infected patients were significantly different from those in uninfected subjects. HNPs 1-3 concentrations in gastric juice correlated negatively with plasma pepsinogen I levels and I/II ratios. HBD-2 levels in gastric juice correlated positively and negatively with plasma pepsinogen II concentrations and I/II ratios, respectively.

CONCLUSION: HNPs 1-3 and HBD-2 levels in gastric juice are diverse among various gastrointestinal diseases, reflecting the inflammatory and atrophic events of the background gastric mucosa affected by H pylori.

Species of the family Helicobacteraceae detected in an Australian sea lion (Neophoca cinerea) with chronic gastritis

We describe the first case of gastritis in a male Australian sea lion (Neophoca cinerea) in which members of the family Helicobacteraceae, particularly the genus Wolinella, were detected. The sea lion exhibited clinical signs of gastrointestinal disease, including abdominal pain, lack of appetite, and lethargy. Examination of one ileal and five gastric biopsy specimens collected over a 10-year period revealed persistent fibrosis and/or superficial focal erosion and ulceration of the lamina propria. Spiral-shaped organisms 5 to 12 microm long were observed in two of the gut biopsy specimens. While Helicobacter species were detected by PCR in one of the gastric biopsy specimens, Wolinella species were detected in four of the five gastric specimens, including those in which spiral-shaped organisms were observed. Comparisons of biopsy specimen ribosomal DNA sequences with those obtained from the feces of this animal, the gastric tissue of a clinically healthy individual, and the feces of several other cohoused sea lions and fur seals revealed a separate and possibly novel gastric Helicobacter species. A possibly novel Wolinella species, along with Wolinella succinogenes, was also identified. These findings highlight the pathogenic potential of other members of this family in the etiopathogenesis of gastric disease in these animals.

Coinfection Modulates Inflammatory Responses and Clinical Outcome ofHelicobacter felisandToxoplasma gondiiInfections

The host immune response plays a critical role in determining disease manifestations of chronic infections. Inadequate immune response may fail to control infection, although in other cases the specific immune response may be the cause of tissue damage and disease. The majority of patients with chronic infections are infected by more than one organism yet the interaction between multiple active infections is not known, nor is the impact on disease outcome clear. Using the BALB/c strain of mice, we show that Toxoplasma gondii infection in a host infected with Helicobacter felis alters the natural outcome of T. gondii infection, allowing uncontrolled tachyzoite replication and severe organ damage. Survival rates decrease from 95% in T. gondii infection alone to 50% in dual-infected mice. In addition, infection with T. gondii alters the specific H. felis immune response, converting a previously resistant host to a susceptible phenotype. Gastric mucosal IFN-gamma and IL-12 were significantly elevated and IL-10 substantially reduced in dual-infected mice. These changes were associated with severe gastric mucosal inflammation, parietal cell loss, atrophy, and metaplastic cell changes. These data demonstrate the profound interactions between the immune response to unrelated organisms, and suggest these types of interactions my impact clinical disease.