Interference by S-nitroso compounds with the measurement of nitrate in methods requiring reduction of nitrate to nitrite by cadmium

Various methods suited for the measurement of nitrate require its reduction to nitrite by cadmium under acidic or alkaline conditions. N^G-Nitroarginine analogs have been shown to interfere with the measurement of nitrate by such assays. In the present work we show by gas chromatography−mass spectrometry that under alkaline reduction conditions the S-nitroso compounds S-nitrosoglutathione and S-nitrosohomocysteine but not S-nitroso-N-acetylcysteine and S-nitroso-N-acetylpenicillamine can considerably contribute to nitrate and thus interfere with its measurement. Our results suggest that S-nitroso compounds may interfere with the measurement of nitrate in methods requiring cadmium-catalyzed reduction of nitrate to nitrite.     

Microbial Formation of Nitrosamines In Vitro

Mortierella parvispora and an unidentified bacterium converted trimethylamine to dimethylamine, and the bacterium (but not the fungus) formed dimethylnitrosamine in the presence of nitrite. Dimethylnitrosamine also appeared in cell suspensions of Escherichia coli and Streptococcus epidermidis and in hyphal mats of Aspergillus oryzae incubated with dimethylamine and nitrate. Suspensions of a number of microorganisms produced N-nitrosodiphenylamine from diphenylamine and nitrite at pH 7.5, and soluble enzymes catalyzing the N-nitrosation of diphenylamine were obtained from two of these organisms. In the presence of these enzymes, several dialkylamines were converted to the corresponding N-nitroso compounds.     

Effect of body-mass index on the risk of gastric cancer: A population-based cohort study in A Japanese population

BackgroundBody fatness and weight gain are considered probable causes of gastric cancer, specifically in the cardia region. However, limited evidence is available in Asia, where the burden of gastric cancer is high. The objective of this study was to determine an association between body-mass index (BMI) and gastric cancer risk using a large population prospective cohort.Methods92,056 subjects enrolled in the Japan Public Health Center-based prospective Study who reported their height and weight were followed up until the end of 2013. A Cox proportional hazards model was used to estimate the risk for gastric cancer and its subsite based on baseline BMI. A subgroup analysis was conducted taking account of Helicobacter pylori (H. pylori) infection and atrophic gastritis status.Results2,860 gastric cancer cases (2,047 men, 813 women), 307 proximal gastric cancer cases (244 men, 63 women), and 1967 distal gastric cancer cases (1,405 men, 562 women) were found during the follow-up period. Among men, baseline BMI ≥ 27 kg/m² increased the risk of overall gastric cancer (hazards ratio (HR) 1.23, 95% confidence interval (CI) 1.00–1.53). For both sexes, U-shaped increase in the risk was observed for proximal gastric cancer. Subgroup analysis showed a statistically significant association between the risk of proximal gastric cancer and BMI ≥ 27 kg/m² among those who were atrophic gastritis positive, H. pylori antibody positive, and those who tested positive to either or both atrophic gastritis and H. pylori antibody.ConclusionOur result suggests that gastric cancer risk increases for men with BMI ≥ 27 kg/m².     

Physiological recycling of endogenous nitrate by oral bacteria regulates gastric mucus thickness

BackgroundInorganic nitrate from exogenous and endogenous sources is accumulated in saliva, reduced to nitrite by oral bacteria and further converted to nitric oxide (NO) and other bioactive nitrogen oxides in the acidic gastric lumen. To further explore the role of oral microbiota in this process we examined the gastric mucus layer in germ free (GF) and conventional mice given different doses of nitrate and nitrite.MethodsMice were given either nitrate (100 mg/kg/d) or nitrite (0.55–11 mg/kg/d) in the drinking water for 7 days, with the lowest nitrite dose resembling the levels provided by swallowing of fasting saliva. The gastric mucus layer was measured in vivo.ResultsGF animals were almost devoid of the firmly adherent mucus layer compared to conventional mice. Dietary nitrate increased the mucus thickness in conventional animals but had no effect in GF mice. In contrast, nitrite at all doses, restored the mucus thickness in GF mice to the same levels as in conventional animals. The nitrite-mediated increase in gastric mucus thickness was not inhibited by the soluble guanylyl cyclase inhibitor ODQ. Mice treated with antibiotics had significantly thinner mucus than controls. Additional studies on mucin gene expression demonstrated down regulation of Muc5ac and Muc6 in germ free mice after nitrite treatment.ConclusionOral bacteria remotely modulate gastric mucus generation via bioactivation of salivary nitrate. In the absence of a dietary nitrate intake, salivary nitrate originates mainly from NO synthase. Thus, oxidized NO from the endothelium and elsewhere is recycled to regulate gastric mucus homeostasis.     

Effect of Eradication of Helicobacter pylori on Expression Levels of FHIT,IL-8 and P73 in Gastric Mucosa of First-Degree Relatives of Gastric Cancer Patients

Objectives

Helicobacter pylori (H. pylori) infection plays an important role in the carcinogenesis and development of gastric cancer. Eradication of H. pylori can effectively reduce the risk of gastric cancer, but the underlying mechanisms are not fully understood. This study aimed to investigate the effect of eradication of H. pylori on the expression levels of FHIT, IL-8 and P73 in the gastric mucosa of first-degree relatives of gastric cancer patients.

Methods

One hundred and thirty-two patients with functional dyspepsia having first-degree relatives with gastric cancer were prospectively recruited in this study. Nine patients presented with H. pylori infection and family histories of gastric cancer, 61 with H. pylori infection and without family histories of gastric cancer, 6 without H. pylori infection and with family histories of gastric cancer, and 56 without H. pylori infection and family histories of gastric cancer. The protein and mRNA expression levels of FHIT, IL-8 and P73 in gastric mucosa of the subjects were detected by immunohistochemical staining and polymerase chain reaction, respectively.

Results

Compared with the patients without H. pylori infection and family histories of gastric cancer, both the protein and mRNA levels of FIHT significantly decreased in patients with H. pylori infection and/or family histories of gastric cancer, and both the protein and mRNA levels of IL-8 significantly increased. After eradication of H. pylori, both the protein and mRNA levels of FHIT were significantly higher, and both the protein and mRNA levels of IL-8 were significantly lower. However, H. pylori infection and family histories of gastric cancer had no major effect on P73 expression.

Conclusions

Down-regulation of FHIT and up-regulation of IL-8 may be involved in the pathogenesis of H. pylori infection in the first-degree relatives of gastric cancer patients.     

Statins Attenuate Helicobacter pylori CagA Translocation and Reduce Incidence of Gastric Cancer: In Vitro and Population-Based Case-Control Studies

Gastric cancer is the second leading cause of cancer-related death worldwide. The correlation of Helicobacter pylori and the etiology of gastric cancer was substantially certain. Cholesterol-rich microdomains (also called lipid rafts), which provide platforms for signaling, are associated with H. pylori-induced pathogenesis leading to gastric cancer. Patients who have been prescribed statins, inhibitors of 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase, have exhibited a reduced risk of several types of cancer. However, no studies have addressed the effect of statins on H. pylori-associated gastric cancer from the antineoplastic perspective. In this study, we showed that treatment of gastric epithelial cells with simvastatin reduced the level of cellular cholesterol and led to attenuation of translocation and phosphorylation of H. pylori cytotoxin-associated gene A (CagA), which is recognized as a major determinant of gastric cancer development. Additionally, a nationwide case-control study based on data from the Taiwanese National Health Insurance Research Database (NHIRD) was conducted. A population-based case-control study revealed that patients who used simvastatin exhibited a significantly reduced risk of gastric cancer (adjusted odds ratio (OR) = 0.76, 95% confidence interval (CI) = 0.70–0.83). In patients exhibiting H. pylori infection who were prescribed simvastatin, the adjusted OR for gastric cancer was 0.25 (95% CI = 0.12–0.50). Our results combined an in vitro study with a nationwide population analysis reveal that statin use might be a feasible approach to prevent H. pylori-associated gastric cancer.     

Use of selected lactic acid bacteria in the eradication of Helicobacter pylori infection

Helicobacter pylori is among the major pathogenic bacteria that cause chronic gastritis and peptic ulcer disease and is related to the development of gastric cancer. Several chemicals, including antibiotics, have been used to eradicate H. pylori; however, they do not always curb the infection. Ten representative type strains of lactic acid bacteria (LAB) were screened for antagonism toward H. pylori via inhibition of urease activity. Strains inhibiting the binding of H. pylori to human gastric cell line cells and suppressing H. pylori-induced interleukin-8 (IL-8) production were also screened. Of these, Pediococcus pentosaseus (SL4), which inhibited the adhesion of H. pylori to MKN-45 gastric cancer cells, Bifidobacterium longum (BG7), with urease inhibiting activity, and Lactococcus lactis (SL3), and Enterococcus faecalis (SL5), which suppressed H. pylori-induced IL-8 production within MKN-45 and AGS cells, were selected. In mouse model, these LAB stains in combination significantly suppressed IL-8 levels in serum. Gastric pH also recovered to normal values after the administration of these LAB. These stains effectively suppressed H. pylori viability, although not to the extent of antibiotic treatment. When used as probiotics, LAB may help decrease the occurrence of gastritis and reduce the risk of H. pylori infection without, inducing side effects.     

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

BackgroundGenetic variants of nucleotide-binding oligomerization domain-containing protein (NOD) may influence the outcome of Helicobacter pylori (H. pylori) infection and gastric carcinogenesis. To explore genetic variants of NOD1 and NOD2 in association with gastric cancer (GC) and its precursors, a population-based study was conducted in Linqu County, China.MethodsTagSNPs of NOD1 and NOD2 were genotyped by Sequenom MASS array in 132 GCs, and 1,198 subjects with precancerous gastric lesions, and were correlated with evolution of gastric lesions in 766 subjects with follow-up data.ResultsAmong seven tagSNPs, NOD1 rs2709800 and NOD2 rs718226 were associated with gastric lesions. NOD1 rs2709800 TG genotype carriers had a decreased risk of intestinal metaplasia (IM, OR: 0.53; 95% CI: 0.31–0.92), while NOD2 rs718226 G allele (AG/GG) showed increased risks of dysplasia (DYS, OR: 2.96; 95% CI: 1.86–4.71) and GC (OR: 2.35; 95% CI: 1.24–4.46). Moreover, an additive interaction between rs718226 and H. pylori was found in DYS or GC with synergy index of 3.08 (95% CI: 1.38–6.87) or 3.99 (95% CI: 1.55–10.22), respectively. The follow-up data indicated that NOD2 rs2111235 C allele (OR: 0.52; 95% CI: 0.32–0.83) and rs7205423 G allele (OR: 0.56; 95% CI: 0.35–0.89) were associated with decreased risk of progression in H. pylori-infected subjects.ConclusionsNOD1 rs2709800, NOD2 rs718226, rs2111235, rs7205423 and interaction between rs718226 and H. pylori infection may be related to risk of gastric lesions.     

Helicobacter pylori does not mediate the formation of carcinogenic N-nitrosamines

Background. Both N‐nitroso compounds and colonization with Helicobacter pylori represent known risk‐factors for the development of gastric cancer. Endogenous formation of N‐nitroso compounds is thought to occur predominantly in acidic environments such as the stomach. At neutral pH, bacteria can catalyze the formation of N‐nitroso compounds. Based on experiments with a noncarcinogenic N‐nitroso compound as end product, and using only a single H. pylori strain, it was recently reported that H. pylori only displays a low nitrosation capacity. As H. pylori is a highly diverse bacterial species, it is reasonable to question the generality of this finding. In this study, several genetically distinct H. pylori strains are tested for their capacity to form carcinogenic N‐nitrosamines. Materials and Methods. Bacteria were grown in the presence of 0–1000 µM morpholine and nitrite (in a 1 : 1 molar ratio), at pH 7, 5 and 3. Results. Incubation of Neisseria cinerea (positive control) with 500 µM morpholine and 500 µM nitrite, resulted in a significant increase in formation of N‐nitrosomorpholine, but there was no significant induction of N‐nitrosomorpholine formation by any of the H. pylori strains, at any of the three pH conditions. Conclusion. H. pylori does not induce formation of the carcinogenic N‐nitrosomorpholine in vitro. The previously reported weak nitrosation capacity of H. pylori is not sufficient to nitrosate the more difficultly nitrosatable morpholine. This probably also holds true for other secondary amines. These results imply that the increased incidence of gastric cancer formation that is associated with gastric colonization by H. pylori is unlikely to result from the direct induced formation of carcinogenic nitrosamines by H. pylori. However, this has to be further confirmed in in vivo studies.     

Gastric S-nitrosothiol formation drives the antihypertensive effects of oral sodium nitrite and nitrate in a rat model of renovascular hypertension

Many effects of nitrite and nitrate are attributed to increased circulating concentrations of nitrite, ultimately converted into nitric oxide (NO^•) in the circulation or in tissues by mechanisms associated with nitrite reductase activity. However, nitrite generates NO^• , nitrous anhydride, and other nitrosating species at low pH, and these reactions promote S-nitrosothiol formation when nitrites are in the stomach. We hypothesized that the antihypertensive effects of orally administered nitrite or nitrate involve the formation of S-nitrosothiols, and that those effects depend on gastric pH. The chronic effects of oral nitrite or nitrate were studied in two-kidney, one-clip (2K1C) hypertensive rats treated with omeprazole (or vehicle). Oral nitrite lowered blood pressure and increased plasma S-nitrosothiol concentrations independently of circulating nitrite levels. Increasing gastric pH with omeprazole did not affect the increases in plasma nitrite and nitrate levels found after treatment with nitrite. However, treatment with omeprazole severely attenuated the increases in plasma S-nitrosothiol concentrations and completely blunted the antihypertensive effects of nitrite. Confirming these findings, very similar results were found with oral nitrate. To further confirm the role of gastric S-nitrosothiol formation, we studied the effects of oral nitrite in hypertensive rats treated with the glutathione synthase inhibitor buthionine sulfoximine (BSO) to induce partial thiol depletion. BSO treatment attenuated the increases in S-nitrosothiol concentrations and antihypertensive effects of oral nitrite. These data show that gastric S-nitrosothiol formation drives the antihypertensive effects of oral nitrite or nitrate and has major implications, particularly to patients taking proton pump inhibitors.     

TEMPOL enhances the antihypertensive effects of sodium nitrite by mechanisms facilitating nitrite-derived gastric nitric oxide formation

Orally administered nitrite exerts antihypertensive effects associated with increased gastric nitric oxide (NO) formation. While reducing agents facilitate NO formation from nitrite, no previous study has examined whether antioxidants with reducing properties improve the antihypertensive responses to orally administered nitrite. We hypothesized that TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) could enhance the hypotensive effects of nitrite in hypertensive rats by exerting antioxidant effects (and enhancing NO bioavailability) and by promoting gastric nitrite-derived NO generation. The hypotensive effects of intravenous and oral sodium nitrite were assessed in unanesthetized freely moving rats with L-NAME (N^ω-nitro-L-arginine methyl ester; 100 mg/kg; po)-induced hypertension treated with TEMPOL (18 mg/kg; po) or vehicle. While TEMPOL exerted antioxidant effects in hypertensive rats, as revealed by lower plasma 8-isoprostane and vascular reactive oxygen species levels, this antioxidant did not affect the hypotensive responses to intravenous nitrite. Conversely, TEMPOL enhanced the dose-dependent hypotensive responses to orally administered nitrite, and this effect was associated with higher increases in plasma nitrite and lower increases in plasma nitrate concentrations. In vitro experiments using electrochemical and chemiluminescence NO detection under variable pH conditions showed that TEMPOL enhanced nitrite-derived NO formation, especially at low pH (2.0 to 4.0). TEMPOL signal evaluated by electron paramagnetic resonance decreased when nitrite was reduced to NO under acidic conditions. Consistent with these findings, increasing gastric pH with omeprazole (30 mg/kg; po) attenuated the hypotensive responses to nitrite and blunted the enhancement in plasma nitrite concentrations and hypotensive effects induced by TEMPOL. Nitrite-derived NO formation in vivo was confirmed by using the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (C-PTIO), which blunted the responses to oral nitrite. Our results showed that TEMPOL promotes nitrite reduction to NO in the stomach and enhanced plasma nitrite concentrations and the hypotensive effects of oral sodium nitrite through mechanisms critically dependent on gastric pH. Interestingly, the effects of TEMPOL on nitrite-mediated hypotension cannot be explained by increased NO formation in the stomach alone, but rather appear more directly related to increased plasma nitrite levels and reduced nitrate levels during TEMPOL treatment. This may relate to enhanced nitrite uptake or reduced nitrate formation from NO or nitrite.     

A functional polymorphism of lymphotoxin-alpha (LTA) gene rs909253 is associated with gastric cancer risk in an Asian population

BackgroundThe potentially functional polymorphism, rs909253 (+252 G>A), in the intron region of the LT-α (TNF-β) gene has been implicated in the risk of gastric cancer (GC) in some individually published studies, but others have shown inconsistent and inconclusive results.MethodsWe conducted a meta-analysis to assess the association between the lymphotoxin-α gene (LTA) + 252 (G>A) polymorphism and gastric cancer susceptibility.ResultsWe demonstrate that there were no significant associations in single-locus analysis between the polymorphism of LTA and gastric cancer risk in all subjects; however, when studies were stratified by ethnicity, these polymorphisms of LTA were found to be associated with a significant cancer risk in different genetic models in an Asian population (heterozygote [GA genotype] comparison: odds ratio [OR] = 1.29, 95% confidence interval [CI]: 1.01–1.65, P = 0.038) in which the risk in the subjects was more than 70% (12 studies with 2074 cases and 3690 controls). Moreover, the susceptibility to gastric carcinogenesis has a substantial influence on the population-attributable risk by modulating the effects of environmental risk factors such as Helicobacter pylori infection (OR = 1.77, 95%CI: 1.05–2.99, P = 0.032).ConclusionsThe present meta-analysis results suggest that the LTA rs909253 GA genotype is a possible risk factor for developing gastric cancer in the Asian population, especially those with H. pylori infection.     

Helicobacter pylori pathogen inhibits cellular responses to oncogenic stress and apoptosis

Helicobacter pylori (H. pylori) is a common gastric pathogen that infects approximately half of the world’s population. Infection with H. pylori can lead to diverse pathological conditions, including chronic gastritis, peptic ulcer disease, and cancer. The latter is the most severe consequence of H. pylori infection. According to epidemiological studies, gastric infection with H. pylori is the strongest known risk factor for non-cardia gastric cancer (GC), which remains one of the leading causes of cancer-related deaths worldwide. However, it still remains to be poorly understood how host-microbe interactions result in cancer development in the human stomach. Here we focus on the H. pylori bacterial factors that affect the host ubiquitin proteasome system. We investigated E3 ubiquitin ligases SIVA1 and ULF that regulate p14ARF (p19ARF in mice) tumor suppressor. ARF plays a key role in regulation of the oncogenic stress response and is frequently inhibited during GC progression. Expression of ARF, SIVA1 and ULF proteins were investigated in gastroids, H. pylori-infected mice and human gastric tissues. The role of the H. pylori type IV secretion system was assessed using various H. pylori isogenic mutants. Our studies demonstrated that H. pylori infection results in induction of ULF, decrease in SIVA1 protein levels, and subsequent ubiquitination and degradation of p14ARF tumor suppressor. Bacterial CagA protein was found to sequentially bind to SIVA1 and ULF proteins. This process is regulated by CagA protein phosphorylation at the EPIYA motifs. Downregulation of ARF protein leads to inhibition of cellular apoptosis and oncogenic stress response that may promote gastric carcinogenesis.     

Transnitrosation of alicyclic N-nitrosamines containing a sulfur atom

Aromatic and aliphatic nitrosamines are known to transfer a nitrosonium ion to another amine. The transnitrosation of alicyclic N-nitroso compounds generates S-nitrosothiols, which are potential nitric oxide donors in vivo. In this study, certain alicyclic N-nitroso compounds based on non-mutagenic N-nitrosoproline or N-nitrosothioproline were synthesised, and the formation of S-nitrosoglutathione (GSNO) was quantified under acidic conditions. We then investigated the effect of a sulfur atom as the substituent and as a ring component on the GSNO formation. In the presence of thiourea under acidic conditions, GSNO was formed from N-nitrosoproline and glutathione, and an N-nitroso compound containing a sulfur atom and glutathione produced GSNO without thiourea. The quantity of GSNO derived from the reaction of the N-nitrosamines containing a sulfur atom and glutathione was higher than that from the N-nitrosoproline and glutathione plus thiourea. Among the analogues that contained a sulfur atom either in the ring or as a substituent, the thiazolidines produced a slightly higher quantity of GSNO than the analogue with a thioamide group. A compound containing sulfur atoms both in the ring and as a substituent exhibited the highest activity for GSNO formation among the alicyclic N-nitrosamines tested. The results indicate that the intramolecular sulfur atom plays an important role in the transnitrosation via alicyclic N-nitroso compounds to form GSNO.     

Proteomics-Based Identification and Analysis of Proteins Associated with Helicobacter pylori in Gastric Cancer

Helicobacter pylori (H. pylori) is a spiral-shaped Gram-negative bacterium that causes the most common chronic infection in the human stomach. Approximately 1%-3% of infected individuals develop gastric cancer. However, the mechanisms by which H. pylori induces gastric cancer are not completely understood. The available evidence indicates a strong link between the virulence factor of H. pylori, cytotoxin-associated gene A (CagA), and gastric cancer. To further characterize H. pylori virulence, we established three cell lines by infecting the gastric cancer cell lines SGC-7901 and AGS with cagA⁺ H. pylori and transfecting SGC-7901 with a vector carrying the full-length cagA gene. We detected 135 differently expressed proteins from the three cell lines using proteome technology, and 10 differential proteins common to the three cell lines were selected and identified by LC-MS/MS as well as verified by western blot: β-actin, L-lactate dehydrogenase (LDH), dihydrolipoamide dehydrogenase (DLD), pre-mRNA-processing factor 19 homolog (PRPF19), ATP synthase, calmodulin (CaM), p64 CLCP, Ran-specific GTPase-activating protein (RanGAP), P43 and calreticulin. Detection of the expression of these proteins and genes encoding these proteins in human gastric cancer tissues by real-time PCR (RT-qPCR) and western blot revealed that the expression of β-ACTIN, LDH, DLD, PRPF19 and CaM genes were up-regulated and RanGAP was down-regulated in gastric cancer tissues and/or metastatic lymph nodes compared to peri-cancerous tissues. High gene expression was observed for H. pylori infection in gastric cancer tissues. Furthermore, the LDH, DLD and CaM genes were demethylated at the promoter -2325, -1885 and -276 sites, respectively, and the RanGAP gene was highly methylated at the promoter -570 and -170 sites in H. pylori-infected and cagA-overexpressing cells. These results provide new insights into the molecular pathogenesis and treatment targets for gastric cancer with H. pylori infection.     

Genetic host factors in Helicobacter pylori-induced carcinogenesis: Emerging new paradigms

Helicobacter Pylori is a gram negative rod shaped microaerophilic bacterium that colonizes the stomach of approximately half the world's population. Infection with c may cause chronic gastritis which via a quite well described process known as Correas cascade can progress through sequential development of atrophic gastritis, intestinal metaplasia and dysplasia to gastric cancer. H. pylori is currently the only bacterium that is classified as a class 1 carcinogen by the WHO, although the exact mechanisms by which this bacterium contributes to gastric carcinogenesis are still poorly understood. Only a minority of H. pylori-infected patients will eventually develop gastric cancer, suggesting that host factors may be important in determining the outcome of H. pylori infection. This is supported by a growing body of evidence suggesting that the host genetic background contributes to risk of H. pylori infection and gastric carcinogenesis. In particular single nucleotide polymorphisms in genes that influence bacterial handling via pattern recognition receptors appear to be involved, further strengthening the link between host risk factors, H. pylori incidence and cancer. Many of these genes influence cellular pathways leading to inflammatory signaling, inflammasome formation and autophagy. In this review we summarize known carcinogenic effects of H. pylori, and discuss recent findings that implicate host genetic pattern recognition pathways in the development of gastric cancer and their relation with H. pylori.     

Effect of interleukin-17A and interleukin-17F gene polymorphisms on the risk of gastric cancer in a Chinese population

We selected six tagged single-nucleotide polymorphisms (SNPs) in the IL-17A and IL-17F genes, and evaluated the relationship between the six common SNPs and H. pylori infection, tobacco smoking and subsites of gastric cancer in gastric cancer patients. Genotyping of IL-17A (rs2275913, rs3748067 and rs3819025) and IL-17A (rs763780, rs9382084, and rs12203582) was performed in a 384-well plate format on the MassARRAY® platform. An unconditional multiple logistical regression model was performed to determine the association between IL-17A and IL-17F genetic variations and gastric cancer risk. Unconditional logistic regression analysis showed that subjects carrying the rs2275913AA and rs3748067 TT genotypes were 1.70 and 3.45 times more likely to develop gastric cancer. Furthermore, rs2275913 and rs3748067 genetic variants significantly interacted with H. pylori infection on the risk of gastric cancer. The interaction between rs3748067 and rs9382084 genetic variants and tobacco smoking trend was significant. In addition, rs2275913, rs3748067 and rs9382084 genetic variants were only associated with non-cardia gastric cancer. The findings suggest that the rs2275913, rs3748067 and rs9382084 polymorphisms increase the risk of gastric cancer, and they interact with H. pylori infection, tobacco smoking and subsites of gastric cancer. These findings could be helpful in identifying individuals at increased risk for developing gastric cancer.     

Helicobacter pylori promotes epithelial-to-mesenchymal transition by downregulating CK2β in gastric cancer cells

Strains of Helicobacter pylori that are positive for the oncoprotein CagA (cytotoxin-associated gene A) are associated with gastric cancer and might be related to the epithelial-to-mesenchymal transition (EMT). Casein kinase 2 (CK2) is a serine/threonine protein kinase that plays a major role in tumorigenesis through signaling pathways related to the EMT. However, the role played by the interaction between CagA and CK2 in gastric carcinogenesis is poorly understood. Although CK2α protein expression remained unchanged during H. pylori infection, we found that CK2α kinase activity was increased in gastric epithelial cells. We also found that the CK2β protein level decreased in H. pylori-infected gastric cancer cells in CagA-dependent manner and demonstrated that CagA induced CK2β degradation via HDM2 (human double minute 2; its murine equivalent is MDM2). We observed that CagA induced HDM2 protein phosphorylation and that p53 levels were decreased in H. pylori-infected gastric cancer cells. In addition, downregulation of CK2β induced AKT Ser473 phosphorylation and decreased the AKT Ser129 phosphorylation level in gastric cancer cells. We also found that the downregulation of CK2β triggered the upregulation of Snail levels in gastric cancer cells. Furthermore, our in vivo experiments and functional assays of migration and colony formation suggest that CK2β downregulation is a major factor responsible for the EMT in gastric cancer. Therefore, CK2 could be a key mediator of the EMT in H. pylori-infected gastric cancer and could serve as a molecular target for gastric cancer treatment.