The prevalence of the duodenal ulcer promoting gene (dupA) in Helicobacter pylori isolates varies by ethnic group and is not universally associated with disease development: a case-control study

<p>Abstract</p> <p>Background</p> <p>The putative <it>H. pylori </it>pathogenicity-associated factor <it>dupA </it>has been associated with IL-8 induction <it>in vitro</it>, and duodenal ulcer (DU) and gastric cancer (GC) development in certain populations, but this association is inconsistent between studies. We aimed to investigate <it>dupA </it>prevalence in clinical isolates from Sweden, Australia and from ethnic Chinese, Indians and Malays resident in Malaysia and Singapore and to examine the association with DU and GC. In addition we investigated the sequence diversity between isolates from these diverse groups and compared the level of IL-8 secretion in isolates possessing and lacking <it>dupA</it>.</p> <p>Methods</p> <p>PCR primers were designed to amplify over the C/T insertion denoting a continuous <it>dupA</it>. PCR products from 29 clinical isolates were sequenced and compared with sequences from three additional strains obtained from GenBank. Clinical isolates from 21 Malaysian patients (8 <it>dupA</it>-positive, 14 <it>dupA</it>-negative) were assessed for their ability to induce IL-8 in AGS cells <it>in vitro</it>. Statistical analysis was performed using Fisher's exact test.</p> <p>Results</p> <p>The prevalence of <it>dupA </it>in isolates from Swedish functional dyspepsia (FD) control patients (65%, 13/20) was higher and in isolates from Indian FD patients (7.1%, 3/42) was lower as compared with isolates from Chinese (28.9%, 13/49, P = 0.005, P = 0.025), Malay (35.7%, 5/14, P = 0.16, P = 0.018) and Australian (37.8%, 17/45, P = 0.060, P < 0.001) FD patients. <it>dupA </it>was associated with DU and GC development in Chinese with 62.5% (10/16) and 54.6% (12/22) of isolates possessing <it>dupA </it>respectively as compared with FD controls (28.9%) (P = 0.015, P = 0.032). No significant difference in prevalence of <it>dupA </it>between FD controls, DU (63.6%, 7/11) and GC (61.9%, 13/21) cases (P = 1.000) was observed in the Swedish population. Sequence analysis revealed a pairwise variation of 1.9% and all isolates possessed the C/T insertion. The average IL-8 induction was 1330 pg/mL for <it>dupA</it>-positive isolates and 1378 pg/mL for <it>dupA</it>-negative isolates.</p> <p>Conclusion</p> <p>Although <it>dupA </it>is highly conserved when present, we identified no consistent association between <it>dupA </it>and DU or GC development across the ethnic groups investigated, with the <it>dupA </it>prevalence in control groups varying significantly. Our results would suggest that in the clinical isolates investigated <it>dupA </it>is not associated with IL-8 induction <it>in vitro</it>.</p

Dysbiosis of the microbiome in gastric carcinogenesis

Abstract The gastric microbiome has been proposed as an etiological factor in gastric carcinogenesis. We compared the gastric microbiota in subjects presenting with gastric cancer (GC, n = 12) and controls (functional dyspepsia (FD), n = 20) from a high GC risk population in Singapore and Malaysia. cDNA from 16S rRNA transcripts were amplified (515F-806R) and sequenced using Illumina MiSeq 2 × 250 bp chemistry. Increased richness and phylogenetic diversity but not Shannon’s diversity was found in GC as compared to controls. nMDS clustered GC and FD subjects separately, with PERMANOVA confirming a significant difference between the groups. H. pylori serological status had a significant impact on gastric microbiome α-diversity and composition. Several bacterial taxa were enriched in GC, including Lactococcus, Veilonella, and Fusobacteriaceae (Fusobacterium and Leptotrichia). Prediction of bacterial metabolic contribution indicated that serological status had a significant impact on metabolic function, while carbohydrate digestion and pathways were enriched in GC. Our findings highlight three mechanisms of interest in GC, including enrichment of pro-inflammatory oral bacterial species, increased abundance of lactic acid producing bacteria, and enrichment of short chain fatty acid production pathways

The NOD-like receptor signalling pathway in Helicobacter pylori infection and related gastric cancer: a case-control study and gene expression analyses.

BACKGROUND: Currently, it is well established that cancer arises in chronically inflamed tissue. A number of NOD-like receptors (NLRs) form inflammasomes, intracellular multiprotein complexes critical for generating mature pro-inflammatory cytokines (IL-1β and IL-18). As chronic inflammation of the gastric mucosa is a consequence of Helicobacter pylori infection, we investigated the role of genetic polymorphisms and expression of genes involved in the NLR signalling pathway in H. pylori infection and related gastric cancer (GC). MATERIALS AND METHODS: Fifty-one genetic polymorphisms were genotyped in 310 ethnic Chinese (87 non-cardia GC cases and 223 controls with functional dyspepsia). In addition, gene expression of 84 molecules involved in the NLR signalling pathway was assessed in THP-1 cells challenged with two H. pylori strains, GC026 (GC) and 26695 (gastritis). RESULTS: CARD8-rs11672725, NLRP3-rs10754558, NLRP3-rs4612666, NLRP12-rs199475867 and NLRX1-rs10790286 showed significant associations with GC. On multivariate analysis, CARD8-rs11672725 remained a risk factor (OR: 4.80, 95% CI: 1.39-16.58). Further, NLRP12-rs2866112 increased the risk of H. pylori infection (OR: 2.13, 95% CI: 1.22-3.71). Statistical analyses assessing the joint effect of H. pylori infection and the selected polymorphisms revealed strong associations with GC (CARD8, NLRP3, CASP1 and NLRP12 polymorphisms). In gene expression analyses, five genes encoding NLRs were significantly regulated in H. pylori-challenged cells (NLRC4, NLRC5, NLRP9, NLRP12 and NLRX1). Interestingly, persistent up-regulation of NFKB1 with simultaneous down-regulation of NLRP12 and NLRX1 was observed in H. pylori GC026-challenged cells. Further, NF-κB target genes encoding pro-inflammatory cytokines, chemokines and molecules involved in carcinogenesis were markedly up-regulated in H. pylori GC026-challenged cells. CONCLUSIONS: Novel associations between polymorphisms in the NLR signalling pathway (CARD8, NLRP3, NLRP12, NLRX1, and CASP1) and GC were identified in Chinese individuals. Our genetic polymorphisms and gene expression results highlight the relevance of the NLR signalling pathway in gastric carcinogenesis and its close interaction with NF-κB