Human Gastric Carcinogenesis Research Articles

SLC26A9 deficiency causes gastric intraepithelial neoplasia in mice and aggressive gastric cancer in humans

BackgroundSolute carrier family 26 member (SLC26A9) is a Cl− uniporter with very high expression levels in the gastric mucosa. Here, we describe morphological and molecular alterations in gastric mucosa of slc26a9−/− mice and in selective parietal cell-deleted slc26a9fl/fl/Atp4b-Cre mice and correlate SLC26A9 expression levels with morphological and clinical parameters in a cohort of gastric cancer (GC) patients.MethodsThe expression patterns of genes related to transport and enzymatic function, proliferation, apoptosis, inflammation, barrier integrity, metaplasia and neoplasia development were studied by immunohistochemistry (IHC), quantitative RT-PCR, in situ hybridization and RNA microarray analysis. SLC26A9 expression and cellular/clinical phenotypes were studied in primary human GC tissues and GC cell lines.ResultsWe found that both complete and parietal cell-selective Slc26a9 deletion in mice caused spontaneous development of gastric premalignant and malignant lesions. Dysregulated differentiation of gastric stem cells in an inflammatory environment, activated Wnt signaling, cellular hyperproliferation, apoptosis inhibition and metaplasia were observed. Analysis of human gastric precancerous and cancerous tissues revealed that SLC26A9 expression progressively decreased from atrophic gastritis to GC, and that downregulation of SLC26A9 was correlated with patient survival. Exogenous expression of SLC26A9 in GC cells induced upregulation of the Cl−/HCO3− exchanger AE2, G2/M cell cycle arrest and apoptosis and suppressed their proliferation, migration and invasion.ConclusionsOur data indicate that SLC26A9 deletion in parietal cells is sufficient to trigger gastric metaplasia and the development of neoplastic lesions. In addition, we found that SLC26A9 expression decreases during human gastric carcinogenesis, and that exogenous SLC26A9 expression in GC cells reduces their malignant behavior.Graphical abstract

Towards Understanding of Gastric Cancer Based upon Physiological Role of Gastrin and ECL Cells.

Simple SummaryGenerally, we know that cancers represent genetic changes in tumour cells, but we most often do not know the causes of cancers or how they develop. Our knowledge of the regulation of gastric acid secretion is well known, with the gastric hormone gastrin maintaining gastric acidity by stimulation of the enterochromaffin-like (ECL) cell to release histamine, which subsequently augments acid secretion. Furthermore, it seems to be a general principle that stimulation of function (which, for the ECL cell, is release of histamine) in a parallel way stimulates the proliferation of the same cell. Long-term hyperstimulation of cell division predisposes to genetic changes and, thus, development of tumours. All conditions with reduced gastric acidity result in an increased risk of gastric tumours due to elevated gastrin in order to restore gastric acidity. It is probable that Helicobacter pylori infection (the most important cause of gastric cancer), as well as drugs inhibiting gastric acid secretion induce gastric cancer in the long-term, due to an elevation of gastrin caused by reduced gastric acidity. Gastric carcinomas have been shown to express ECL cell markers, further strengthening this relationship.The stomach is an ideal organ to study because the gastric juice kills most of the swallowed microbes and, thus, creates rather similar milieu among individuals. Combined with a rather easy access to gastric juice, gastric physiology was among the first areas to be studied. During the last century, a rather complete understanding of the regulation of gastric acidity was obtained, establishing the central role of gastrin and the histamine producing enterochromaffin-like (ECL) cell. Similarly, the close connection between regulation of function and proliferation became evident, and, furthermore, that chronic overstimulation of a cell with the ability to proliferate, results in tumour formation. The ECL cell has long been acknowledged to give rise to neuroendocrine tumours (NETs), but not to play any role in carcinogenesis of gastric adenocarcinomas. However, when examining human gastric adenocarcinomas with the best methods presently available (immunohistochemistry with increased sensitivity and in-situ hybridization), it became clear that many of these cancers expressed neuroendocrine markers, suggesting that some of these tumours were of neuroendocrine, and more specifically, ECL cell origin. Thus, the ECL cell and its main regulator, gastrin, are central in human gastric carcinogenesis, which make new possibilities in prevention, prophylaxis, and treatment of this cancer.

Transcription Factor Myeloid Zinc-Finger 1 Suppresses Human Gastric Carcinogenesis by Interacting with Metallothionein 2A.

Metallothionein 2A (MT2A) suppresses the progression of human gastric cancer potentially through an "MT2A-NF-κB pathway" with unclear mechanisms. This study explored the role of a transcription factor, myeloid zinc-finger 1 (MZF1), in MT2A-NF-κB pathway and its clinical significance in gastric cancer. MZF1 expression and function in gastric cancer were investigated in vitro and in vivo. The relationship between MZF1 and MT2A was determined by gain-of-function and loss-of-function assays in gastric cancer cells and an immortalized gastric cell line GES-1. The prognostic value of MZF1 expression in association with MT2A was evaluated using IHC in two cohorts. MZF1 was epigenetically silenced in human gastric cancer cell lines and primary tumors. Overexpression of MZF1 in gastric cancer cells suppressed cell proliferation and migration, as well as the growth of xenograft tumors in nude mice. Knocking-down of MZF1 transformed GES-1 cells into a malignant phenotype characterized by increased cell growth and migration. Mechanistically, MZF1 was upregulated in both GC and GES-1 cells by MT2A ectopically expressed or induced upon treatment with a garlic-derived compound, diallyl trisulfide (DATS). MZF1 associated with MT2A was colocalized in the nuclei of GES-1 cells to target the promoter of NF-κB inhibitor alpha (NFKBIA). Clinically, MT2A and MZF1 were progressively downregulated in clinical specimens undergoing gastric malignant transformation. Downregulation of MT2A and MZF1 was significantly correlated with poorer patient prognosis. MT2A exerts its anti-gastric cancer effects by complexing with MZF1 to target NFKBIA. MT2A/MZF1 may serve as a valuable prognostic marker and a novel therapeutic target for human gastric cancer.

Helicobacter pylori CagA promotes epithelial mesenchymal transition in gastric carcinogenesis via triggering oncogenic YAP pathway

BackgroundHelicobacter pylori (H. pylori) delivers oncoprotein CagA into gastric epithelial cells via the T4SS and drives activation of multiple oncogenic signalling pathways. YAP, a core effector of the Hippo tumour suppressor pathway, is frequently overexpressed in human cancers, suggesting its potential tumor-promoting role. Although CagA is a casual factor in H. pylori induced gastric carcinogenesis, the link between CagA and YAP pathway has not been identified. In this work, we investigated the regulation of oncogenic YAP pathway by H. pylori CagA.MethodsExpression of YAP and E-cadherin protein in human gastric biopsies were assessed by immunohistochemistry. H. pylori PMSS1 cagA− isogenic mutant strains were generated. Gastric epithelial cells were co-cultured with H. pylori wild-type cagA+ strains or isogenic mutants and were also treated by recombinant CagA expression. Immunofluorescence was performed for YAP localization. Immunoblot and quantitative PCR were performed for examining levels of YAP, downstream effectors and markers of epithelial-mesenchymal transition. Verteporfin and siRNA silencing were used to inhibit YAP activity.ResultsYAP is significantly upregulated in human gastric carcinogenesis. We generated PMSS1 CagA isogenic mutant strains with chloramphenicol resistance successfully. Our analysis indicated that H. pylori infection induced YAP and downstream effectors in gastric epithelial cells. Importantly, knockout of CagA in 7.13 and PMSS1 strains reduced the expression of YAP by H. pylori infection. Moreover, Inhibition of YAP suppressed H. pylori infection-induced Epithelial-mesenchymal transition (EMT).ConclusionOur results indicated that H. pylori CagA as a pathogenic protein promotes oncogenic YAP pathway, which contributes to EMT and gastric tumorigenesis. This study provided a novel mechanistic insight into why cagA+H. pylori infection is associated with a higher risk for the development of gastric cancer.

Divergent Routes toward Wnt and R-spondin Niche Independency during Human Gastric Carcinogenesis

Recent sequencing analyses have shed light on heterogeneous patterns of genomic aberrations in human gastric cancers (GCs). To explore how individual genetic events translate into cancer phenotypes, we established a biological library consisting of genetically engineered gastric organoids carrying various GC mutations and 37 patient-derived organoid lines, including rare genomically stable GCs. Phenotype analyses of GC organoids revealed divergent genetic and epigenetic routes to gain Wnt and R-spondin niche independency. An unbiased phenotype-based genetic screening identified a significant association between CDH1/TP53 compound mutations and the R-spondin independency that was functionally validated by CRISPR-based knockout. Xenografting of GC organoids further established the feasibility of Wnt-targeting therapy for Wnt-dependent GCs. Our results collectively demonstrate that multifaceted genetic abnormalities render human GCs independent of the stem cell niche and highlight the validity of the genotype-phenotype screening strategy in gaining deeper understanding of human cancers.

Mature gastric chief cells are not required for the development of metaplasia.

During human gastric carcinogenesis, intestinal metaplasia is frequently seen in the atrophic stomach. In mice, a distinct type of metaplasia known as spasmolytic polypeptide-expressing metaplasia (SPEM) is found in several inflammatory and genetically engineered models. Given the diversity of long- and short-term models of mouse SPEM, it remains unclear whether all models have a shared or distinct molecular mechanism. The origin of SPEM in mice is presently under debate. It is postulated that stem or progenitor cells acquire genetic alterations that then supply metaplastic cell clones, whereas the possibility of transdifferentiation or dedifferentiation from mature gastric chief cells has also been suggested. In this study, we report that loss of chief cells was sufficient to induce short-term regenerative SPEM-like lesions that originated from chief cell precursors in the gastric neck region. Furthermore, Lgr5+ mature chief cells failed to contribute to both short- and long-term metaplasia, whereas isthmus stem and progenitor cells efficiently contributed to long-term metaplasia. Interestingly, multiple administrations of high-dose pulsed tamoxifen induced expansion of Lgr5 expression and Lgr5-CreERT recombination within the isthmus progenitors apart from basal chief cells. Thus we conclude that short-term SPEM represents a regenerative process arising from neck progenitors following chief cell loss, whereas true long-term SPEM originates from isthmus progenitors. Mature gastric chief cells may be dispensable for SPEM development. NEW & NOTEWORTHY Recently, dedifferentiation ability in gastric chief cells during metaplasia development has been proposed. Our findings reveal that lesions that were thought to be acute metaplasia in fact represent normal regeneration supplied from neck lineage and that isthmus stem/progenitors are more responsible for sustained metaplastic changes. Cellular plasticity in gastric chief cells may be more limited than recently highlighted.

MicroRNA-93 promotes proliferation and metastasis of gastric cancer via targeting TIMP2.

MicroRNAs (miRNAs) are important regulators of pathobiological processes in various cancer. In the present study, we demonstrated that miR-93 expression was significantly up-regulated in gastric cancer tissues compared with that in matched normal mucosal tissues. High expression of miR-93 was significantly associated with lymph node metastasis and tumor-node-metastasis (TNM) stage. Functionally, ectopic expression of miR-93 promoted cell proliferation, migration, invasion, EMT phenotypes, and repressed apoptosis and G1 cell cycle arrest in vitro, and promoted tumor formation in vivo. We further identified that tissue inhibitor of metalloproteinase 2 (TIMP2) was a direct target of miR-93 by using luciferase reporter assay, qRT-PCR, and immunoblotting assay. Furthermore, knockdown of TIMP2 with specific siRNA showed similar oncogenic effects in gastric cancer cells with that transfected with miR-93 mimics. Our findings indicated that miR-93 serves as a tumor promoter in human gastric carcinogenesis by targeting TIMP2, suggesting that miR-93 might be a promising biomarker and therapeutic target for treatment of gastric cancer.

Species-specific role of gene-adjacent retroelements in human and mouse gastric carcinogenesis.

Helicobacter pylori (HP) infection promotes the recruitment of bone marrow stem cells into chronic gastritis lesions. Some of these marrow stem cells can differentiate into gastric epithelial cells and neoplastic cells. We propose that HP-associated methylation could stabilize trans-differentiation of marrow-derived stem cells and that an unstable methylation status is associated with a risk of gastric cancer. Pathobiologic behavior of experimental mouse gastric cancer is mild compared to invasive and metastatic human gastric cancer. Differences in epigenetic stabilization of adult cell phenotypes between humans and mice could provide a foundation to explore the development of invasive and metastatic gastric cancer. Retroelements are highly repetitive sequences that play an essential role in the generation of species diversity. In this review, we analyzed retroelements adjacent to human and mouse housekeeping genes and proposed a possible epigenetic mechanism for HP-associated carcinogenesis.

MicroRNA-197 inhibits gastric cancer progression by directly targeting metadherin.

Gastric cancer is the fifth most frequent malignancy and the fourth most common cause of cancer‑associated mortality worldwide. MicroRNAs (miRNAs) are a group of small RNAs that regulate several cellular processes. In particular, a large number of miRNAs are involved in gastric cancer formation and progression. Thus, miRNAs may be considered as effective diagnostic biomarkers and therapeutic methods for gastric cancer. The aim of the current study was to detect miRNA (miR)‑197 expression in gastric cancer and to investigate its biological role and associated mechanism in gastric cancer. In the present study, miR‑197 expression was demonstrated to be considerably downregulated in gastric cancer tissues and cell lines. Its low expression level was associated with tumour size, invasive depth, tumour‑node‑metastasis staging and lymph node metastasis. High expression of miR‑197 inhibited tumour cell proliferation and invasion invitro. Subsequently, metadherin (MTDH) was identified as a direct target gene of miR‑197 in gastric cancer, and this was confirmed by bioinformatics analysis, Dual‑luciferase reporter assay, reverse transcription quantitative polymerase chain reaction and western blot analysis. MTDH expression was upregulated in gastric cancer and was inversely correlated with miR‑197 expression levels. In addition, MTDH overexpression prevented the proliferation and inhibited invasion induced by miR‑197 overexpression. In addition, miR‑197 was demonstrated to regulate the phosphatase and tensin homolog (PTEN)/AKT signalling pathway in gastric cancer. The results of the present study suggested that miR‑197 serves a tumour‑suppressing role in human gastric carcinogenesis and progression by regulating the MTDH/PTEN/AKT signalling pathway. The miR‑197/MTDH axis may provide a novel effective therapeutic target for patients with gastric cancer.

Fas-associated factor 1 inhibits tumor growth by suppressing Helicobacter pylori-induced activation of NF-κB signaling in human gastric carcinoma.

Loss of Fas-associated factor 1 (FAF1) may act as a pro-survival signal in diseased cells, but whether this is true in gastric carcinoma remains unclear. Here we report that FAF1 was expressed at low levels in gastric carcinoma tissues and cell lines, and its expression correlated with larger tumors, higher histology grade, higher TNM stage, tumor infiltration, and lymph node metastasis. Univariate analysis and survival curve analysis identified low FAF1 expression as a predictor of poor prognosis. FAF1 overexpression in HGC-27 gastric cancer cells induced cell apoptosis and inhibited cell proliferation and growth. It also reduced colony formation in vitro and tumor growth in mice. We found that Helicobacter pylori, a risk factor for gastric cancer, down-regulated FAF1 expression via NF-κB signaling. Knock-down of IKKβ or p65 expression in gastric cancer cells reversed H. pylori-induced down-regulation of FAF1 expression and partially blocked H. pylori-induced secretion of inflammatory cytokines TNF-α and IL-8. Our results suggest that loss of FAF1 contributes to human gastric carcinogenesis by allowing H. pylori to activate NF-κB signaling.

MiR-148a Functions as a Tumor Suppressor by Targeting CCK-BR via Inactivating STAT3 and Akt in Human Gastric Cancer.

MicroRNAs (miRNAs) have been widely accepted as a class of gene expression regulators which post-translationally regulate protein expression. These small noncoding RNAs have been proved closely involved in the modulation of various pathobiological processes in cancer. In this research, we demonstrated that miR-148a expression was significantly down-regulated in gastric cancer tissues in comparison with the matched normal mucosal tissues, and its expression was statistically associated with lymph node metastasis. Ectopic expression of miR-148a inhibited tumor cell proliferation and migration in vitro, and inhibited tumor formation in vivo. Subsequently, we identified cholecystokinin B receptor (CCK-BR) as a direct target of miR-148a using western blot and luciferase activity assay. More importantly, siRNA-induced knockdown of CCK-BR elicited similar anti-oncogenic effects (decreased proliferation and migration) as those induced by enforced miR-148a expression. We also found that miR-148a-mediated anti-cancer effects are dependent on the inhibition of STAT3 and Akt activation, which subsequently regulates the pathways involved in cell proliferation and migration. Taken together, our results suggest that miR-148a serves as a tumor suppressor in human gastric carcinogenesis by targeting CCK-BR via inactivating STAT3 and Akt.

Stage-specific Dietary Factors Associated with the Correa Multistep and Multifactorial Process of Human Gastric Carcinogenesis

ABSTRACTWe assessed how individual dietary intakes act at different points in the chain of sequential stage of the Correa model in an area of Taiwan with high incidence of gastric cancer (GC). Using data on 2,201 participants in a two-stage screening for gastric neoplasia with pepsinogen test, we identified 154 superficial gastritis (SG), 32 atrophic gastritis (AG), 117 intestinal metaplasia (IM), and 22 GC. Effects of individual item-based and construct-based dietary variables aggregated by factor analysis on each stage of gastric neoplasm were assessed. Based on 1,211 subjects with complete information on serological test and dietary questionnaire, SG was associated with positive quartile trend for the intake of meat (trend test P = 0.0014) and the intake of fruits and leafy vegetables (trend test P = 0.0177), but with the negative trend for the intake of shrimp sauce (trend test P = 0.039). A significant positive association was noted between milk and AG (trend test P = 0.014) and IM (P = 0.0087). A positive association between seafood and IM was noted (P = 0.011). Frequent leafy vegetable intake based on individual item was inversely associated with GC (P = 0.0084), whereas frequent intake of meat showed a high positive association (P<0.001). Stage-specific dietary factors underpinning the Correa model were identified.

Helicobacter pylori induces Snail expression through ROS-mediated activation of Erk and inactivation of GSK-3β in human gastric cancer cells.

Helicobacter pylori (H. pylori) infection has been known to be implicated in human gastric carcinogenesis. Snail, the zinc-finger transcription factor known as a key inducer of changes in the cell shape and morphogenetic movement, is aberrantly overexpressed and correlates with lymph node metastasis in gastric cancer. In the present study, we investigated whether H. pylori could induce Snail activation to provoke these changes. Using a cell scatter assay, we noticed that human gastric cancer AGS cells infected with H. pylori underwent morphological changes as well as disruption of cell-cell interaction, which was then reversed by silencing of Snail by use of small interfering RNA (siRNA). In addition, infection with H. pylori resulted in an increased intracellular level of Snail in gastric cancer cells, which was abrogated in the presence of U0126 and LY294002, inhibitors of MEK/Erk and PI3K/Akt pathways, respectively. Cycloheximide pulse-chase experiments coupled with immunocytochemical analysis revealed that the induction of Snail by H. pylori was regulated at multiple levels, including increased transcription of Snail mRNA, inhibition of protein degradation, and enhancement of nuclear translocation of Snail. Pre-treatment of AGS cells with N-acetylcysteine, a well-known reactive oxygen species (ROS) scavenger, attenuated the H. pylori-induced activation of Erk, its binding to Snail promoter, inactivation of GSK-3β, and accumulation of Snail. Collectively, these findings suggest that the upregulation of Snail expression induced by H. pylori and transformation to a spindle-like shape as a consequence in gastric cancer cells are attributable to ROS-mediated activation of Erk and the inhibition of GSK-3β signaling. © 2016 Wiley Periodicals, Inc.

Recapitulating Human Gastric Cancer Pathogenesis: Experimental Models of Gastric Cancer.

This review focuses on the various experimental models to study gastric cancer pathogenesis, with the role of genetically engineered mouse models (GEMMs) used as the major examples. We review differences in human stomach anatomy compared to the stomachs of the experimental models, including the mouse and invertebrate models such as Drosophila and C. elegans. The contribution of major signaling pathways, e.g., Notch, Hedgehog, AKT/PI3K is discussed in the context of their potential contribution to foregut tumorigenesis. We critically examine the rationale behind specific GEMMs, chemical carcinogens, dietary promoters, Helicobacter infection, and direct mutagenesis of relevant oncogenes and tumor suppressor that have been developed to study gastric cancer pathogenesis. Despite species differences, more efficient and effective models to test specific genes and pathways disrupted in human gastric carcinogenesis have yet to emerge. As we better understand these species differences, "humanized" versions of mouse models will more closely approximate human gastric cancer pathogenesis. Towards that end, epigenetic marks on chromatin, the gut microbiota, and ways of manipulating the immune system will likely move center stage, permitting greater overlap between rodent and human cancer phenotypes thus providing a unified progression model.

MicroRNA-339, an epigenetic modulating target is involved in human gastric carcinogenesis through targeting NOVA1

The role of miR-339 in human gastric cancer (GC) remains unclear. Here, we found that miR-339 is remarkably decreased in primary GC tissues. Overexpression of miR-339 in GC cells significantly suppressed proliferation, migration, invasion, and tumorigenicity. Furthermore, NOVA1 was confirmed as a target of miR-339. Restoration of NOVA1 in miR-339-overexpressing GC cells partially impaired the inhibitory effects of miR-339. More importantly, epigenetic modification may be involved in the modulation of miR-339 expression. These findings uncover a novel role for miR-339 in gastric carcinogenesis, and restoration of miR-339 could be considered as a potential therapeutic strategy for GC treatment.

PWE-190 Passive transmission of helicobacter felis occurs in a specific pathogen free (SPF) laboratory environment

<h3>Introduction</h3> <i>Helicobacter felis</i>infection of C57BL/6 mice is an established model of human gastric carcinogenesis. Mice infected with <i>H. felis</i>by orogastric gavage show acute gastritis, and subsequently develop pre-neoplastic pathology. The acute component of this model mimics the pathology that has been identified in cases of acute <i>Helicobacter pylori </i>infection in humans, however most of these reports describe the consequences of ingestion of large <i>H. pylori</i>inocula. It is not clear how this reflects the natural acquisition of <i>H. pylori</i>which is usually a subclinical event. Previous studies have reported that co-housing <i>H. felis</i>infected mice with uninfected littermates did not lead to <i>H. felis</i>transmission, but these experiments were performed before molecular diagnostic tests for bacterial colonisation were available. <h3>Method</h3> A C57BL/6 mouse, conventionally infected with<i>H. felis</i>, was co-housed with 9 uninfected littermates. Prokaryotic DNA was extracted from stool samples collected from individual mice at regular intervals. Mice were culled at week 7.Gastric mucosal samples were collected for nucleic acid and histological assessment. <i>H. felis</i>transmission was assessed by H+E, modified Giemsa and Warthin-Starry stains and by quantitative PCR (qPCR) for the <i>H. felis</i>gene <i>flaA</i>. Longitudinal changes in faecal microbiota were assessed by qPCR for selected bacterial phyla. <h3>Results</h3> <i>FlaA </i>was identified by qPCR in gastric and stool samples from the actively infected mouse. All 3 histological stains identified <i>H. felis</i>in the gastric antrum of this mouse, its gastric corpus exhibited early atrophy and inflammation. qPCR of stool samples from the other 9 mice did not identify <i>flaA </i>DNA. In keeping with previous studies, <i>H. felis </i>was not detected histologically in the gastric antral mucosa of these mice and the gastric corpus mucosa wasmorphologically normal. However <i>flaA </i>template DNA was identified in gastric mucosal samples from 2 of the 9 mice.Selected bacterial phyla were quantified from stool samples taken longitudinally from each mouse. PCA analysis demonstrated that the colonic microbiota of mice converged over time. A particular shift in faecal microbiota was observed in the actively infected mouse. No differences were identified in the mice that had been passively colonised with <i>H. felis</i>compared to uninfected mice. <h3>Conclusion</h3> <i>H. felis</i>was transmitted between co-housed mice in SPF conditions. Passive colonisation led to little inflammation and no gross shift in faecal microbiotal composition was seen. This may represent a model of asymptomatic human <i>H. pylori</i>acquisition. Further investigation using larger cohorts of animals maintained for longer times will address whether the mode of acquisition of <i>H. felis </i>influences eventual pathological outcome. <h3>Disclosure of interest</h3> None Declared.

Su1927 Passive Transmission of Helicobacter felis Occurs in a Specific Pathogen Free (SPF) Laboratory Environment

Introduction Helicobacter felisinfection of C57BL/6 mice is an established model of human gastric carcinogenesis. Mice infected with H. felisby orogastric gavage show acute gastritis, and subsequently develop pre-neoplastic pathology. The acute component of this model mimics the pathology that has been identified in cases of acute Helicobacter pylori infection in humans, however most of these reports describe the consequences of ingestion of large H. pyloriinocula. It is not clear how this reflects the natural acquisition of H. pyloriwhich is usually a subclinical event. Previous studies have reported that co-housing H. felisinfected mice with uninfected littermates did not lead to H. felistransmission, but these experiments were performed before molecular diagnostic tests for bacterial colonisation were available. Method A C57BL/6 mouse, conventionally infected withH. felis, was co-housed with 9 uninfected littermates. Prokaryotic DNA was extracted from stool samples collected from individual mice at regular intervals. Mice were culled at week 7.Gastric mucosal samples were collected for nucleic acid and histological assessment. H. felistransmission was assessed by H+E, modified Giemsa and Warthin-Starry stains and by quantitative PCR (qPCR) for the H. felisgene flaA. Longitudinal changes in faecal microbiota were assessed by qPCR for selected bacterial phyla. Results FlaA was identified by qPCR in gastric and stool samples from the actively infected mouse. All 3 histological stains identified H. felisin the gastric antrum of this mouse, its gastric corpus exhibited early atrophy and inflammation. qPCR of stool samples from the other 9 mice did not identify flaA DNA. In keeping with previous studies, H. felis was not detected histologically in the gastric antral mucosa of these mice and the gastric corpus mucosa wasmorphologically normal. However flaA template DNA was identified in gastric mucosal samples from 2 of the 9 mice.Selected bacterial phyla were quantified from stool samples taken longitudinally from each mouse. PCA analysis demonstrated that the colonic microbiota of mice converged over time. A particular shift in faecal microbiota was observed in the actively infected mouse. No differences were identified in the mice that had been passively colonised with H. feliscompared to uninfected mice. Conclusion H. feliswas transmitted between co-housed mice in SPF conditions. Passive colonisation led to little inflammation and no gross shift in faecal microbiotal composition was seen. This may represent a model of asymptomatic human H. pyloriacquisition. Further investigation using larger cohorts of animals maintained for longer times will address whether the mode of acquisition of H. felis influences eventual pathological outcome. Disclosure of interest None Declared.

Gastrin May Mediate the Carcinogenic Effect of Helicobacter pylori Infection of the Stomach.

Gastric cancer occurs almost exclusively in patients with gastritis. Since Helicobacter pylori (Hp) was proved to cause gastritis, Hp was also expected to play a role in gastric carcinogenesis. Despite extensive studies, the mechanisms by which Hp cause gastric cancer are still poorly understood. However, there is evidence that the anatomical site of Hp infection is of major importance. Infection confined to the antral mucosa protects against gastric cancer but predisposes to duodenal ulcer, whereas Hp infection of the oxyntic mucosa increases the risk of gastric cancer. Hp infection does not predispose to cancers in the gastric cardia. In patients with atrophic gastritis of the oxyntic mucosa, the intragastric pH is elevated and the concentration of microorganisms in the stomach is increased. This does not lead to increased risk of gastric cancer at all anatomical sites. The site specificity of Hp infection in relation to cancer risk indicates that neither Hp nor the changes in gastric microflora due to gastric hypoacidity are carcinogenic per se. However, reduced gastric acidity also leads to hypergastrinemia, which stimulates the function and proliferation of enterochromaffin-like (ECL) cells located in the oxyntic mucosa. The ECL cell may be more important in human gastric carcinogenesis than previously realized, as every condition causing long-term hypergastrinemia in animals results in the development of neoplasia in the oxyntic mucosa. Patients with hypergastrinemia will far more often develop carcinomas in the gastric corpus. In conclusion, hypergastrinemia may explain the carcinogenic effect of Hp.

MiR-375 inhibits the proliferation of gastric cancer cells by repressing ERBB2 expression.

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate the expression of targeted genes in a post-transcriptional manner. Increasing evidence indicates that miRNAs play important roles in cancer pathogenesis, including apoptosis, proliferation and differentiation, as oncogenes or tumor suppressors. Previously, miR-375 was shown to be involved in human gastric cancer, however, the mechanism remains poorly understood. In the present study, miR-375 was shown to be downregulated in gastric cancer tissues, particularly human epidermal growth factor receptor 2 (ERBB2)-positive gastric cancer tissues. Identified by dual luciferase assays and western blot analysis, ERBB2 was demonstrated to be a target gene of miR-375. In addition, miR-375 overexpression suppressed the proliferation of human gastric cancer cells in vitro and the suppression effect was restored by ERBB2 overexpression. Thus, the results of the present study indicate that miR-375 is associated with human gastric carcinogenesis by targeting ERBB2. Therefore, miR-375 may be used as a potential clinical classification marker and therapeutic target for human gastric cancer.

SALL4, a novel marker for human gastric carcinogenesis and metastasis

SALL4, a zinc-finger transcriptional factor for embryonic stem cell self-renewal and pluripotency, has been suggested to be involved in tumorigenesis. The role of SALL4 in human gastric cancer, however, remains largely unknown. In this study, we demonstrated that SALL4 was aberrantly expressed at both mRNA and protein levels in human gastric cancer tissues, and SALL4 level was highly correlated with lymph node metastasis. Enforced expression of SALL4 enhanced the proliferation and migration of human gastric cancer cells, whereas knockdown of SALL4 by siRNA led to the opposite effects. In addition, SALL4 overexpression promoted the growth and metastasis of gastric xenograft tumor in vivo. SALL4 overexpression induced epithelial-mesenchymal transition (EMT) in gastric cancer cells, with increased expression of Twist1, N-cadherin and decreased expression of E-cadherin. Moreover, SALL4 promoted the acquirement of stemness in gastric cancer cells through the induction of Bmi-1 and Lin28B. Taken together, our findings indicate that SALL4 has oncogenic roles in gastric cancer through the modulation of EMT and cell stemness, suggesting SALL4 as a novel target for human gastric cancer diagnosis and therapy.