Re-expression of sonic hedgehog and reduction of CDX2 after Helicobacter pylori eradication prior to incomplete intestinal metaplasia

The immune microenvironment in gastric adenocarcinoma

Like most solid tumours, the microenvironment of epithelial-derived gastric adenocarcinoma (GAC) consists of a variety of stromal cell types, including fibroblasts, and neuronal, endothelial and immune cells. In this article, we review the role of the immune microenvironment in the progression of chronic inflammation to GAC, primarily the immune microenvironment driven by the gram-negative bacterial species Helicobacter pylori. The infection-driven nature of most GACs has renewed awareness of the immune microenvironment and its effect on tumour development and progression. About 75-90% of GACs are associated with prior H. pylori infection and 5-10% with Epstein-Barr virus infection. Although 50% of the world's population is infected with H. pylori, only 1-3% will progress to GAC, with progression the result of a combination of the H. pylori strain, host susceptibility and composition of the chronic inflammatory response. Other environmental risk factors include exposure to a high-salt diet and nitrates. Genetically, chromosome instability occurs in ~50% of GACs and 21% of GACs are microsatellite instability-high tumours. Here, we review the timeline and pathogenesis of the events triggered by H. pylori that can create an immunosuppressive microenvironment by modulating the host's innate and adaptive immune responses, and subsequently favour GAC development.

Caudal type homeoboxes as a driving force in Helicobacter pylori infection-induced gastric intestinal metaplasia

(H. pylori), a common pathogenic bacterium in the stomach, has been demonstrated to be a major cause of gastric cancer (GC). The typical pathological evolution of H. pylori infection-induced GC involves development from gastric atrophy, via intestinal metaplasia (IM) and dysplasia, to intestinal-type GC. During this process, IM is considered to be an "irreversible point" that significantly increases the risk for GC. Therefore, the elucidation of the mechanism underlying IM is of great significance for the prevention and treatment of gastric mucosal carcinogenesis associated with H. pylori infection. Caudal type homeoboxes (CDXs) are transcription factors involved in intestinal differentiation establishment and the maintenance of normal intestinal mucosa and IM. H. pylori infection increases the expression of CDXs through epigenetic regulation, the nuclear factor-kappaB signaling pathway and its downstream proinflammatory factors, and the transforming growth factor-beta signaling pathway, leading to the progression from normal gastric mucosa to IM. However, the precise mechanisms of gastric intestinal metaplasia have not yet been fully elucidated. In this review, we focus on research progress revealing the functions of CDXs in H. pylori infection-induced IM, as well as the regulators modulating this process.

The Hedgehog Signaling Pathway Emerges as a Pathogenic Target

The Hedgehog (Hh) signaling pathway plays an essential role in the growth, development, and homeostatis of many tissues in vertebrates and invertebrates. Much of what is known about Hh signaling is in the context of embryonic development and tumor formation. However, a growing body of evidence is emerging indicating that Hh signaling is also involved in postnatal processes such as tissue repair and adult immune responses. To that extent, Hh signaling has also been shown to be a target for some pathogens that presumably utilize the pathway to control the local infected environment. In this review, we discuss what is currently known regarding pathogenic interactions with Hh signaling and speculate on the reasons for this pathway being a target. We also hope to shed light on the possibility of using small molecule modulators of Hh signaling as effective therapies for a wider range of human diseases beyond their current use in a limited number of cancers.

From inflammation to gastric cancer - the importance of Hedgehog/GLI signaling in Helicobacter pylori-induced chronic inflammatory and neoplastic diseases

Infections with the human pathogen Helicobacter pylori (H. pylori) are closely associated with the development of inflammatory disorders and neoplastic transformation of the gastric epithelium. Drastic changes in the micromilieu involve a complex network of H. pylori-regulated signal transduction pathways leading to the release of proinflammatory cytokines, gut hormones and a wide range of signaling molecules. Besides controlling embryonic development, the Hedgehog/GLI signaling pathway also plays important roles in epithelial proliferation, differentiation, and regeneration of the gastric physiology, but also in the induction and progression of inflammation and neoplastic transformation in H. pylori infections. Here, we summarize recent findings of H. pylori-associated Hedgehog/GLI signaling in gastric homeostasis, malignant development and the modulation of the gastric tumor microenvironment.

Endoscopic gastric atrophy is strongly associated with gastric cancer development after Helicobacter pylori eradication

Background

Risk factors for gastric cancer during continuous infection with Helicobacter pylori have been well documented; however, little has been reported on the risk factors for primary gastric cancer after H. pylori eradication. We conducted a retrospective, endoscopy-based, long-term, large-cohort study to clarify the risk factors for gastric cancer following H. pylori eradication.

Methods

Patients who achieved successful H. pylori eradication and periodically underwent esophagogastroduodenoscopy surveillance thereafter at Toyoshima Endoscopy Clinic were enrolled. The primary endpoint was the development of gastric cancer. Statistical analysis was performed using the Kaplan–Meier method and Cox’s proportional hazards models.

Results

Gastric cancer developed in 15 of 1232 patients. The cumulative incidence rates were 1.0 % at 2 years, 2.6 % at 5 years, and 6.8 % at 10 years. Histology showed that all gastric cancers (17 lesions) in the 15 patients were of the intestinal type, within the mucosal layer, and <20 mm in diameter. Based on univariate analysis, older age and higher endoscopic grade of gastric atrophy were significantly associated with gastric cancer development after eradication of H. pylori, and gastric ulcers were marginally associated. Multivariate analysis identified higher grade of gastric atrophy (hazard ratio 1.77; 95 % confidence interval 1.12–2.78; P = 0.01) as the only independently associated parameter.

Conclusions

Endoscopic gastric atrophy is a major risk factor for gastric cancer development after H. pylori eradication. Further long-term studies are required to determine whether H. pylori eradication leads to regression of H. pylori-related gastritis and reduces the risk of gastric cancer.

Helicobacter pylori Eradication Reduces the Metachronous Recurrence of Gastric Neoplasms by Attenuating the Precancerous Process

PURPOSE

The importance of Helicobacter pylori eradication after endoscopic resection (ER) of gastric neoplasms remains controversial. In this study, we clarified the importance of H. pylori eradication for metachronous lesions after ER.

MATERIALS AND METHODS

This study included 3,882 patients with gastric neoplasms who underwent ER. We included patients infected with H. pylori who received eradication therapy. Among them, 34 patients with metachronous lesions after ER and 102 age- and sex-matched patients (nonmetachronous group) were enrolled. Background mucosal pathologies such as atrophy and intestinal metaplasia (IM) were evaluated endoscopically. The expression levels of CDX1, CDX2, Sonic hedgehog (SHH), and SOX2 were evaluated based on H. pylori eradication and the development of metachronous lesions.

RESULTS

The eradication failure rate was higher in the metachronous group than in the nonmetachronous group (P=0.036). Open-type atrophy (P=0.003) and moderate-to-severe IM (P=0.001) occurred more frequently in the metachronous group. In patients with an initial diagnosis of dysplasia, the eradication failure rate was higher in the metachronous group than in the nonmetachronous group (P=0.002). In addition, open-type atrophy was more frequent in the metachronous group (P=0.047). In patients with an initial diagnosis of carcinoma, moderate-to-severe IM occurred more frequently in the metachronous group (P=0.003); however, the eradication failure rate was not significantly different between the two groups. SHH and SOX2 expression was increased, and CDX2 expression was decreased in the nonmetachronous group after eradication (P<0.05).

CONCLUSIONS

Open-type atrophy, moderate-to-severe IM, and H. pylori eradication failure were significantly associated with metachronous lesions. However, eradication failure was significantly associated with dysplasia, but not carcinoma, in the metachronous group. Thus, H. pylori eradication may play an important role in preventing metachronous lesions after ER for precancerous lesions before carcinomatous transformation.

Role of Helicobacter pylori infection in gastric carcinogenesis: Current knowledge and future directions

Helicobacter pylori (H. pylori) plays a role in the pathogenesis of gastric cancer. The outcome of the infection depends on environmental factors and bacterial and host characteristics. Gastric carcinogenesis is a multistep process that is reversible in the early phase of mucosal damage, but the exact point of no return has not been identified. Therefore, two main therapeutic strategies could reduce gastric cancer incidence: (1) eradication of the already present infection; and (2) immunization (prior to or during the course of the infection). The success of a gastric cancer prevention strategy depends on timing because the prevention strategy must be introduced before the point of no return in gastric carcinogenesis. Although the exact point of no return has not been identified, infection should be eradicated before severe atrophy of the gastric mucosa develops. Eradication therapy rates remain suboptimal due to increasing H. pylori resistance to antibiotics and patient noncompliance. Vaccination against H. pylori would reduce the cost of eradication therapies and lower gastric cancer incidence. A vaccine against H. pylori is still a research challenge. An effective vaccine should have an adequate route of delivery, appropriate bacterial antigens and effective and safe adjuvants. Future research should focus on the development of rescue eradication therapy protocols until an efficacious vaccine against the bacterium becomes available.

Rebamipide improves chronic inflammation in the lesser curvature of the corpus after Helicobacter pylori eradication: a multicenter study

Background and Aim. Although many epidemiologic studies have shown that Helicobacter pylori eradication has prophylactic effects on gastric cancer, it does not completely eliminate the risk of gastric cancer. We aimed to investigate the changes in histological gastritis in patients receiving rebamipide treatment after H. pylori eradication. Methods. 206 patients who had undergone H. pylori eradication were evaluated. Of these, 169 patients who achieved successful eradication were randomly allocated to 2 groups: the rebamipide group (n = 82) and the untreated group (n = 87). The primary endpoints were histopathological findings according to the updated Sydney system at the start of the study and after 1 year. Results. Final assessment for histological gastritis was possible in 50 cases from the rebamipide group and 53 cases from the untreated group. The activity and atrophy improved in both the rebamipide and untreated groups, and no significant intergroup differences were observed. Chronic inflammation affecting the lesser curvature of the corpus was significantly improved in the rebamipide group compared to in the untreated group (1.12 ± 0.08 versus 1.35 ± 0.08; P = 0.043). Conclusions. Rebamipide treatment after H. pylori eradication alleviated chronic inflammation in the lesser curvature of the corpus compared to that in the untreated group. This trial is registered with UMIN000002369.

Metachronous gastric cancer after successful Helicobacter pylori eradication

The high incidence of gastric cancer in Japan initially resulted in establishment of a country-wide gastric cancer screening program to detect early and treatable cancers. In 2013 countrywide Helicobacter pylori (H. pylori) eradication was approved coupled with endoscopy to assess for the presence of chronic gastritis. Current data support the notion that cure of the infection in those with non-atrophic gastritis will prevent development of gastric cancer. However, while progression to more severe damage is halted in those who have already developed, atrophic gastritis/gastric atrophy remain at risk for subsequent development of gastric cancer. That risk is directly related to the extent and severity of atrophic gastritis. Methods to stratify cancer risk include those based on endoscopic assessment of the atrophic border, histologic grading, and non-invasive methods based on serologic testing of pepsinogen levels. Continued surveillance is required because those with atrophic gastritis/gastric atrophy retain considerable gastric cancer risk even after H. pylori eradication. Those who have already experienced a resectable early gastric cancer are among those at highest risk as metachronous lesions are frequent even after H. pylori eradication. We review the role of H. pylori and effect of H. pylori eradication indicating the incidence and the predictive factors on development of metachronous cancer after endoscopic therapy of early gastric cancer. Studies to refine risk markers to stratify for risk, surveillance methods, intervals, and duration after successful H. pylori eradication, and whether adjuvant therapy would change risk are needed.

Current progress toward eradicating Helicobacter pylori in East Asian countries: Differences in the 2013 revised guidelines between China, Japan, and South Korea

New 2013 guidelines on Helicobacter pylori (H. pylori) infection have been published in China, Japan, and South Korea. Like the previous ones, these new guidelines differ between the three countries with regard to the indications for H. pylori eradication, diagnostic methods, and treatment regimens. The most profound change among all of the guidelines is that the Japanese national health insurance system now covers the expenses for all infected subjects up to second-line treatment. This makes the Japanese indications for eradication much wider than those in China and South Korea. With regard to the diagnosis, a serum H. pylori antibody test is not recommended in China, whereas it is considered to be the most reliable method in Japan. A decrease relative to the initial antibody titer of more than 50% after 6-12 mo is considered to be the most accurate method for determining successful eradication in Japan. In contrast, only the urea breath test is recommended after eradication in China, while either noninvasive or invasive methods (except the bacterial culture) are recommended in South Korea. Due to the increased rate of antibiotics resistance, first-line treatment is omitted in China and South Korea in cases of clarithromycin resistance. Notably, the Japanese regimen consists of a lower dose of antibiotics for a shorter duration (7 d) than in the other countries. There is neither 14 d nor bismuth-based regimen in the first-line and second-line treatment in Japan. Such differences among countries might be due to differences in the approvals granted by the governments and national health insurance system in each country. Further studies are required to achieve the best results in the diagnosis and treatment of H. pylori infection based on cost-effectiveness in East Asian countries.

H. pylori eradication did not improve dysregulation of specific oncogenic miRNAs in intestinal metaplastic glands

BACKGROUND

Many microRNAs (miRNAs) are differentially expressed in Helicobacter pylori-infected gastric mucosa and in gastric cancer tissue.

AIM

We aimed to compare the effect of H. pylori eradication on gastric mucosal miRNAs in subjects in a high-risk group for gastric cancer compared to controls.

METHODS

Patients with a recent history of endoscopic resection for early gastric cancer and sex- and age-matched non-cancer controls were enrolled. The expression of 21 miRNAs was examined using gastric mucosal biopsy specimens and microdissected gastric glands from the lesser and greater curvatures of the gastric corpus both before and one year after H. pylori eradication.

RESULTS

Twenty patients and 14 controls were enrolled. The expression of oncogenic miRNAs (miR-17/92 and the miR-106b-93-25 cluster, miR-21, miR-194, and miR-196) was significantly higher in the gastric mucosa of the cancer group than in the controls. H. pylori eradication resulted in a significant fall in the expression of oncogenic miRNAs only in the controls, whereas miR-223 expression was decreased and let-7d expression was increased in both groups. miR-196 was expressed only in intestinal metaplastic glands. The expression of oncogenic miRNAs was significantly higher in the intestinal metaplastic glands than in the non-intestinal metaplastic glands irrespective of H. pylori eradication. In neither group did H. pylori eradication significantly change any miRNA expression in the intestinal metaplastic glands.

CONCLUSION

Dysregulation of specific miRNAs is present in H. pylori-induced corpus gastritis. H. pylori eradication improved miRNA dysregulation, but not in intestinal metaplastic glands or in the gastric mucosa of patients in a high-risk group for gastric cancer.

Eradication of H. pylori did not improve abnormal sonic hedgehog expression in the high risk group for gastric cancer

BACKGROUND

Sonic hedgehog (SHH) acts as a proliferation factor in both the normal mucosa and in malignant lesions. Helicobacter pylori-associated atrophic gastritis is characterized by loss of SHH.

AIM

The purpose of this study was to investigate the effects of H. pylori eradication on SHH mRNA and methylation levels in the patients at high risk for gastric cancer comparing to those in the controls.

METHODS

Gastric corpus biopsies taken from 20 patients with endoscopic resection for early gastric cancer and 14 sex- and age-matched controls before and 1 year after eradication were examined for SHH and downstream regulators mRNA expression using whole biopsy specimens and microdissected gastric glands. Methylation of SHH promoter was evaluated using quantitative methylation-specific PCR.

RESULTS

SHH mRNA levels eradication were significantly lower (2.75 × 10(-2) vs. 7.37 × 10(-2), P = 0.004) in the cancer group than in the controls. PTCH and BMP4 mRNA levels as well as MUC5AC were significantly increased only in the control group and were significantly higher in the controls than those in the cancer group after eradication. After eradication, SHH methylation levels in the non-metaplastic glands were significantly higher (86.4% vs. 22.2%, P < 0.001) in the cancer group than in the controls.

CONCLUSIONS

H. pylori eradication can enhance SHH and its downstream regulators expression diminishing SHH methylation and reverse gastric phenotype, but not in the patients with high risk for gastric cancer.

Future candidates for indications of Helicobacter pylori eradication: do the indications need to be revised?

Since the discovery of Helicobacter pylori in 1982, the development of several treatment guidelines has allowed a consensus on the indications for H. pylori eradication. Beyond these currently accepted indications, including various upper gastrointestinal disorders and extragastric diseases, a significant amount of new information regarding H. pylori eradication is emerging. Certain types of acute gastritis, such as nodular gastritis, hypertrophic gastritis, Ménétrier's disease, hemorrhagic gastritis, and granulomatous gastritis are reversible after H. pylori eradication. Further, for chronic gastritis, closed-type atrophic gastritis and complete-type intestinal metaplasia appear to be more reversible after H. pylori eradication than open-type atrophic gastritis and incomplete-type intestinal metaplasia. Eradication can also be considered in subjects younger than 40 years who have a family history of gastric cancer and in subjects with long-term medications that might lead to bleeding (antiplatelet agents) or atrophy (proton pump inhibitors). Emerging evidence indicates that H. pylori eradication could be an effective treatment for some extragastric diseases that are unresponsive to conventional therapy. In such conditions, routine screening for eradication of H. pylori has not previously been recommended; a "test-and-treat" approach is suggested in the aforementioned situations. Given that H. pylori eradication is effective when the gastritis is reversible, future indications should be expanded to include acute gastric lesions that show marked improvement upon H. pylori eradication rather than just focusing on chronic gastric lesions. Future indications for H. pylori eradication should focus more on reversible lesions before preneoplastic conditions develop.

The Role of CDX2 in Intestinal Metaplasia Evaluated Using Immunohistochemistry

Background/Aims

Intestinal metaplasia (IM) has been regarded as a premalignant condition. This study evaluated the role of the transforming factor CDX2 according to the severity and type of IM.

Methods

This analysis was performed on 383 subjects with IM in the antrum and/or body, with diagnoses that were categorized as controls, dysplasias, and gastric cancers. The IM grades were classified into four groups as negative, mild, moderate or severe using the updated Sydney scoring system. The IM subtypes were categorized as type I, type II, and type III using high iron diamine and alcian blue (pH 2.5) staining. The CDX2 expression in the IM foci was evaluated using immunohistochemistry in specimens from the antrum and/or body.

Results

CDX2 expression increased according to IM severity (p=0.001) but was not associated with the IM subtype (p=0.881) in the antrum specimens. Similarly, CDX2 expression increased according to the IM grade (p=0.001) but was not associated with the IM subtype (p=0.755) in the body specimens. CDX2 expression was also increased according to baseline disease in the antrum, especially dysplastic and GC group (p=0.003), but not in the body (p=0.582). However, status of Helicobacter pylori infection was not associated with CDX2 expression in the antrum (p=0.692) and body (p=0.271).

Conclusions

These results show that CDX2 expression is associated with the IM grade regardless of the IM subtype and that it was more frequent in the dysplasia group. These results suggest that CDX2 expression might play an important role in the progression of IM in various environments that can affect neoplastic change.

Activation of Hedgehog pathway in gastrointestinal cancers

The hedgehog (Hh) pathway is a major regulator for cell differentiation, tissue polarity, and cell proliferation in embryonic development and homeostasis in adult tissue. Studies from many laboratories reveal activation of this pathway in a variety of human cancer, including basal cell carcinomas (BCCs), medulloblastomas, leukemia, gastrointestinal, lung, ovarian, breast, and prostate cancers. It is thus believed that targeted inhibition of Hh signaling may be effective in treatment and prevention of human cancer. Even more exciting is the discovery and synthesis of specific signaling antagonists for the Hh pathway, which have significant clinical implications in novel cancer therapeutics. In this review, we summarize major advances in the past 2 years in our understanding of Hh signaling activation in human gastrointestinal cancer and their potential in clinical treatment with Hh pathway inhibitors.

The role of Sonic Hedgehog as a regulator of gastric function and differentiation

The Hedgehog (Hh) genes play a key role in the regulation of embryonic development and govern processes such as cell differentiation, cell proliferation, and tissue patterning. In vertebrate embryos, Hh gene expression regulates correct formation of limbs, skeleton, muscles, and organs including stomach. In the adult, the Hh pathway functions in tissue repair and regeneration, along with maintenance of stem cells. Sonic Hedgehog (Shh) signaling has been extensively studied for its role in developmental and cancer biology. Recent advances in the field of gastroenterology show that in the stomach, Shh is responsible for proper differentiation of the gastric glands. The aberrant activity of the Shh signaling pathway leads to an altered gastric differentiation program and loss of gastric acid secretion that is the predominant function of the stomach. In this chapter, we review the most recent findings that reveal the role of Shh as a regulator of gastric function and differentiation and how this signaling is dysregulated during the development of gastric cancer in response bacterial infection.

Role of Sonic Hedgehog signaling during progression from inflammation to cancer in the stomach

Despite advances in treatment and the declining incidence, gastric cancer remains the second leading cause of cancer-related deaths in the world. Understanding the progression from inflammation to cancer in the stomach is crucial in the development of novel therapies and strategies for treating this disease. Chronic inflammation of the stomach is typically caused by Helicobacter pylori (H. pylori) and resulting lesions may lead to gastric cancer. During the progression from inflammation to cancer, the stomach epithelium changes with evidence of the disruption of normal epithelial cell differentiation and infiltrating inflammatory cells. Coincident with the development of atrophic gastritis and metaplasia, is the loss of the gastric morphogen Sonic Hedgehog (Shh). Given its critical role as a regulator of gastric tissue homeostasis, the disruption of Shh expression during inflammation correlates with the loss of normal epithelial cell differentiation, but this has only recently been rigorously tested in vivo using a unique mouse model of targeted gastric Shh deletion. While pre-neoplastic lesions such as atrophic gastritis and intestinal metaplasia are associated with the loss of Shh within the acid-secreting glands of the stomach, there is a clear link between elevated Shh and signaling to gastric cancers. The current review focuses on the effects of aberrant Shh expression and its role in the development of gastric cancer, specifically in response to H. pylori infection.

CDX1 and CDX2 expression in intestinal metaplasia, dysplasia and gastric cancer

Intestinal metaplasia (IM) has been regarded as a premalignant condition. However, the pathogenesis of IM is not fully understood. The aim of this study was to evaluate the role of CDX1 and CDX2 in the formation of IM and the progression to dysplasia and gastric cancer (GC). A total of 270 subjects included 90 with GC, dysplasia and age- and sex-matched controls. Real-time PCR (RT-PCR) was performed with body specimens for CDX1 and CDX2. The expression of CDX2 was significantly higher in H. pylori positive group than H. pylori negative group (P = 0.045). CDX1 and CDX2 expression increased proportional to the IM grade of the body (P < 0.001). CDX2 expression was significantly higher in incomplete type of IM than in complete type (P = 0.045). The expression of CDX1 in dysplasia group was significantly higher than in the control group (P = 0.001); in addition, CDX1 and CDX2 in cancer group was significantly higher than control group (P < 0.001, and P < 0.001, respectively). Aberrant expression of CDX1 and CDX2 correlated with H. pylori infection and grade of IM in the body. Furthermore, the results suggest that CDX1 and CDX2 play a role in the progression to GC and dysplasia.

Endoscopic diagnosis of open-type atrophic gastritis is related to the histological diagnosis of intestinal metaplasia and Cdx2 expression

BACKGROUND AND OBJECTIVES

Long-term Helicobacter pylori infection results in atrophic gastritis and intestinal metaplasia (IM) with Cdx2 expression. We have tried to determine if there was a link between endoscopic and histological diagnosis of IM based on the status of aberrant Cdx2 expression.

METHODS

One hundred and one subjects agreed to upper gastrointestinal endoscopic examination, with biopsy sampling for histology, Giemsa, and Cdx2 immunohistochemical staining before and after the treatment. On endoscopic examination, atrophic gastritis was defined as discoloration with blood vessel transparency, and was classified as either closed or open. Metaplastic gastritis was defined by the presence of whitish patches, whitish plaques, and/or homogeneous whitish discoloration. Histologic analysis was performed to determine H. pylori density, intensity of acute polymorphonuclear cell infiltrates and chronic mononuclear infiltrates, gastric atrophy, and IM as demonstrated using immunohistochemistry for cdx2.

RESULTS

Cdx2 protein expression (P=0.018) and the prevalence of histologically detected IM (P=0.011) were higher in cases of endoscopically diagnosed open-type atrophic gastritis and metaplastic gastritis than in closed-type atrophic gastritis and nonatrophic/nonmetaplastic cases. The degree of activity (P=0.006) and inflammation (P=0.007) improved significantly after four weeks of successful H. pylori eradication treatment, whereas the degree of atrophy, metaplasia, and Cdx2 expression did not.

CONCLUSIONS

Unlike endoscopic diagnosis of closed-type atrophic gastritis, that of open-type atrophic gastritis is highly correlated with the histological diagnosis of IM and Cdx2 expression. Endoscopically diagnosed open-type atrophic gastritis and endoscopically diagnosed metaplastic gastritis have similar histological features, which suggests that a high percentage of IM cases are diagnosed as open-type atrophic gastritis by endoscopic examination.

XBP1 controls maturation of gastric zymogenic cells by induction of MIST1 and expansion of the rough endoplasmic reticulum

BACKGROUND & AIMS

The transition of gastric epithelial mucous neck cells (NCs) to digestive enzyme-secreting zymogenic cells (ZCs) involves an increase in rough endoplasmic reticulum (ER) and formation of many large secretory vesicles. The transcription factor MIST1 is required for granulogenesis of ZCs. The transcription factor XBP1 binds the Mist1 promoter and induces its expression in vitro and expands the ER in other cell types. We investigated whether XBP1 activates Mist1 to regulate ZC differentiation.

METHODS

Xbp1 was inducibly deleted in mice using a tamoxifen/Cre-loxP system; effects on ZC size and structure (ER and granule formation) and gastric differentiation were studied and quantified for up to 13 months after deletion using morphologic, immunofluorescence, quantitative reverse-transcriptase polymerase chain reaction, and immunoblot analyses. Interactions between XBP1 and the Mist1 promoter were studied by chromatin immunoprecipitation from mouse stomach and in XBP1-transfected gastric cell lines.

RESULTS

Tamoxifen-induced deletion of Xbp1 (Xbp1Δ) did not affect survival of ZCs but prevented formation of their structure. Xbp1Δ ZCs shrank 4-fold, compared with those of wild-type mice, with granulogenesis and cell shape abnormalities and disrupted rough ER. XBP1 was required and sufficient for transcriptional activation of MIST1. ZCs that developed in the absence of XBP1 induced ZC markers (intrinsic factor, pepsinogen C) but showed abnormal retention of progenitor NC markers.

CONCLUSIONS

XBP1 controls the transcriptional regulation of ZC structural development; it expands the lamellar rough ER and induces MIST1 expression to regulate formation of large granules. XBP1 is also required for loss of mucous NC markers as ZCs form.

Intestinal metaplasia -the effect of Acid on the gastric mucosa and gastric carcinogenesis-

This review concerns stem cells and their relation to intestinal metaplasia. When gastric regions of mice, Mongolian gerbils or several strains of rats were irradiated with a total dose of 20 Gy of X-rays given in two fractions, intestinal metaplasia was only induced in rats. In addition, it was greatly influenced by rat strain and sex. Alkaline phosphatase (ALP) positive metaplastic foci were increased by administration of ranitidine (H₂ receptor antagonist), crude stomach antigens or subtotal resection of the fundus and decreased by cysteamine (gastric acid secretion stimulator), histamine or removal of the submandibular glands. Recent studies have shown that Cdx2 transgenic mice with gastric achlorhydria develop intestinal metaplasia and that in men and animals, Helicobacterpylori (H. pyrlori) infection can cause intestinal metaplasias that are reversible on eradication. Our results combined with findings for H. pylori infection or eradication and transgenic mice suggest that an elevation in the pH of the gastric juice due to disappearance of parietal cells is one of the principal factors for development of reversible intestinal metaplasia. When different organs were transplanted into the stomach or duodenum, they were found to transdifferentiate into gastric or duodenal mucosae, respectively. Organ-specific stem cells in normal non-liver tissues (heart, kidney, brain and skin) also differentiate into hepatocytes when transplanted into an injured liver. Therefore, stem cells have a multipotential ability, transdifferentiating into different organs when transplanted into different environments. Finally, intestinal metaplasia has been found to possibly increase sensitivity to the induction of tumors by colon carcinogens of the 1,2-dimethylhydrazine (DMH), azoxymethane (AOM) or 2-amino-1-methyl-6-phenylimidazo[4.5-b]pyridine (PhIP) type. This carcinogenic process, however, may be relatively minor compared with the main gastric carcinogenesis process induced by N-methy1-N’-nitro-N-nitrosoguanidine (MMNG) or N-methylnitrosourea (MNU), which is not affected by the presence of intestinal metaplasia. The protocol used in these experiments may provide a new approach to help distinguish between developmental events associated with intestinal metaplasia and gastric tumors.

Sonic hedgehog and CDX2 expression in the stomach

Sonic hedgehog (Shh) is an essential regulator of patterning processes throughout development, and CDX proteins act as the master regulators for intestinal development and differentiation. Shh and CDX2 seem to be interdependently linked with cellular differentiation through different signal cascades. We have recently shown that the loss of Shh and aberrant expression of CDX2 in Helicobacter pylori (H. pylori)-associated atrophic gastritis can be modified by H. pylori eradication prior to incomplete intestinal metaplasia. On the other hand, abnormal signaling of the hedgehog pathway has been reported in gastric cancer, especially diffuse-type cancer and advanced gastric cancer, and Shh acts as a proliferation factor in both the normal mucosa and malignant lesions. CDX2 expressed in the early stage of gastric carcinogenesis is associated with the intestinal phenotypic region and thus with a better outcome. However, it remains unclear how Shh and CDX2 are involved with intestinal transformation and further carcinogenesis.

Helicobacter and gastric malignancies

Individuals infected with Helicobacter pylori, a stomach colonizing bacteria, have an increased risk of developing gastric malignancies. The risk for developing cancer relates to the physiologic and histologic changes that H. pylori infection induces in the stomach. In the last year numerous studies have been conducted in order to characterize the association between H. pylori infection and gastric cancer. These studies range from epidemiologic approaches aiming at the identification of environmental, host genetic, and bacterial factors associated with risk of gastric cancer, to molecular and cell biology approaches aiming at understanding the interaction between H. pylori and the transforming epithelial cell. In this review an account of the last year's research activity on the relationship between H. pylori and gastric cancer will be given.