Why is the coexistence of gastric cancer and duodenal ulcer rare? Examination of factors related to both gastric cancer and duodenal ulcer

The coexistence of gastric cancer with duodenal ulcer has been found empirically to be rare, but why it is rare is difficult to explain satisfactorily. To elucidate this question, we carried out a literature review of the subject. The frequency with which the two diseases coexist is 0.1–1.7%, and the main factor associated with both gastric cancer and duodenal ulcer is Helicobacter pylori infection. However, there are marked differences between the disorders of hyperchlorhydria in duodenal ulcer, and hypochlorhydria in gastric cancer. The most acceptable view of the reason for the difference may be that the acquisition of H. pylori infection occurs mainly in childhood, so that the time of acquisition of atrophic gastritis may be the most important, and if atrophic gastritis is not acquired early, high levels of gastric acid may occur, and consequently acute antral gastritis and duodenal ulcer may occur in youth, whereas, in elderly individuals, persistent H. pylori infections and the early appearance of atrophic gastritis may be the causes of low gastric acid, and consequently gastric cancer may occur. In patients with duodenal ulcer, factors such as nonsteroidal anti-inflammatory drugs (NSAIDs) and dupA-H. pylori strains may contribute to preventing the early acquisition of atrophic gastritis, while acid-suppressive therapy and vascular endothelial growth factor and other entities may inhibit atrophic gastritis. In contrast, in gastric cancer, factors such as excessive salt intake, acid-suppressive therapy, polymorphisms of inflammatory cytokines, and the homB-H. pylori strain may contribute to the early acquisition of atrophic gastritis, while factors such as NSAIDs; fruits and vegetables; vitamins A, C, and E; and good nutrition may inhibit it.     

Inverse association between a pro-inflammatory genetic profile and Helicobacter pylori seropositivity among patients with chronic atrophic gastritis: Enhanced elimination of the infection during disease progression?

BackgroundHelicobacter pylori infection is a key risk factor for chronic atrophic gastritis (CAG), an established precursor of gastric cancer. There is increasing evidence of frequent clearance of the infection during progression of CAG. We aimed to assess the association between host inflammatory polymorphisms and H. pylori seropositivity among CAG patients from Germany.MethodsIn the baseline examination of ESTHER, a population-based study conducted in Saarland, serum pepsinogens I and II and H. pylori serostatus were measured by ELISA, and selected genetic polymorphisms (IL1A C-889T, IL1B C-511T, IL1RN A9589T, IL8 T-251A, IL10 T-819C, IL10 A-1082G, LTA C+80A and TNFA G-308A) were assessed by Pyrosequencing? for 534 serologically defined CAG cases.ResultsH. pylori seropositivity strongly decreased with disease severity, which is defined by quintiles of serum pepsinogen I, from higher than 90% in the least severe cases to hardly over 50% in the most severe cases. The pro-inflammatory genotypes IL10 -819CC and IL1RN 9589TT were significantly associated with decreased H. pylori seroprevalences with odds ratios of 0.45 (95% confidence interval (CI): 0.23–0.88) and 0.41 (95% CI: 0.18–0.92), respectively, after controlling for age, sex and disease severity. H. pylori seropositivity decreased with the number of pro-inflammatory genotypes (p < 0.01).ConclusionsOur results disclose a clear inverse association between a pro-inflammatory genetic profile and H. pylori seropositivity among cases with CAG, supporting suggestions of enhanced elimination of H. pylori during the development of the disease.     

Polymorphisms in mucin genes in the development of gastric cancer

Gastric cancer (GC) is the third leading cause of cancer-related death worldwide. In areas of high prevalence, such as Japan, South Korea and China, most cases of GC are related to Helicobacter pylori (H. pylori), which involves well-characterized sequential stages, including infection, atrophic gastritis, intestinal metaplasia, dysplasia, and GC. Mucins are the most abundant high-molecular-weight glycoproteins in mucus, which is the first line of defense and plays a major role in blocking pathogenic factors. Normal gastric mucosa shows expression of MUC1, MUC5AC and MUC6 that is specific to cell type. However, the specific pattern of MUC1, MUC5AC and MUC6 expression is changed in gastric carcinogenesis, accompanied by de novo expression of secreted MUC2. Recent studies have provided evidence that variations in these mucin genes affect many steps of GC development, such as H. pylori infection, and gastric precancerous lesions. In this review, we focus on studies of the association between polymorphisms in mucin genes and development of GC. This information should be helpful for the early detection, surveillance, and treatment of GC.     

Helicobacter pylori in gastric carcinogenesis

Gastric cancer still is a major concern as the third most common cancer worldwide, despite declining rates of incidence in many Western countries. Helicobacter pylori (H. pylori) is the major cause of gastric carcinogenesis, and its infection insults gastric mucosa leading to the occurrence of atrophic gastritis which progress to intestinal metaplasia, dysplasia, early gastric cancer, and advanced gastric cancer consequently. This review focuses on multiple factors including microbial virulence factors, host genetic factors, and environmental factors, which can heighten the chance of occurrence of gastric adenocarcinoma due to H. pylori infection. Bacterial virulence factors are key components in controlling the immune response associated with the induction of carcinogenesis, and cagA and vacA are the most well-known pathogenic factors. Host genetic polymorphisms contribute to regulating the inflammatory response to H. pylori and will become increasingly important with advancing techniques. Environmental factors such as high salt and smoking may also play a role in gastric carcinogenesis. It is important to understand the virulence factors, host genetic factors, and environmental factors interacting in the multistep process of gastric carcinogenesis. To conclude, prevention via H. pylori eradication and controlling environmental factors such as diet, smoking, and alcohol is an important strategy to avoid H. pylori-associated gastric carcinogenesis.     

Gastric mucosal proliferative and total tyrosine kinases activities increase in Helicobacter pylori-induced chronic gastritis

Background. The intestinal type of gastric cancer is thought to originate from cancer precursor lesions, progressing from H. pylori-induced chronic gastritis, atrophic gastritis, to intestinal metaplasia (IM) and dysplasia. Tyrosine kinases (tyr-k) represent the family of proteins that are widely expressed during cell metabolism and are considered as secondary markers for cellular proliferation and malignant transformation. Aim of Study. The aim of the study was to evaluate the correlation between gastric mucosal histopathologic changes, total tyrosine kinases, and proliferative activities in patients with H. pylori infection. Methods. Biopsy specimens from the gastric mucosa of 94 patients were assessed for H. pylori infection, histopathology (according to the Sydney classification), proliferative activity [Ki-67 immunohistochemistry with labeling index (LI) estimation], and total tyr-k activities (ELISA assay kit). Results. Total tyr-k activities and Ki-67 LI were significantly higher in H. pylori (+) than H. pylori (?) group (728.1±175.3 vs 360.1±44.4 pmol P/mg/min. p<0,01 and 20,0±5.8 vs 10.9±1.3 %, respectively). A significant correlation has been observed between the Ki-67 LI and total tyr-k activities in patients with and without H. pylori infection. In cases of gastritis accompanied with atrophic changes or intestinal metaplasia in H. pylori (+) patients, Ki-67 LI and total tyr-k activities were particularly high compared to chronic gastritis without atrophy or intestinal metaplasia. Conclusion. Those results suggest that tyrosine kinases may play an important role in the development of gastric mucosal hyperproliferation in H. pylori-induced gastritis and possibly in early phase of gastric carcinogenesis.     

Interaction among Caveolin-1 genotypes (rs3807987/rs7804372), H. pylori infection,and risk of gastric cancer in a Chinese population

Caveolin-1, a candidate tumor suppressor, interacts with a number of transducing molecules and plays a regulatory role in several signaling pathways. Recently, a study revealed that Cav-1 G14713A (rs3807987)/T29107A (rs7804372) polymorphisms might be associated with the susceptibility to certain cancers. In this study, we evaluated the interaction among Caveolin-1 genotypes (rs3807987/rs7804372) and Helicobacter pylori infection and increased risk of gastric cancer among the Chinese population. Blood specimens were collected from 412 gastric cancer cases to 412 noncancer controls between January 2004 and December 2012 in Liaoning Province, China. Caveolin-1 genotypes (rs3807987/rs7804372) were determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Enzyme-linked immunosorbent assays were used to measure serum levels of anti-H. pylori IgG. Odds ratio and 95 % confidence interval were calculated using multivariate logistic regression adjusted by sex and age. There were significant differences between gastric cancer and control groups in the distribution of their genotypes and allelic frequencies of the Cav-1 G14713A (rs3807987) and T29107A (rs7804372) polymorphisms, respectively. An elevated risk of gastric cancer was observed in patients with H. pylori infection combined with the Cav-1 G14713A, but not T29107A genotypes. The A allele of G14713A shows an interaction with H. pylori infection that increases the risk of gastric cancer.     

Analysis of the association of interleukin-17 gene polymorphisms with gastric cancer risk and interaction with Helicobacter pylori infection in a Chinese population

We aimed to explore the association between interleukin-17 (IL-17) polymorphisms, Helicobacter pylori infection, and subsites in gastric cancer risk in a Chinese population. We genotyped three promoter polymorphisms (rs2275913G>A, rs3748067C>T, and rs763780T>C) of IL-17 in a case–control study of 260 gastric cancer patients and 512 healthy controls. An unconditional multiple logistical regression model was used to calculate the effects of IL-17 gene polymorphisms on gastric cancer risk. The rs2275913 AA (adjusted OR?=?1.69, 95 % CI?=?1.15–2.49) and rs3748067 TT (adjusted OR?=?1.73, 95 % CI?=?1.03–2.94) genotypes were associated with an increased risk of gastric cancer. We observed a significant interaction among rs2275913G>A, rs3748067C>T, and H. pylori infection on the risk of gastric cancer (p for interaction of 0.036 and 0.048, respectively). H. pylori infection subjects carrying the rs2275913 AA (adjusted OR?=?2.48, 95 % CI?=?1.49–4.12) and rs3748067 TT (adjusted OR?=?2.54, 95 % CI?=?1.34–5.12) genotypes had a greatly increased risk of gastric cancer compared to negative H. pylori participants. Similarly, subjects carrying the rs2275913 AA (adjusted OR?=?2.09, 95 % CI?=?1.25–3.45) and rs3748067 TT (adjusted OR?=?2.29, 95 % CI?=?1.20–4.20) genotypes had a moderately increased risk of noncardia gastric cancer. A significant interaction was observed between the rs2275913G>A and rs3748067C>T genotype and subsites of gastric cancer (p for interaction of 0.044 and 0.008, respectively). The rs2275913G>A and rs763780T>C polymorphisms increase gastric cancer risk, and interact with H. pylori infection and subsites. These findings could be helpful in identifying individuals at increased risk for developing gastric cancer.     

Prevalence of Helicobacter pylori infection in gastric remnant after distal gastrectomy for primary gastric cancer

Background. The development of a second primary cancer in the gastric remnant after gastrectomy for early gastric carcinoma is a problem, and eradication of Helicobacter pylori after the operation has been recommended. However, to date, practical indications for H. pylori eradication after gastric cancer surgery have not yet been reported. Methods. We examined H. pylori infection in the gastric remnant after distal gastrectomy for primary gastric cancer. One hundred and nine patients who had had a gastrectomy were studied. Endoscopic findings and results from the urease test, bacteriologic assessment, serological test, and histopathological examination were analyzed. Results. Seventy-one patients (65.1%) were judged to be positive for H. pylori infection. The prevalence of H. pylori infection was found to be significantly decreased in older patients, patients in whom the operation had been performed a long time before examination, patients with symptoms, and patients with severe reflux gastritis. On the other hand, histologically, chronic and acute gastritis correlated significantly with H. pylori infection. H. pylori prevalence was highest in mildly atrophic mucosa and decreased with more extensive atrophic changes of the mucosa. Conclusions. The persistence of H. pylori -related active gastritis in the gastric remnant after gastric cancer surgery was suggested in younger patients with mild atrophic gastritis and without reflux gastritis. These patients may be the best candidates for H. pylori eradication therapy. Received: April 13, 2001 / Accepted: June 18, 2001     

Interleukins as new prognostic genetic biomarkers in non-small cell lung cancer

Background

Surgery is the standard treatment for early-stage NSCLC, and platinum-based chemotherapy remains as the treatment of choice for advanced-stage NSCLC patients with naïve EGFR status. However, overall 5-years relative survival rates are low. Interleukins (ILs) are crucial for processes associated with tumor development. In NSCLC, IL1B, IL6, IL12A, IL13 and IL16 gene polymorphisms may contribute to individual variation in terms of patient survival. The purpose of this study was to evaluate the association between IL gene polymorphisms and survival in NSCLC patients.

Late reactivation of sonic hedgehog by Helicobacter pylori results in population of gastric epithelial cells that are resistant to apoptosis: Implication for gastric carcinogenesis

As much as that a disturbance of tissue homeostasis through dysregulated apoptosis is generally associated with carcinogenesis, gastric carcinogenesis after Helicobacter pylori infection could be the accumulated consequence of imbalances between apoptosis and proliferation. Since sonic hedgehog (Shh) has been reported to play versatile roles in various tumorigenesis, we hypothesized that late reactivation of sonic hedgehog by H. pylori infection results in population of gastric epithelial cells that are resistant to apoptosis. The Resistant Clones against H. pylori-induced Apoptosis (RCHA) were established and maintained up to 19th cell passages, during which the serial changes of Shh expression were measured. Apoptosis was measured in N-Shh over-expressed stable cell lines and compared with parent cell line after either infected with H. pylori or treated with cyclopamine. For clinical relevance, the expressions of Shh were compared in tissues from gastric adenoma or adenocarcinoma according to H. pylori infection. Longer passages of RCHA after H. pylori infection, the higher expressions of Shh, suggesting RCHA was associated with the reactivation of Shh. Significant decrement in subG1 phase of cell cycle and attenuated executions of apoptosis after H. pylori infection in cells of Shh overexpression, whereas either Shh siRNA or cyclopamine increased the H. pylori-induced cytotoxicity and significantly abrogated anti-apoptotic actions imposed by Shh. Significantly higher expressions of Shh were seen in H. pylori-associated gastric cancers than H. pylori-not associated gastric cancer. Late reactivation of sonic hedgehog by H. pylori infection results in population of gastric epithelial cells that are resistant to apoptosis and imposes proliferative changes under the background of atrophic gastritis, providing the carcinogenic basis.     

Histological diagnosis of Helicobacter pylori gastritis is predictive of a high risk of gastric carcinoma

Chronic Helicobacter pylori infection has been identified as a major risk factor for the subsequent development of gastric carcinoma. On the basis of seroepidemiological studies the relative risk for infected persons was estimated to range between 3 and 6. Our study attempted to determine the relative risk of gastric carcinoma in H. pylori-infected individuals based on the histological evaluation of gastritis in gastric carcinoma patients in the light of a declining prevalence of H. pylori infection in Western countries. We histologically determined the H. pylori infection rate in 215 patients with early gastric carcinoma (tumor stage pT1), and compared it with that of 215 asymptomatic persons matched by age and sex who were tested by the 13C urea breath test. On the basis of these data an odds ratio of 16.7 (CI 9.6–29.1) was calculated for the relative risk of developing gastric carcinoma in H. pylori-infected people. The histological diagnosis of gastritis permits a separate risk assessment for patients with autoimmune gastritis, and by excluding these patients from the analysis we calculated an odds ratio for H. pylori-infected persons of 150 (CI 36.4–622.9). The endoscopic-histological diagnosis of H. pylori infection is associated with an increased risk of the subsequent development of gastric carcinoma of approximately 150-fold compared with H. pylori-negative patients who do not have chronic atrophic corpus gastritis of the autoimmune type (type A gastritis). Int. J. Cancer 73:837–839, 1997. © 1997 Wiley-Liss, Inc.     

GSTP1 polymorphisms and gastric cancer in a high-risk Chinese population

Objectives: In a population-based case–control study in Yangzhong, China, we investigated the relationship between genetic polymorphisms of GSTP1 and susceptibility to gastric cancer and its premalignant lesion, chronic gastritis. The possible gene–gene interactions between GSTP1 polymorphisms and GSTM1, GSTT1 genes were explored. Methods: Epidemiologic data were collected by standard questionnaire from 133 gastric cancer cases, 166 chronic gastritis cases, and 433 cancer-free population controls. Blood samples for Helicobacter pylori and molecular marker assays were collected from 84 gastric cancer cases, 146 chronic gastritis, and 429 population controls. GSTP1 polymorphisms were determined by the PCR-RFLP method and H. pylori infection was measured by the ELISA method. Associations between certain GSTP1 genotypes and both gastric cancer and chronic gastritis were assessed by odds ratios (ORs) and 95% confidence intervals (CIs) derived from logistic regression. Results: The distributions of three GSTP1 genotypes, Ile/Ile, Ile/Val, and Val/Val, were similar in gastric cancer cases, chronic gastritis, and controls. After adjusting for age, gender, education, body mass index, pack-year of smoking, alcohol drinking, H. pylori infection, salt and fruit intakes, the adjusted ORs of Val/Val were 1.3 (95% CI: 0.1–11.2) for gastric cancer and 0.9 (95% CI: 0.2–4.8) for chronic gastritis. Combining the Val alleles (Val/Val and Ile/Val) into one group, no association was observed between GSTP1 and both gastric cancer and chronic gastritis. In addition, the allelism at the GSTP1 locus did not increase gastric cancer and chronic gastritis risks associated with the GSTM1 or GSTT1 genotypes. Conclusion: Our data suggest that the GSTP1 genotype seems not to be associated with the risk of gastric cancer and chronic gastritis in a high-risk Chinese population.     

Genetic polymorphisms and tissue expression of interleukin-22 associated with risk and therapeutic response of gastric mucosa-associated lymphoid tissue lymphoma

Chronic Helicobacter pylori-stimulated immune reactions determine the pathogenesis of gastric mucosa-associated lymphoid tissue (MALT) lymphoma. We aimed to explore the genetic predisposition to this lymphoma and its clinical implication. A total of 68 patients and 140 unrelated controls were genotyped for 84 single-nucleotide polymorphisms in genes encoding cytokines, chemokines and related receptors that play important roles in T cell-mediated gastrointestinal immunity. Five genotypes in IL-22, namely CC at rs1179246, CC at rs2227485, AA at rs4913428, AA at rs1026788 and TT at rs7314777, were associated with disease susceptibility. The former four genotypes resided in the same linkage disequilibrium block (r²=0.99) that conferred an approximately threefold higher risk. In vitro experiments demonstrated that co-culturing peripheral mononuclear cells or CD4⁺ T cells with H. pylori stimulated the secretion of interleukin-22 (IL-22), and that IL-22 induced the expression of antimicrobial proteins, RegIIIα and lipocalin-2, in gastric epithelial cells. Furthermore, patients with gastric tissue expressing IL-22 were more likely to respond to H. pylori eradication (14/22 vs 4/19, P<0.006). We conclude that susceptibility of gastric MALT lymphoma is influenced by genetic polymorphisms in IL-22, the product of which is involved in mucosal immunity against H. pylori and associated with tumor response to H. pylori eradication.     

Correlation between genetic polymorphisms within IL-1B and TLR4 genes and cancer risk in a Russian population: a case-control study

In the last decade, a growing interest has been devoted to the evaluation of the impact of single nucleotide polymorphisms (SNP) on cancer risk. According to the results of multiple studies, among the genes that have a considerable influence on cancer risk are those encoding pattern recognition receptors, cytokines, and antioxidant defense enzymes. Nonetheless, the effect of numerous SNPs within these genes on cancer risk has been scarcely investigated. A case-control study of 401 cases and 300 sex- and age-matched controls was performed in order to explore the role of IL1B_1473G/C (rs1143623), SOD1_7958A/G (rs4998557), TLR4_1196C/T (rs4986791), IL10_1082A/G (rs1800896), IL17A_197G/A (rs2275913), and TLR4_896A/G (rs4986790) polymorphisms in the susceptibility to colorectal cancer (n?=?244), gastric carcinoma (n?=?72), and ovarian cancer (n?=?85). The analysis revealed a significant relationship between the presence of heterozygous genotypes for IL1B_1473G/C and TLR4_896A/G polymorphisms and higher risk of rectal cancer (codominant model, OR?=?1.67; 95 % CI, 1.06–2.63; p?=?0.048 and OR?=?2.25; 95 % CI, 1.26–4.02; p?=?0.014, respectively). In addition, the variant G/G genotype of the IL10_1082A/G SNP was associated with a 2.5-fold increase in ovarian cancer risk with a borderline significance (codominant model, OR?=?2.45; 95 % CI, 1.14–5.25; p?=?0.069). Similarly, the carriers of the C/T genotype for the TLR4_1196C/T polymorphism were more susceptible to rectal cancer with a borderline significance (codominant model, OR?=?1.42; 95 % CI, 0.80–2.51 p?=?0.06). No statistically significant associations were found when stratifying the sample by subgroups of age, sex, and clinicopathological characteristics. Finally, we observed six combinations of haplotypes for the examined SNPs, each of which either profoundly increased or decreased cancer risk. The results from our study provided evidence that IL1B_1473G/C and TLR4_896A/G SNPs are implicated in rectal cancer development in a Russian population. Further research should be addressed to clarify the role of the abovementioned polymorphisms in cancer etiology.     

Grb2‐associated binder 1 (Gab1) genetic polymorphism,Helicobacter pylori infection,and chronic atrophic gastritis among older adults from Germany

Grb2‐associated binder 1 (Gab1) plays an important role in the regulation of cell growth and transformation. A single nucleotide polymorphism (SNP) (rs3805246) in the Gab1 gene has been suggested to be related to the risk of Helicobacter pylori infection and chronic atrophic gastritis (CAG) in a study from Japan. We aimed to assess the associations in a population‐based study from Germany. In the baseline examination of ESTHER, a population‐based study conducted in Saarland, serum pepsinogen I and II and H. pylori serostatus were measured by ELISA. The Gab1 SNP (rs3805246) was genotyped in 351 serologically defined CAG cases and 351 age‐ and sex‐matched non‐CAG controls. A nonsignificant association was observed between the Gab1 SNP and CAG, with an adjusted odds ratio of 1.15 (0.85–1.55) for AA/AG carriers compared to GG carriers. The magnitude of the association did not change when the analysis was restricted to H. pylori seropositive subjects. Furthermore, no significant relation was found between the SNP and H. pylori seropositivity among non‐CAG controls. We could not confirm a major association between Gab1 SNP (rs3805246) and the predisposition to H. pylori infection and CAG in this study population from Germany. Further studies with larger sample size are needed to clarify a potential modest effect of Gab1 genetic polymorphisms. © 2010 Wiley‐Liss, Inc.     

The influence of cytokine gene polymorphisms on the risk of developing gastric cancer in patients with Helicobacter pylori infection

Background

Helicobacter pylori infection is the main cause of gastric cancer. The disease progression is influenced by the host inflammatory responses, and cytokine single nucleotide polymorphisms (SNPs) may have a role in the course of the disease. The aim of our study was to investigate proinflammatory cytokine polymorphisms, previously associated with the development of gastric cancer, in a Slovenian population.

Patients and methods.

In total 318 patients and controls were selected for the study and divided into three groups: (i) patients with gastric cancer (n = 58), (ii) patients with chronic gastritis (n = 60) and (iii) healthy control group (n = 200). H. pylori infection in patient groups was determined by serology, histology and culture. Four proinflammatory gene polymorphisms were determined (IL-1β, IL-1ra, TNF-α, TLR-4) in all subjects.

Results

We found a statistically significant difference between males and females for the groups (p = 0.025). Odds ratio (OR) for gastric cancer risk for females was 0.557 (95% confidence interval [CI]: 0.233–1.329) and for chronic gastritis 2.073 (95% CI: 1.005–4.277). IL-1B-511*T/T homozygous allele for cancer group had OR = 2.349 (95% CI: 0.583–9.462), heterozygous IL-1B-511*T had OR = 1.470 (95% CI: 0.583–3.709) and heterozygotes in TNF-A-308 genotype for chronic gastritis had OR = 1.402 (95% CI: 0.626–3.139). Other alleles had OR less than 1.

Conclusions

We could not prove association between gastric cancer and chronic gastritis due to H. pylori in any cytokine SNPs studied in Slovenian population. Other SNPs might be responsible besides infection with H. pylori for the progression from atrophy to neoplastic transformation.     

No association between AICDA 7888 C/T polymorphism, Helicobacter pylori seropositivity, and the risk of atrophic gastritis and gastric cancer in Japanese

Background  

The aberrant expression of activation-induced cytidine deaminase (AICDA) was reportedly induced in gastric epithelial cells infected with cytotoxin-associated gene A (cagA)-positive Helicobacter pylori, resulting in the accumulation of alterations in the TP53 tumor suppressor gene in gastric cells. We investigated the association of the AICDA 7888 C/T polymorphism with H. pylori infection and the risk of gastric cancer and atrophic gastritis in Japanese subjects.