Helicobacter pylori as a risk factor for cancer

Anti-ulcer activity of Cyrtocarpa procera analogous to that of Amphipterygium adstringens, both assayed on the experimental gastric injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

The bark of Amphipterygium adstringens (Aa) is commonly mixed or adulterated with the bark of Cyrtocarpa procera (Cp) and sold in Mexican markets. Aa is a well known species in Mexico used as decoction to relieve ulcers. Scientific reports reinforcing the anti-ulcer activity of Aa have been previously described, but those describing the anti-ulcer properties of Cp as a substitute for Aa in folk medicine are scarce.

AIM OF THE STUDY

To investigate anatomical and phytochemical differences between these species, as well as to assess the anti-ulcer effect of Cp extracts in comparison to the Aa extracts.

MATERIAL AND METHODS

Anatomical micro-technique and physical and spectroscopic data were used to analyze differences between Cp and Aa. Regard to the pharmacological activity, it was assessed by using the ethanol-induced gastric damage model in rats.

RESULTS

Whereas the bark anatomy of Aa was characterized by vertical canals in the periderm and the rare occurrence of fibers in its phloem, a periderm without vertical canals and abundant fibers in the phloem were distinctive features of Cp. Phytochemical analysis allowed the identification of tirucallane, masticadienonic and 3α-hydroxymasticadienonic acids as major components in Aa, while β-amyrin and β-sitosterol were obtained from Cp. Gastric lesions observed in the control group decreased in the presence of 100mg/kg of hexane, ethyl acetate and methanol extracts from the normal or regenerated bark of Cp, thus resembling the anti-ulcer effect of Aa. Nevertheless, major anti-ulcer potency was observed with the most active methanol extract from Cp obtained from normal [the effective dose fifty ED(50)=45.54 mg/kg] or regenerated (ED(50)=36.68 mg/kg) bark in comparison to Aa (ED(50)=115.64 mg/kg).

CONCLUSION

Chemical and anatomical differences were found between these species, but since the anti-ulcer activity of Cp is similar to that shown by Aa our results reinforce the use of both species for the relief of gastric ulcer in folk medicine.

Theoretical study on interactions of β-cyclodextrin with Helicobacter pylori eradicating agent (TG44)

The inclusion complex of β-cyclodextrin (β-CD) and 4-methylbenzyl-4'-[trans-4- (guanidinomethyl)cylohexylcarbonyloxy]-biphenyl-4-carboxlylate monohydrochloride (TG44) had been investigated by using densify functional theory (DFT) and PM3 semiempirical method. The results indicate that the β-CD includes predominantly the biphenyl moiety of TG44, and the inclusion complex formed by TG44 entering into the cavity of β-CD from its narrow side (the primary hydroxyl group side) is more stable than that formed by TG44 entering into the cavity of β-CD from its wide side (the secondary hydroxyl group side). The negative enthalpy changes calculated from the statistical thermodynamic calculations at 1 atm and 298.15 K suggest that the inclusion complexes are favored enthalpy-driven processes. The molecular modeling results are in good agreement with the experiment for 2D (1)H-(13)C H HETCOR spectroscopic and H-NMR spectroscopic observations.

Prevalence of Helicobacter pylori infection in advanced gastric carcinoma

BACKGROUND

[corrected] There is substantial evidence that infection with Helicobacter pylori plays a role in the development of gastric cancer and that it is rarely found in gastric biopsy of atrophic gastritis and gastric cancer. On advanced gastric tumors, the bacteria can be lost from the stomach.

AIMS

To analyze the hypothesis that the prevalence of H.pylori in operated advanced gastric carcinomas and adjacent non-tumor tissues is high, comparing intestinal and diffuse tumors according to Lauren's classification

METHODS

A prospective controlled study enrolled 56 patients from "Hospital Universitário", Federal University of Rio Grande do Norte, Natal, RN, Brazil, with advanced gastric cancer, treated from February 2000 to March 2003. Immediately after partial gastrectomy, the resected stomach was opened and several mucosal biopsy samples were taken from the gastric tumor and from the adjacent mucosa within 4 cm distance from the tumor margin. Tissue sections were stained with hematoxylin and eosin. Lauren's classification for gastric cancer was used, to analyse the prevalence of H. pylori in intestinal or diffuse carcinomas assessed by the urease rapid test, IgG by ELISA and Giemsa staining. H. pylori infected patients were treated with omeprazole, clarithromycin and amoxicillin for 7 days. Follow-up endoscopy and serology were performed 6 months after treatment to determine successful eradication of H. pylori in non-tumor tissue. Thereafter, follow-up endoscopies were scheduled annually. Chi-square and MacNemar tests with 0.05 significance were used.

RESULTS

Thirty-four tumors (60.7%) were intestinal-type and 22 (39.3%) diffuse type carcinomas. In adjacent non-tumor gastric mucosa, chronic gastritis were found in 53 cases (94.6%) and atrophic mucosa in 36 patients (64.3%). All the patients with atrophic mucosa were H. pylori positive. When examined by Giemsa and urease test, H. pylori positive rate in tumor tissue of intestinal type carcinomas was higher than that in diffuse carcinomas. In tumor tissues, 34 (60.7%) H. pylori-positive in gastric carcinomas were detected by Giemsa method. H. pylori was observed in 30 of 56 cases (53.5%) in tissues 4 cm adjacent to tumors. This difference was not significant. Eradication of H. pylori in non-tumor tissue of gastric remnant led to a complete negativity on the 12th postoperative month

CONCLUSIONS

The data confirmed the hypothesis of a high prevalence of H. pylori in tumor tissue of gastric advanced carcinomas and in adjacent non-tumor mucosa of operated stomachs. The presence of H. pylori was predominant in the intestinal-type carcinoma.

Synthesis and in vitro anti-Helicobacter pylori activity of N-[5-(5-nitro-2-heteroaryl)-1,3,4-thiadiazol-2-yl]thiomorpholines and related compounds

Synthesis and in vitro anti-Helicobacter pylori activity of N-[5-(5-nitro-2-heteroaryl)-1,3,4-thiadiazol-2-yl]thiomorpholines 5-7(a-c) and some related compounds 8a-c and 9a-c were described. The anti-H. pylori activity of target compounds along with commercially available antibiotics such as metronidazole and amoxicillin was evaluated by comparing the inhibition zone diameters determined by the paper disc diffusion bioassay. From our bioassay results against 20 clinical isolates, it is evident that most compounds still had strong activity at 4 and 2 microg/disc (average of inhibition zone >20 mm) while metronidazole had little activity at these doses. Nitrofuran analog 7b containing thiomorpholine S,S-dioxide moiety was the most potent compound tested.

Interleukin-6 polymorphisms, Helicobacter pylori infection in adult Brazilian patients with chronic gastritis and gastric adenocarcinoma

BACKGROUND

The discovery of Helicobacter pylori offered the etiologic agent of the initiating event of the inflammatory cascade. It has been confirmed that the development of gastric cancer spans over several decades sequentially starting with the acquisition of H. pylori infection and the development of chronic gastritis. The IL-6 gene (Il-6), inflammatory cytokine and the single-nucleotide polymorphisms (SNPs) at the 5' flanking region of the Il-6 gene promoter (G or C at -174 base and at -572 or -597 C or A) have been identified with increased Il-6 levels.

METHODS

Biopsies were collected from 168 patients. SNPs in Il-6-174 were analyzed by PCR-RFLP.

RESULTS

Promoter SNP of Il-6 at -174 base were within Hardy-Weinberg equilibrium. We did not find any association between the frequencies of -174 polymorphism with specific histological type of gastric adenocarcinoma, but the G (guanine) allele at -174 was significantly higher in gastric adenocarcinoma than in patients with chronic gastritis.

CONCLUSIONS

We observed an association between GG allele on -174 base with gastric cancer.

[Gastric adenocarcinoma: approach to a complex biological reality]

The authors review the complex biological reality of gastric adenocarcinoma from several viewpoints. It is a neoplasm histologically expressed as a dual process (intestinal and diffuse types) with a broad cytological diversity. From an epidemiological point of view, it behaves as an entity with a deep geographical asymmetry and a changing incidence, currently decreasing. There is a multifactorial etiology with a combination of genetic, infectious (H. pylori), nutritional and environmental factors. It might have a multiphasic gestation from precancerous lesions, though not always following a lineal sequence. We only know fragmentary portions of its pathogenesis whose common denominator is a potentially mutagenic mitogenic activation of the epithelial cells implicated. A good knowledge of this complex biological reality will allow the identification of better markers for an early diagnosis as well as vulnerable etiopathogenetic points for a useful prevention and therapy.

In vitro activity of a novel antimicrobial agent, TG44, for treatment of Helicobacter pylori infection

Due to concerns about the current therapeutic modalities for Helicobacter pylori infection, e.g., the increased emergence of drug-resistant strains and the adverse reactions of drugs currently administered, there is a need to develop an anti-H. pylori agent with higher efficacy and less toxicity. The antibacterial activity of TG44, an anti-H. pylori agent with a novel structural formula, against 54 clinical isolates of H. pylori was examined and compared with those of amoxicillin (AMX), clarithromycin (CLR), and metronidazole (MNZ). Consequently, TG44 inhibited the growth of H. pylori in an MIC range of 0.0625 to 1 microg/ml. The MIC ranges of AMX, CLR, and MNZ were 0.0078 to 8 microg/ml, 0.0156 to 64 microg/ml, and 2 to 128 microg/ml, respectively. The antibacterial activity of TG44 against AMX-, CLR-, and MNZ-resistant strains was nearly comparable to that against drug-susceptible ones. In a pH range of 3 to 7, TG44 at 3.13 to 12.5 microg/ml exhibited potent bactericidal activity against H. pylori in the stationary phase of growth as early as 1 h after treatment began, in contrast to AMX, which showed no bactericidal activity at concentrations of up to 50 microg/ml at the same time point of treatment. TG44 at 25 microg/ml exhibited no antibacterial activity against 13 strains of aerobic bacteria, suggesting that its antibacterial activity against H. pylori is potent and highly specific. The present study indicated that TG44 possesses antibacterial activity which manifests quickly and is potentially useful for eradicating not only the antibiotic-susceptible but also the antibiotic-resistant strains of H. pylori by monotherapy.

Synthesis and in vitro selective anti-Helicobacter pylori activity of N-substituted-2-oxo-2H-1-benzopyran-3-carboxamides

In order to develop new anti-Helicobacter pylori agents, five new and three already known N-substituted-2-oxo-2H-1-benzopyran-3-carboxamides (coumarin-3-carboxamides) were prepared and evaluated for their antibacterial activity. All synthesized compounds showed little or no activity against different species of Gram-positive and Gram-negative bacteria of clinical relevance and against various strains of pathogenic fungi. Among the prepared compounds those with a 4-acyl-phenyl group showed the best activity against H. pylori metronidazole resistant strains in the 0.25-1 microg/ml MIC range, indicating the presence of an acyl function as an important feature for activity.

Epidemiology - identifying the causes and preventability of cancer?

It has been almost 25 years since Doll and Peto performed their landmark analysis of epidemiological data to identify the causes of cancers and possible modes of cancer prevention. Since then, there have been many additional studies of cancer incidence using various epidemiological techniques. These studies revealed expanded opportunities for cancer prevention through approaches that include vaccination, increased physical activity, weight control and avoidance of post-menopausal hormone therapy.

Synthesis and in vitro selective anti-Helicobacter pylori activity of pyrazoline derivatives

In order to develop new anti-Helicobacter pylori agents, a series of N1-substituted 3,5-diphenyl pyrazolines P1-P13 was prepared and evaluated for their antibacterial activity. All synthesized compounds showed little or no activity against different species of Gram-positive and Gram-negative bacteria of clinical relevance and against various strains of pathogenic fungi. The same derivatives exhibited a significant degree of activity against a range of H. pylori strains, including those resistant to the reference compound metronidazole. Among the prepared compounds those with an N1-acetyl group and a 4-methoxy substituent in the 5-phenyl ring showed the best activity against H. pylori metronidazole resistant strains in the 1-4 microg/mL MIC range.

Interactions of the gastrotropic bacterium Helicobacter pylori with the leukocyte-endothelium adhesion molecules, the selectins--a preliminary report

The deleterious effects of Helicobacter pylori infection of the stomach are largely the result of a vigorous chronic inflammatory response, and include chronic gastritis, peptic ulceration and gastric cancer. We are exploring the possibility that carbohydrate components on H. pylori contribute to the persistent inflammation through interactions with leukocyte-endothelial adhesion molecules of the host. Lipopolysaccharides of most H. pylori strains contain sequences related to the Lewis (Le(x) or Le(a)) antigens. Carbohydrate sequences of this family encompass ligands for the leukocyte-endothelium adhesion molecules of the host, namely, the E- and P-selectins, which are expressed on inflamed endothelia, and L-selectin, which is constitutively expressed on leukocytes. Here we investigate H. pylori isolates from patients with chronic gastritis, duodenal ulcer and gastric cancer for their interactions with the selectins. Our results provide unequivocal evidence of interactions of isolates from each of the diagnostic groups with E- and L-selectins.

Increased risk of noncardia gastric cancer associated with proinflammatory cytokine gene polymorphisms

BACKGROUND & AIMS

Genetic variations in proinflammatory and anti-inflammatory cytokine genes influence individual response to carcinogenic exposures. Polymorphisms in interleukin (IL)-1 beta and its endogenous receptor antagonist are associated with risk of Helicobacter pylori-related gastric cancer. The aim of this study was to evaluate the role of proinflammatory cytokine gene polymorphisms in gastric and esophageal cancers defined by anatomic subsite.

METHODS

We assessed polymorphisms of the IL-1 gene cluster and 4 other cytokine genes in a population-based case-control study of upper gastrointestinal cancers, including gastric cardia (n = 126) and noncardia adenocarcinoma (n = 188), esophageal squamous cell carcinoma (n = 53), and adenocarcinoma (n = 108), and frequency-matched controls (n = 212). ORs for the different cancers were computed from logistic regression models adjusted for potential confounding factors.

RESULTS

Proinflammatory genotypes of tumor necrosis factor alpha and IL-10 were each associated with more than doubling of the risk of noncardia gastric cancer. Carriage of multiple proinflammatory polymorphisms of IL-1B(o) IL-1 receptor antagonist, tumor necrosis factor A, and IL-10 conferred greater risk, with ORs (and 95% confidence intervals) of 2.8 (1.6-5.1) for one, 5.4 (2.7-10.6) for 2, and 27.3 (7.4-99.8) for 3 or 4 high-risk genotypes. In contrast, these polymorphisms were not consistently related to the risks of esophageal or gastric cardia cancers. Polymorphisms in IL-4 and IL-6 were not associated with any of the cancers studied.

CONCLUSIONS

A proinflammatory cytokine genetic profile increases the risk of noncardia gastric adenocarcinoma but not other upper gastrointestinal cancers, possibly by inducing a hypochlorhydric and atrophic response to gastric H. pylori infection.

Gastric cancer epidemiology and risk factors

We performed a detailed analysis of the epidemiology of gastric carcinoma, based upon a review of the literature in English. The analysis reveals many puzzling features. There has been a steady fall in the incidence of gastric carcinoma in most societies studied, but a more recent steady rise in the incidence of adenocarcinoma of the cardia and lower esophagus, largely confined to White males. Although the evidence for a major role for Helicobacter pylori (H. pylori) in the etiology of gastric corpus cancer is compelling; in Western society, it probably accounts for fewer than half the cases. The relative roles of dietary constituents such as salt and nitrites and the phenotyping of H. pylori in causation and the beneficial effects of a high fruit and vegetable diet and an affluent lifestyle, for all of which there is some evidence, are yet to be quantified.

Seroreactivity to 19.5-kDa antigen in combination with absence of seroreactivity to 35-kDa antigen is associated with an increased risk of gastric adenocarcinoma

BACKGROUND

Only a minority of those infected with Helicobacter pylori will develop gastric cancer. Stratification of H. pylori strains based on carcinogenic potential will provide a basis for selective surveillance and eradication therapy. We studied the anti-H. pylori antibody profile in Asian patients with gastric adenocarcinoma to identify any H. pylori antigen that may be associated with an increased or decreased risk of gastric carcinoma.

PATIENTS AND METHODS

A case-control study comparing the seroprevalence of antibodies with various H. pylori antigens in Singaporeans with gastric adenocarcinoma and the normal Singaporean population was carried out using both conventional immunoglobulin (Ig) G enzyme-linked immunosorbent assay (ELISA) and Western blot immunoassay.

RESULTS

The seroprevalence among 44 gastric adenocarcinoma cases (70.5% males, mean age 66.7 +/- 13.5 years) and 261 controls (49.8% males, mean age 61.5 +/- 4.1 years) was 90.9% vs. 50.2% by IgG ELISA. In the H. pylori-positive male population, those suffering from gastric adenocarcinoma had significantly lower seroreactivity to the 35-kDa antigen compared with asymptomatic controls (p =.0198, OR = 3.79, 95% CI 1.24-11.61). Seropositivity to the 19.5 kDa antigen was also found to be associated with the presence of gastric adenocarcinoma in Singaporean males (p =.022, OR = 4.17, 95% CI 1.22-14.28). A 'high-risk' phenotype consisting of absence of a band at 35-kDa in combination with the presence of a band at 19.5-kDa was significantly associated with the presence of gastric adenocarcinoma (p =.002, OR = 3.7, 95% CI 1.6-8.6).

CONCLUSIONS

Stratification of H. pylori strains based on their potential for carcinogenesis, such as those strains that are seropositive for the 19.5 kDa antigen and seronegative for the 35-kDa antigen, may provide a basis for selective eradication of H. pylori infection and future vaccine development.

In vitro and in vivo antibacterial activities of TAK-083, an agent for treatment of Helicobacter pylori infection

The antibacterial activity of TAK-083 was tested against 54 clinical isolates of Helicobacter pylori and was compared with those of amoxicillin, clarithromycin, and metronidazole. The growth-inhibitory activity of TAK-083 was more potent than that of amoxicillin, clarithromycin, or metronidazole (the MICs at which 90% of the strains are inhibited were 0.031, 0.125, 64, and 8 microg/ml, respectively). The antibacterial activity of TAK-083 was highly selective against H. pylori; there was a >30-fold difference between the concentration of TAK-083 required to inhibit the growth of H. pylori and that required to inhibit the growth of common aerobic and anaerobic bacteria. Exposure of H. pylori strains to TAK-083 at the MIC or at a greater concentration resulted in an extensive loss of viability. When four H. pylori strains were successively subcultured in the medium containing subinhibitory concentrations of TAK-083, no significant change in the MICs of this compound was observed. TAK-083 strongly inhibited the formation of tryptophanyl-tRNA in H. pylori while exhibiting little effect on the same system in eukaryotes. TAK-083 was efficacious in the treatment of gastric infection caused by H. pylori in Mongolian gerbils. The results presented here indicate that TAK-083 is a promising candidate for the treatment of H. pylori infection.

Helicobacter pylori-gastrin link in MALT lymphoma

BACKGROUND

There is accumulating evidence for the role of Helicobacter pylori in the development of gastric cancer as well as of lymphomas that arise in mucosa-associated lymphoid tissue (MALT). We reported recently that gastric cancer patients show high prevalence of cagA-positive H. pylori and express gastrin and gastrin receptors enabling them to stimulate tumour growth in autocrine fashion.

AIMS

Since the H. pylori infection is considered to be more strongly associated with MALT lymphoma than with gastric cancer, we decided to determine the gastrin and its receptors' mRNA expression and gastrin content in this tumour as well as the release of this hormone both into plasma and gastric lumen. Twenty MALT lymphoma patients were compared with 100 age- and gender-matched controls with similar dyspeptic symptoms.

RESULTS

The overall H. pylori seropositivity in MALT lymphoma was about 90% and CagA positivity was 70%, compared to 56% and 33%, respectively, in controls. The serum gastrin in MALT lymphoma was about sixfold higher than in controls while gastric luminal gastrin in these patients was over 70 times higher than in controls. Gastrin content in tumour was about 10-fold higher than in antral mucosa. Gastrin and gastrin-receptor (CCKB-receptor) mRNA were detected by reverse transcriptase-polymerase chain reaction in cancer tissue whilst in the fundic and antral mucosa, only enhanced expression of CCKB-receptor mRNA and gastrin mRNA was detected, respectively. Histamine stimulation in MALT lymphoma induced acid secretion that was only about 30% of control value due to atrophic gastritis. This study confirms an important role of CagA-positive H. pylori in the pathogenesis of MALT lymphoma and shows that this lymphoma is capable of synthesizing and releasing potent growth promoting gastrin, possibly due to the action on G-cells of H. pylori-originated Nalpha-methyl histamine and cytokines (tumour necrosis factor alpha and interleukin-8).

CONCLUSIONS

Gastric MALT lymphoma is closely linked to CagA-positive H. pylori infection. Gastrin and its receptors may be implicated in the pathogenesis of gastric lymphoma.

Review article: Helicobacter pylori and gastric cancer--the clinicians'point of view

Although the incidence of gastric cancer has declined dramatically in Western countries, the most recent data from the International Agency for Research on Cancer show that it remains the second most common cancer worldwide and caused 628 000 deaths in 1990. The incidence and prevalence of gastric cancer are projected to increase over the next few decades in less developed countries as a result of the increased longevity of H. pylori-infected populations and improved therapies. Gastric carcinogenesis is a multistep and multifactorial process beginning with H. pylori-associated gastritis in most cases. H. pylori infection, together with other environmental factors and individual susceptibility, determine the final risk for the development of gastric cancer. The magnitude of H. pylori infection as a risk factor for gastric cancer in the published H. pylori and gastric cancer epidemiology studies may have been underestimated due to the inclusion of improperly selected controls. Eradication of the infection has been shown to prevent the occurrence of metachronous gastric cancer following endoscopic resection of early gastric cancer in a Japanese study. However, the generalization of this study to other populations is difficult because of the vast differences in the definition of gastric atrophy and early gastric cancer between Japanese and Western pathologists. Until an international consensus on the pathological diagnosis of gastric atrophy and early gastric cancer is reached, interpretation of studies performed in different countries remains difficult. Clinicians rely on the correct pathological diagnosis to guide the management of H. pylori infection-associated gastrointestinal diseases.

Helicobacter pylori infection and gastric cancer: systematic review of the epidemiological studies

BACKGROUND

The published epidemiological studies of chronic Helicobacter pylori infection and gastric cancer yield conflicting results, so there is uncertainty as to whether any material association exists and, if so, how strong it is.

AIM

To review these studies quantitatively.

METHODS

A systematic review of sero-epidemiological studies published before 1998 of H. pylori and gastric cancer, as identified by computer-assisted literature searches of relevant journals, reference lists and discussions with authors. All relevant studies identified were included, subdivided by study design. The following was abstracted from published reports: adjusted odds ratio (or, in prospective studies, the risk ratio) and confidence interval, study design, type of controls, mean age, mean duration of follow-up, assay methods, location of study, and degree of adjustment for confounders.

RESULTS

The 34 retrospective studies included in total 3300 gastric cancers, but their controls were of uncertain validity. The 10 'nested' case-control comparisons in prospective studies included in total only 800 gastric cancers, and combined analysis of them yielded a risk ratio of 2.5 (95% CI: 1.9-3.4; 2P < 0.00001) for gastric cancer in people seropositive for H. pylori antibodies.

CONCLUSIONS

The prospective studies suggest that gastric cancer is 2 or 3 times as common in those chronically infected by H. pylori, but to help investigate causality, further observational studies are still needed, as are large-scale randomized trials of whether antibacterial regimens reduce the eventual incidence of gastric cancer.

Helicobacter pylori attaches to NeuAc alpha 2,3Gal beta 1,4 glycoconjugates produced in the stomach of transgenic mice lacking parietal cells

Helicobacter pylori infection of the human stomach is associated with altered acid secretion, loss of acid-producing parietal cells, and, in some hosts, adenocarcinoma. We have used a transgenic mouse model to study the effects of parietal cell ablation on H. pylori pathogenesis. Ablation results in amplification of the presumptive gastric epithelial stem cell and its immediate committed daughters. The amplified cells produce sialylated oncofetal carbohydrate antigens that function as receptors for H. pylori adhesins. Attachment results in enhanced cellular and humoral immune responses. NeuAc alpha 2,3Gal beta 1,4 glycoconjugates may not only facilitate persistent H. pylori infection in a changing gastric ecosystem, but by promoting interactions with lineage progenitors and/or initiated cells contribute to tumorigenesis in patients with chronic atrophic gastritis.

Gastric cancer, cytotoxin-associated gene A-positive Helicobacter pylori, and serum pepsinogens: an international study. The Eurogst Study Group

BACKGROUND & AIMS

CagA-positive Helicobacter pylori infection has been more closely associated with gastric disease than CagA-negative infection. This study evaluated whether geographic variation in the prevalence of CagA could explain variation in gastric cancer rates.

METHODS

The Eurogast study was conducted in 17 centers in 13 countries. Gastric cancer rates were calculated for each center, and serum samples from approximately 2850 subjects were assayed for immunoglobulin G antibodies to H. pylori and CagA and for pepsinogens A and C.

RESULTS

The proportion of CagA-positive H. pylori infections varied across the centers, but this variation did not explain any more of the variation in gastric cancer rates than H. pylori alone. Subjects with CagA-positive infection had, however, significantly higher pepsinogen levels and a lower pepsinogen A/C ratio than subjects with CagA-negative infection; this pattern was observed consistently across the study centers.

CONCLUSIONS

Variation in the seroprevalence of CagA did not explain geographic variation in gastric cancer rates any better than H. pylori alone. However, the consistent variation in pepsinogen levels with CagA status across the study centers supports the importance of the role of CagA in the development of gastric disease.

Creating and maintaining the gastrointestinal ecosystem: what we know and need to know from gnotobiology

Studying the cross talk between nonpathogenic organisms and their mammalian hosts represents an experimental challenge because these interactions are typically subtle and the microbial societies that associate with mammalian hosts are very complex and dynamic. A large, functionally stable, climax community of microbes is maintained in the murine and human gastrointestinal tracts. This open ecosystem exhibits not only regional differences in the composition of its microbiota but also regional differences in the differentiation programs of its epithelial cells and in the spatial distribution of its component immune cells. A key experimental strategy for determining whether "nonpathogenic" microorganisms actively create their own regional habitats in this ecosystem is to define cellular function in germ-free animals and then evaluate the effects of adding single or several microbial species. This review focuses on how gnotobiotics-the study of germ-free animals-has been and needs to be used to examine how the gastrointestinal ecosystem is created and maintained. Areas discussed include the generation of simplified ecosystems by using genetically manipulatable microbes and hosts to determine whether components of the microbiota actively regulate epithelial differentiation to create niches for themselves and for other organisms; the ways in which gnotobiology can help reveal collaborative interactions among the microbiota, epithelium, and mucosal immune system; and the ways in which gnotobiology is and will be useful for identifying host and microbial factors that define the continuum between nonpathogenic and pathogenic. A series of tests of microbial contributions to several pathologic states, using germ-free and ex-germ-free mice, are proposed.

Testing for Helicobacter pylori in primary care: trouble in store?

STUDY OBJECTIVE

To assess the role of testing for Helicobacter pylori in the management of dyspeptic patients in primary care.

DESIGN

Selective review of literature frequently quoted to support use of H pylori testing.

MAIN RESULTS

Testing for H pylori and referral of only positive cases for endoscopy aims to reduce the number of "unnecessary" endoscopies. Patients with negative results may receive short-term reassurance and subsequently place fewer demands on health services. However, studies to date have only assessed this practice in secondary care settings. Given the relatively high prevalence of both dyspepsia and H pylori infection, the transfer of this practice to primary care may lead to a paradoxical increase in endoscopy referrals. Identification of H pylori and prescribing of eradication treatment also aims to reduce endoscopy referrals. No primary care trials have yet assessed this approach. Given that fewer than one in four of dyspeptic patients have peptic ulceration, a high proportion may fail to respond to eradication treatment and subsequently require referral for endoscopy. The longer term clinical and psychosocial sequelae of treating or labelling patients with an infection associated with gastric cancer remain unknown.

CONCLUSIONS

Given uncertainty concerning the possible adverse effects of H pylori testing in primary care, we suggest a moratorium on its use in this setting until results from relevant clinical trials become available.

Epithelial attachment alters the outcome of Helicobacter pylori infection

Genetically defined in vivo models are needed to assess the importance of target cell attachment in bacterial pathogenesis. Gastric colonization by Helicobacter pylori in human populations is common and persistent, and has various outcomes including peptic ulcers and cancer. The impact of attachment on the course of infection was examined in transgenic mice expressing a human receptor for H. pylori in their gastric epithelium. Persistent infection by a clinical isolate occurred at comparable microbial densities in transgenic and nontransgenic littermates. However, microbial attachment in transgenic mice resulted in production of autoantibodies to Lewisx carbohydrate epitopes shared by bacteria and acid-secreting parietal cells, chronic gastritis, and parietal cell loss. This model should help identify bacterial and host genes that produce attachment-related pathology.

Helicobacter pylori

Helicobacter pylori infection causes peptic ulcer disease, gastric adenocarcinoma, gastric lymphoma, and probably nonulcer dyspepsia. Although the prevalence of infection is declining over time, the organism still infects approximately one half of the world's population. Only a minority will ever suffer serious consequences from their infection. This article reviews current knowledge about H. pylori and presents some of the dilemmas surrounding clinical and public health approaches to this widespread pathogen.

An age- and gender-specific analysis of H. Pylori infection

The objective of this study was to determine the incidence of Helicobacter pylori infection in different age and sex groups from the southern region of Saudi Arabia, and to relate the results to the high incidence of gastric cancer in this region. The carcinogenic effect of H. pylori is considered to be age-dependent. H. pylori infection early in life predisposes patients to gastric cancer. In contrast, acquisition of infection later in life leads to development of duodenal ulcer. We studied 528 consecutive endoscopic biopsies over a period from March 1995 to August 1996. The presence or absence of H. pylori was tabulated according to age and sex of the patients. Three hundred and fifty-three (67%) of 528 patients were positive for H. pylori. There were 313 males, among whom 217 (69%) were positive. There were 215 females, among whom 136 (63%) were positive for H. pylori. The presence of H. pylori in various age groups was as follows: under 16 years, 62%; 16 to 25 years, 67%; 26-35 years, 69%; 36-45 years, 67%; 46-55 years, 66%; and 56 years and above, 65%. Statistical analysis revealed no significant difference between the groups. No significant rise in the infection rate was noted from childhood to advanced age. These data support the belief that H. pylori infection was acquired early in life, leading to multifocal gastritis and thus predisposing the patients to gastric cancer later in life. However, H. pylori may not be the single agent of gastric cancer inasmuch as the infection affects both genders equally, whereas gastric cancer has a male preference. Perhaps some additional factors augment the pivotal role of H. pylori.

Gastric cancer and Helicobacter pylori: a critical evaluation of the epidemiological evidence

Despite a dramatic reduction in incidence and mortality, gastric cancer (GC) still was recently reported to be the second most common neoplastic cause of death worldwide. GC treatment has not been improved substantially, and large-scale early diagnosis programs have not proved feasible outside Japan. On the other hand, even if diet has been shown to play a relevant role in the etiology of GC, primary prevention programs based on dietary modifications are difficult to implement, and results of human chemoprevention trials, although encouraging, have not been confirmed. Overall, the observed reduction in GC risk can reasonably be considered to be the result of a spontaneous trend, somehow related to the wide-spread improvements in socioeconomic conditions. Domestic refrigeration, an increased availability of fresh fruit and vegetables, and a reduced use of salt are considered to be the most relevant factors in explaining the decreasing temporal trend and the geographical patterns of GC. Recently, evidence of an association between Helicobacter pylori infection and GC has been provided by epidemiological studies, particularly three studies specifically designed as nested case-control studies in which blood samples were collected well before diagnosis was made. The results of these studies, however, have been confirmed only in part. A strong direct association is not yet widely accepted, and no specific carcinogenic compound or mechanism has been identified. Relevant aspects of GC and H. pylori epidemiology actually do not fit perfectly in a causal hypothesis (i.e., the geographical and gender distribution, the paradoxical association with duodenal ulcer) though, on the other hand, several other factors certainly play a role in the complex multifactorial process leading, over several decades, to GC. Studies focused on H. pylori eradication and its effects on lesions that predispose to GC (atrophic gastritis and metaplasia), however, represent a priority for research, in view of the potential preventive applications. This issue remains controversial, and it is possible that progression of these lesions might occur after eradication.

Immunochemical properties of a 60 kDa cell surface-associated heat shock-protein (Hsp60) from Helicobacter pylori

Western blot analysis (immunoblotting) of cell surface-associated proteins from Helicobacter pylori confirmed our previous findings that binding of human IgG is a common property (among H. pylori strains). Purification of the IgG-binding proteins (IGBP) was achieved by two purification steps, affinity chromatography on IgG-Sepharose and nickel chelate affinity chromatography. SDS-PAGE and immunoblotting analysis revealed a 60 kDa protein with affinity for peroxidase labeled human IgG. Solid phase binding assays showed that IgG binds to an immobilized protein (IGBP). The 60 kDa IGBP binds human IgG1, IgG3 and IgM. Binding could be inhibited by the kappa chain of the human IgG, but not with its Fc fragment, nor with IgA or IgM. In addition, rabbit polyclonal antibodies raised against the 60 kDa IGBP blocked IgG binding. Monoclonal antibodies, specific to the Hsp60 heat shock protein of H. pylori recognized the 60 kDa IGBP as revealed by immunoblotting analysis, both in crude preparations and in the purified fractions.

Cryptic domains of a 60 kDa heat shock protein of Helicobacter pylori bound to bovine lactoferrin

Bovine lactoferrin binds to a 60 kDa heat shock protein of Helicobacter pylori. Binding ability was related to human immunoglobulin G because bovine lactoferrin binding proteins were isolated by extraction of cell surface associated proteins with distilled water, applied on IgG-Sepharose and nickel sulphate chelate affinity chromatography. Binding was demonstrated by Western blot after purified protein was digested with alpha-chymotrypsin and incubated with peroxidase-labeled bovine lactoferrin. Binding was inhibited by bovine lactoferrin, lactose, rhamnose, galactose, and two iron-containing proteins, ferritin and haptoglobin. Helicobacter pylori binds ferritin and haptoglobin via charge or hydrophobic interactions because this binding was not inhibited by specific and various glycoproteins or carbohydrates. Carbohydrate moieties of bovine lactoferrin molecules seem to be involved in binding because glycoproteins with similar carbohydrate structures strongly inhibited binding. Scatchard plot analysis of the binding of peroxidase-labeled bovine lactoferrin to H. pylori cells yielded a kd 2.88 x 10(-6) M. In addition, binding of H. pylori cells to bovine lactoferrin was enhanced when bacteria treated with pepsin or alpha-chymotrypsin after isolation from iron-restricted and iron-containing media.