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.     

Helicobacter pylori infection and gastric carcinogenesis in animal models

The effects of Helicobacter pylori infection on gastric disorders have been proven by many epidemiological and experimental studies. To explore the relationships between H. pylori infection and gastric carcinogenesis, many factors, including host responses, environmental status, and the virulence factors of the bacteria should be taken into account. Mongolian gerbils ( Meriones unguiculatus ) can be easily infected with H. pylori , and provide an excellent in-vivo experimental model to clarify the role of H. pylori in active gastritis, peptic ulcers, intestinal metaplasia, and gastric carcinoma. Studies have revealed that H. pylori infection markedly enhances all histological types of gastric cancers in gerbils treated with a chemical carcinogen. Eradication reduced the enhancing effect of H. pylori on gastric carcinogenesis, whereas a high-salt diet synergistically enhanced the effect of H. pylori . Various factors involving inflammation, cell proliferation, and cell differentiation could be examined with this experimental model to help elucidate this mechanisms of gastric carcinogenesis. Received: October 23, 2002 / Accepted: December 9, 2002 Acknowledgments We thank Dr. Toshiko Kumagai, Central Clinical Laboratories, Shinshu University Hospital; Dr. Atsushi Sugiyama, First Department of Surgery, Shinshu University; Professor Tsutomu Katsuyama, Department of Laboratory Medicine, Shinshu University School of Medicine; and Dr. Nobuyuki Shimizu and Professor Michio Kaminishi, Department of Gastrointestinal Surgery, Postgraduate School of Medicine, The University of Tokyo. Offprint requests to: M. Tatematsu     

Helicobacter pylori and carcinogenesis of gastric B-cell lymphomas

Primary non-Hodgkin's lymphomas of the stomach are associated with Helicobacter pylori infection. We analyzed gastric lymphoma onset data with respect to prior H. pylori infections based on the multistage theory of carcinogenesis. This theory provides a link between epidemiological data and biological processes. The study involved 133 patients, aged 29-75 years, diagnosed with marginal zone B-cell lymphoma (MZBL) and diffuse large cell B-cell lymphoma (DLBL). A 2-parametric Weibull model was applied to MZBL and DLBL onset data. Median age of diagnosis of MZBL (DLBL) was 59 years (55 years) in males and 65.5 years (64 years) in females. Infection with H. pylori was found in 81.3% (59.5%) of the patients diagnosed with MZBL (DLBL). Lymphoma latency data were fitted to Weibull distributions with a shape parameter of 5.7 for MZBL cases and 4.2 for DLBL. The shape parameter that indicates the number of steps in carcinogenesis was approximately independent of the status of infection with H. pylori in DLBL in contrast to MZBL. It was shown that gastric lymphoma onset data can be described by Weibull distribution functions. The findings support the hypothesis that MZBL and DLBL have different lines of development. There is indication of stronger antigen dependency in the carcinogenesis of MZBL in comparison to DLBL.     

Helicobacter pylori,gastric microbiota and gastric cancer relationship: Unrolling the tangle

Helicobacter pylori infection (Hp-I) represents a typical microbial agent intervening in the complex mechanisms of gastric homeostasis by disturbing the balance between the host gastric microbiota and mucosa-related factors, leading to inflammatory changes, dysbiosis and eventually gastric cancer. The normal gastric microbiota shows diversity, with Proteobacteria [Helicobacter pylori (H. pylori) belongs to this family], Firmicutes, Actinobacteria, Bacteroides and Fusobacteria being the most abundant phyla. Most studies indicate that H. pylori has inhibitory effects on the colonization of other bacteria, harboring a lower diversity of them in the stomach. When comparing the healthy with the diseased stomach, there is a change in the composition of the gastric microbiome with increasing abundance of H. pylori (where present) in the gastritis stage, while as the gastric carcinogenesis cascade progresses to gastric cancer, the oral and intestinal-type pathogenic microbial strains predominate. Hp-I creates a premalignant environment of atrophy and intestinal metaplasia and the subsequent alteration in gastric microbiota seems to play a crucial role in gastric tumorigenesis itself. Successful H. pylori eradication is suggested to restore gastric microbiota, at least in primary stages. It is more than clear that Hp-I, gastric microbiota and gastric cancer constitute a challenging tangle and the strong interaction between them makes it difficult to unroll. Future studies are considered of crucial importance to test the complex interaction on the modulation of the gastric microbiota by H. pylori as well as on the relationships between the gastric microbiota and gastric carcinogenesis.     

幽门螺杆菌相关性胃病的细胞增殖与凋亡的研究

目的 观察幽门螺杆菌（Ｈｅｌｉｃｏｂａｃｔｅｒ ｐｙｌｏｒｉ,Ｈｐ）感染对其相关性胃病的细胞增殖与凋亡的影响,进行探讨胃癌的发生机理。方法 研究对象为正常人（ｎｏｒｍａｌ ｓｕｂｊｅｃｔｓ,ＮＳ）及慢性浅表性胃炎（ｃｈｒｏｎｉｃ ｓｕｐｅｒｆｉｃｉａｌ ｇａｓｔｒｉｔｉｓ,ＣＳＧ）、慢性萎缩性胃炎（ｃｈｒｏｎｉｃ ａｔｒｏｐｈｉｃ ｇａｓｔｒｉｔｉｓ,ＣＡＧ）、慢性萎缩性胃炎伴肠上皮化生（ｃｈｒｏ     

Earlier Helicobacter pylori Infection Increases the Risk for the N-Methyl-N-nitrosourea-induced Stomach Carcinogenesis in Mongolian Gerbils

Helicobacter pylori (H. pylori) is now well known to be associated with stomach cancer, with infection during childhood rather than as an adult considered to be more important for carcinogenesis. To evaluate the difference in susceptibility to stomach carcinogenesis in relation to age of acquisition of H. pylori infection, we designed an experiment involving inoculation of H. pylori ATCC43504 followed by N -methyl- N -nitrosourea (MNU) treatment at different ages. Four-week- old male Mongolian gerbils (MGs) were divided into twelve groups. H. pylori was inoculated at 4, 18 and 32 weeks of age, as representatives of early, middle and late infection, respectively. Two weeks later, the animals were treated with MNU. Groups without H. pylori and/or MNU were included as controls. The incidences of adenocarcinomas at 52 weeks after the inoculation in the early ( H. pylori +MNU), middle (H. pylori +MNU), and late (H. pylori +MNU) group were 60% (12/ 20), 18.4% (2/11), and 10% (2/20), respectively. The corresponding figures were 14.8% (4/27), 0% (0/11), and 0% (0/21) in the MNU-alone groups. A higher titer of serum IgG for H. pylori and higher gastrin level were seen in the early-infected compared to the middle and the late groups ( P <0.01). The results clearly demonstrated that early acquisition of H. pylori significantly increases gastric chemical carcinogenesis with MNU, as compared to the case with later infection, possibly because of differences in host gastric mucosal factors and immunologic responses.     

Influence of Helicobacter pylori oncoprotein CagA in gastric cancer: A critical-reflective analysis

Gastric cancer is the fifth most common malignancy and third leading cancer-related cause of death worldwide. Helicobacter pylori is a Gram-negative bacterium that inhabits the gastric environment of 60.3% of the world’s population and represents the main risk factor for the onset of gastric neoplasms. CagA is the most important virulence factor in H. pylori, and is a translocated oncoprotein that induces morphofunctional modifications in gastric epithelial cells and a chronic inflammatory response that increases the risk of developing precancerous lesions. Upon translocation and tyrosine phosphorylation, CagA moves to the cell membrane and acts as a pathological scaffold protein that simultaneously interacts with multiple intracellular signaling pathways, thereby disrupting cell proliferation, differentiation and apoptosis. All these alterations in cell biology increase the risk of damaged cells acquiring pro-oncogenic genetic changes. In this sense, once gastric cancer sets in, its perpetuation is independent of the presence of the oncoprotein, characterizing a “hit-and-run” carcinogenic mechanism. Therefore, this review aims to describe H. pylori- and CagA-related oncogenic mechanisms, to update readers and discuss the novelties and perspectives in this field.     

Helicobacter pylori CagA -- a bacterial intruder conspiring gastric carcinogenesis

Infection with cagA-positive Helicobacter pylori (H. pylori) is associated with the development of gastric adenocarcinoma. The cagA gene product CagA is delivered from the bacterium into the cytoplasm of the bacterium-attached gastric epithelial cell via the type-IV secretion system. Upon membrane localization and subsequent tyrosine phosphorylation by Src family kinases, translocated CagA functions as a scaffolding adaptor that interacts with a number of host proteins involved in cell signaling in both tyrosine phosphorylation-dependent and -independent manners. Of special interest is the interaction of CagA with the SHP-2 tyrosine phosphatase, of which gain-of-function mutations have recently been found in human malignancies. Through the complex formation, SHP-2 is catalytically activated and induces morphological transformation that is associated with increased cell motility. In addition to the perturbation of intracellular signaling, CagA disrupts the apical junctional complex that regulates the cell-cell contact and maintains the integrity of the epithelial structure. These CagA activities may collectively cause cellular dysfunctions that promote accumulation of multiple genetic changes involved in malignant transformation. Further elucidation of host cell signaling targeted by CagA should provide a new paradigm for 'bacterial carcinogenesis' and also give insights into general understanding of inflammation-mediated cancers. Clinically, detailed studies on the relationship between structural diversity and degree of pathogenic activity of CagA should make it possible to identify a high-risk group for gastric carcinoma among H. pylori-infected populations through cagA genotyping.     

Helicobacter pylori Does Not Promote N-Methyl-N-nitrosourea-induced Gastric Carcinogenesis in SPF C57BL/6 Mice

Helicobacter pylori (H. pylori) infection has been acknowledged as a promoter and an initiator for gastric carcinogenesis in experimental models using Mongolian gerbils with H. pylori strains TN2GF4 and ATCC 43504, which have +ve cagA and vacA phenotype s1/ml. To get more insight into the role of H. pylori in gastric carcinogenesis, we studied the effect of H. pylori SS1, which has +ve cagA and vacA phenotype s2/m2, on Af-methyl-N-nitrosourea (MNU)-induced chemical gastric carcinogenesis using SPF C57BL/6 mice. Thus, H. pylori SSI was inoculated 1 week after the completion of MNU treatment to examine the promoting effect of this bacterium. The incidences of polypoid lesions, differentiated adenocarcinomas, and adenomatous hyperplasias were 67% (10/ 15), 47% (7/15) and 80% (12/15), respectively, in the MNU-alone group. The corresponding figures were 31% (8/26), 23% (6/26) and 35% (9/26) in the MNU+ H. pylori group. The incidences of polypoid lesions and adenomatous hyperplasia were significantly different between the groups. Thus, the results indicate that H. pylori SSI infection reduced susceptibility to chemical gastric carcinogenesis in this model. The discrepancy between the present result and previous results is likely to have been caused by differences in host factors and bacterial factors. Further study of the relationship between gastric carcinogenesis and H. pylori infection is needed.     

胃粘膜上皮异型增生细胞增殖活性及凋亡与幽门螺杆菌感染的关系

背景与目的:异型增生是胃癌的癌前病变,但其癌变机制目前仍不清楚,本文通过对异型增生自然转归过程中细胞增殖活性和凋亡变化及幽门螺杆菌(Helicobacterpylori,HP)感染状态的研究,探讨二者之间的关系及其对异型增生癌变的影响。方法:取12例正常胃粘膜(对照组)和105例有随访结果的胃粘膜异型增生胃镜活检标本〔其中高度异型增生35例(癌变30例、未癌变5例);低度异型增生70例(癌变18例、未癌变52例)〕。全部标本均采用TUNEL(terminaldeoxynucleotidyltransferasemediatednickendlabeling)法检测凋亡情况;采用免疫组化法检测增殖细胞核抗原(proliferatingcellnuclearantigen,PCNA)表达情况;采用多聚酶链反应(polymerasechainreaction,PCR)检测HP及其CagA(+)株感染状况。结果:异型增生的HP感染率为84.76%,与对照组的83.33%相比差异无统计学意义,但CagA(+)株感染率为85.39%,高于对照组的60.00%。HP(+)和CagA(+)病例的增殖指数分别较HP(-)和CagA(-)为高(P<0.05),异型增生中PCNA的异常与HP及CagA(+)株感染有关(P<0.05)。凋亡/增殖比的变化与Hp的CagA(+)株感染有关(P<0.05)。结论:胃粘膜异型增生的形成及其自然转归过程中,异型增生的细胞动力学异常与HP、CagA(+)株感染有关。     

Role of polymorphisms in genes that encode cytokines and Helicobacter pylori virulence factors in gastric carcinogenesis

The Helicobacter pylori (H. pylori) infection is a determinant factor in gastric cancer (GC) development. However, the infection outcomes are variable and depend on both host and bacterial characteristics. Some host cytokines such as interleukin (IL)-1β, IL-1Ra, IL-8, IL-10 and tumor necrosis factor-α play important roles in the host immune system response to the pathogen, in the development of gastric mucosal lesions and in cell malignant transformation. Therefore, these host factors are crucial in neoplastic processes. Certain polymorphisms in genes that encode these cytokines have been associated with an increased risk of GC. On the other hand, various virulence factors found in distinct H. pylori bacterial strains, including cytotoxin-associated antigen A, vacuolating cytotoxin, duodenal ulcer promoting gene A protein, outer inflammatory protein and blood group antigen binding adhesin, have been associated with the pathogenesis of different gastric diseases. The virulent factors mentioned above allow the successful infection by the bacterium and play crucial roles in gastric mucosa lesions, including malignant transformation. Moreover, the role of host polymorphisms and bacterial virulence factors in gastric carcinogenesis seems to vary among different countries and populations. The identification of host and bacterium factors that are associated with an increased risk of GC development may be useful in determining the prognosis of infection in patients, what could help in clinical decision-making and in providing of an optimized clinical approach.     

Helicobacter pylori induces epithelial-mesenchymal transition in gastric carcinogenesis via the AKT/GSK3β signaling pathway

Helicobacter pylori (H. pylori) is a main risk factor for gastric cancer (GC). Epithelial-mesenchymal transition (EMT) is involved in the development and progression of H. pylori-associated GC. However, the exact molecular mechanism of this process remains unclear. The AKT/GSK3β signaling pathway has been demonstrated to promote EMT in several types of cancer. The present study investigated whether H. pylori infection induced EMT, and promoted the development and metastasis of cancer in the normal gastric mucosa, and whether this process was dependent on AKT activation. The expression levels of the EMT-associated proteins, including E-cadherin and N-cadherin, were determined in 165 gastric mucosal samples of different disease stages by immunohistochemical analysis. The expression levels of E-cadherin, N-cadherin, AKT, phosphorylated (p-)AKT (Ser473), GSK3β and p-GSK3β (Ser9) were further determined in H. pylori-infected Mongolian gerbil gastric tissues and cells co-cultured with H. pylori by immunohistochemical analysis and western blotting. The results indicated that the expression levels of the epithelial marker E-cadherin were decreased, whereas the expression levels of the mesenchymal marker N-cadherin were increased during gastric carcinogenesis. Their expression levels were associated with H. pylori infection. Furthermore, H. pylori infection resulted in downregulation of E-cadherin expression and upregulation of N-cadherin expression in Mongolian gerbils and GES-1 cells. In addition, an investigation of the associated mechanism of action revealed that p-AKT (Ser473) and p-GSK3β (Ser9) were activated in GES-1 cells following co-culture with H. pylori. Furthermore, following pretreatment of the cells with the AKT inhibitor VIII, the expression levels of E-cadherin, N-cadherin, p-AKT and p-GSK3β did not show significant differences between GES-1 cells that were co-cultured with or without H. pylori. The levels of p-AKT and p-GSK3β were increased in H. pylori-infected Mongolian gerbils. In conclusion, the present study demonstrated that H. pylori infection activated AKT and resulted in the phosphorylation and inactivation of GSK3β, which in turn promoted early stage EMT. These effects were AKT-dependent. This mechanism may serve as a prerequisite for GC development.     

幽门螺杆菌感染诱导微小RNA?181c对胃癌细胞增殖和侵袭的影响

目的探讨幽门螺杆菌(Hp)感染诱导微小RNA-181c(miR-181c)对胃癌细胞增殖、侵袭和迁移的影响。方法采用实时定量PCR(QPCR)检测Hp感染人正常胃黏膜GES-1细胞和胃癌细胞(BGC-823、SGC-7901、AGS)的miR-181c水平。采用脂质体向SGC-7901细胞转染miR-181c抑制物(Inhibitor组)或阴性对照序列(NC组),另取未转染的细胞为对照组;转染48 h后采用QPCR检测miR-181c水平,活细胞计数(CCK-8)法、划痕实验和Transwell小室实验检测细胞增殖活力、划痕愈合率和穿膜细胞数以评估细胞增殖、迁移和侵袭能力,QPCR和Western blotting检测Bcl-2、基质金属蛋白酶(MMP)-9和神经型钙黏蛋白(N-cad)水平。结果QPCR检测结果显示Hp感染后各细胞的miR-181水平较感染前均升高(P<0.05),GES-1、BGC-823、SGC-7901和AGS细胞Hp感染后的miR-181c水平分别为感染前的4.37、1.63、3.25和2.09倍。与对照组和NC组相比,Inhibitor组SGC-7901细胞的miR-181c水平和转染48、72 h后的增殖活力降低(P<0.05);Inhibitor组SGC-7901细胞的划痕愈合率和穿膜细胞数量分别为(21.679±3.762)%和(128.056±21.463)个,低于对照组的(65.004±2.309)%和(325.07±34.082)个及NC组的(65.675±2.914)%和(328.035±31.391)个,差异有统计学意义(P<0.05);与对照组和NC组相比,Inhibitor组的Bcl-2、MMP-9和N-cad水平均降低(P<0.05)。对照组和NC组上述指标的差异无统计学意义(P>0.05)。结论Hp感染可升高胃癌细胞的miR-181c水平,下调该miR-181c水平对增殖、侵袭和迁移具有明显抑制作用,为Hp感染的胃癌治疗提供了新的靶点。     

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     

幽门螺杆菌感染与胃癌及癌前病变中P21蛋白的表达

 用LSAB免疫组化法，对20例谓癌、22例异型增生、30例肠化生及13例正常组织进行了P21蛋白表达的检测。结果发现，胃癌、异型增生和肠化生的P21阳性者分别为13例（65.0%）,12例（60.0%）,11例（36.6%）,正常组织全部阴性；三种组织中，HP阳性病人的P21阳性率为41.6%（30/72）,明显高于HP阴性病人的8.3%（6/72）,有显着差别（P<0.01）.说明HP感染与P21过度表达存在着明显的相关性。提示HP感染可能通过ras癌基因的突变而参予致癌作用。     

幽门螺杆菌感染和环氧合酶-2表达在胃癌发生中的作用

目的探讨幽门螺杆菌 (Hp) 感染和环氧合酶-2(COX-2)表达在胃癌发生中的作用.方法 138例胃镜活检标本包括慢性非萎缩性胃炎30例,慢性萎缩性胃炎85例(其中伴有中度以上肠化生45例,中、重度异型增生12例),和胃癌23例.快速尿素酶试验和组织学改良Giemsa染色联合检测Hp,免疫组化检查COX-1和COX-2表达.结果胃癌的Hp阳性率为69.6%,显著高于慢性非萎缩性胃炎的36.7%(P<0.05).慢性非萎缩性胃炎、慢性萎缩性胃炎、肠化生、异型增生和胃癌的COX-2表达率分别为10.0%、37.6%、37.8%、41.7%和69.6%,而不同胃黏膜病变中COX-1表达无明显差异.慢性萎缩性胃炎、肠化生和异型增生中Hp阳性病例的COX-2表达显著高于Hp阴性病例(P<0.01).结论 Hp感染及其诱导的COX-2表达可能是胃癌发生的早期事件之一.     

From Helicobacter pylori infection to gastric cancer: Current evidence on the immune response

Gastric cancer (GC) is the result of a multifactorial process whose main components are infection by Helicobacter pylori (H. pylori), bacterial virulence factors, host immune response and environmental factors. The development of the neoplastic microenvironment also depends on genetic and epigenetic changes in oncogenes and tumor suppressor genes, which results in deregulation of cell signaling pathways and apoptosis process. This review summarizes the main aspects of the pathogenesis of GC and the immune response involved in chronic inflammation generated by H. pylori.     

根治幽门螺杆菌对胃粘膜上皮p53蛋白表达的影响

目的　研究幽门螺杆菌 (Hp)根除治疗对p5 3蛋白表达的影响 ,探讨Hp与胃癌的关系。 方法　利用免疫组化染色对 2 0 6例胃粘膜活检组织 ,包括正常胃粘膜、Hp阴性胃癌前各阶段病变、Hp阳性胃癌前各阶段病变Hp根除治疗前后及胃癌 ,进行 p5 3蛋白表达的分析。 结果　正常胃粘膜未见 p5 3蛋白表达。Hp阳性胃癌前阶段病变 p5 3蛋白表达阳性率显著高于正常胃粘膜及Hp阴性胃癌前阶段病变 ,其中Hp阳性肠上皮化生 p5 3蛋白表达阳性率显著高于Hp阴性相应病变组 ,低于Hp阳性异型增生组。Hp阳性胃癌前阶段病变Hp根除治疗后 ,其 p5 3蛋白表达阳性率显著降低。结论　Hp根除治疗后 ,胃癌前阶段病变p5 3蛋白表达阳性率明显降低 ;Hp感染可促进突变型 p5 3基因表达增强。