High JC virus load in gastric cancer and adjacent non-cancerous mucosa

The JC virus (JCV) infects a large proportion of the worldwide population and approximately 90% of adults are seropositive. Recent reports have described the possibility of its oncogenetic role in several malignancies. The aim of the present study was to assess the oncogenetic significance of JCV for gastric cancer. Twenty-two sample pairs of fresh tumor and adjacent non-cancerous tissue (ANCT) as well as 10 normal gastric mucosa specimens were investigated on the basis of nested polymerase chain reaction (PCR) followed by Southern blotting, DNA direct sequencing, real-time PCR, in situ PCR and immunohistochemistry. The T antigen sequence was detected in 86.4% of gastric cancers and ANCT, and in 100% of the normal mucosa samples, as for virus capsid protein, 54.1%, 68.1% and 70%, respectively. A generally low incidence was noted for agnoprotein. The JCV DNA load was approximately 10-fold higher in both gastric cancers and paired ANCT (4784 +/- 759 and 5394 +/- 1466 copies/microg DNA, respectively) than in normal gastric tissue (542.4 +/- 476.0 copies/microg DNA, P < 0.0001). In situ PCR revealed sporadic JCV genome-positive cancer cells and foveolar epithelial cells. T antigen protein expression assessed by immunohistochemistry was detected only in one case (1/22; 4.5%), probably because the half life of T antigen might be short. It was concluded that the gastric epithelium in most Japanese people is infected with JCV at a low rate but levels of infection are increased markedly in both cancer cells and ANCT, indicating that multiplication of JCV copies might be a risk factor and a background for gastric carcinogenesis.

Long-term remission of primary gastric T cell lymphoma associated with human T lymphotropic virus type 1: a report of two cases and review of the literature

Two cases of primary gastric T-cell lymphoma associated with human T lymphotropic virus type 1 (HTLV-1) are presented. Case 1 was a 54-year-old man who had multiple ulcerating tumors in the lower corpus and gastric antrum. Case 2, a 60-year-old man, showed a large ulcerating tumor in the upper corpus. Both patients were positive for serum anti-HTLV-1 antibody and for the monoclonal integration of HTLV-1 proviral DNA in the tumor cells by Southern blot analysis. The patients were thus diagnosed as having primary gastric T-cell lymphoma associated with HTLV-1 of stage II(1). Case 1 underwent total gastrectomy followed by chemotherapy, while Case 2 was treated by chemotherapy and radiotherapy. Both patients have been in complete remission for more than 4 years (96 months in Case 1 and 50 months in Case 2) after the treatments. Although primary gastric T-cell lymphomas associated with HTLV-1 is characterized by an extremely poor prognosis, the present cases suggest that in the early stage, long-term survival can possibly be achieved with appropriate treatments.

Establishment and characterization of an in vivo model for Epstein–Barr virus positive gastric carcinoma

Research regarding the role of the Epstein-Barr virus (EBV) in gastric carcinogenesis has been hampered by the absence of a suitable model system. SNU-719 is a gastric carcinoma cell line naturally infected with EBV. This cell line developed tumors in nude mice approximately 40-56 days after inoculation. SNU-719 also showed low serum dependency and anchorage independent growth in vitro. The developed tumors expressed EBERs, EBNA1, and LMP2A but not other EBV latent genes. Additionally, Qp was active and either mono- or bi-clonal EBV genome was observed in the tumor tissues. Because the developed tumors retained characteristics of EBV-associated gastric cancer, this cell line could serve as a useful in vivo system to investigate the tumorigenesis mechanism and treatment methods for this type of tumor.

Interplay between Helicobacter pylori and host gene polymorphisms in inducing oxidative DNA damage in the gastric mucosa

Infection by Helicobacter pylori is the most important risk factor for gastric cancer. However, only a small fraction of colonized individuals, representing at least half of the world's population, develop this malignancy. In order to shed light on host-microbial interactions, gastric mucosa biopsies were collected from 119 patients suffering from dyspeptic symptoms. 8-Hydroxy-2'-deoxyguanosine (8-oxo-dG) levels in the gastric mucosa were increased in carriers of H.pylori, detected either by cultural method or by polymerase chain reaction, and were further increased in subjects infected with strains positive for the cagA gene, encoding the cytotoxin-associated protein, cagA. Oxidative DNA damage was more pronounced in males, in older subjects, and in H.pylori-positive subjects suffering from gastric dysplasia. Moreover, 8-oxo-dG levels were significantly higher in a small subset of subjects having a homozygous variant allele of the 8-oxoguanosine-glycosylase 1 (OGG1) gene, encoding the enzyme removing 8-oxo-dG from DNA. Conversely, they were not significantly elevated in glutathione S-transferase M1 (GSTM1)-null subjects. Thus, both bacterial and host gene polymorphisms affect oxidative stress and DNA damage, which is believed to represent a key mechanism in the pathogenesis of gastric cancer. The interplay between bacterial and host gene polymorphisms may explain why gastric cancer only occurs in a small fraction of H.pylori-infected individuals.

Effect of Helicobacter pylori infection combined with CagA and pepsinogen status on gastric cancer development among Japanese men and women: a nested case-control study

BACKGROUND

Although accumulating evidence suggests that Helicobacter pylori plays a role in gastric carcinogenesis, the magnitude of the risk remains uncertain.

AIM

We aimed to estimate the magnitude of the risk of gastric cancer associated with H. pylori infection by a large case-control study nested within a prospective cohort. Possible effect modification by CagA status, and serum pepsinogen status, as a marker of atrophic gastritis, was also considered to see its effect on developing gastric cancer.

SUBJECTS AND METHODS

Subjects (n = 123,576) were followed up from 1990 to 2004; 511 gastric cancer cases matched to 511 controls were used in the analysis. Plasma immunoglobulin G antibody to H. pylori, CagA, and pepsinogen I and II were measured.

RESULTS

The adjusted odds ratio (95% confidence interval) of gastric cancer associated with H. pylori infection was 5.1 (3.2-8.0). Assuming all CagA-positive subjects are true H. pylori positives doubled this risk. Atrophic gastritis was also associated with an elevated risk of gastric cancer and the risk increased further with pepsinogen levels.

CONCLUSIONS

Subjects with pepsinogen levels indicative of severe atrophic gastritis may need careful examination regularly regardless of H. pylori infection. Those who have other pepsinogen levels but who are H. pylori seropositive are likely to benefit from H. pylori eradication therapy. Considering both the cost and the potential for misclassification that may occur using multiple serologic tests, caution is needed in interpreting or extrapolating these findings into a screening strategy.

Expression of viral microRNAs in Epstein-Barr virus-associated gastric carcinoma

Epstein-Barr virus (EBV) is associated with about 6 to 16% of gastric carcinoma cases worldwide. Expression of the EBV microRNAs (miRNAs) was observed in B cells and nasopharyngeal carcinoma cells infected with EBV. However, it is not clear if the EBV miRNAs are expressed in EBV-associated gastric carcinomas (EBVaGCs). We found that BART miRNAs but not BHRF1 miRNAs were expressed in EBV-infected gastric carcinoma cell lines and the tumor tissues from patients as well as the animal model. The expression of viral miRNAs in EBVaGCs suggests that these EBV miRNAs may play important roles in the tumorigenesis of EBVaGCs.

Environmental factors related to gastric cancer associated with Epstein-Barr virus in Colombia

Epstein-Barr virus (EBV)-encoded small RNA can be detected in about 1-17 % of gastric carcinomas. To elucidate lifestyles and other factors related to such an EBV-associated gastric carcinoma (EBV-GC), we conducted a case-control study in Cali, Colombia. The study subjects were 368 patients with gastric carcinoma newly diagnosed during the period between September 2000 and June 2003, including 42 EBV-GC cases. We obtained information on lifestyles, dietary habits, and occupational exposure by a questionnaire. The frequency of EBV-GC was related to birth order of patients (P for trend =0.025). More precisely, EBV-GC was much less frequent among the patients who were the eldest child in a family (P=0.007). Those findings were contrary to what was reported by the study conducted in Japan, where EBV-GC was more frequently observed among eldest brothers/sisters. A possible explanation for the apparently conflicting results is that EBV-GC risk is related to the age at first EBV infection but its relationship is not monotonic. In addition to the relationship with birth order, the present study showed that high salt intake and metal dust exposure may be related to EBV-GC as reported by the Japanese study although these associations observed in the present study were not statistically significant. No significant association was observed in other factors, including dietary habits. Further studies seem warranted to elucidate the difference between Japan and Colombia with respect to the environmental factors related to EBV-GC cases.

Oncogenic T-antigen of JC virus is present frequently in human gastric cancers

BACKGROUND

JC virus (JCV) is a polyomavirus that commonly infects humans and is the causative agent of progressive multifocal leukoencephalopathy in immune-compromised patients. An association between JCV and human cancers long has been suspected, because this virus induces brain tumors in several animal models. The oncogenic potential of JCV is mediated by a transforming protein, the T-antigen (T-Ag), which is a multifunctional protein that transforms cells through interactions with various growth-regulatory genes, including p53 and pRb, and by stabilizing beta-catenin. Previously, the laboratory at the authors' institution demonstrated that JCV is present frequently in the human gastrointestinal tract and may play a role in colorectal carcinogenesis. However, to date, no studies have determined whether JCV sequences are present specifically in gastric cancers. The current study was designed to investigate whether JCV sequences and expression are found in human gastric cancers.

METHODS

DNA was extracted from 23 paraffin embedded and 14 frozen gastric cancer specimens. For the detection of JCV gene sequences, polymerase chain reaction amplifications were performed using gene-specific primers for T-Ag, VP-1 (a JCV capsid gene), and the viral regulatory region (or transcriptional control region). Immunohistochemical staining was performed with an anti-T-Ag monoclonal antibody to detect protein expression.

RESULTS

Twenty-one of 37 gastric cancers (57%) harbored JCV T-Ag sequences, and 13 of 37 gastric cancers (30%) contained VP-1 sequences. T-Ag sequences also were found in adjacent nonneoplastic mucosa. In addition, JCV regulatory region sequences were present frequently in gastric cancers and adjacent nonneoplastic mucosa. T-Ag protein expression was found in 9 of 23 gastric cancers (39%), whereas no expression was observed in any of the nonneoplastic tissues.

CONCLUSIONS

To the authors' knowledge, this is the first demonstration of the presence of JCV T-Ag expression in human gastric cancers. These findings suggest a possible role for this polyomavirus in gastric carcinogenesis.

Differential expression of apoptosis related proteins and nitric oxide synthases in Epstein Barr associated gastric carcinomas

AIM: To determine the incidence of Epstein Barr virus associated gastric carcinoma (GC) in Brazil and compare the expressions of apoptosis related proteins and nitric oxide synthases between EBV positive and negative gastric carcinoma.

METHODS: In situ hybridization of EBV-encoded small RNA-1 (EBER-1) and PCR was performed to identify the presence of EBV in GCs. Immunohistochemistry was used to identify expressions of bcl-2, bcl-xl, bak, bax, p53, NOS-1, NOS-2, and NOS-3 proteins in 25 EBV positive GCs and in 103 EBV negative GCS.

RESULTS: 12% of the cases of GC (25/208) showed EBER-1 and EBNA-1 expression. The cases were preferentially of diffuse type with intense lymphoid infiltrate in the stroma. EBV associated GCs showed higher expression of bcl-2 protein and lower expression of bak protein than in EBV negative GCs. Indeed, expressions of NOS-1 and NOS-3 were frequently observed in EBV associated GCs.

CONCLUSION: Our data suggest that EBV infection may protect tumor cells from apoptosis, giving them the capacity for permanent cell cycling and proliferation. In addition, EBV positive GCs show high expression of constitutive NOS that could influence tumor progression and aggressiveness.

Phenotype analysis by MUC2, MUC5AC, MUC6, and CD10 expression in Epstein-Barr virus-associated gastric carcinoma

BACKGROUND

Gastric marker mucins (MUC5AC and MUC6) and intestinal marker molecules (MUC2 and CD10) have been used to determine the cell lineage of epithelial cell of gastric carcinoma (GC).

METHODS

To clarify the characteristics of Epstein-Barr virus (EBV)-associated GC, 18 cases were immunohistochemically evaluated along with 56 cases of EBV-negative GC.

RESULTS

MUC2 expression was lower in EBV-associated GC: immunostaining grades 0, 1, 2, 3, and 4 were observed in 10, 6, 1, 1, and 0 cases of EBV-associated GC, respectively, and in 18, 11, 15, 6, and 6 cases of EBV-negative GC, respectively (P = 0.013). CD10 positivity (grades 2-4) in EBV-associated GC was 6%, significantly lower than in EBV-negative GC (34%) (P = 0.030). When phenotypes of GC were categorized by the combined positivities of gastric markers (either MUC5AC or MUC6) and intestinal markers (either MUC2 or CD10), EBV-associated GC included primarily null (44%) and gastric (39%) types, but EBV-negative GC comprised null (7%), gastric (30%), intestinal (27%), and mixed (36%) types. The age of patients with gastric types was significantly younger for both EBV-associated GC and EBV-negative GC cases.

CONCLUSIONS

Neoplastic epithelial cells of EBV-associated GC did not express MUC2 or CD10, and most of them were categorized as null or gastric types. EBV infection may occur in the epithelial cells of null or gastric phenotypes, which may be devoid of transdifferentiation potential toward intestinal phenotypes.

CpG island methylation status in gastric carcinoma with and without infection of Epstein-Barr virus

PURPOSE

EBV-associated gastric carcinoma shows global CpG island methylation of the promoter region of various cancer-related genes. To further clarify the significance of CpG island methylator phenotype (CIMP) status in gastric carcinoma, we investigated methylation profile and clinicopathologic features including overall survival in four subgroups defined by EBV infection and CIMP status: EBV-associated gastric carcinoma and EBV-negative/CIMP-high (H), EBV-intermediate (I), and EBV-negative (N) gastric carcinoma.

EXPERIMENTAL DESIGN

Methylation-specific PCR was applied to 106 gastric carcinoma cases. CIMP-N, CIMP-I, and CIMP-H status was determined by the number (0, 1-3, and 4-5, respectively) of methylated marker genes (LOX, HRASLS, FLNc, HAND1, and TM), that were newly identified as highly methylated in gastric cancer cell lines. The methylation status of 10 other cancer-related genes (p14, p15, p16, p73, TIMP-3, E-cadherin, DAPK, GSTP1, hMLH1, and MGMT) was also evaluated.

RESULTS

Nearly all (14 of 15) of EBV-associated gastric carcinoma exhibited CIMP-H, constituting a homogenous group (14%). EBV-negative gastric carcinoma consisted of CIMP-H (24%), CIMP-I (38%), and CIMP-N (24%). EBV-associated gastric carcinoma showed significantly higher frequencies of methylation of cancer-related genes (mean number +/- SD = 6.9 +/- 1.5) even if compared with EBV-negative/CIMP-H gastric carcinoma (3.5 +/- 1.8). Among EBV-negative gastric carcinoma subgroups, CIMP-H gastric carcinoma showed comparatively higher frequency of methylation than CIMP-I or CIMP-N, especially of p16 and hMLH1. CIMP-N gastric carcinoma predominantly consisted of advanced carcinoma with significantly higher frequency of lymph node metastasis. The prognosis of the patients of CIMP-N was significantly worse compared with other groups overall by univariate analysis (P = 0.0313).

CONCLUSION

The methylation profile of five representative genes is useful to stratify gastric carcinomas into biologically different subgroups. EBV-associated gastric carcinoma showed global CpG island methylation, comprising a pathogenetically distinct subgroup in CIMP-H gastric carcinoma.

Characterization of immune responses in gastric cancer patients: a possible impact of H. pylori to polarize a tumor-specific type 1 response?

Recently, we were able to show that Helicobacter pylori-positive gastric cancer (GC) patients have a significantly better survival after the complete resection of their tumor compared to H. pylori-negative GC patients. H. pylori is known to polarize an immune response towards a type 1 cytokine profile and tumor-specific type 1 cytokine responses are associated with protection from tumor challenge and T-cell-mediated tumor regression. Therefore, we hypothesized that the improved survival in H. pylori-positive patients may be secondary to the induction of a GC-specific type 1 T cell response. To characterize the anti-tumor immune response in GC patients we analyzed tumor-infiltrating lymphocytes (TIL) isolated from primary tumors. The CD3+ T cell population contained 50% CD4+ (range 0.4-81%) and 39% CD8+ cells (range 22-53%). The number of B cells (CD19+, P = 0.03) was significantly increased and the number of T cells (CD3+, P = 0.02) significantly decreased in intestinal compared to diffuse type of tumors. Four tumor cell lines were established from primary GCs and three from lymph node metastases. T cell cultures were established from isolated TIL from four H. pylori-positive and one H. pylori-negative GC patients and tested for tumor-specific cytokine secretion. Eight of ten T cell cultures derived from H. pylori-positive patients secreted both IFN-gamma and IL-5 after restimulation with autologous tumor cells. The only tumor-specific TIL line expressing a dominant IL-5 response was derived from an H. pylori-negative patient.

No association of primary adenocarcinomas of the small bowel with Epstein-Barr virus infection

Epstein-Barr Virus (EBV) infection is considered to play an etiologic role in human malignancies, including a subset of gastric and cardiac cancers. Adenocarcinomas of the small bowel comprise a very rare entity, with little knowledge about molecular properties and etiological aspects. We have investigated the prevalence of EBER expression (EBV-encoded small RNAs) in a series of small bowel adenocarcinomas (n=56) utilizing RNA in situ hybridization (EBER-RISH). The patients had undergone primary surgical resection at either the Technical University of Munich or at the University of Graz. A surgical series of 82 primary resected gastric (n=36) or cardiac (n=46) adenocarcinomas (TU Munich) was used as control group. None of the 56 small bowel carcinomas exhibited EBER expression whereas in the control group the rate of EBER expression accounted for 4.4% in the group of cardia carcinomas and 8.6% in the group of gastric cancers. These results indicate that EBV infection plays no etiologic role in primary small bowel adenocarcinomas.

Complete regression of low-grade mucosa-associated lymphoid tissue (MALT) lymphoma in the gastric stump after eradication of Helicobacter pylori

Recent studies have suggested that Helicobacter pylori (H. pylori)-associated gastritis may play an important role in the pathogenesis of primary gastric lymphoma. Recently, triple therapy using proton pump inhibitor, amoxicillin, and clarithromycin, has been established for the eradication therapy of H. pylori infection, and is also recommended for the treatment of the superficial type of low-grade gastric MALT (mucosa-associated lymphoid tissue ) lymphoma. MALT lymphoma of the gastric stump is rare, and total resection or chemotherapy for MALT lymphoma of the gastric stump has been previously reported. Therefore, there is no evidence that eradication therapy is effective for low-grade MALT lymphoma of the gastric stump. Our case illustrates the remarkable efficacy of eradication of H. pylori for low-grade MALT lymphoma of the gastric stump without other modalities such as surgery and systemic chemotherapy.

Down-regulation of locus-specific human lymphocyte antigen class I expression in Epstein-Barr virus-associated gastric cancer: implication for viral-induced immune evasion

BACKGROUND

To understand whether the association between Epstein-Barr Virus (EBV) and gastric cancer (GC) has any role in loss of surface expression of human lymphocyte antigen (HLA) class I, the authors analyzed locus-specific transcriptional expression of HLA-A, HLA-B, HLA-C, and HLA-E along with other HLA-associated molecules (beta2-microglobulin [beta2M], cellular latent membrane protein [LMP], and transporter associated with antigen presentation [TAP]) in EBV-associated, primary GC (EBVaGC) and EBV-negative GC (EBVnGC) tissues.

METHODS

Approximately 20 EBVaGC tissues and 40 EBVnGC tissues and their corresponding normal tissues were used in the study. The presence of EBV in GC was established by EBV-encoded small RNA in situ hybridization analysis and BamHI W polymerase chain reaction (PCR) analysis. Transcriptional expression of viral LMP2A and several HLA class I genes were analyzed by reverse transcriptase (RT)-PCR. Surface expression levels of HLA class I proteins in cancer samples along with their normal counterparts also were quantified by flow cytometry.

RESULTS

The RT-PCR data suggested selective down-regulation of the HLA-A/HLA-B locus along with over-expression of HLA-E transcripts in EBVaGC (P < .05). This was confirmed further by the flow-cytometric studies using antibodies to HLA-ABC and HLA-E. Among the accessory molecules, LMP7 transcript was down-regulated in a number of EBVaGC tissues compared with EBVnGC.

CONCLUSIONS

The current results suggested that the establishment of EBV latent infection in gastric tissues allows malignant cells to avoid the immune surveillance of both cytotoxic T-lymphocytes and natural killer cells by regulating the differential expression of HLA class I molecules.

Lytic induction and apoptosis of Epstein-Barr virus-associated gastric cancer cell line with epigenetic modifiers and ganciclovir

Epstein-Barr virus (EBV) is an oncogenic herpes virus. EBV gene transcription is regulated by an epigenetic mechanism to establish a persistent infection and to evade the host immune system. We found that low concentrations of epigenetic modifying agents, 5-aza-2'-deoxycytidine (5-aza-CdR) or trichostatin A (TSA), induced the expression of BMRF1, BZLF1, and BRLF1 genes, which are found in the lytic form of the virus, in an EBV-positive gastric cancer cell line. This effect did not involve PI3 kinase, MAP/ERK kinase, protein kinase C delta, or p38 MAPK signaling pathway. The cytotoxic effect of ganciclovir (GCV) was enhanced after the lytic induction by epigenetic modifiers, and the combination of GCV and epigenetic modifiers induced apoptosis, which is dependent on caspases. In conclusion, the combination of GCV with 5-aza-CdR or TSA might be a useful therapeutic strategy for EBV-induced human gastric cancer.

Genetic, epigenetic, and clinicopathologic features of gastric carcinomas with the CpG island methylator phenotype and an association with Epstein-Barr virus

BACKGROUND

The CpG island methylator phenotype (CIMP), which is characterized by simultaneous methylation of the CpG islands of multiple genes, has been recognized as one of the important mechanisms in gastrointestinal carcinogenesis.

METHODS

Methylation of the 5 methylated-in-tumors (MINT) loci and 12 tumor-related genes in 78 primary gastric carcinomas was examined using combined bisulfite-restriction analysis. Epstein-Barr virus (EBV)-associated gastric tumors were detected using real-time polymerase chain reaction analysis followed by an evaluation of the correlations between CIMP status, EBV-association, and genetic alteration of p53 and K-ras. The authors compared the clinicopathologic features of gastric carcinomas that had high CIMP methylation (CIMP-H) with tumors that had low CIMP methylation (CIMP-L) or negative CIMP methylation (CIMP-N).

RESULTS

The methylation profiles of 12 genes showed nonrandom methylation, supporting the presence of CIMP in gastric carcinoma. No p53 mutations were detected among CIMP-H tumors, and no EBV association was detected in tumors that showed mutation of p53 and K-ras. In a multiple logistic regression model with CIMP-H as the dependent variable, proximal location (P = .011), diffuse type (P = .019), and less advanced pathologic TNM status (P = .043) contributed significantly to CIMP-H. Patients who had CIMP-N gastric tumors had a significantly worse survival than patients who had CIMP-H tumors (P = .004) or CIMP-L tumors (P = .012). EBV-associated tumors were associated strongly with CIMP-H, hypermethylation of tumor-related genes, and no p53 or K-ras mutation.

CONCLUSIONS

CIMP status appeared to be associated with distinct genetic, epigenetic, and clinicopathologic features in gastric carcinomas. The finding that gastric carcinomas arose through different molecular pathways may affect not only tumor characteristics but also patient prognosis.

Evolution of human herpesvirus type 8-associated gastric Kaposi's sarcoma following corticosteroid treatment for asthma

The association of gastric Kaposi's sarcoma (KS) with human herpesvirus type 8 (HHV-8) may be found in immunosuppressed patients such as those with AIDS or transplant recipients. A 64-year-old man with a 2-year history of corticosteroid treatment was admitted due to the impression of chronic obstructive pulmonary disease with secondary infection. Abdominal fullness and tarry stool led to the performance of panendoscopy, which revealed two hypertrophic gastric mucosal lesions. These lesions had transformed into a large polyp 2 months later. KS was not diagnosed until a third endoscopic biopsy was performed. The polyp further transformed into a flattened, elongated tumor within a month. The patient died from acute cardiopulmonary insufficiency 4 days after radical gastrectomy. Polymerase chain reaction study identified HHV-8 in all biopsied specimens and resected tumor lesions. Immunostaining further demonstrated the virus in the tumor cells. Both of these methods seemed more sensitive in diagnosing KS than histologic examination of small biopsied specimens. This case suggests the existence of a relationship between gastric KS and HHV-8 infection.

H. pylori genotypes and cytokine gene polymorphisms influence the development of gastric intestinal metaplasia in a Chinese population

BACKGROUND

Cytokine gene polymorphisms and Helicobacter pylori (HP) genotypes have been linked to gastric cancer development in Western countries. We determined the role of host cytokine polymorphisms and bacterial virulent factors in the development of gastric intestinal metaplasia (IM) in a Chinese population with a high background gastric cancer incidence.

METHODS

Three hundred two HP-infected noncancer individuals living in Shandong province of China with available DNA were studied. Polymorphisms in different loci of inflammatory cytokines Interleukin IL-1B, IL-1RN, Interleukin IL-8, IL-10, IL-18, tumor necrosis factor-A (TNF-A), and Transforming growth factor (TGF-B), were determined by allelic discriminating TaqMan polymerase chain reaction (PCR) or a variable number of tandem repeats. Presence of HP virulence factors in cagA, vacA, and babA2 were determined by PCR. Baseline gastric biopsies were assessed for the presence of IM.

RESULTS

Among HP-infected subjects, carriers of the IL-1B-511 T allele were associated with a modestly greater prevalence of IM (adjusted OR 2.0, 95% CI 1.0-3.7). There was no association between the presence of IM and polymorphisms in other inflammatory cytokines. Although most subjects from this region harbored the virulent HP strains, carriage of the vacA m1 strain was associated with a significantly higher prevalence of IM (adjusted OR 1.8, 1.1-3.0). The presence of both host (IL-1B-511 T) and HP (vacA m1) genotypes further increased the risk of IM (OR 5.7, 2.0-16) when compared with individuals with the low-risk genotype.

CONCLUSION

The carriage of proinflammatory IL-1B-511 and HP vacA m1 genotypes was associated with the development of gastric IM in the Chinese.

Association of a distinctive strain of Epstein-Barr virus with gastric cancer

Epstein-Barr virus (EBV) has been linked to gastric carcinoma (GC) with worldwide geographical variations attributable to types and variants of EBV. Here, we compare EBV strains between EBVaGC and healthy donors in Latin America, a high frequency area for EBVaGC. Tumor samples from 73 EBVaGC cases and throat washings from 329 healthy adults were examined for types 1 and 2 EBV and polymorphism at BamHI-F and BamHI-W1/I1 boundary regions and XhoI restriction site in LMP1 gene. Type 1 and prototype F of BamHI- F polymorphism accounted 59 (81%) and 69 (95%) of EBVaGC cases and 257 (78%) and 267 (81%) of healthy donors, respectively. Types I and "i" of BamHI W1/I1 polymorphism accounted 2 (3%) and 62 (85%) of EBVaGC and 85 (26%) and 170 (52%) of healthy donors, respectively (p<0.001). XhoI+ and - polymorphism accounted 60 (82%) and 4 (5%) of EBVaGC and 142 (43%) and 92 (28%) of healthy donors, respectively (p<0.001). Cosegregation analysis demonstrated that most of the 62 type "i" EBVaGC cases harbor XhoI+ strain (81%). However, among 143 type "i" healthy adults, both XhoI polymorphism were present in relatively similar frequencies (XhoI+ 58% and XhoI- 42%) (OR 9.0; 95% CI 1.2-69). Our findings are against to the proposed hypothesis that EBV strains are geographically but not disease-restricted. We conclude that most of the EBVaGC cases harbor a distinctive EBV strain (type "i"/XhoI +), but in healthy donors, this strain was as common as other strains. This finding is contrary to the proposed hypothesis that EBV strains are geographically but not disease-restricted and identified a healthy population group that share the same strain that predominate in EBVaGC cases.

Correlation of Epstein-Barr virus and its encoded proteins with Helicobacter pylori and expression of c-met and c-myc in gastric carcinoma

AIM

To investigate the interrelationship of Epstein-Barr virus (EBV) and EBV- encoded proteins with Helicobacter pylori (H pylori) infection and the expression of c-met and c-myc oncogene proteins in gastric carcinoma, and to explore their role in gastric carcinogenesis.

METHODS

One hundred and eighty-five gastric carcinoma tissues were detected by polymerase chain reaction (PCR)-Southern blot for EBV genome and in situ hybridization (ISH) for EBV-encoded small RNA 1 (EBER1). Gastric carcinoma with positive EBER1 signals was confirmed EBV-associated gastric carcinoma (EBVaGC). The status of H pylori infection in 185 gastric carcinomas was assessed by rapid urease test and PCR. The samples with positive PCR and urease test were defined as H pylori infection. The expression of c-met and c-myc oncogene proteins in tissues of EBVaGC and matched EBV-negative gastric carcinoma (EBVnGC) were examined by immunohistochemistry. RT-PCR and Southern hybridization were used to detect the expression of nuclear antigens (EBNAs) 1 and 2, latent membrane protein (LMP) 1, early genes BARF1 and BHRF1 in EBVaGC cases.

RESULTS

The positive rate of H pylori and EBV in 185 gastric carcinomas was 59.45% (110/185) and 7.03% (13/185) respectively. No difference was found in sex, age, pathological differentiation, clinical stages and lymph node metastasis between H pylori-positive and H pylori-negative gastric carcinomas. However, the positive rate of H pylori infection in the antrum gastric carcinomas was higher than that of cardia and body gastric carcinomas. In our series, age, pathological differentiation, clinical stages, lymph node metastasis and location of cancer were not different between EBVnGC and EBVaGC, while the positive rate of EBV in male patients was significantly higher than that of female patients. The positivity of H pylori in EBV-associated and EBV-negative gastric carcinomas was 46.15% (6/13) and 81.40%(104/172) respectively. There was no significant correlation between EBV and H pylori infection. The c-met overexpression was significantly higher in the EBVaGC group than in the EBVnGC group. However, c-met and c-myc expression did not show significant difference between the two groups. Transcripts of EBNA1 were detected in all 13 EBVaGCs, while both EBNA2 and LMP1 mRNA were not detected. Six of the 13 cases exhibited BARF1 transcripts and 2 exhibited BHRF1 transcripts.

CONCLUSION

The positivity of H pylori in EBVnGCs is higher than that of EBVaGCs, but no significant correlation is found between EBV infection and H pylori infection. H pylori-positive gastric carcinoma is predominant in antrum location, while EBVaGC has a tendency of predominance in cardia/body location. EBV infection is associated with c-met abnormal expression but not with c-myc protein in EBVaGC. c-met overexpression is not induced by LMP1. BARF1 and BHRF1 may play important roles in the tumorigenesis of EBVaGC through different pathways.

Helicobacter pylori-Induced invasion and angiogenesis of gastric cells is mediated by cyclooxygenase-2 induction through TLR2/TLR9 and promoter regulation

Cyclooxygenase-2 (COX-2) plays a crucial role in Helicobacter pylori-associated gastric cancer. In this study, we report that H. pylori-induced COX-2 expression enhances the cancer cell invasion and angiogenesis via TLR2 and TLR9, which can be attenuated by the specific COX-2 inhibitor NS398 or celecoxib. The cAMP response element (CRE) and AP1 sites, but not kappaB on the COX-2 promoter, are involved in MAPKs-regulated COX-2 expression. Differential bindings of the CREB-1, ATF-2, c-jun to the CRE site, and the c-fos, c-jun, ATF-2 to the AP1 site are demonstrated by DNA affinity protein-binding, supershift, and chromatin immunoprecipitation assays. Activations of these transcription factors were attenuated by different MAPKs inhibitors. The mutants of TLR2, TLR9, or MAPKs inhibited H. pylori-induced COX-2 promoter, CRE, and AP-1 activities. MAPKs inhibitors attenuated the H. pylori-induced COX-2 mRNA and protein expressions. These results indicate that H. pylori acts through TLR2 and TLR9 to activate MAPKs, especially p38, and their downstream transcription factors (CREB-1, ATF-2, c-jun, and c-fos), resulting in the activations of CRE and AP-1 on the COX-2 promoter. These intracellular networks drive the COX-2-dependent PGE2 release and contribute to cell invasion and angiogenesis.

[Significance of the expression of P53 protein and P21WAF1 protein in the gastric carcinoma tissues associated with Epstein-Barr virus (EBV) infections]

BACKGROUND

To study the difference in gene expression between the EBV associated gastric carcinoma (EBVaGC) tissues. To explore the mechanism of gastric carcinoma pathogenesis initiated by EBV.

METHODS

In situ hybridization was used to study the frequencies of EBV small RNA expression in 155 cases of gastric carcinoma tissues. The expression levels of P53 protein and P21WAF1 protein were detected by immunohistochemistry in all gastric carcinoma tissues.

RESULTS

The expression of EBV small RNA was positive in 10 out of 155 cases (6.45%). The expression of P53 protein was weakly positive in 4 of the 10 cases. The expression level of P53 protein in EBVaGC was much lower than that in EBVnGC and was weakly positive in 30 of 145 cases with EBVnGC). P21WAF1 expression was detected in 7 of 10 cases with EBVaGC, but in 55 out of 145 cases with EBVaGC, P21WAF1 expression in EBVaGC was much higher than that in EBVnGC.

CONCLUSION

There seems existing a special mechanism of pathogenesis in EBVaGC. In which P53 gene mutation may not play an important role.

CDH1 Gene Promoter Hypermethylation in Gastric Cancer

Hypermethylation of the CDH1 promoter region seems to be the most common epigenetic mechanism in this gene silencing in gastric cancer. In this study, CDH1 promoter hypermethylation was observed in 54.8% (46/84) of the analyzed sporadic gastric carcinomas. We introduce a new relation: clustering of Goseki grading into 3 grade was determined by CDH1 promoter hypermethylation. The percentage of methylation in Goseki III cancers was significantly higher (83%) when compared with other grades; the lowest proportion was detected in IV (36%) and II (38%) groups, whereas grade I demonstrated typical percentage of promoter hypermethylation. A novel polymorphism R732R in exon 14 of the CDH1 gene was detected by mutational analysis. Additionally, all cases with the MSI-high phenotype revealed CDH1 promoter hypermethylation. In MSI-low and MSS gastric cancers, this percentage was lower, reaching 71% and 41%, respectively. Moreover, the methylation status was correlated with the LOH phenotype. We detected CDH1 promoter hypermethylation in all EBV-positive gastric cancers (5/5), whereas methylation in the EBV-negative group occurred in 58% of cases. We also report that "methylated" tumors were slightly larger than "nonmethylated," whereas the second group revealed a higher probability of longer patient survival, though these relationships were not statistically significant. These results suggest that downregulation of E-cadherin, caused by promoter hypermethylation, in sporadic gastric carcinomas may be associated with a worse prognosis and specific tumor phenotype.

P16 protein abnormality in Epstein-Barr virus-associated gastric carcinomas

BACKGROUND

The Epstein-Barr virus (EBV) has been detected in lymphoepithelioma of the nasopharynx and lymphoepithelioma-like carcinomas in various organs. Ten percent of gastric carcinomas, including lymphepithelioma-like carcinoma and adenocarcinoma, are associated with EBV infection. The p16 protein is a cyclin-dependent kinase (CDK) inhibitor that decelerates the cell cycle, inactivating the CDKs that phosphorylate retinoblastoma (Rb) protein.

MATERIALS AND METHODS

To clarify the relationship between p16 overexpression and EBV-associated gastric carcinomas, immunohistochemical analysis of p16 and detection of EBV by in situ hybridization were performed on 238 formalin-fixed and paraffin-embedded samples of gastric carcinomas.

RESULTS

The non-expression of p16 protein in EBV-positive and -negative carcinoma was 81.5% (53 out of 65 samples) and 26.6% (46 out of 173 samples), respectively (p < 0.001).

CONCLUSION

We suggest that the carcinogenesis of EBV-associated gastric cancers may be closely associated with a p16 abnormality.