Interrelationship between Epstein-Barr virus infection in gastric carcinomas and the expression of apoptosis-associated proteins

Estimating the Global Burden of Epstein-Barr Virus-Associated Gastric Cancer: A Systematic Review and Meta-Analysis

BACKGROUND & AIMS

Evidence suggests that a fraction of new gastric cancer cases may be etiologically associated with Epstein-Barr virus (EBV), a known carcinogenic agent. We aimed to systematically explore the proportion of EBV-positive gastric cancer.

METHODS

We did a systematic review (PROSPERO CRD42020164473) from January 1990 to August 2021. For each country and geographical region with available data, pooled prevalence and corresponding 95% confidence intervals (CIs) of EBV in gastric tumors were calculated for 3 subtypes of gastric adenocarcinoma (conventional adenocarcinoma, lymphoepithelioma-like gastric carcinoma, and remnant/stump carcinoma). For conventional adenocarcinoma, prevalence ratios (PRs) were presented for sex, Lauren's classification, gastric cancer stage, and anatomical location of the stomach.

RESULTS

In 220 eligible studies including over 68,000 cases of conventional gastric adenocarcinoma, EBV prevalence in tumor cells was 7.5% (95% CI, 6.9%-8.1%) and was higher in men compared with women (PR, 2.1; 95% CI, 1.9-2.4), in diffuse type compared with intestinal type (PR, 1.3; 95% CI, 1.1-1.5), and in the proximal region compared with the distal region (PR, 2.5; 95% CI, 2.0-3.1). There was no difference in EBV prevalence by gastric cancer stage. EBV prevalence was 75.9% (95% CI, 62.8%-85.5%) among lymphoepithelioma-like gastric carcinoma and 26.3% (95% CI, 22.2%-32.0%) among remnant or stump carcinoma.

CONCLUSIONS

Assuming a causal association between EBV and gastric cancer, our findings, when applied to the GLOBOCAN 2020 gastric cancer incidence, suggest that primary prevention such as the development of an effective EBV vaccine might prevent 81,000 EBV-associated gastric cancer cases worldwide annually.

Detection of Epstein-Barr virus in gastric adenocarcinoma: qPCR and FISH comparison

EBV-associated gastric cancer accounts for about 10% of all gastric carcinomas worldwide. We aimed to verify the prevalence of EBV in gastric adenocarcinoma samples using FISH and qPCR and comparing the results obtained by both techniques. Gastric cancer samples from 191 cases were analyzed. The FISH assay was performed to detect small EBV RNAs (EBER1) and qPCR was performed to detect the EBV-EBNA-1 gene region. Cohen's kappa index and the chi-square test were used to compare the methodologies and investigate correlations with the clinical-pathological data of the gastric adenocarcinoma patients. Most of the patients were men, and the average age was 60 years. The intestinal subtype cancer presented more aggressive stages with 90% of patients having a reactive FISH for EBV (EBV+), although the virus infection frequency in epithelial gastric tissue was only 1%. No positive association with clinicopathological features and EBV+ was found by FISH. Using qPCR analysis, the percentage of positive samples was lower (52.4%), and a positive association was found in samples from older patients (> 60 years). Interestingly, 71 qPCR-negative cases were detected by FISH in the presence of non-epithelial cells and in 10 qPCR-positive cases with no evidence of EBV according to FISH. The concordance between the two techniques was low, with only 57.6%. FISH is more informative for associating the gastric carcinoma with EBV positivity in tumor/epithelial cells; however, qPCR can provide relevant information regarding the progression and characteristics of neoplasia.

Metabolic Control by DNA Tumor Virus-Encoded Proteins

Viruses co-opt a multitude of host cell metabolic processes in order to meet the energy and substrate requirements for successful viral replication. However, due to their limited coding capacity, viruses must enact most, if not all, of these metabolic changes by influencing the function of available host cell regulatory proteins. Typically, certain viral proteins, some of which can function as viral oncoproteins, interact with these cellular regulatory proteins directly in order to effect changes in downstream metabolic pathways. This review highlights recent research into how four different DNA tumor viruses, namely human adenovirus, human papillomavirus, Epstein-Barr virus and Kaposi's associated-sarcoma herpesvirus, can influence host cell metabolism through their interactions with either MYC, p53 or the pRb/E2F complex. Interestingly, some of these host cell regulators can be activated or inhibited by the same virus, depending on which viral oncoprotein is interacting with the regulatory protein. This review highlights how MYC, p53 and pRb/E2F regulate host cell metabolism, followed by an outline of how each of these DNA tumor viruses control their activities. Understanding how DNA tumor viruses regulate metabolism through viral oncoproteins could assist in the discovery or repurposing of metabolic inhibitors for antiviral therapy or treatment of virus-dependent cancers.

Association between Epstein-Barr virus infection and gastric cancer: a systematic review and meta-analysis

BACKGROUND

Numerous studies conducted over the past 30 years have pointed to the presence of Epstein-Barr virus (EBV) in gastric cancer samples. This study was aimed to provide a meta-analytic review of the prevalence of EBV in gastric cancer patients, and to clarify the relationship between EBV infection and gastric cancer.

METHODS

A literature search was performed electronically using online databases for English language publications until July 1, 2019. The pooled EBV prevalence and 95% confidence intervals (CIs) were estimated using a random-effects model. To determine the association between EBV and gastric cancer, pooled odds ratio (OR) and its 95% CI were computed for case-control studies. Two separate analyses were performed on data from case-control studies with matched and non-match pairs designs to calculate the pooled estimates of ORs.

RESULTS

The pooled prevalence of EBV in 20,361 gastric cancer patients was 8.77% (95% CI: 7.73-9.92%; I² = 83.2%). There were 20 studies with matched pairs design, including tumor and tumor-adjacent normal tissue pairs from 4116 gastric cancer patients. The pooled ORs were 18.56 (95% CI: 15.68-21.97; I² = 55.4%) for studies with matched pairs design and 3.31 (95% CI: 0.95-11.54; I² = 55.0%) for studies with non-matched pairs design. The proportion of EBV-associated gastric cancer among male cases was significantly higher than among female cases (10.83%, vs. 5.72%) (P < 0.0001). However, the pooled OR estimate for EBV-associated gastric cancer was significantly higher among females (21.47; 95% CI: 15.55-29.63; I² = 0%) than in males (14.07; 95% CI: 10.46-18.93; I² = 49.0%) (P = 0.06). EBV was more prevalent in the cardia (12.47%) and the body (11.68%) compared to the antrum (6.29%) (P = 0.0002).

CONCLUSIONS

EBV infection is associated with more than 18 times increase the risk of gastric cancer. Although the prevalence of EBV was higher in male patients than in female patients with gastric cancer, women are more likely than men to develop EBV-associated gastric cancer. Our findings showed that using tumor-adjacent normal tissues as the control group provides more robust and accurate results regarding the relationship between EBV infection and gastric cancer.

Chromosome 8q as the most frequent target for amplification in early gastric carcinoma

Early gastric carcinoma (GC) is considered to be a curable cancer, as it progresses to the advanced stage following varying durations. Understanding the early stage of GC may provide an insight into its pathogenesis and contribute to reducing the mortality rate of this disease. To investigate the genomic aberrations associated with 22 cases of early GC, high-density microarray comparative genomic hybridization was performed in the present study. The most notable finding was copy number gains (log₂ ratio >0.25) on the long arm of chromosome 8, which occurred in 77.3% (17/22) of GC cases, and the delineated minimal common region was 8q22.1-q24.3. More specifically, two amplified (log₂ ratio >1) loci in the 8q22.1-q24.3 region were detected in 18.2% (4/22) of GC cases. The first loci covered a region of 102.4–107.9 kb, mapping on 8q22.3-q23.1, and comprised the transcription factor CP2-like 3 gene. The second loci, spanning 128.7–145.7 kb on 8q24.21-q24.3, comprised the representative oncogene of myelocytomatosis. Furthermore, the following possible target genes that were not previously considered to play a pathogenic role in GC were identified: Plasmacytoma variant translocation 1, cysteine/histidine rich 1, kinesin family member C2, forkhead box H1, protein phosphatase 1 regulatory subunit 16A, glutamic-pyruvate transaminase, LOC113655 and RecQ protein-like 4. In the present study, previous findings showing that 8q mutations accumulate early during the multistage pathogenesis of GC were confirmed and expanded upon. The confirmation of previously reported 8q gains and the identification of novel target genes at 8q22.1-q24.3 amplified chromosomal sites should aid in improving our understanding of the molecular mechanisms underlying the tumorigenesis of early GC.

Expression of c-myc and PCNA in Epstein-Barr virus-associated gastric carcinoma

The aim of this study was to detect the expression of proliferatng cell nuclear antigen (PCNA) and c-myc in Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC) and EBV-negative gastric carcinoma (EBVnGC), as well as the expression of EBV-encoded proteins in EBVaGC and their effect on carcinogenesis and the development of gastric cancer. The PCNA and c-myc protein levels were assessed by immunohistochemistry in 13 EBVaGC and 45 EBVnGC specimens. The expression of related genes of EBV, including EB nuclear antigen (NA)-1 and EBNA2 genes, latent membrane protein 1 (LMP1) and early genes BARF1 and BHRF1 were tested by reverse transcription-polymerase chain reaction (RT-PCR) and southern blotting. The PCNA labeling index (LI) of EBVaGCs, EBVnGCs and the corresponding adjacent tissues of EBVaGCs were 49.3768±12.1832, 14.839±7.1847, 35.613±8.3831 and 24.2735±10.1332, respectively. The PCNA LI was significantly different between EBVaGC and EBVnGC of EBVaGC (t=4.686, P<0.01). The difference between EBVaGC and corresponding adjacent tissues of EBVaGC was also significant (t=8.805, P<0.01). The expression of c-myc protein was detected in 33 of 58 (55.39%) gastric carcinomas and in 21 of 58 (36.21%) adjacent tissues. There was a significant difference between the two groups (χ²=4.989, P<0.05). The expression of the c-myc protein was detected in 8 of 13 (61.54%) EBVaGCs and in 25 of 45 (55.56%) EBVnGCs. The difference between the two groups was not significant (χ²=0.147, P>0.05). EBNA1 mRNA was detected in all 13 EBVaGC cases, while EBNA2 and LMP1 mRNA was not detected in these cases. Of the 13 EBV-positive samples, 6 exhibited BARF1 transcripts and 2 exhibited BHRF1 transcripts. c-myc expression did not correlate with the presence of EBV in EBVaGC. EBV infection may induce PCNA expression. The lack of EBNA2 and LMP1 protein expression in EBVaGC suggests that EBNA2 and LMP1 do not correlate with cell apoptosis and c-myc expression. Early genes BARF1 and BHRF1 may play an important role in the development and progression of gastric carcinomas by immortalizing epithelial cells.

Epstein-Barr virus-associated gastric carcinoma in Brazil: comparison between in situ hybridization and polymerase chain reaction detection

Epstein-Barr virus (EBV) has been associated with 10% of gastric carcinomas. The aim of this study was to determine the frequency of EBV in gastric carcinomas in Brazil assessed by in situ hybridization (ISH) and PCR, which would contribute to the characterization of the clinical and pathological aspects of EBV-associated gastric carcinomas. One hundred and ninety-two gastric carcinoma cases were collected at hospitals in two Brazilian states. Seventy-three out of 151 cases were PCR(+), while 11/160 cases were ISH(+). Nine out of eleven ISH(+) cases displayed a diffuse staining pattern and 2 out of 11 a focal pattern. Both techniques showed that the EBV(+) cases were characterized by their association with males, older patients, lower gastric region, intestinal type, advanced stage and poorly to moderately differentiated tumors. The concordance between the two techniques was 55.8% (Cohen's kappa index = 0.034). Four cases were ISH(+)/PCR(-), while 49 cases were PCR(+)/ISH(-). Only two cases showed stained lymphocytes by ISH and one of them was PCR(-). The observed discrepancy between the two techniques could not be explained just by the elevated accuracy of PCR. ISH(+)/PCR(-) carcinomas may be encountered if EBV is not present in the whole tumor tissue or if there are polymorphisms in the sequences of the viral genome amplified. On the other hand, the high frequency of PCR(+) results associated with the absence of ISH staining in lymphocytes and/or tumors cells suggests that the virus may be present in tumor cells or other cell types without expressing EBER1, the target of the ISH technique.

Down-regulation of c-Myc expression inhibits the invasion of bile duct carcinoma cells

Cholangiocarcinoma is the second most common primary hepatic tumour originating from biliary tract epithelial cells with poor prognosis. Enhanced c-Myc protein expression contributes to many aspects of tumour cell biology. Although the ability of c-Myc to drive unrestricted cell proliferation and to inhibit cell differentiation had been well recognized, whether down-regulated c-Myc expression can inhibit tumour cell invasion still remains to be explored. The c-Myc ASODN (antisense oligodeoxyribonucleotide) and NSODN (nonsense oligodeoxyribonucleotide) were designed, synthesized and transfected into human QBC939 bile duct carcinoma cells using the Lipofectamine 2000 reagent. The protein expression of c-Myc was detected by Western blot. A transwell experiment was applied to evaluate the invasive capacity of the QBC939 cells. c-Myc ASODN could significantly suppress the c-Myc protein expression (P<0.05) and the invasion (P<0.01) of QBC939 cells transfected with c-Myc ASODN compared with that in the control and c-Myc NSODN-transfected group. Thus in the present study we show that down-regulation of c-Myc expression can inhibit the invasion of QBC939 cells in vitro.

MYC and gastric adenocarcinoma carcinogenesis

MYC is an oncogene involved in cell cycle regulation, cell growth arrest, cell adhesion, metabolism, ribosome biogenesis, protein synthesis, and mitochondrial function. It has been described as a key element of several carcinogenesis processes in humans. Many studies have shown an association between MYC deregulation and gastric cancer. MYC deregulation is also seen in gastric preneoplastic lesions and thus it may have a role in early gastric carcinogenesis. Several studies have suggested that amplification is the main mechanism of MYC deregulation in gastric cancer. In the present review, we focus on the deregulation of the MYC oncogene in gastric adenocarcinoma carcinogenesis, including its association with Helicobacter pylori (H pylori) and clinical applications.

Influence of Epstein-Barr virus latent membrane protein 2A on the proliferation of human gastric cancer cells

AIM: To construct recombinant adenovirus expression vector containing Epstein-Barr virus (EBV) latent membrane protein 2A (LMP2A) and investigate the effects of LMP2A on the proliferation of human gastric cancer cell line.

METHODS: The target gene LMP2A was amplified by reverse transcription-polymerase chain reaction (RT-PCR), and the recombinant adenovirus vector carrying LMP2A gene was constructed with AdEasy system. The recombinant adenovirus vector pAd-2A was transfected into HEK293 cells with lipofectamine 2000 to package recombinant adenovirus, and then gastric cancer cells SGC with negative EBV were infected by recombinant adenovirus. The expression of LMP2A and its effect on the proliferation of SGC cells were analyzed by PT-PCR, MTT assay, fluorescence activated cell sorting (FACS) and confocal microscopy.

RESULTS: The recombinant adenovirus vector pAd-2A was successfully constructed and identified by PCR, restrictive enzyme analysis, and DNA sequencing. The recombinant adenovirus vAd-2A packaged by HEK293 cells had stable infectivity. The virus titer was 3.16×10¹² pfu/L. MTT assay, FACS and confocal microscopy showed that vAd-2A transfection significantly increased the proliferation of SGC cells (P < 0.01). The ratio of S-phase cells was markedly elevated after vAd-2A transfection in comparison with that after vAd transfection and non-transfection (24 h: 35.2% ± 5.1% vs 14.0% ± 3.4%, 13.2% ± 4.6%, P < 0.01; 48 h: 25.6% ± 4.1% vs 12.9% ± 2.6%, 12.5% ± 3.2%, P < 0.01). The expression of Cyclin E protein was also induced by LMP2A.

CONCLUSION: The recombinant adenovirus vector carrying EBV LMP2A gene is constructed successfully. Meanwhile, it is confirmed that LMP2A may promote the proliferation of SGC cells by induction of Cyclin E expression.

Interrelationship between chromosome 8 aneuploidy, C-MYC amplification and increased expression in individuals from northern Brazil with gastric adenocarcinoma

AIM: To investigate chromosome 8 numerical aberrations, C-MYC oncogene alterations and its expression in gastric cancer and to correlate these findings with histopathological characteristics of gastric tumors.

METHODS: Specimens were collected surgically from seven patients with gastric adenocarcinomas. Immunostaining for C-MYC and dual-color fluorescence in situ hybridization (FISH) for C-MYC gene and chromosome 8 centromere were performed.

RESULTS: All the cases showed chromosome 8 aneuploidy and C-MYC amplification, in both the diffuse and intestinal histopathological types of Lauren. No significant difference (P < 0.05) was observed between the level of chromosome 8 ploidy and the site, stage or histological type of the adenocarcinomas. C-MYC high amplification, like homogeneously stained regions (HSRs) and double minutes (DMs), was observed only in the intestinal-type. Structural rearrangement of C-MYC, like translocation, was observed only in the diffuse type. Regarding C-MYC gene, a significant difference (P < 0.05) was observed between the two histological types. The C-MYC protein was expressed in all the studied cases. In the intestinal-type the C-MYC immunoreactivity was localized only in the nucleus and in the diffuse type in the nucleus and cytoplasm.

CONCLUSION: Distinct patterns of alterations between intestinal and diffuse types of gastric tumors support the hypothesis that these types follow different genetic pathways.

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.

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.

Relationship between Epstein-Barr virus-encoded proteins with cell proliferation, apoptosis, and apoptosis-related proteins in gastric carcinoma

AIM: To investigate the interrelationship between Epstein-Barr virus (EBV)-encoded proteins and cell proliferation, apoptosis and apoptosis-related proteins in gastric carcinoma, and to explore their role in gastric carcinogenesis.

METHODS: Tissues from 13 cases of EBV-associated gastric carcinoma (EBVaGC) and 45 cases of matched EBV-negative gastric carcinoma (EBVnGC) were collected, and then subjected to analysis for apoptotic index (AI) using the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end-labeling (TUNEL) assay. Nuclear cell proliferation-associated antigen ki-67 index (KI), bcl-2, and p53 expression were examined by immunohistochemistry. p53 mutation in exons 5-8 of 13 EBVaGC cases was determined by single-strand conformation polymorphism (SSCP) and DNA sequencing. RT-PCR and Southern hybridization were used to detect the expression of nuclear antigens (EBNAs) 1 and 2, latent membrane protein (LMP) 1, immediately early gene BZLF1 and early genes BARF1 and BHRF1 in 13 EBVaGC cases.

RESULTS: The percentage of AI, KI and p53 overexpression was significantly lower in the EBVaGC group than in the EBVnGC group. However, bcl-2 expression did not show significant difference between the two groups. p53 gene mutations were not found in 13 EBVaGCs. Transcripts of EBNA1 were detected in all 13 EBVaGCs, while both EBNA2 and LMP1 mRNA were not detected. Six of the thirteen cases exhibited BZLF1 transcripts and two exhibited BHRF1 transcripts. BARF1 mRNA was detected in six cases.

CONCLUSION: Lower AI and KI may reflect a low biological activity in EBVaGC. EBV infection is associated with p53 abnormal expression but not bcl-2 protein in EBVaGC. BZLF1, BARF1, and BHRF1 may play important roles in inhibiting cell apoptosis and tumorigenesis of EBVaGC through different pathways.

Relationship between Epstein-Barr virus and overexpression of c-Met protein in gastric carcinoma

AIM: To detect the amplification and expression of c-Met in Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC) and EBV-negative gastric carcinoma (EBVnGC), and to investigate the relationshi pof the amplification and expression of c-Met with EBV infection in the process of gastric carcinogenesis.

METHODS: The amplification of c-Met gene and the expression of c-Met protein in the tissues of EBVaGC (n = 13) and EBVnGC (n = 45) were detected by semi-quantitative polymerase chain reaction (PCR) and immunohistochemical methods, respectively.

RESULTS: The amplification of c-Met was observed in both EBVaGC and EBVnGC. The overamplification rates were 53.8% (7/13) in EBVaGC and 44.4% (20/45) in EBVnGC. There was no significant difference between the two types of caners. c-Met protein was positive in 76.9% (10/13) EBVaGC, and 64.4% (29/45) EBVnGC tissues. The difference between them was not significant either. The overexpression rate of c-Met protein in EBVaGC was significantly higher than that in EBVnGC (69.2% vs 37.8%, P = 0.0 446). No significant correlation was observed between the amplification and expression of c-Met with the tumor size, location, lymph node metastasis, differentiation degree or clinical staging.

CONCLUSION: c-Met is amplified in both EBVaGC and EBVnGC tissues. The amplification level of c-Met gene and the positive rate of c-Met protein are not significantly different between EBVaGC and EBVnGC. However, the overexpression rate of c-Met protein in EBVaGC is higher than that in EBVnGC.

Epstein-Barr virus and aberrant expression of mdm2 and p53 in pathogenesis and development of gastric carcinoma

AIM: To investigate the role of p53 and mdm2 gene abnormality in oncogenesis and development of Epstein-Barr virus (EBV) -associated gastric carcinoma (EBVaGC) and to explore the relationship between EBV infection and p53 and mdm2 protein expression.

METHODS: p53 gene mutation in exon 5-8 was detected by polymerase chain reaction and single strand conformation polymorphism analysis (PCR-SSCP), and DNA sequencing. p53 and mdm2 protein expression was tested by immunohistochemistry in EBVaGCs (n = 13), EBVnGCs (EBV negative gastric carcinomas, n = 45) with matched clinicopathological parameters and corresponding adjacent tissues of gastric carcinoma (n = 58).

RESULTS: The positive rates of p53 and mdm2 protein in gastric carcinomas were significantly higher than those in corresponding adjacent normal tissues (86.2%, 29.3% vs 0%, 0% respectively; P < 0.01). There were no significant difference between the positive rates of p53 and mdm2 protein in EBVnGCs and EBVaGCs. The overexpression rate of p53 protein was 15.4% (2/13) in EBVaGCs. This was in marked contrast to the rate of 57.8% (26/45) in EBVnGCs (χ² = 7.2593, P = 0.0 085 < 0.01). There was significant positive correlation between mdm2 expression and p53 overexpression (χ² = 11.1 839, P = 0.0 008 < 0.01, r = 0.4 391). p53 gene mutation was found in only 2 cases of EBVnGCs and both occurred at exon 5. No p53 gene mutation was detected in 13 cases of EBVaGCs and 58 corresponding adjacent tissues.

CONCLUSION: Abnormal accumulation of p53 protein might not result from p53 gene mutation. mdm2 protein may play an important role in the pathogenesis of gastric carcinoma through suppressing the function of wild type p53 protein. The infection of EBV relates to the abnomal expression of p53 protein, but not to the abnomal expression of mdm2 protein and p53 gene mutation in gastric carcinoma

Apoptosis and expression of Bcl-2 in Epstein-Barr virus-associated gastric carcinoma

AIM: To understand the relationship between Epstein-Barr virus related genes expression, Bcl-2 expression and apoptosis in EBV-associated gastric carcinoma (EBVaGC) and their roles in the oncogenesis and development of gastric carcinoma.

METHODS: The apoptotic index (AI) and the expression of Bcl-2 protein were detected by terminal deoxynucleotidy1 transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) and immunohistochemistry, respectively, in 13 cases of EBVaGC and 45 EBVnGC. The expression of EBV related genes was tested by RT-PCR and Southern blotting.

RESULTS: AI of EBVaGC, EBVnGC and the corresponding adjacent tissues of EBVaGC were 0.97±0.41, 2.03±0.60 and 3.25±0.46, respectively. AI of EBVaGC was significantly lower than that of EBVnGC (t = 5.9 795, P = 0) and corresponding adjacent tissues of EBVaGC (t = 13.2 229, P = 0). The expression of Bcl-2 protein was detectded in 7 of 13 (53.8%) EBVaGC and in 22 of 45 (48.9%) EBVnGC. The difference between the two groups was not significant(χ² = 0.0 991, P = 0.7 529). EBNA1 mRNA was detected in all of 13 EBVaGC, while both EBNA2 and LMP1 mRNA were not detected in the cases. Of the 13 EBV-positive samples,6 exhibited BARF1 transcripts and 2 exhibited BHRF1 transcripts.

CONCLUSION: Bcl-2 expression does not correlate with the presence of EBV in EBVaGC. EBV infection can inhibit cell apoptosis not by Bcl-2 expression. Early genes BARF1 and BHRF1 might play an important role in the development and progression of gastric carcinomas by the mechanisms of immortalizing epithelial cells and inhibiting cell apoptosis.

Adénocarcinomes de l’estomac et de l’œsophage distal

AIMS

Our study aimed to evaluate the incidence of EBV-associated adenocarcinomas of the stomach and distal esophagus in Lyons area and to assess their phenotypic characteristics.

METHODS

85 cases of gastric adenocarcinomas and 40 cases of esophageal adenocarcinomas were screened for EBV by in situ hybridization (EBER-1 and -2) and immunohistochemistry (LMP1 and EBNA-1); all cases positive for EBER by in situ hybridization were studied by PCR for demonstration of EBV DNA. The clinical, histological and immunophenotypic features of EBV-associated adenocarcinomas were assessed.

RESULTS

5 cases of EBV-associated adenocarcinomas, all gastric, were identified in our series (5.8%); one was diagnosed in a migrant from Algeria, a region of high endemia of EBV infection. 3 cases were located in the proximal stomach, 1 in the distal; 1 was diffuse. 4 cases were of the intestinal histological type. Proliferation index and microvessel density were high in all 5 cases. The expression of tumor markers was markedly heterogeneous from one case to another.

CONCLUSIONS

Our study shows that EBV infection is restricted to gastric adenocarcinomas. Its incidence is evaluated to 5.8% in our series: this shows that Lyons area must be considered as a low risk area. In the absence of specific histological or phenotypic features, the screening of EBV+gastric adenocarcinomas is possible only with special techniques.

Apoptosis and cell proliferation in the development of gastric carcinomas: associations with c-myc and p53 protein expression

BACKGROUND AND AIM

Patients with gastric carcinomas have a poor prognosis and low survival rates. The aim of the present paper was to characterize cellular and molecular properties to provide insight into aspects of tumor progression in early compared with advanced gastric cancers.

METHODS

One hundred and nine graded gastric carcinomas (early or advanced stage, undifferentiated or differentiated type) with paired non-cancer tissue were studied to define the correlation between apoptosis (morphology, terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labeling), cell proliferation (Ki-67 expression, morphology) and expression and localization of two proteins frequently having altered expression in cancers, namely p53 and c-myc.

RESULTS

Overall, apoptosis was lower in early stage, differentiated and undifferentiated gastric carcinomas compared with advanced-stage cancers. Cell proliferation was comparatively high in all stages. There was a high level of p53 positivity in all stages. Only the early- and advanced-stage undifferentiated cancers that were p53 positive had a significantly higher level of apoptosis (P < 0.05). Cell proliferation was significantly greater (P < 0.05) only in the early undifferentiated cancers that had either c-myc or p53-positivity.

CONCLUSIONS

The results indicate that low apoptosis and high cell proliferation combine to drive gastric cancer development. The molecular controls for high cell proliferation of the early stage undifferentiated gastric cancers involve overexpression of both p53 and c-myc. Overexpression of p53 may also control cancer development in that its expression is associated with higher levels of apoptosis in early and late-stage undifferentiated, cancers.