Loss of p16/CDKN2A tumor suppressor protein in gastric adenocarcinoma is associated with Epstein-Barr virus and anatomic location in the body of the stomach

Rate of Epstein-Barr Virus in Gastric Adenocarcinoma in Egyptian Patients in View of the WHO Classification and Correlation with p16 Immunoreactivity

BACKGROUND AND AIM: Gastric cancer (GC) is one of the top causes of cancer-related deaths worldwide. According to the Cancer Genome Atlas, there are four subtypes of GC, with the Epstein-Barr virus (EBV) subtype accounting for about 10% of cases. EBV infection causes EBV-associated GC (EBVaGC). The previous research suggested that the presence of the EBV viral genome in gastric carcinomas could be used as a surrogate marker for targeted therapy and optimal GC treatment. AIM: We aimed to explore the rate of EBV involvement in gastric carcinogenesis from molecular perspective view and to evaluate the role of the tumor-suppressor protein p16 as a marker for diagnosis in GC Egyptian patients in relation to EBV infection. METHODS: One hundred-four surgically resected GC cases were analyzed. Two methods including quantitative real-time polymerase chain reaction (qPCR) for detecting EBV-derived latent membrane protein-1 (LMP-1) and Epstein-Barr nuclear antigen-1 (EBNA-1) genes as well as immunohistochemistry (IHC) detection of LMP-1 protein and p16 protein on paraffinized tissue blocks were applied. RESULTS: Using IHC, p16 protein was presented in 90/104 (86.5%) of the GC cases, and EBV LMP-1 was detected in 4 cases (3.84%). qPCR detected 14 cases positive for EBV (13.46%). In EBV positive cases detected using qPCR, no expression of p16 was detected. CONCLUSION: EBVaGC has a low incidence in Egypt; loss of p16 expression was recognized in EBVaGC and could be considered as a promising biomarker of EBVaGC. The combination of the two methods IHC and qPCR in addition to p16 is recommended for improving the accuracy of identification of infected cancer.

Epstein-Barr virus infection and genome polymorphisms on gastric remnant carcinoma: a meta-analysis

Background

Previous studies reported that Epstein–Barr virus (EBV) may play a causal role in the pathogenesis of gastric remnant carcinoma (GRC). However, there was still some controversy.

Methods

Articles published until July 15, 2020, in PubMed, MEDLINE, Embase and CNKI databases were selected. According to the inclusion criteria, corresponding data of included articles were abstracted and used for statistical analysis.

Results

Thirteen papers were finally enrolled, nine of which showed the result that the risk of EBV infection rate in the GRC was higher than conventional gastric carcinoma (OR = 5.22, 95% CI 3.89–7.00). In addition, we found that EBV associated GRC (EBVaGRC) had higher rate of Billroth-II (OR = 3.80, 95% CI 1.90–7.57), carcinoma in anastomotic site (OR = 2.41, 95% CI 1.27–4.56) and diffuse type (Lauren classification) (OR = 1.97, 95% CI 1.04–3.73),while sex, initial diagnosis and lymphocytic infiltration were calculated no statistical difference. By genetic polymorphism analysis, “V-val” subtype of EBNA1 (OR = 21.84, 95% CI 11.92–31.76) and “C” subtype of BamHI-W1/I1 (OR = 7.07, 95% CI 1.47–34.03) were observed to be highly expressed in EBVaGRC.

Conclusion

EBV infection rate in the GRC was higher. Further analysis showed that Billroth-II, carcinoma in anastomotic site and diffuse type (Lauren classification) were associated to EBVaGRC. Through analysis of EBV genome polymorphisms, we thought that “V-val” subtype of EBNA1 and “C” subtype of BamHI-W1/I1 may become predictor of EBVaGRC.

The oncogenic role of Epstein-Barr virus-encoded microRNAs in Epstein-Barr virus-associated gastric carcinoma

Epstein–Barr virus (EBV) infection is detected in various epithelial malignancies, such as nasopharyngeal carcinoma (NPC) and gastric cancer (GC). EBV comprises some unique molecular features and encodes viral genes and microRNAs (miRNAs) by its own DNA sequence. EBV genes are required to maintain latency and contribute to oncogenic property. miRNAs encoded by EBV have been shown to contribute to initiation and progression of EBV‐related malignancies. By a number of genomic profiling studies, some EBV miRNAs were confirmed to be highly expressed in EBV‐associated gastric cancer (EBVaGC) samples and cell lines. The majority host targets of the EBV miRNAs are important for promoting cell growth and inhibiting apoptosis, facilitating cell survival and immune evasion. However, the integrated molecular mechanisms related to EBV miRNAs remain to be investigated. In this review, we summarized the crucial role of EBV miRNAs in epithelial malignancies, especially in EBVaGC. Collectively, EBV miRNAs play a significant role in the viral and host gene regulation network. Understanding the comprehensive potential targets and relevant functions of EBV miRNAs in gastric carcinogenesis might provide better clinical translation.

Epstein-Barr virus: more than 50 years old and still providing surprises

It is more than 50 years since the Epstein-Barr virus (EBV), the first human tumour virus, was discovered. EBV has subsequently been found to be associated with a diverse range of tumours of both lymphoid and epithelial origin. Progress in the molecular analysis of EBV has revealed fundamental mechanisms of more general relevance to the oncogenic process. This Timeline article highlights key milestones in the 50-year history of EBV and discusses how this virus provides a paradigm for exploiting insights at the molecular level in the diagnosis, treatment and prevention of cancer.

Epstein-Barr virus and nasopharyngeal carcinoma

Since its discovery 50 years ago, Epstein-Barr virus (EBV) has been linked to the development of cancers originating from both lymphoid and epithelial cells. Approximately 95% of the world's population sustains an asymptomatic, life-long infection with EBV. The virus persists in the memory B-cell pool of normal healthy individuals, and any disruption of this interaction results in virus-associated B-cell tumors. The association of EBV with epithelial cell tumors, specifically nasopharyngeal carcinoma (NPC) and EBV-positive gastric carcinoma (EBV-GC), is less clear and is currently thought to be caused by the aberrant establishment of virus latency in epithelial cells that display premalignant genetic changes. Although the precise role of EBV in the carcinogenic process is currently poorly understood, the presence of the virus in all tumor cells provides opportunities for developing novel therapeutic and diagnostic approaches. The study of EBV and its role in carcinomas continues to provide insight into the carcinogenic process that is relevant to a broader understanding of tumor pathogenesis and to the development of targeted cancer therapies.

Late, isolated metastasis from poorly differentiated gastric cancer to the uterine cervix

•Metastases from extrapelvic organs to the uterine cervix are rare.•Cervical metastases from the stomach are often accompanied by extrauterine metastases.•We report a case of cervical metastasis of gastric cancer, occurring 10 years after the first surgical treatment.

TSGene: a web resource for tumor suppressor genes

Tumor suppressor genes (TSGs) are guardian genes that play important roles in controlling cell proliferation processes such as cell-cycle checkpoints and inducing apoptosis. Identification of these genes and understanding their functions are critical for further investigation of tumorigenesis. So far, many studies have identified numerous TSGs and illustrated their functions in various types of tumors or normal samples. Furthermore, accumulating evidence has shown that non-coding RNAs can act as TSGs to prevent the tumorigenesis processes. Therefore, there is a growing demand to integrate TSGs with large-scale experimental evidence (e.g. gene expression and epigenetic signatures) to provide a comprehensive resource for further investigation of TSGs and their molecular mechanisms in cancer. To achieve this goal, we first developed a comprehensive literature-based database called TSGene (tumor suppressor gene database), freely available at http://bioinfo.mc.vanderbilt.edu/TSGene/. In the current release, TSGene contains 716 human (637 protein-coding and 79 non-coding genes), 628 mouse and 567 rat TSGs curated from UniProtKB, the Tumor Associated Gene database and 5795 PubMed abstracts. Additionally, the TSGene provides detailed annotations for each TSG, such as cancer mutations, gene expressions, methylation sites, TF regulations and protein–protein interactions.

Epstein-barr virus infected gastric adenocarcinoma expresses latent and lytic viral transcripts and has a distinct human gene expression profile

BACKGROUND

EBV DNA is found within the malignant cells of 10% of gastric cancers. Modern molecular technology facilitates identification of virus-related biochemical effects that could assist in early diagnosis and disease management.

METHODS

In this study, RNA expression profiling was performed on 326 macrodissected paraffin-embedded tissues including 204 cancers and, when available, adjacent non-malignant mucosa. Nanostring nCounter probes targeted 96 RNAs (20 viral, 73 human, and 3 spiked RNAs).

RESULTS

In 182 tissues with adequate housekeeper RNAs, distinct profiles were found in infected versus uninfected cancers, and in malignant versus adjacent benign mucosa. EBV-infected gastric cancers expressed nearly all of the 18 latent and lytic EBV RNAs in the test panel. Levels of EBER1 and EBER2 RNA were highest and were proportional to the quantity of EBV genomes as measured by Q-PCR. Among protein coding EBV RNAs, EBNA1 from the Q promoter and BRLF1 were highly expressed while EBNA2 levels were low positive in only 6/14 infected cancers. Concomitant upregulation of cellular factors implies that virus is not an innocent bystander but rather is linked to NFKB signaling (FCER2, TRAF1) and immune response (TNFSF9, CXCL11, IFITM1, FCRL3, MS4A1 and PLUNC), with PPARG expression implicating altered cellular metabolism. Compared to adjacent non-malignant mucosa, gastric cancers consistently expressed INHBA, SPP1, THY1, SERPINH1, CXCL1, FSCN1, PTGS2 (COX2), BBC3, ICAM1, TNFSF9, SULF1, SLC2A1, TYMS, three collagens, the cell proliferation markers MYC and PCNA, and EBV BLLF1 while they lacked CDH1 (E-cadherin), CLDN18, PTEN, SDC1 (CD138), GAST (gastrin) and its downstream effector CHGA (chromogranin). Compared to lymphoepithelioma-like carcinoma of the uterine cervix, gastric cancers expressed CLDN18, EPCAM, REG4, BBC3, OLFM4, PPARG, and CDH17 while they had diminished levels of IFITM1 and HIF1A. The druggable targets ERBB2 (Her2), MET, and the HIF pathway, as well as several other potential pharmacogenetic indicators (including EBV infection itself, as well as SPARC, TYMS, FCGR2B and REG4) were identified in some tumor specimens.

CONCLUSION

This study shows how modern molecular technology applied to archival fixed tissues yields novel insights into viral oncogenesis that could be useful in managing affected patients.

Epstein-Barr virus infection is common in inflamed gastrointestinal mucosa

BACKGROUND AND AIMS

Epstein-Barr virus (EBV) is present in the malignant epithelial cells of 10% of all gastric adenocarcinomas; however, localization of the virus in normal gastrointestinal mucosa is largely unexplored. In the present study, we measured EBV DNA and localized viral gene products in gastritis specimens (n = 89), normal gastric and colonic mucosa (n = 14), Crohn's disease (n = 9), and ulcerative colitis (n = 11) tissues.

METHODS

A battery of sensitive and specific quantitative polymerase chain reactions targeted six disparate regions of the EBV genome: BamH1 W, EBNA1, LMP1, LMP2, BZLF1, and EBER1. EBV infection was localized by EBV-encoded RNA (EBER) in situ hybridization and by immunohistochemical stains for viral latent proteins LMP1 and LMP2 and for viral lytic proteins BMRF1 and BZLF1. B lymphocytes were identified using CD20 immunostains.

RESULTS

EBV DNA was essentially undetectable in normal gastric mucosa but was present in 46% of gastritis lesions, 44% of normal colonic mucosa, 55% of Crohn's disease, and 64% of ulcerative colitis samples. Levels of EBV DNA exceeded what would be expected based on the numbers of B lymphocytes in inflamed tissues, suggesting that EBV is preferentially localized to inflammatory gastrointestinal lesions. Histochemical staining revealed EBER expression in lymphoid cells of some PCR-positive lesions. The viral lytic viral proteins, BMRF1 and BZLF1, were expressed in lymphoid cells of two ulcerative colitis tissues, both of which had relatively high viral loads by quantitative PCR.

CONCLUSION

EBV-infected lymphocytes are frequently present in inflamed gastric and colonic mucosa. Active viral replication in some lesions raises the possibility of virus-related perpetuation of gastrointestinal inflammation.

Epstein-Barr virus-specific methylation of human genes in gastric cancer cells

Background

Epstein-Barr Virus (EBV) is found in 10% of all gastric adenocarcinomas but its role in tumor development and maintenance remains unclear. The objective of this study was to examine EBV-mediated dysregulation of cellular factors implicated in gastric carcinogenesis.

Methods

Gene expression patterns were examined in EBV-negative and EBV-positive AGS gastric epithelial cells using a low density microarray, reverse transcription PCR, histochemical stains, and methylation-specific DNA sequencing. Expression of PTGS2 (COX2) was measured in AGS cells and in primary gastric adenocarcinoma tissues.

Results

In array studies, nearly half of the 96 human genes tested, representing 15 different cancer-related signal transduction pathways, were dysregulated after EBV infection. Reverse transcription PCR confirmed significant impact on factors having diverse functions such as cell cycle regulation (IGFBP3, CDKN2A, CCND1, HSP70, ID2, ID4), DNA repair (BRCA1, TFF1), cell adhesion (ICAM1), inflammation (COX2), and angiogenesis (HIF1A). Demethylation using 5-aza-2'-deoxycytidine reversed the EBV-mediated dysregulation for all 11 genes listed here. For some promoter sequences, CpG island methylation and demethylation occurred in an EBV-specific pattern as shown by bisulfite DNA sequencing. Immunohistochemistry was less sensitive than was western blot for detecting downregulation of COX2 upon EBV infection. Virus-related dysregulation of COX2 levels in vitro was not recapitulated in vivo among naturally infected gastric cancer tissues.

Conclusions

EBV alters human gene expression in ways that could contribute to the unique pathobiology of virus-associated cancer. Furthermore, the frequency and reversability of methylation-related transcriptional alterations suggest that demethylating agents have therapeutic potential for managing EBV-related carcinoma.

High levels of Epstein-Barr virus DNA in latently infected gastric adenocarcinoma

Gastric adenocarcinoma is the second leading cause of cancer death worldwide. Epstein-Barr virus (EBV) is present in the malignant cells of approximately 10% of cases. It is unclear whether EBV is being missed in some gastric adenocarcinomas due to insensitive test methods or partial EBV genome loss. In this study, we screened 113 gastric adenocarcinomas from low- and high-incidence regions (United States and Central America) for the presence of EBV using a battery quantitative real-time PCR (Q-PCR) assays targeting disparate segments of the EBV genome (BamH1W, EBNA1, LMP1, LMP2, BZLF1, EBER1) and histochemical stains targeting EBV-encoded RNA (EBER), the latent proteins LMP1 and LMP2, and the lytic proteins BMRF1 and BZLF1. EBV DNA was detected by Q-PCR in 48/75 United States cancers (64%) and in 38/38 Central American cancers (100%), which was a significant difference. EBER was localized to malignant epithelial cells in 8/48 (17%) United States and 3/38 (8%) Central American cancers. Viral loads were considerably higher for EBER-positive vs EBER-negative cancers (mean 162 986 vs 62 EBV DNA copies per 100,000 cells). A viral load of 2000 copies per 100,000 cells is recommended as the threshold distinguishing EBER-positive from EBER-negative tumors. One infected cancer selectively failed to amplify the LMP2 gene because of a point mutation, whereas another cancer had an atypical pattern of Q-PCR positivity suggesting deletion of large segments of the EBV genome. Three different viral latency profiles were observed in the cancers based on constant expression of EBER and focal or variable expression of LMP1 or LMP2, without lytic protein expression. We conclude that EBV DNA levels generally reflect EBER status, and a panel of at least two Q-PCR assays is recommended for sensitive identification of infected cancers.

Abnormal expression of p16(INK4a), cyclin D1, cyclin-dependent kinase 4 and retinoblastoma protein in gastric carcinomas

BACKGROUND AND OBJECTIVES

The p16(INK4a) (p16), cyclin D1, cyclin-dependent kinase (CDK) 4 and retinoblastoma (Rb) genes are components of the Rb pathway that controls the G1-S checkpoint of the cell cycle. The aim of this study was to assess the relationship between their abnormalities and clinicopathological features in gastric carcinomas.

METHODS

Immunohistochemical analysis of the encoded proteins was performed on a series of 158 cases.

RESULTS

Loss of p16/Rb protein (pRb) expression and overexpression of cyclin D1/CDK4 were observed in 49%/40% and 37%/37% of gastric carcinomas, respectively. At least 1 of these abnormalities was found in 86% of the cases and a positive correlation was noted between p16 and pRb (P = 0.009). Cyclin D1 (P = 0.042) and CDK4 (P = 0.008) overexpession was inversely associated with lymph node metastasis and depth of invasion, respectively. Loss of pRb expression was more frequently in diffuse type lesions than in the intestinal type (P = 0.022). The patients with p16+/pRb-/cyclin D1-/CDK4- or p16-/pRb+/cyclin D1-/CDK4- tumors demonstrated particularly poor survival. With multivariate survival analysis, only depth of invasion and TNM stage could be proven as independent predictors.

CONCLUSIONS

The Rb pathway is disrupted in the vast majority of gastric carcinomas. This study also identified specific immunohistochemical marker profiles for prognosis.

Aberrant promoter methylation of insulin-like growth factor binding protein-3 gene in human cancers

Insulin-like growth factor binding protein-3 (IGFBP-3) is postulated to be a mediator of growth suppression signals. Here, we examined the methylation status of IGFBP-3 to correlate to clinicopathological factors in human cancers. The methylation status of IGFBP-3 was determined by bisulfite DNA sequencing and was correlated with expression semi-quantified by real-time RT-PCR to develop a methylation-specific PCR (MSP) assay for IGFBP-3. Using the MSP assay, we examined the methylation status of IGFBP-3 in gastric cancer (GC), colorectal cancer (CRC), breast cancer (BC) and malignant mesothelioma (MM). IGFBP-3 methylation was detected in 6 of 13 (46%) and 16 of 24 (67%) GC cell lines and tumors, respectively; 4 of 8 (50%) and 15 of 26 (58%) CRC cell lines and tumors, respectively; 3 of 11 (27%) and 7 of 39 (18%) BC cell lines and tumors, respectively and 1 of 5 (20%) and 18 of 56 (32%) MM cell lines and tumors, respectively. Interestingly, the methylation status of MM specimens from Japanese patients (75%, 12 out of 16 patients) was significantly higher than those from the USA (15%, 6 out of 40 patients) (p < 0.0001), suggesting the presence of ethnic differences in the IGFBP-3 methylation status. We also found that IGFBP-3 methylation was preferentially present in GCs arising in the lower-third of the stomach (p = 0.079). In summary, our results showed that IGFBP-3 methylation played an important role in the silencing of its expression, suggesting that IGFBP-3 may act as a tumor suppressor gene in several human cancers examined.

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.

Epstein-Barr virus in human malignancy: a special reference to Epstein-Barr virus associated gastric carcinoma

Epstein-Bar virus (EBV), a human herpesvirus, establishes a life-long persistent infection in 90 approximately 95% of human adult population worldwide. EBV is the etiologic agent of infectious mononucleosis, and EBV is associated with a variety of human malignancy including lymphoma and gastric carcinoma. Recently, EBV has been classified as group 1 carcinogen by the WHO International Agency for Research on Cancer. Evidence is presented which suggests that failures of the EBV-specific immunity may play a role in the pathogenesis of EBV-associated malignancy. At present, the precise mechanisms by which EBV transforms B lymphocytes have been disclosed. Encouragingly, they have had enough success so far to keep them enthusiastic about novel therapeutic trial in the field of EBV-associated lymphoma. However, information on EBV-associated gastric carcinoma is still at dawn. This article reviews EBV biology, immunological response of EBV infection, unique oncogenic property of EBV, peculiarity of EBV-associated gastric carcinoma, and lastly, EBV-targeted therapy and vaccination.

Epstein-Barr virus and p16INK4A methylation in squamous cell carcinoma and precancerous lesions of the cervix uteri

Methylation of p16 is an important mechanism in cervical carcinogenesis. However, the relationship between cervical squamous cell carcinoma (SCC) and Epstein-Barr virus (EBV) remains controversial. Here, we explored whether EBV infection and/or p16 gene inactivation would play any role in cervical carcinogenesis. Eighty-two specimens included 41 invasive SCCs, 30 cervical intraepithelial neoplasm (CIN; CIN 1, 11 cases, CIN II, 3 cases, CIN III 16 cases) and 11 nonneoplastic cervices. EBV was detected by polymerase chain reaction (PCR) for EBNA-1 and in situ hybridization for EBER-1. The p16 methylation-status and the expression of p16 protein were studied by methylation-specific PCR and immunohistochemistry, respectively. The materials were divided into four groups: 1) nonneoplastic cervices, 2) CIN I, 3) CIN II-III and 4) invasive SCCs. p16 methylation and p16 immunoexpressions increased in CIN and invasive SCCs than nonneoplastic tissue. p16-methylation and p16-immunoreactivities were higher in the EBV-positive group (p=0.009, p<0.001) than in the EBV-negative group. EBV was detected more frequently in CIN and SCCs than nonneoplastic cervices. In conclusion, a correlation between p16 methylation, p16 immunoreactivity and the detection of EBV strongly suggested that the cooperation of EBV and p16 gene may play a synergic effect on cell cycle deregulation.

Aberrant promoter methylation in human DAB2 interactive protein (hDAB2IP) gene in gastrointestinal tumour

The human DOC-2/DAB2 interactive protein (hDAB2IP) gene is a novel member of the Ras GTPase-activating family and has been demonstrated to be a tumour-suppressor gene inactivated by methylation in several cancers. In this study, we analysed the methylation and expression status of hDAB2IP in gastrointestinal tumours. The promoter region of hDAB2IP was divided into two regions (m2a and m2b) based on our previous report, and the methylation status was determined by bisulphite DNA sequencing in gastric cancer cell lines. The gene expression was semiquantified by real-time RT–PCR, and the results indicated that the m2b promoter region might be an authentic methylation-mediated key regulator of the gene expression. Based on the sequence data, we developed a methylation-specific PCR (MSP) for the m2a and m2b regions and applied it to the samples. Methylation-specific PCR revealed aberrant methylation in the m2a region in eight of 12 gastric cancer cell lines (67%), 16 of 35 gastric cancer tissues (46%) and 29 of 60 colorectal cancer tissues (48%), and in the m2b region in eight of 12 cell lines (67%), 15 of 35 gastric cancer tissues (43%) and 28 of 60 colorectal cancer tissues (47%). On the other hand, seven (12%) and 11 (19%) of 59 gastrointestinal nonmalignant mucosal specimens showed methylation in the m2a and m2b regions, respectively, suggesting that hDAB2IP methylation might play a causative role in carcinogenesis. The 5-aza-2′-deoxycytidine treatment restored the gene expression in the m2b-methylated cell lines, confirming that the methylation caused gene downregulation. We also examined the relationship between hDAB2IP methylation and the clinicopathological features in patients with primary tumours, and determined that methylation in the m2b region was associated with location of the tumour in the stomach. In summary, our results demonstrated that hDAB2IP methylation is frequently present in gastrointestinal tumours and that the resulting gene silencing plays an important role in gastrointestinal carcinogenesis.

Epstein-barr virus-positive gastric carcinoma has a distinct protein expression profile in comparison with epstein-barr virus-negative carcinoma

PURPOSE

EBV has been detected in 2-16% of gastric carcinomas. However, there is little information available about the gene expression profile of EBV-positive gastric carcinomas.

EXPERIMENTAL DESIGN

EBV infection was examined using EBV-encoded small RNAs (EBERs) in situ hybridization, and 63 (5.6%) of 1127 consecutive gastric carcinomas were found to be EBV-positive. The expressions of 27 tumor-associated proteins were evaluated immunohistochemically in 63 EBV-positive gastric carcinomas and 287 EBV-negative carcinomas using the tissue array method. In addition, the genotype of EBV was investigated by PCR amplification of LMP1 (latent membrane protein 1), Epstein-Barr nuclear antigen 2 (EBNA2), and EBNA3B genes.

RESULTS

EBV-positive gastric carcinomas are characterized by the presence of lymphoid stroma, proximal location, and predominance in males. In comparison with EBV-negative carcinomas, EBV-positive carcinomas showed frequent loss of expression of p16, smad4, FHIT, and KAI-1 (kangai 1; P < 0.05), but retained the expression of APC (adenomatous polyposis coli), DCC (deleted in colorectal cancer), and some DNA repair proteins (P < 0.05). There was negative association between EBV infection and the expression of MUC1, MUC2, MUC5AC, p53, CEA, C-erbB2, and smad7. Using hierarchical cluster analysis, we divided EBV-positive gastric carcinomas into two clusters. Those patients with cluster 1 (42 cases) carcinomas had a better prognosis than those with cluster 2 (12 cases; P = 0.0002) or those with EBV-negative carcinomas (280 cases; P = 0.0251). Fifty-one (92.7%) of 55 EBV-positive carcinomas demonstrated the 30-bp deletion in LMP1 gene, and 53 (96.4%) of 55 cases were type 1 for EBNA2 and EBNA3B genes.

CONCLUSION

EBV-positive gastric carcinomas have a distinct protein expression profile as well as distinct clinicopathological features, as compared with EBV-negative carcinomas. The subclassification of EBV-positive carcinomas, by hierarchical cluster analysis, is significantly associated with patient survival.

Epstein-Barr virus: 40 years on

Epstein-Barr virus (EBV) was discovered 40 years ago from examining electron micrographs of cells cultured from Burkitt's lymphoma, a childhood tumour that is common in sub-Saharan Africa, where its unusual geographical distribution - which matches that of holoendemic malaria -indicated a viral aetiology. However, far from showing a restricted distribution, EBV - a gamma-herpesvirus - was found to be widespread in all human populations and to persist in the vast majority of individuals as a lifelong, asymptomatic infection of the B-lymphocyte pool. Despite such ubiquity, the link between EBV and 'endemic' Burkitt's lymphoma proved consistent and became the first of an unexpectedly wide range of associations discovered between this virus and tumours.

Abnormal expression of pRb, p16, and cyclin D1 in gastric adenocarcinoma and its lymph node metastases: relationship with pathological features and survival

The retinoblastoma (Rb) pathway controls the G1-S checkpoint of the cell cycle. Inactivating mutations and deletions of p16 and Rb and up-regulation of cyclin D1 disrupt this pathway and occur in many cancers. However, the concurrent expression of these genes in primary and metastatic gastric cancer is unknown, and the prognostic value of their expression is unclear. In this study, the expression of cyclin D1, retinoblastoma protein (pRb), and p16 in 67 resected gastric adenocarcinomas, and of pRb and p16 in 40 associated lymph node metastases, was determined using a streptavidin-biotin-peroxidase immunohistochemical method. Relationships with clinical and pathological features were analyzed. Cyclin D1 overexpression (>/=5% expression) was seen in 55% of cancers; pRb loss (<20% expression), in 33%; p16 loss (<10% expression), in 49%; and at least 1 of these abnormalities, in 92.5%. Cyclin D1 overexpression was associated with poor differentiation (P = 0.027) and signet ring cell type (P = 0.029). pRb expression was lower in lymph node metastases than in the corresponding primary tumors (P <0.001). Univariate and multivariate survival analysis (minimum follow-up 72 months or until death) revealed that <20% pRb expression, <30% pRb expression, and International Union Against Cancer stage >2 were associated with worse overall survival. The results suggest that Rb pathway disturbances play an important role in gastric carcinogenesis. The poor prognosis of cancers with low pRb expression and the reduced pRb expression in lymph node metastases raise the possibility that Rb and related genes also influence progression.

Promoter methylation status of DAP-kinase and RUNX3 genes in neoplastic and non-neoplastic gastric epithelia

Silencing of tumor suppressor and tumor-related genes by hypermethylation at promoter CpG islands is frequently found in human tumors, including gastric cancer. Promoter methylation is not restricted to cancer cells, and is also present in non-neoplastic cells as an age-related tissue-specific phenomenon. To clarify the physiological consequence of DAP-kinase and RUNX3 age-related methylation in gastric epithelia, we investigated the promoter methylation status of these genes in both neoplastic and non-neoplastic gastric epithelia obtained at autopsy and surgery, as well as in 10 gastric cancer cell lines. Methylation of DAP-kinase and RUNX3 was detected in 10% (1/10) and 70% (7/10) of the cell lines, respectively, and was almost concordant with their expression status. Among autopsy samples, methylation of these genes was not seen in non-neoplastic gastric epithelia from persons who were aged 22 years and below (0%; 0/4). DAP-kinase was methylated in 87% (13/15) of non-neoplastic gastric epithelia of persons who were aged 45 years or older, while RUNX3 methylation in non-neoplastic gastric epithelia was restricted to individuals who were aged 77 years or older. Among samples obtained from patients with stomach cancer, methylation was observed in both the neoplastic and the corresponding non-neoplastic gastric epithelia; 43% (40/93) and 73% (68/93) for DAP-kinase, and 45% (42/93) and 8% (7/93) for RUNX3, respectively. Frequencies of DAP-kinase and RUNX3 methylation differed significantly in non-neoplastic gastric epithelia (P < 0.01), although those in gastric cancers were almost the same. RUNX3 methylation is mostly cancer-specific, except for very old individuals, and therefore may be a possible molecular diagnostic marker and malignancy predictor.

Epstein-Barr virus and microsatellite instability in gastric carcinogenesis

Little information is available concerning the relationship between transforming viruses and microsatellite instability (MSI). We evaluated Epstein-Barr virus (EBV) using in situ hybridization for EBV-encoded small RNAs and MSI using the polymerase chain reaction in surgically resected gastric cancer. The study subjects included 298 consecutive cases of solitary gastric carcinoma, 63 gastric carcinomas in young patients (</=30 years old), 64 cases of gastric cancer coexisting with gastric adenoma in a single lesion, 26 cases of gastric remnant cancer, and 98 carcinomas from 47 patients with synchronous multiple gastric carcinomas. There was no overlapping case among these subsets of gastric cancer. None of these 549 gastric carcinomas demonstrated both EBV positivity and MSI positivity. Furthermore, the EBV-positive and the MSI-positive cases showed a mutually negative association in all subsets of gastric cancer. 5.7% of consecutive solitary gastric carcinomas were EBV positive, and 9.7% were MSI positive. EBV was positive in 1.6% of gastric cancers coexisting with gastric adenoma, 12.7% of younger patients, 28.6% of gastric remnant cancer with previous gastrectomy for benign disease, and 14.5% of synchronous cancers without adenoma. MSI was found in 1.6% of younger patients, 18.8% of gastric cancers coexisting with gastric adenoma, 25% of gastric remnant cancer with previous gastrectomy for gastric cancer, and in 53.3% of synchronous gastric carcinomas having gastric adenoma remote from the cancer. In conclusion, the carcinogenic roles of EBV and MSI may be different in terms of each subset of gastric cancer. EBV and MSI may contribute to functionally equivalent pathways in gastric carcinogenesis.

CDKN2A promoter methylation in gastric adenocarcinomas: clinical variables

The CDKN2A gene encodes a cyclin-dependent kinase inhibitor, p16, which promotes cell cycle arrest. Methylation of the promoter region of the gene transcriptionally inactivates the gene. We have analyzed the methylation status of the promoter region of the CDKN2A gene in gastric adenocarcinomas using methylation-specific polymerase chain reaction. We also examined the tumors by immunohistochemistry for p16 protein. Of 114 gastric adenocarcinomas analyzed by immunohistochemistry, 34 cases (30%) were negative for p16 protein. Twenty-four of these 34 cases (71%) had methylation of the promoter region of the CDKN2A gene. Methylation of the promoter was strongly associated with loss of p16 protein by immunohistochemistry (P <0.0001). Neither stage, grade, anatomic site, or histologic subtype of the tumor nor age, gender, ethnic origin, or survival time of the patient were significantly different between the groups characterized by tumors with and without methylation. CDKN2A promoter methylation was not significantly associated with microsatellite instability.

Reduced expression and promoter methylation of p16 gene in Epstein-Barr virus-associated gastric carcinoma

Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC) is a unique type of gastric carcinoma (GC), which is considered to develop in a different pathway from EBV-negative GC. To evaluate a possible role of p16, an inhibitor of G1/S transition of the cell cycle, in the carcinogenesis of EBVaGC, p16-immunohistochemistry and methylation-specific PCR analysis (MSP) were applied to surgically resected gastric carcinomas. When the percentage of p16-positive cells in more than 1000 carcinoma cells was expressed as p16 labeling index (p16-LI), it ranged from 2.5 to 88.1 (mean 42.9+/-24.4) in 70 gastric carcinomas. EBVaGC showed significantly lower values (n=15, 26.1+/ -22.1) than EBV-negative GC (n=55, 47.5+/-23.2) (P=0.0036). Fresh frozen tissues of 55 gastric carcinomas (16 EBVaGC and 39 EBV-negative GC) were further subjected to MSP, to evaluate abnormal methylation of the promoter region of the p16 gene. The frequency of methylation was significantly higher in EBVaGC (14/16) than in EBV-negative GC (9/39) (<0.0001). The methylation-positive carcinomas showed significantly lower p16-LI (35.9+/-21.6) than the unmethylated ones (55.2+/-22.7) (P=0.0014). Thus, a marked decrease of p16 expression, caused by the aberrant methylation of the p16 gene promoter, is closely associated with the development of EBVaGC.

Epstein-Barr virus in gastric adenocarcinomas: association with ethnicity and CDKN2A promoter methylation

AIMS

It has been shown previously (by immunohistochemistry) that gastric adenocarcinomas harbouring Epstein-Barr virus (EBV) frequently lose p16 protein. This study aimed to examine the mechanisms of inactivation of the CDKN2A gene and correlate the results with clinicopathological features.

METHODS

Methylation specific polymerase chain reaction was used to detect CDKN2A promoter methylation in gastric adenocarcinomas from American patients. In addition, immunohistochemistry was used to detect the loss of the p16 protein and in situ hybridisation was used to detect the presence of EBV. The tumours were also analysed for the presence of microsatellite instability.

RESULTS

Eleven (10%) of 107 tumours harboured EBV in the malignant cells. In gastric cancers without EBV, 32% exhibited CDKN2A promoter methylation and 26% had p16 protein loss. In contrast, 91% of the tumours containing EBV had CDKN2A promoter methylation (p = 0.0003) and 90% showed p16 protein loss (p = 0.0001). The presence of EBV was also associated with male sex (p = 0.03) and was more common in tumours from Texas Hispanics than from non-Hispanic whites or African-Americans (p = 0.01). EBV was not associated with microsatellite instability, histological subtype, stage, or grade of the tumour, or age or survival time of the patient.

CONCLUSIONS

The presence of EBV in gastric adenocarcinomas is strongly associated with CDKN2A inactivation by promoter methylation. In addition, these findings suggest that there are ethnic differences in tumour virology and pathogenesis.

Promoter methylation status of E-cadherin, hMLH1, and p16 genes in nonneoplastic gastric epithelia

Silencing of tumor suppressor and tumor-related genes by hypermethylation at promoter CpG islands is one of the major events in human tumorigenesis. Promoter methylation is also present in nonneoplastic cells as an age-related tissue-specific phenomenon that precedes the development of neoplasia. To clarify the significance of promoter methylation in nonneoplastic gastric epithelia as a precancerous signal, we investigated promoter methylation status of E-cadherin, hMLH1, and p16 genes in nonneoplastic cells of various organs obtained at autopsy, and compared the results with those of nonneoplastic epithelia of a cancerous stomach. Methylation of these genes was not seen in nonneoplastic cells of organs from people who were 22 years and younger (0%, 0 of 6). In contrast, E-cadherin and p16 were methylated in nonneoplastic gastric epithelia of persons who were 45 years or older. The numbers were 86% (12 of 14) and 29% (4 of 14), respectively. E-cadherin methylation occurred preferentially in the intestines, whereas p16 methylation was almost restricted to the stomach. For samples obtained from patients with stomach cancer, methylation was frequently observed in both neoplastic and corresponding nonneoplastic gastric epithelia: 47% (44 of 94) and 67% (63 of 94) for E-cadherin, 32% (30 of 94) and 24% (23 of 94) for hMLH1, and 22% (21 of 94) and 44% (41 of 94) for p16, respectively. hMLH1 methylation was not seen in nonneoplastic gastric epithelia from autopsy samples but occurred significantly in samples from nonneoplastic tissues of individuals with stomach cancer. Therefore, detection of hMLH1 methylation in nonneoplastic gastric epithelia may be useful for screening patients who may be at risk of developing gastric cancer.

Hypermethylation of the TSLC1 gene promoter in primary gastric cancers and gastric cancer cell lines

The TSLC1 (tumor suppressor in lung cancer-1) gene is a novel tumor suppressor gene on chromosomal region 11q23.2, and is frequently inactivated by concordant promoter hypermethylation and loss of heterozygosity (LOH) in non-small cell lung cancer (NSCLC). Because LOH on 11q has also been observed frequently in other human neoplasms including gastric cancer, we investigated the promoter methylation status of TSLC1 in 10 gastric cancer cell lines and 97 primary gastric cancers, as well as the corresponding non-cancerous gastric tissues, by bisulfite-SSCP analysis followed by direct sequencing. Allelic status of the TSLC1 gene was also investigated in these cell lines and primary gastric cancers. The TSLC1 promoter was methylated in two gastric cancer cell lines, KATO-III and ECC10, and in 15 out of 97 (16%) primary gastric cancers. It was not methylated in non-cancerous gastric tissues, suggesting that this hypermethylation is a cancer-specific alteration. KATO-III and ECC10 cells retained two alleles of TSLC1, both of which showed hypermethylation, associated with complete loss of gene expression. Most of the primary gastric cancers with promoter methylation also retained heterozygosity at the TSLC1 locus on 11q23.2. These data indicate that bi-allelic hypermethylation of the TSLC1 promoter and resulting gene silencing occur in a subset of primary gastric cancers.

Altered expression of G1 regulatory proteins in human soft tissue sarcomas

CONTEXT

Soft tissue sarcomas constitute a heterogeneous group of tumors for which tumorigenesis is not fully understood. Altered cell-cycle regulation may underlie the development and/or progression of human malignancies. However, data concerning the occurrence of cell-cycle aberrations in soft tissue sarcomas are very limited.

OBJECTIVES

To detect the abnormal features of cell-cycle regulatory proteins in soft tissue sarcomas and to determine the potential role of these proteins in clinical behavior.

DESIGN

The p53 and Rb-cyclin D pathways were investigated by immunohistochemical studies of p53, mdm2, pRb, p16, cyclin D1, and cdk4 proteins, respectively.

RESULTS

Of the 67 sarcomas analyzed, nuclear accumulation of p53 was detected in 25 samples (37%), and overexpression of mdm2 was found in 16 samples (24%). Both p53 and mdm2 expression correlated with tumor grade. Abnormalities involving the Rb-cyclin D pathway were identified in all of the tumors by the altered expression of either pRb (72%) or p16 (94%). Fourteen (21%) and 64 (96%) cases demonstrated cyclin D1 or cdk4 expression, respectively. Overexpression of cyclin D1 showed an association with pRb and p53. There was no correlation between pRb, p16, cyclin D1, or cdk4 and tumor grade or relapse.

CONCLUSION

Disturbance in the cell-cycle regulatory system involving the p53 pathway and the Rb-cyclin D pathway is relatively frequent in soft tissue sarcomas and may be a contributing factor in the tumorigenesis of these tumors. The alterations in the Rb-cyclin D pathway probably constitute an early event, whereas the abnormalities in the p53 pathway seem to be involved in tumor progression. It is noteworthy that cyclin D1 may play a key role in linking both pathways.

Epstein-barr virus-positive gastric carcinoma demonstrates frequent aberrant methylation of multiple genes and constitutes CpG island methylator phenotype-positive gastric carcinoma

CpG island methylation is an important mechanism for inactivating the genes involved in tumorigenesis. Gastric carcinoma (GC) is one of the tumors that exhibits a high frequency of aberrant CpG island methylation. There have been many reports suggesting a close link between Epstein-Barr virus (EBV) and the development of GC. However, little is known about the oncogenic mechanism of EBV in gastric carcinogenesis. Twenty-one cases of EBV-positive GC and 56 cases of EBV-negative GC were examined for aberrant DNA methylation of the CpG islands of 19 genes or loci and the differences in the methylation frequency between EBV-positive and -negative GCs were investigated to determine a role of aberrant methylation in EBV-related gastric carcinogenesis. The average number of methylated genes or loci was higher in EBV-positive GCs than in EBV-negative GCs (13.4 versus 7.8, respectively, P < 0.001). EBV-positive GCs showed methylation in at least 10 CpG islands (52.6% of the tested genes), whereas 62.5% of EBV-negative GCs showed methylation in <10 CpG islands. THBS1, APC, p16, 14-3-3 sigma, MINT1, and MINT25 were methylated at a frequency >90% in EBV-positive GCs. The methylation frequency difference in the respective CpG islands between EBV-positive and -negative GCs was statistically significant (P < 0.05). Among these genes or loci, the methylation frequency of p16 in the EBV-positive GCs was more than three times higher than in the EBV-negative GCs. The PTEN, RASSF1A, GSTP1, MGMT, and MINT2 were methylated in EBV-positive GCs at a frequency of more than three times that of the EBV-negative GCs. These results demonstrate a relationship between EBV and aberrant methylation in GC and suggest that aberrant methylation may be an important mechanism of EBV-related gastric carcinogenesis.

Clinicopathologic characteristics of Epstein-Barr virus-incorporated gastric cancers in Korea

We evaluated the rate of Epstein-Barr virus (EBV) infection in gastric carcinomas of Korean patients and investigated the associations between EBV infection and clinicopathological characteristics, the survival rates of patients, and p53 overexpression. EBV-encoded small RNA (EBER)-in situ hybridization and immunohistochemistry for p53 protein were done in 306 consecutive gastric carcinoma cases, of which 17 (5.6%) showed EBV infection. Of these 17 EBV-positive cases, one case strongly expressed p53 protein, while 98 (34%) of 285 EBV-negative cases overexpressed p53 (p < 0.05). The EBV-positive gastric carcinomas tended to have lymphoid stroma. They were mostly of the poorly differentiated type, negative for p53 immunoexpression, more prevalent in male patients, and diffuse according to Lauren's classification (p < 0.05). There was no significant difference in the survival rate for the EBV status. In conclusion, the EBV infection rate among gastric carcinomas in Korea is similar to that ascertained in other countries. An inverse correlation between EBV and p53 overexpression was disclosed. Further study is needed to find out whether or not two genetic changes could be functionally overlapping during gastric carcinogenesis.

Distinct chromosomal aberrations in Epstein-Barr virus-carrying gastric carcinomas tested by comparative genomic hybridization

BACKGROUND & AIMS

Approximately 10% of gastric adenocarcinomas carry the human pathogenic Epstein-Barr virus (EBV). The role of EBV in the pathogenesis of these carcinomas remains to be established.

METHODS

To obtain a comprehensive overview of chromosomal aberrations in EBV-carrying and EBV-negative gastric carcinomas we performed comparative genomic hybridization (CGH) on 44 gastric carcinomas, 10 EBV-positive, and 34 EBV-negative. Additionally, DNA flow cytometry was done.

RESULTS

Loss of chromosome 4p (P < 0.001) and of 11p (P < 0.02) was exclusively restricted to EBV-carrying gastric carcinomas. In addition, loss of 18q (P < 0.02) was significantly more frequent in EBV-carrying gastric carcinomas. The latter involves loci, which have already been linked to gastric carcinogenesis such as the DCC and SMAD4 gene. In contrast, the losses on chromosome 4 and 11 do not yet harbor a gene related to gastric carcinogenesis. No significant correlation was found between DNA-ploidy and the EBV-status. A number of chromosomal aberrations were found at comparable frequencies in both groups, i.e., losses of chromosome 17, 12q, and loss of 1p. Interestingly, gains of 13q (10/34) and 3q (5/34) and loss of 1q (5/34) were solely observed in EBV-negative gastric carcinomas.

CONCLUSIONS

These data indicate that EBV-carrying and EBV-negative gastric carcinomas have different pathogenetic pathways in which EBV might play a crucial role.

Expression, deletion [was deleton] and mutation of p16 gene in human gastric cancer

AIM

To investigate the relationship between the expression of p16 gene and the gastric carcinogenesis, depth of invasion and lymph node metastases, and to evaluate the deletion and mutation of exon 2 in p16 gene in gastric carcinoma.

METHODS

The expression of p16 protein was examined by streptavidin-peroxidase conjugated method (S-P);the deletion and mutation of p16 gene were respectively examined by polymerase chain reaction (PCR) and polymerase chain reaction single-strand conformation polymorphism analysis (PCR-SSCP) in gastric carcinoma.

RESULTS

Expression of p16 protein was detected in 96.25% (77/80) of the normal gastric mucosa, in 92.00% (45/50) of the dysplastic gastric mucosa and in 47.54% (58/122) of the gastric carcinoma. The positive rate of p16 protein expression in gastric carcinoma was significantly lower than that in normal gastric mucosa and dysplastic gastric mucosa (P < 0.05). The positive rate of p16 protein expression in mucoid carcinoma 10.00% (1/10) was significantly lower than that in poorly differentiated carcinoma 51.22% (21/41), undifferentiated carcinoma 57.69% (15/26) and signet ring cell carcinoma 62.50% (10/16) (P < 0.05). The positive rate of p16 protein in 30 cases paired primary and lymph node metastatic gastric carcinoma: There was 46.67% (14/30) in primary gastric carcinoma, 16.67% (5/30) in lymph node metastatic gastric carcinoma. The positive rate of lymph node metastatic carcinoma was significantly lower than that of primary carcinoma (P < 0.05). There was of p16 gene mutation in exon 2, but 5 cases displayed deletion of p16 gene in exon 2 in the 25 primary gastric carcinomas.

CONCLUSIONS

The expression loss of p16 protein related to the gastric carcinogenesis, gastric carcinoma histopathological subtypes and lymph metastasis. The mutation of p16 gene in exon 2 may not be involved in gastric carcinogenesis. But the deletion of p16 gene in exon 2 may be involved in gastric carcinogenesis.