EBV infection and mismatch repair deficiency mediated by loss of hMLH1 expression contribute independently to the development of multiple synchronous gastric carcinomas

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.

Programmed death ligand-1 and MET co-expression is a poor prognostic factor in gastric cancers after resection

Programmed death-ligand 1 (PD-L1) plays an essential protein for immune evasion, contributing to tumor development and progression. Recent studies have reported MET as an upregulator for PD-L1 overexpression through an oncogenic pathway. However, an association between PD-L1 expression with MET has not been reported in gastric cancer.The prognostic significance of PD-L1 and its association with Epstein-Barr virus (EBV), microsatellite instability (MSI), and mucin phenotype remain controversial. We performed in situ hybridization for EBV-encoded RNA and immunohistochemistry in tissue microarrays for 394 gastric cancers. A multiplex polymerase chain reaction with five quasimonomorphic markers was performed for MSI. PD-L1 expression was observed in 123 cases (31.2%), and clinicopathological features such as MET overexpression, high pT stage, and a lack of lymphatic invasion represent significant risk factors associated with PD-L1 overexpression in gastric cancers. No associations of EBV, MSI, or mucin phenotype with PD-L1 expression were statistically significant. PD-L1 expression was a strong indicator for worse overall survival (OS) but borderline significant in disease-free survival (DFS). A combined analysis of PD-L1 and MET expression indicated that the PD-L1+/MET+ subgroup showed the worst prognosis when compared to the PD-L1-/MET- subgroup, which had the best clinical outcome. Furthermore, PD-L1 overexpression exhibited poor prognosis in terms of both OS and DFS in EBV-negative, microsatellite stable, and intestinal mucin phenotype tumors. In conclusion, this is the first study to evaluate the overexpression of MET as a risk factor for PD-L1 positivity in gastric cancer tissue as well as the reliability and prognostic relevance of PD-L1/MET co-expression after surgery.

Epstein-Barr virus infection serves as an independent predictor of survival in patients with lymphoepithelioma-like gastric carcinoma

BACKGROUND

The pathogenesis and clinicopathologic characteristics of Epstein-Barr virus (EBV)-negative lymphoepithelioma-like gastric carcinoma (LELC) are still unclear. In addition, it remains controversial whether EBV infection itself affects the prognosis of LELC.

METHODS

Between 1995 and 2011, 145 LELC patients (124 patients with EBV infection and 21 patients without EBV infection) underwent radical gastrectomy with D2 lymph node dissection. The clinicopathologic features and prognosis of EBV-negative LELC cases were compared with those of EBV-positive LELC cases. The median duration of follow-up after surgery was 55 months. Microsatellite instability (MSI) analysis was performed on 20 EBV-negative LELC cases.

RESULTS

EBV-negative LELC accounted for 14.5 % of the total LELC cases. EBV-negative LELC was significantly associated with older age, female sex, advanced T stage, and advanced American Joint Committee on Cancer (AJCC) tumor stage compared with EBV-positive LELC. In univariate analysis, patients with EBV-negative LELC had significantly shorter overall, disease-specific, and recurrence-free survival than those with EBV-positive LELC. The 5-year overall survival rates were 81.0 % for patients with EBV-negative LELC and 96.2 % for patients with EBV-positive LELC. In a Cox proportional hazards model, EBV infection, age, and AJCC tumor stage were identified as independent predictors of overall survival. MSI-high, MSI-low, and microsatellite-stable tumors accounted for 25, 10, and 65 % of EBV-negative LELC cases, respectively. MSI status did not affect the prognosis of EBV-negative LELC cases.

CONCLUSIONS

EBV infection serves as an independent predictor of survival in patients with LELC. EBV-negative LELC exhibited clinicopathologic features and prognosis distinct from those of EBV-positive LELC.

Epstein-barr virus in gastro-esophageal adenocarcinomas - single center experiences in the context of current literature

Epstein–Barr virus (EBV)-associated gastric carcinomas (GC) represent a distinct and well-recognized subtype of gastric cancer with a prevalence of around 10% of all GC. In contrast, EBV has not been reported to play a major role in esophageal adenocarcinomas (EAC) and adenocarcinomas of the gastro-esophageal junction (GEJ). We report our experiences on EBV in collections of gastro-esophageal adenocarcinomas from two surgical centers and discuss the current state of research in this field. Tumor samples from 465 primary resected gastro-esophageal adenocarcinomas (118 EAC, 73 GEJ, and 274 GC) were investigated. Presence of EBV was determined by EBV-encoded small RNAs (EBER) in situ hybridization. Results were correlated with pathologic parameters (UICC pTNM category, Her2 status, tumor grading) and survival. EBER positivity was observed in 14 cases. None of the EAC were positive for EBER. In contrast, we observed EBER positivity in 2/73 adenocarcinomas of the GEJ (2.7%) and 12/274 GC (4.4%). These were of intestinal type (seven cases) or unclassifiable (six cases), while only one case was of diffuse type according to the Lauren classification. No association between EBV and pT, pN, or tumor grading was found, neither was there a correlation with clinical outcome. None of the EBER positive cases were Her2 positive. In conclusion, EBV does not seem to play a role in the carcinogenesis of EAC. Moreover, adenocarcinomas of the GEJ show lower rates of EBV positivity compared to GC. Our data only partially correlate with previous reports from the literature. This highlights the need for further research on this distinct entity. Recent reports, however, have identified specific epigenetic and genetic alterations in EBV-associated GC, which might lead to a distinct treatment approach for this specific subtype of GC in the future.

Update on Epstein-Barr virus and gastric cancer (review)

Epstein-Barr virus-associated gastric carcinoma (EBVaGC) is a distinct subtype that accounts for nearly 10% of gastric carcinomas. EBVaGC is defined by monoclonal proliferation of carcinoma cells with latent EBV infection, as demonstrated by EBV-encoded small RNA (EBER) in situ hybridization. EBVaGC has characteristic clinicopathological features, including predominance among males, a proximal location in the stomach, lymphoepithelioma-like histology and a favorable prognosis. EBVaGC belongs to latency type I or II, in which EBERs, EBNA-1, BARTs, LMP-2A and BART miRNAs are expressed. Previous studies have shown that some EBV latent genes have oncogenic properties. Recent advances in genome-wide and comprehensive molecular analyses have demonstrated that both genetic and epigenetic changes contribute to EBVaGC carcinogenesis. Genetic changes that are characteristic of EBVaGC include frequent mutations in PIK3CA and ARID1A and amplification of JAK2 and PD-L1/L2. Global CpG island hypermethylation, which induces epigenetic silencing of tumor suppressor genes, is also a unique feature of EBVaGC and is considered to be crucial for its carcinogenesis. Furthermore, post-transcriptional gene expression regulation by cellular and/or EBV-derived microRNAs has attracted considerable attention. These abnormalities result in significant alterations in gene expression related to cell proliferation, apoptosis, migration and immune signaling pathways. In the present review we highlight the latest findings on EBVaGC from clinicopathological and molecular perspectives to provide a better understanding of EBV involvement in gastric carcinogenesis.

Deregulation of immune response genes in patients with Epstein-Barr virus-associated gastric cancer and outcomes

BACKGROUND & AIMS

Patients with Epstein-Barr virus-associated gastric carcinoma (EBVaGC) have a better prognosis than those with gastric cancer not associated with EBV infection (EBVnGC). This is partly because EBV infection recruits lymphocytes, which infiltrate the tumor. A high degree of tumor heterogeneity is likely to be associated with poor response. We investigated differences in gene expression patterns between EBVaGC and EBVnGC.

METHODS

We used gene expression profile analysis to compare tumor and nontumor gastric tissues from 12 patients with EBVaGC and 14 patients with EBVnGC. Findings were validated by whole transcriptome RNAseq and real-time quantitative polymerase chain reaction analyses. CD3(+) primary T cells were isolated from human blood samples; migration of these cells and of Jurkat cells were measured in culture with EBV-infected and uninfected gastric cancer cells.

RESULTS

Based on Pearson correlation matrix analysis, EBVaGCs had a higher degree of homogeneity than EBVnGCs. Although 4550 genes were differentially expressed between tumor and nontumor gastric tissues of patients with EBVnGC, only 186 genes were differentially expressed between tumor and nontumor gastric tissues of patients with EBVaGC (P < .001). This finding supports the concept that EBVaGCs have fewer genetic and epigenetic alterations than EBVnGCs. Expression of major histocompatibility complex class II genes and genes that regulate chemokine activity were more often deregulated in EBVaGCs compared with nontumor tissues. In culture, more T cells migrated to EBV-infected gastric cancer cells than to uninfected cells; migration was blocked with a neutralizing antibody against CXCR3 (a receptor for many chemokines).

CONCLUSIONS

Fewer genes are deregulated in EBVaGC than in EBVnGC. Most changes in EBVaGCs occur in immune response genes. These changes might allow EBVaGC to recruit reactive immune cells; this might contribute to the better outcomes of these patients compared with those with EBVnGC.

Pyloric gland adenoma in Lynch syndrome

The prevalence of gastric cancer associated with Lynch syndrome (LS) is highly variable, and the underlying histologic pathway or molecular mechanisms remain unclear. From 1995 to 2012, 15 patients had been treated for both gastric and colonic adenocarcinomas and diagnosed as LS. In all cases, pathologic review, immunohistochemical analysis for mismatch-repair proteins, and microsatellite instability (MSI) tests were performed. To confirm LS, germline mutation tests and multiplex ligation-dependent probe amplification were performed. All gastric and colonic carcinomas were MSI-high and lost expressions of MLH1/PMS2 in 11 (73%) cases and MSH2/MSH6 in 4 (27%) cases. Remarkably, in a patient with LS and germline mutation of MLH1 gene, pyloric gland adenoma (PGA) transformed to adenocarcinoma during follow-up. In 2 additional cases, PGA was found adjacent to advanced gastric cancers. All PGAs in LS patients were MSI-high and lost expression of mismatch-repair proteins (MLH1/PMS2 in 2 cases and MSH2/MSH6 in 1 case), whereas none of the 14 sporadic PGAs was MSI-high or had lost expression of mismatch-repair proteins. On the basis of these observations, although very rare, we suggest the possibility that PGA may be a precursor lesion to gastric adenocarcinoma in LS and that the mismatch-repair deficient pathway of carcinogenesis is involved early in the gastric carcinogenesis pathway.