Epstein-Barr virus, p53 protein, and microsatellite instability in the adenoma-carcinoma sequence of the stomach

Epstein-Barr virus associated gastric dysplasia: a new rare entity?

Epstein-Barr virus (EBV) infection characterizes a portion of gastric adenocarcinomas. However, since there is lack of evidence of EBV presence in pre-neoplastic lesions of gastric mucosa, the etiologic role of EBV in gastric carcinogenesis is still debated. We report an unusual case of an EBV-associated foveolar gastric dysplasia associated with a focus of EBV-positive low-grade tubular adenocarcinoma, arisen in the context of a lymphocytic-like (EBV-positive) gastritis. The present case offers the unique opportunity to determine whether EBV is an early or late event in gastric cancer development and to evaluate its prevalence in patients with gastric dysplasia. To properly address this question, we investigated EBER expression in a large mono-institutional series of gastric and gastro-esophageal cancers (n = 594) and associated precursor lesions (n = 84). All the selected gastric dysplastic lesions (n = 43) resulted EBV negative. In most cases, EBV is present only in gastric and gastroesophageal junction adenocarcinomas, but not in their precursor lesions. However, the reported case indicates that non-conventional EBV-associated dysplasia may represent a novel histopathological entity in the gastric dysplasia scenario and that EBV could play an early direct role in gastric carcinogenesis.

Clinicopathologic Characteristics of Microsatellite Instable Gastric Carcinomas Revisited: Urgent Need for Standardization

Microsatellite instable gastric cancer (MSI-GC) is a specific molecular subtype of GC. We studied the phenotypes, genotypes, and clinicopathologic characteristics of MSI-GC in a white GC cohort and compared our findings with an extended literature review. The study cohort consisted of 482 patients. Specimens were available from 452 cases and were used for immunostaining (MLH1, PMS2, MSH2, MSH6) and molecular biological analyses (BAT-25, BAT-26, NR-21, NR-24, NR-27; Epstein-Barr virus in situ hybridization). Thirty-four (7.5%) GCs were MSI. Loss of MLH1 and/or PMS2 was found in 30 (88%) MSI-GC, 3 (9%) showed loss of MSH2 and/or MSH6. One (3%) MSI-GC was identified only by molecular biological testing. A single case was heterogeneous and contained microsatellite-stable and instable tumor areas. Twenty-one (62%) MSI-GCs showed unusual histologic features. MSI-GC was not found in diffuse-type or Epstein-Barr virus-positive GC. MSI-GC was significantly more prevalent in elderly patients, distal stomach, and was associated with a significantly lower number of lymph node metastases and a significantly better overall and tumor-specific survival. MSI-GC constitutes a small but relevant subgroup of GC with distinct clinicopathologic characteristics. Our literature review illustrates the shortcomings of missing standardized testing algorithms with prevalences of MSI-GC ranging from 0% to 44.5%. Future studies should test the hypothesis that patients with MSI-GCs may not need adjuvant/perioperative chemotherapy. However, this will require a standardized, quality-controlled diagnostic algorithm of MSI for GC.

Molecular markers of mucosa harboring gastric adenomas

CONTEXT

Gastric adenoma is a precursor lesion of the adenocarcinoma.

OBJECTIVE

To characterize gastric adenomas according to the mucin immunoexpression and to evaluate the immunoexpression of p53, p16ink4a, BCL-2, cyclin D, Ki-67, in the adenoma and in the gastric mucosa harboring adenoma.

METHODS

Forty gastric specimens from 20 patients were classified as intestinal (MUC2-goblet cell mucin) or foveolar (MUC5AC-gastric-foveolar mucin) adenomas. Immunohistochemistry was performed using streptavidin-biotin-complex method.

RESULTS

Twelve (60%) patients were men. The mean age was 67.9±12.9 years-old. Intestinal adenomas were detected in 13 (65%) patients and gastric type in 7 (35%). Low-grade dysplasia was present in 13 (65%) of the adenomas, high-grade in 3 (15%), and adenocarcinoma within the polyp in 4 (20%). Six (30%) patients had synchronous adenocarcinoma. p53 immunoexpression was observed in 6/20 (30%) of adenomas, and in 2/6 (33.3%) of synchronous tumors. There was an association between p53 immunoexpression and intestinal type of adenoma/tumor, P=0.04. There was no association between p16ink4a, Bcl-2, cyclin D and Ki-67 and adenoma clinicopathological characteristics.

CONCLUSION

Immunohistochemistry may be useful to classify the adenomas subtypes and may define the pathway of adenoma to carcinoma sequence.

Clinical characterization of gastric lesions initially diagnosed as low-grade adenomas on forceps biopsy

AIM

The aim of this study was to elucidate characteristics of gastric lesions that are initially diagnosed as low-grade adenomas and to establish appropriate treatment.

METHODS

We retrospectively reviewed 231 lesions initially diagnosed as gastric adenomas. All forceps biopsy samples were histologically diagnosed as category 3 low-grade adenomas according to the revised Vienna Classification. All patients underwent endoscopic resection with endoscopic findings and post-resection diagnoses evaluated subsequently.

RESULTS

Sixty-three lesions were initially diagnosed as depressed adenomas, and 168 lesions were diagnosed as protruding adenomas. The depressed lesions were significantly smaller (11.6 ± 5.0 mm) than the protruding lesions (17.0 ± 10.8 mm) (P < 0.001). Diagnoses reclassified to category 4 mucosal high-grade neoplasia (i.e. high-grade adenoma, adenocarcinoma in adenoma and adenocarcinoma) were more frequent among depressed lesions (52.4%) than among protruding lesions (31.0%) (P = 0.004). Multivariate analysis of all 231 lesions showed that lesion size larger than 20 mm (P < 0.001) and depressed appearance (including central depression) (P < 0.001) were significant independent factors suggesting cancer. For the 168 protruding lesions, lesion size larger than 20 mm (P < 0.001) and central depression (P < 0.001) were significant independent factors suggesting cancer. For the 63 depressed lesions, lesion size larger than 15 mm (P = 0.016) and a moth-eaten appearance (P = 0.017) were significant independent factors in the pre-treatment diagnosis of cancer.

CONCLUSIONS

Adenocarcinoma lesions were often found in depressed lesions and protruding lesions with central depression. Endoscopic resection for total biopsy is recommended, even if forceps biopsy indicates low-grade adenoma, as pre-treatment biopsy may be inadequate for an accurate histological diagnosis.

Gastric epithelial dysplasia: the Western perspective

The need for early diagnosis of gastric cancer is emphasized by the fact that gastric cancer remains the second most common cause of cancer related deaths worldwide. The aggressive surveillance and definite therapy for low and high-grade dysplasia, which can be achieved endoscopic means, remains the cornerstone of clinical management. Although the precursor status of dysplasia is not contested, its classification is controversial and fraught with marked inter-observer variations. Most cases of gastric dysplasia have an "intestinal" phenotype referred to as adenomatous dysplasia. Hyperplastic (type II dysplasia) is another less common variant. The progression of dysplasia to carcinoma is paralleled by a stepwise accumulation of multiple, but yet uncertain, genetic abnormalities. There are no immunohistochemical or molecular assays that can stratify with certainty the risk of progression to cancer. Given the low rate of transformation of low-grade dysplasia, annual endoscopic surveillance with re-biopsy is advocated. A diagnosis of indefinite for dysplasia should also prompt endoscopic surveillance. A diagnosis of high-grade dysplasia is more ominous, since it progress to cancer in most cases. However, the novel imaging and endoscopic modalities have modified management strategies with mucosal lesions amenable to endoscopic resection, while surgical resection is reserved to invasive adenocarcinoma with submucosal invasion.

Gastric preneoplastic lesions and epithelial dysplasia

The incidence of gastric cancer is declining; however, it remains the second most common cause of cancer-related deaths worldwide. This article describes gastric preneoplastic lesions and epithelial dysplasia. The possible role of Helicobacter pylori infection is emphasized.

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.

Microsatellite instability and gastric non-invasive neoplasia in a high risk population in Cesena, Italy

BACKGROUND/AIMS

In the natural history of gastric cancer, non-invasive neoplasia (NiN) precedes invasive carcinoma. A histological classification of gastric NiN has recently been proposed by a World Health Organisation international panel of experts. Genetic instability is known to be among the molecular pathways involved in gastric oncogenesis. In this retrospective cross sectional study, microsatellite instability (MSI) was analysed in a consecutive series of NiN and NiN related histological alterations from a northern Italian region at high risk for gastric cancer.

PATIENTS/METHODS

Fifty five consecutive cases (indefinite for NiN, 29 cases; low grade NiN, 17 cases; high grade NiN, nine cases) were analysed by radioactive polymerase chain reaction and electrophoresis for microsatellite alterations at six loci (BAT25, BAT26, D2S123, D5S346, D17S250, and D3S1317). MSI was defined according to the Bethesda criteria distinguishing: (1) no instability in the analysed loci; (2) low frequency MSI (MSI-L); and (3) high frequency MSI (MSI-H). Immunohistochemical expression of MLH1 and MSH2 proteins was also analysed in all cases.

RESULTS

Overall, MSI was found in 11 of 55 cases (indefinite for NiN, five of 29 (MSI-L, four; MSI-H, one); low grade NiN, three of 17 (MSI-L, one; MSI-H, two); high grade NiN, three of nine (MSI-L, one; MSI-H, two).

CONCLUSIONS

In an Italian high risk area for gastric cancer, MSI is part of the spectrum of genetic alterations in gastric non-invasive neoplasia. In European populations at high risk of gastric cancer, DNA repair system alterations are thought to be among the early molecular events in gastric carcinogenesis.

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.

Molecule action mechanisms of NM-3 on human gastric cancer SGC-7901 cells in vivo or in vitro

AIM: To study the molecule action mechanisms of NM-3 on the growth of human gastric cancer SGC-7901 cells in vivo or in vitro.

METHODS: SGC-7901 from human non-differentiated gastric cancer cell line was cultured with NM-3 at 100 mg/mL for 24 h. We observed its inhibitory rate and the density of micro-vascular growth in grafted mice with human gastric cancer SGC-7901. The apoptosis of human gastric cancer SGC-7901 was revealed in NM-3 treatment group by using terminal deoxynucleotidyl transferase-mediated deoxy-uridine triphosphate-fluorescene nick end labeling (TUNEL) method and flow cytometry analysis.

RESULTS: The growth of SGC-7901 cells was markedly inhibited compared with control growp, which was smaller than that in normal saline control group (4.17 g ± 0.22 g vs 9.45 g ± 1.38 g, P < 0.01). The level of apoptosis of human gastric cell line SGC-7901 was obviously increased in NM-3 treatment group at 1 mg.L^-1 for 24 h. NM-3 inducing apoptotic index in NM-3 plus carboplatin group was 3.5 times that of carboplatin control group (TUNEL: 27.98% ± 6.12% vs 12.94% ± 2.12%, FACScan: 26.86% ± 5.69% vs 11.86% ± 1.09%, P < 0.01). Western blot analysis showed that the apoptotic index of human gastric cancer was elevated for 12, 24 and 36 h with an evident time-effect relationship in groups at 100 mg.L^-1. NM-3 enhanced the inhibitive effects and sensitivity of chemotherapy for human gastric cancer in nude mice. These results suggested that NM-3 played a key inhibitive role in the growth of grafted human gastric cancer in nude mice.

CONCLUSION: NM-3 can inhibit the growth of human gastric cancer cell line SGC-7901, and enhance the sensitivity of carboplatin on SGC-7901 and induced its apoptosis.

A gene encoding an apurinic/apyrimidinic endonuclease-like protein is up-regulated in human gastric cancer

AIM: To identify the gene that may predispose to human gastric cancer and to analyze its expression in gastric cancer and non-tumorous gastric mucosa.

METHODS: Cancer, para-tumor, and non-tumor gastric tissues were studied for gene expression profile using fluorescent differential display reverse transcription polymerase chain reaction (DDRT-PCR). The differentially expressed bands of interest were analyzed by cloning, Northern blotting, and sequencing. The sequencing results were compared with the GenBank database for homology and conserved domain analysis. In situ hybridization with DIG-labeled cRNA probes was used to detect the expression of gene in paraffin embedded gastric adenocarcinoma and non-cancerous tissues.

RESULTS: A gene expressed higher in tumor and para-tumor tissues than in their non-tumor counterparts of all 7 tested gastric adenocarcinoma patients was identified by means of DDRT-PCR analysis. It was named GCRG213 (gastric cancer related gene 213). Northern blot confirmed the differential expression. GCRG213 (GenBank No. AY053451) consisted of 1094 base pairs with an open reading frame (ORF) which encoded 142 amino acids. The deduced amino acid sequence contained a putative conserved domain, apurinic/apyrimidinic endonuclease (APE). In situ hybridization analysis showed that GCRG213 was expressed higher in gastric cancer tissues than in their corresponding non-tumor ones. Precancerous leisions of gastric adenocarcinoma showed a high GCRG213 expression, too. No difference of the expression patterns was found between the early and advanced gastric cancer.

CONCLUSION: A gene named GCRG213 was identified in human gastric adenocarcinoma. It encoded an APE-like protein which was probably a new member of the APE family. GCRG213 was over-expressed not only in gastric cancer, but also in its precancerous leisions. The role of GCRG213 expression in carcinogenesis needs further study.