A comparison of microsatellite instability in early onset gastric carcinomas from relatively low and high incidence European populations

Autoimmune responses induced by Helicobacter pylori improve the prognosis of gastric carcinoma

Gastric carcinoma (GC) remains one of most serious malignant tumors worldwide, with Helicobacter pylori being the definite carcinogen. The H. pylori components, cytotoxin-associated gene A (CagA), vacuolating toxin A (VacA) and blood-group antigen-binding adhesin gene (BabA), can mimic and bind to specific receptors or surface molecules both on gastric epithelial cells and platelets, in which CagA and VacA may also be directly involved in loosening of tight junctions in monolayers of polarized gastric epithelial cells. It has been shown that a history of H. pylori infection is found in the majority of patients with GC, and that anti-CagA, anti-VacA and anti-BabA antibodies targeting both H. pylori components and host mimic molecules can be detected in them with increased levels. Patients with GC who are positive for H. pylori prospectively have a better outlook than those negative. The stimulation of mentioned autoantibodies in antigen processing and presentation and subsequent T-cell activation and proliferation improves host immune status. On the other hand, in an autoimmune response, autoantibodies can induce the cross-reaction against those localized or circulating GC cells, which are characterized by mimic or absorbed H. pylori antigens, and lead to the killing and even suppressing of metastasis of cancer cells. Therefore, we here hypothesize that autoimmune responses induced by H. pylori components may play a key role in improving the prognosis of patients with gastric carcinoma.

Helicobacter pylori as a prognostic indicator after curative resection of gastric carcinoma: a prospective study

BACKGROUND

The effect of Helicobacter-pylori status on survival after curative resection for gastric adenocarcinoma is unknown. We aimed to follow-up patients who were positive or negative for infection with H pylori who had curative (ie, R0) resection for gastric adenocarcinoma to assess differences in relapse-free survival and overall survival.

METHODS

Before surgery, we assessed the H pylori status of 166 patients who had R0 resection for gastric adenocarcinoma between 1992 and 2002 with bacterial culture, histological analyses (ie, staining with haematoxylin and eosin and with Warthin-Starry), and serological analyses.

FINDINGS

At a median follow-up of 53.0 months (range 1-146), relapse-free survival was 56.7 months (95% CI 4.7-108.7) and overall survival was 61.9 months (13.0-110.9) in patients positive for H pylori, compared with 19.2 months (12.7-25.6) and 19.2 months (7.1-31.3), respectively, in patients negative for H pylori (p=0.0009 for difference in relapse-free survival between groups, and p=0.0017 for difference in overall survival between groups). In multivariate analyses, H pylori was an independent prognostic factor for relapse-free survival (hazard ratio 2.16 [95% CI 1.33-3.49]) and overall survival (2.00 [1.22-3.27]). Depth of tumour invasion (2.60 [1.66-4.08]), lymph-node metastasis (2.11 [1.25-3.57]), and patient age 67.5 years or older (1.75 [1.11-2.75]) were also independent prognostic factors for overall survival.

INTERPRETATION

Tumour-specific immune responses might be downregulated in patients who are negative for H pylori, and these patients should be followed up carefully because of a poor outlook.

Tumor microsatellite instability in early onset gastric cancer

Gastric cancer (GC) remains a leading cause of cancer mortality worldwide. Genetic factors are implicated, including DNA mismatch repair (MMR) deficiency manifested as tumor microsatellite instability (MSI). However, a standardized panel of markers and a definition of low-versus-high level MSI in GC are lacking. We examined a population-based cohort of early onset (or=3 markers MSI+/MSI-high) demonstrated MMR protein deficiency. Three novel hMLH1 mutations (two germline frameshift and one somatic nonsense) were also found. The only significant clinicopathological associations were increased tumor size in MSI+ cases (P=0.04) and Lauren histotype (P=0.006) and tumor grade (P=0.007) in MSI-high cases. Tumor size, location, depth, nodal status, and Ming subtype were significant prognostic variables. Therefore, we propose a new definition of high-level MSI based on unifying characteristics of instability of more than or equal to three of six mononucleotide markers and loss of MMR protein expression.

Inverse association between cyclooxygenase-2 overexpression and microsatellite instability in gastric cancer

This study examined the association between cyclooxygenase-2 (COX-2) overexpression and microsatellite instability (MSI) in gastric cancer. COX-2 expression was assessed by immunohistochemistry and scored in a semi-quantitative manner whereas MSI status was characterized by nine microsatellite markers. The clinicopathological features of cancers including survival data were analyzed. Of the 109 gastric cancers studied, COX-2 overexpression and high level of MSI (MSI-H) was detected in 64.2 and 22.0% cases respectively. Gastric tumors with MSI-H phenotypes had significantly lower level of COX-2 expression levels when compared to MSI-L and MSS tumors (P=0.002). Moreover, COX-2 overexpression was associated with tumor invasion beyond submucosa (P=0.045) and there was a trend favoring better survival in gastric cancers without COX-2 overexpression (P=0.07). The results from this study suggest that gastric cancer with microsatellite instability or COX-2 overexpression present with diverse clinicopathological features.