Alteraciones genéticas en gastritis crónica: Estudio de inestabilidad microsatelital y pérdida de la heterocigocidad / Genetic changes in chronic gastritis: study of microsatellite instability and loss of heterozygosity

Background: Multifocal chronic gastritis, associated to intestinal metaplasia, is considered a preneoplastic lesion, closely associated to intestinal type gastric cancer. Aim: To study the frequency of microsatellite instability (MSI) and loss of heterozygosity (LOH) in areas of chronic gastritis and intestinal metaplasia in gastric biopsies of patients without cancer. Material and methods: Gastric biopsy samples from 34 patients without cancer (22 with multifocal atrophic gastritis and 12 with diffuse antral gastritis), were studied. Glands from areas of chonic gastritis and intestinal metaplasia and lymphocytes, were collected using laser microdissection of paraffin embedded samples. The analysis of 15 mono and dinucleotide microsatellites was used to assess LOH and MSI. Results: LOH and MSI were found in some of the markers in 55% (12/22) and 59% (13/22) of cases with intestinal metaplasia, respectively. Only one of 12 areas with diffuse atrophic gastritis had MSI and a different area had LOH (p <0.05 or less, when compared with areas of multifocal atrophic gastritis). Three areas of normal epithelium in patients with multifocal atrophic gastritis, also had alterations. Most of these alterations were concordant with adjacent areas with intestinal metaplasia. Conclusions: LOH and MSI was found in areas of intestinal metaplasia in more than half of the studied cases and in few areas of atrophic gastritis without intestinal metaplasia. These findings suggest that genotypic alterations may precede phenotypic modifications and that intestinal metaplasia is a preneoplastic lesion (Rev Méd Chile 2003; 131: 1365-74).

Helicobacter pylori in recently-diagnosed versus Chronic duodenal ulcer

Helicobacter pylori is one of the main causes of type B gastritis and is frequently found in the gastric antrum or in areas of gastric metaplasia in duodenal ulcer patients. The aim of this study was to evaluate Helicobacter pylori and gastric metaplasia prevalence in duodenal ulcer patients within their first diagnosed episode compared to those with chronic ulcer disease. Eighty three patients were prospectively studied in a 2- year period. they were divided into 3 groups: Group I, control, included 29 patients; Group II, 17 patients, included patients with first diagnosed duodenal ulcer episode; and Group III, 37 patients, with chronic ulcer disease. Helicobacter pylori prevalence in duodenum was significatively lower in Group II versus Group III and controls (67.5 percent; 0 percent and 3.2 percent respectively) p<0.001). In the antrum Hp prevalnce was also lower in Group II compared to Group III and I (41 percent, 78,3 percent and 24.1 percent) with a significative difference (p<0.001). Gastric metaplasia was significantly higher in Group III versus Group II and controls. These results suggest that Helicobacter pylori plays an important but not exclusive role in the pathogenesis of these disease together with other factors.