Proteomics signature of autoimmune atrophic gastritis: towards a link with gastric cancer

Abstract

Background: Autoimmune atrophic gastritis (AAG) is a chronic disease that can progress to gastric cancer (GC). To better understand AAG pathology, this proteomics study investigated gastric proteins whose expression levels are altered in this disease and also in GC.

Methods: Using two-dimensional difference gel electrophoresis (2D-DIGE), we compared protein maps of gastric corpus biopsies from AAG patients and controls. Differentially abundant spots (|fold change|≥ 1.5, P < 0.01) were selected and identified by LC-MS/MS. The spots were further assessed in gastric antrum biopsies from AAG patients (without and with Helicobacter pylori infection) and from GC patients and unaffected first-degree relatives of GC patients.

Results: 2D-DIGE identified 67 differentially abundant spots, with 28 more and 39 less abundant in AAG-corpus than controls. LC-MS/MS identified these as 53 distinct proteins. The most significant (adjusted P < 0.01) biological process associated with the less abundant proteins was "tricarboxylic acid cycle". Of the 67 spots, 57 were similarly differentially abundant in AAG-antrum biopsies irrespective of H. pylori infection status. The differential abundance was also observed in GC biopsies for 14 of 28 more abundant and 35 of 39 less abundant spots, and in normal gastric biopsies of relatives of GC patients for 6 and 25 spots, respectively. Immunoblotting confirmed the different expression levels of two more abundant proteins (PDIA3, GSTP gene products) and four less abundant proteins (ATP5F1A, PGA3, SDHB, PGC).

Conclusion: This study identified a proteomics signature of AAG. Many differential proteins were shared by GC and may be involved in the progression of AAG to GC.

Keywords: Autoimmune disease; Biological markers; Gastric cancer; Gastritis; Proteomics.

Fig. 1

Two-dimensional proteome map of pooled proteins (450 µg) of gastric corpus biopsy specimens from patients with AAG-corpus and controls. Proteins were resolved on an immobilized pH 3–10 gradient, followed by SDS-PAGE (8–16% acrylamide). The numbers indicate the 67 differentially abundant spots between AAG-corpus and control groups (i.e. present on > 70% of spot maps, |fold change|≥ 1.5, Student's t test P < 0.01). IEF, isoelectric focusing

Fig. 2

Grouping of differentially abundant spots on 2D-DIGE between AAG-corpus and control groups. a Principal component analysis. Each circle represents an individual spot map. b Hierarchical clustering. The dendrogram on the left orders the spots so that similar data are displayed next to each other. The dendrogram on the top orders the samples by similarity

Fig. 3

Abundances of seven differentially abundant spots in the five experimental groups and controls, expressed as log standardized abundance from 2D-DIGE. Dots mark individual samples, and the line connects group mean values. Different letters indicate significantly different groups (P < 0.01, one-way ANOVA). a Three selected spots more abundant in AAG-corpus than controls; b Four selected spots less abundant in AAG-corpus than controls. Data for the remaining 60 spots are shown in Figure S1

Fig. 4

Validation analysis for seven differentially abundant spots in two additional sets of gastric biopsies vs. controls, expressed as log standardized abundance from 2D-DIGE. Dots mark individual samples, and the line connects group mean values. Different letters indicate significantly different groups (P < 0.01, one-way ANOVA). a Three selected spots more abundant in AAG-corpus than controls; b Four selected spots less abundant in AAG-corpus than controls

Fig. 5

Immunochemical detection of seven differentially abundant proteins, indicated by gene names on the right. Samples are pools of extracted protein from six gastric biopsy specimens per study group. a Image of the gel acquired with Chemidoc system before transfer to nitrocellulose membranes. b Western blots of the selected proteins