Relationship between Helicobacter pylori infection and expression of c-myc, Bcl-2, and Bax protein in different gastric mucosa lesions

Objective: Helicobacter pylori (HP) has been believed to be a carcinogen of gastric carcinoma. However, its mechanism was yet not clearly understood. This study was designed to investigate the relationship between HP infection and gastric epithelial cell proliferation as well as apoptosis in different gastric mucosa lesions and elucidate the probable mechanism of gastric carcinogenesis relating with HP infection.

Methods: A total of 272 cases were available for the study including 42 cases of chronic gastritis (CG), 46 cases of intestinal metaplasia I or II (IM I- II), 25 cases of intestinal metaplasia III (IM III), 21 cases of mild dysplasia (Dys I), 54 cases of modest or severe dysplasia (Dys II- III), and 84 cases of gastric cancer (GC). HP infection was detected by Warthin-Starry bacterium staining method and streptavidin-peroxidase (SP) immunohistochemical method. HID-AB(pH2.5)- PAS method was used to define the quality of mucus. The expression of c-myc, Bcl-2, and Bax were detected using SP immunohistochemical method. The chi-square test and the Fisher's exact probability test were used to compare the frequencies.

Results: (1)The expression of c-myc and Bcl-2 increased as gastric mucosa lesions developed from CG,IM,Dys to GC,but the expression of Bax decreased. The expression of c-myc was significantly higher in GC than that in Dys II- III and IM III(all P< 0.01), but the expression of Bax was significantly lower in GC than that in Dys II- III and IM III(P< 0.05 or P< 0.01). (2)The expression of c-myc in IM III and Dys II- III with HP infection was 62.50% and 66.67%,respectively, significantly higher than that without infection(11.11%,27.78%,all P< 0.05). The expression of Bax in CG, IM I- II and IM III with HP infection were 87.10%, 81.25%, and 62.50%, respectively, significantly higher than those without infection (54.55%, 42.86%, 11.11%, all P< 0.05). Furthermore HP infection was associated with the expression of Bcl-2 in IM III, Dys II- III and GC (P< 0.05 or P< 0.01).

Conclusions: HP infection can cause serious imbalance between cell proliferation and apoptosis in the precancerous lesions (IM III and Dys II- III), giving chances for gastric carcinogenesis.