CpG island methylator phenotype and Helicobacter pylori infection associated with gastric cancer

To investigate the association between the CpG island methylator phenotype (CIMP) and serum Helicobacter pylori (H. pylori) levels for clinical prediction of gastric cancer (GC) progression.

We analyzed the serum CIMP status of 75 patients with GC using a methylation marker panel and a methylation-specific polymerase chain reaction. Serum samples from 40 healthy persons were examined at the same time. The genes examined were APC, WIF-1, RUNX-3, DLC-1, SFRP-1, DKK and E-cad. H. pylori infection in serum was assayed with an anti-H. pylori immunoglobulin G antibody test and a rapid urease test.

The frequencies of high-level methylation in GC tissues for the seven genes were: 48% for APC, 57.33% for WIF-1, 56% for RUNX-3, 50.67% for DLC-1, 52% for SFRP-1, 54.67% for DKK, and 48% for E-cad. The frequencies in GC serum were 30.67% for APC, 34.67% for WIF-1, 37.33% for RUNX-3, 29.33% for DLC-1, 33.33% for SFRP-1, 32% for DKK, and 26.67% for E-cad. CIMP+ (defined as ≥ 3 methylated genes) was associated with 47 (62.67%) GC tissue samples and 44 (58.67%) GC serum samples. CIMP+ was not associated with non-neoplastic mucosal tissues or the serum of healthy persons. Of the 75 GC cases, 51 (68%) were H. pylori+, and 24 (32%) were H. pylori-. Of the 51 H. pylori+ cases, 36 were CIMP+ and 15 were CIMP-. In contrast, for the 24 H. pylori- cases, 11 were CIMP+, and 13 were CIMP-. The difference was significant between the H. pylori+ and H. pylori- groups (χ(2) = 4.27, P < 0.05). Of the 51 H. pylori+ GC patients, 34 were CIMP+ and 17 were CIMP-, while among the 24 H. pylori- GC cases, 10 were CIMP+ and 14 were CIMP-. The difference was significant between the H. pylori+ and H. pylori- groups (χ(2) = 4.21, P < 0.05). A 2-year follow-up showed significant difference in the rates of metastasis and recurrence between H. pylori+/CIMP+ cases and the H. pylori+/CIMP- cases or CIMP- cases associated with H. pylori assayed in serum (P < 0.05). However, there were no significant differences in survival rates between the two groups.

H. pylori+/CIMP+ cases are associated with higher rates of metastasis and recurrence than H. pylori+/CIMP- cases. Serum may be useful for examining CIMP status.