Objective  To investigate the effects of Helicobacter pylori (HP) infection on polycomb repressive complex 2 (PRC2) and H3K27me3 expression and to explore the role of HP infection in the development of gastric cancer.

  Methods  Fast urease tests, Giemsa staining, and polymerase chain reaction (PCR) assays were conducted to detect HP in specimens from 84 gastric cancer patients, who had received surgeries in the Fifth People's Hospital of Shanghai from January 2014 to October 2017. Immunohistochemistry staining was applied to examine PRC2 and H3K27me3 expression in gastric cancer tissues and para-tumor tissues. The relationship between HP infection and PRC2 and H3K27me3 expression was analyzed.

  Results  The infection rates of HP were 70.24%, 61.90%, and 76.19% as detected by the three methods, respectively. The expression of enhancer of zeste homolog 2 (EZH2), suppressor of zeste 12 (SUZ12), embryonic ectoderm development (EED), and H3K27me3 protein were detected in 79.76% (67/84), 77.38% (65/84), 40.48% (34/84), and 69.05% (58/84) of gastric cancer tissues, respectively, all of which were significantly higher than those of para-tumor tissues (22.62%, 34.52%, 8.33%, and 14.29%, respectively; P < 0.05). The expression of EZH2 and H3K27me3 were positively correlated with lymph node metastasis, and the expression of these two proteins were also positively correlated. In gastric cancer tissues with HP infection, the expression of EZH2, SUZ12, EED, and H3K27me3 protein were detected at rates of 89.06% (57/64), 84.38% (54/64), 46.88% (30/64), and 82.81% (53/64), respectively, which were significantly higher than in gastric cancer tissues without HP infection (50.00%, 55.00%, 20.00%, and 25.00%, respectively; P < 0.05).

  Conclusions  HP infection is associated with increased expression of PRC2 and H3K27me3 proteins in gastric cancer.