Abstract: Objective To explore the role of miR-34a methylation in the development of gastric cancer,and explore the correlation of miR-34a methylation with gastric cancer, pathological features and Helicobacter pylori(HP)infection. Methods The methylation level of miR-34a gene CpG island of thirty-one gastric cancer patients and tweenty-four healthy people were detected by matrix-assisted laser desorption/ionisation-time-of-flight mass spectrometry(MALDI-TOF MS)technique. Results The overall average methylation level of miR-34a was higher in gastric cancer than that in the control, the average methylation of miR-34a CpG_5,CpG_12.13 was significantly higher in the gastric cancer group than they were in the control group(51.7%±5.9% vs. 37.8%±7.8%,84.61%±8.2% vs. 68.1%±12.1%,P＜0.01).The methylation level of miR-34a CpG_5 in the lymph node metastasis group was significantly higher than that in the non-lymph node metastasis group (53.55%±4.86% vs. 47.22%±6.07%,P＜0.01),and the methylation of CpG_5 in TNM stage (stage Ⅱ + stage Ⅲ) was higher than that in stage Ⅰ(53.21%±4.8% vs. 46.57%±6.9%, P＜0.05). Conclusions The miR-34a methylation is potentially associated with the occurrence and development of gastric cancer.

Key words: gastric cancer, peripheral blood, miR-34a, methylation, matrix-assisted laser desorption/ionisation-time-of-flight mass spectrometry(MALDI-TOF MS)