Objective  This study aims to detect the CpG island methylation status of the ERCC1 gene promoter and the expression of the ERCC1 protein in gastric cancer tissues, as well as to investigate the correlation and significance between ERCC1 gene promoter CpG island methylation and protein expression.

  Methods  Methylation-specific PCR was performed to detect the methylation status of the ERCC1 gene in tumor tissues and adjacent cancerous tissues from 30 gastric cancer patients. Ten cases of normal gastric tissues were used as control. Expression of the ERCC1 protein in gastric cancer tissues, adjacent cancerous tissues, and normal gastric tissues was examined by immunohistochemistry S-P method.

  Results  The methylation rate of the ERCC1 gene promoter CpG island in gastric cancer tissues was significantly higher than that in adjacent cancerous tissues (76.7% vs. 13.3%, P < 0.05), and the difference was statistically significant. The incidence of promoter methylation was not found in 10 normal gastric tissues. The negative rate of ERCC1 protein expression in 30 cases of gastric carcinoma tissues was significantly higher than that in adjacent cancerous tissues (70.0% vs. 33.3%, P < 0.05), whereas 10 normal gastric tissues all exhibited positive expression for the ERCC1 protein. The tumor tissues with ERCC1 gene promoter CpG island methylation showed a lower expression of ERCC1 protein than the unmethylated tumor tissues in gastric cancer patients.

  Conclusion  Methylation of the ERCC1 gene promoter CpG island and protein expression are negatively correlated, and methylation of the CpG island of the ERCC1 gene may be one of the main reasons for the down-regulation of protein expression.