DNA Methylation of NDRG2 in Gastric Cancer and Its Clinical Significance

Gastric cancer is one of the most common digestive malignancies worldwide. N-myc downstream-regulated gene 2 (NDRG2) is a differentiation-related gene that is considered to be a metastasis suppressor gene. In this study, we examined the expression and DNA methylation of NDRG2 in gastric cancer cell lines and tissues, as well as its clinical significance. Six gastric cancer cell lines and 42 paired normal and gastric cancer tissue samples were used to assess NDRG2 mRNA expression using RT-PCR. NDRG2 DNA methylation status was evaluated by methylation-specific PCR (MSP) in gastric cancer cell lines and tissues. The suppression of NDRG2 in BGC823 cells by siRNA transfection was utilized to detect the role of NDRG2 in gastric cancer progression. NDRG2 mRNA was down-regulated in gastric cancer cell lines and tissues, and its expression was just related to lymph node metastasis (p = 0.032). MSP showed methylation of NDRG2 in 54.0 % (47/87) of primary gastric cancer specimens and in 20.0 % (16/80) of corresponding nonmalignant gastric tissues. NDRG2 methylation was related to depth of tumor invasion, Borrmann classification and TNM stage (p < 0.05). Upon treatment with 5-aza-2'-deoxycytidine and trichostatin A, NDRG2 expression was upregulated in HGC27 cells, and demethylation of the highly metastatic cell line, MKN45, inhibited cell invasion. Furthermore, the suppression of NDRG2 by siRNA transfection enhanced BGC823 cells invasion. Our results suggest that the aberrant methylation of NDRG2 may be mainly responsible for its downregulation in gastric cancer, and may play an important role in the metastasis of gastric cancer.