Identification of a DNA methylation marker that detects the presence of lymph node metastases of gastric cancers.

The accurate detection of the presence of lymph node metastases (LNM) of gastric cancers (GCs) is useful for the implementation of necessary and sufficient treatment, but current methods of detection are unsatisfactory. In the present study, we focused on DNA methylation markers since they have several advantages, including biological and chemical stability and informativeness even in the presence of contaminating cells. Using three metastatic lymph nodes and three primary GCs without LNM, methylation bead array analyses were performed, which enabled the interrogation of 485,577 CpG sites. A total of 31 CpG sites that were hypermethylated in the metastatic lymph nodes, compared with the GCs without LNM, were isolated. Using primary GCs with and without LNM (28 GCs with LNM and 10 without), their methylation levels were measured using quantitative PCR following treatment with sodium bisulfite or a methylation-sensitive restriction enzyme. Of the genomic regions around the 31 CpG sites, 10 regions demonstrated higher methylation levels in the GCs with LNM compared with the GCs without LNM (P<0.05). Finally, the hypermethylation of the 10 regions was validated using another set of samples (129 GCs with LNM and 20 without). Hypermethylation of the region around the cg06436185 CpG site predicted the presence of LNM at a sensitivity of 43% and specificity of 85%. Additionally, the hypermethylation of the region was associated with a poor survival rate among GC patients with LNM. The results of the present study indicated that the methylation status of the region was a promising candidate marker to detect the presence of LNM of GCs and may reflect the malignant potential of GCs.