To assess the degree of CpG island methylation, we selected the CpG sites of four genes (p14ARF, p16INK4a, DAPK, and CDH1), because we previously reported that increased CpG island hypermethylation in these four genes of the non-neoplastic gastric mucosa correlates with a higher risk of gastric cancer [21]. Here, CDKN2A is linked to gastric cancer.