DNA methylation of leukocyte DNA has been proposed to be a biomarker for cancer that can be used to target patients for appropriate clinical implementation. We investigated IGF2 DMR and LINE1 methylation in the leukocyte DNA and their association with clinicopathological features and prognosis of gastric cancer (GC) patients. Methylation status of IGF2 DMR and LINE1 in the leukocyte DNA was quantified using bisulfite pyrosequencing in 207 GC patients. Methylation of both IGF2 DMR and the LINE1 was significantly higher in the undifferentiated histologic type compared to the differentiated histologic type (both P = 0.0002). Hypermethylation of both the IGF2 DMR and the LINE1 was associated with more aggressive features of GC such as advanced stage (IGF2 DMR, P = 0.0002; LINE1, P < 0.0001), lymphatic invasion positive (IGF2 DMR, P = 0.004; LINE1, P = 0.002), venous invasion positive (IGF2 DMR, LINE1, both P = 0.03), lymph node metastasis positive (IGF2 DMR, P = 0.01; LINE1, P = 0.001), peritoneal dissemination positive (IGF2 DMR, P = 0.04; LINE1, P = 0.002), liver metastasis positive (IGF2 DMR, P = 0.008; LINE1, P = 0.001), and other distant metastasis positive (IGF2 DMR, P = 0.04). Our data suggest that high LINE1 and IGF2 DMR methylation status would be a phenomenon that is observed with the progression of GC, supporting their potential utility as a biomarker in GC patients.
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