Circulating DNA in the Blood of Gastric Cancer Patients

The concentration of cell‐free DNA and promoter methylation status of the MGMT, p15, and hMLH1 genes were analyzed by a fluorescence‐based assay and methylation‐specific PCR (MSP) in the blood of gastric cancer patients (n= 20) and healthy subjects (n= 22). Gastric cancer patients were characterized by an increased concentration of circulating DNA in the plasma; the amount of cell‐surface‐bound DNA was not decreased compared with controls and amounted to 80 ± 15% of the total circulating DNA. MSP analysis of three genes in the cell‐surface‐bound DNA permits the detection of gastric cancer patients with a sensitivity of 75% and a specificity of 54%. Thus, the cell‐surface‐bound DNA is a convenient source of DNA for MSP analysis of cancer‐specific markers. The data on the presence of methylated DNA in plasma combined with the analysis of other cancer‐related changes in DNA can significantly contribute to cancer diagnostics.