Detection of aberrant methylation of tumor suppressor genes in plasma from cancer patients

PurposeFor personalized medicine, a novel biomarker is necessary for screening and monitoring of cancer. DNA methylation of the promoter region of tumor suppressor gene(s) has been detected in tumor tissue and plasma/serum from patients with various types of cancer. To investigate the methylation status of gene promoters in plasma from cancer patients, we examined the frequency of methylation in the promoter regions of the APC, DCC, p16INK4a, p14ARF, and RASSF1A genes in plasma.MethodsSamples of plasma were obtained from 244 patients with colon cancer, lung cancer, pancreatic cancer, gastric cancer, hepatocellular carcinoma, and breast cancer. Cell-free DNA was extracted from each plasma sample and the methylation status of the promoters of the APC, DCC, p16INK4a, p14ARF, and RASSF1A genes were examined by methylation-specific PCR.ResultsMethylation of the promoter of the APC and RASSF1A genes was detected in plasma from patients with each type of cancer. Notably, methylation of the APC and RASSF1A promoters was detected in plasma from patients with HCC at a high frequency. However, the frequency of methylation of the promoters of the DCC and p14ARF genes from patients with HCC was lower than that of patients with colon cancer.ConclusionOur results indicate that the frequency of methylation of cancer-related genes is dependent on the type of cancer and patient. Therefore, DNA methylation of cancer-related genes has a high potential as a biomarker for personalized medicine.