Immunoprecipitation of nucleosomal DNA is a novel procedure to improve the sensitivity of serum screening for the p16 hypermethylation associated with colon cancer

Background: We developed a novel method of methylation-specific PCR (MSP) using immunoprecipitation with anti-histone antibody (IP-MSP) to efficiently detect serum methylated DNA tightly bound to de-acetylated histones. Materials and methods: The detection limit of IP-MSP for p16 methylation was determined with a standard made by cell line (SKCO-1) lysate. p16 methylation of tumor and/or serum of 51 colorectal cancers and 10 adenoma patients, and 10 healthy volunteers was detected with conventional MSP or IP-MSP. Results: IP-MSP detected p16 methylation from 0.5 pg/μl of the cell lysate. The sensitivity of IP-MSP for detecting serum p16 methylation in 27 patients with tumors characterized by p16 methylation was significantly higher than that with conventional method (81% versus 59%), particularly in Stage II patients (91% versus 45%). IP-MSP detected no p16 hypermethylation in sera of adenoma patients and volunteers. Conclusions: IP-MSP is thus considered to be a promising procedure to detect serum methylated DNA in colorectal cancer patients.