A second-generation profiling system for quantitative methylation analysis of multiple gene promoters: application to...

Cancer-specific gene promoter methylation has been described in many types of cancers, and various semi-quantified results have shown their usefulness. Here, we show a more sensitive and specific second-generation system for profiling the DNA methylation status. This method is based on bisulfite reaction of DNA and real-time PCR using two TaqMan MGB probes labeled with different fluorescence, followed by clustering analysis. Primers were designed with CpG-less sequences, and TaqMan MGB probes were designed to contain three or four CpG sites and to be shorter than conventional TaqMan probes. We have added new criteria for primer and probe design for further specificity. We confirmed the reliability of this system and applied it to analysis of lung cancers. Using 10 promoters, 90 primary lung cancers were clustered into six groups consisting of cases having similar smoking status and pathological findings. EGFR mutation and p16 promoter DNA methylation were exclusive, as previously reported; however, DNA methylation in other genes was unrelated to EGFR mutation. This system was also useful to distinguish double primary lung cancers from a single cancer with intrapulmonary metastasis. As above, our system has widespread availability in clinical use and biological research.