Standardization of the methylation‑specific PCR method for analyzing BRCA1 and ER methylation

The significant differences in DNA methylation that are considered to be a biomarker for the diagnosis of cancer are a barrier to the application of biomarkers in the clinical field. In the present study, new primers were designed and further standard controls were set up to validate the accuracy of the methylation‑specific PCR (MSP), a method widely used to analyze DNA methylation. By analyzing the methylation pattern of breast cancer 1 (BRCA1) and estrogen receptor (ER) in 60 patients with breast cancer, the number of cases of methylated BRCA1 and ER detected by the primer was 7/60 and 21/60, respectively, whereas that detected by the previous widely used primers was 25/60 and 47/60, respectively. Sequencing of the MSP products indicated that the 18 and 26 false-positive methylations of BRCA1 and ER, respectively, were due to insufficient validation of the previously used primers. Thus, the present study proposes that all studies based on the MSP approach should incorporate more controls to validate the precision of the MSP primers.