Quantitative multiplex methylation-specific PCR assay for the detection of promoter hypermethylation in multiple genes in breast cancer

If detected early, breast cancer is eminently curable. To detect breast cancer in samples with little cellularity, a high level of sensitivity is needed. Tumor-specific promoter hypermethylation has provided such a valuable tool for detection of cancer cells in biological samples. To accurately assess promoter hypermethylation for many genes simultaneously in small samples, we developed a novel method, quantitative multiplex-methylation-specific PCR (QM-MSP). QM-MSP is highly sensitive (1 in 10⁴-10⁵ copies of DNA) and linear over 5 orders of magnitude. For RASSF1A, TWIST, Cyclin D2, and HIN1, we observed significant differences in both the degree (P < 0.003) and incidence (P < 0.02) of hypermethylation between normal and malignant breast tissues. Evaluation of the cumulative hypermethylation of the four genes within each sample revealed a high level of sensitivity (84%) and specificity (89%) of detection of methylation. We demonstrate the application of this technique for detecting hypermethylated RASSF1A, TWIST, Cyclin D2, HIN1, and RARB in 50-1000 epithelial cells collected from breast ducts during endoscopy or by lavage. Such an approach could be used in a variety of small samples derived from different tissues, with these or different biomarkers to enhance detection of malignancy.