Quantitative bisulfite conversion–PCR (BSC–PCR) analysis of DNA extracted from breast cancer cells with NEP methylation-specific and control beta-actin primers demonstrated that when normalized to control methylated DNA, MDA-MB-231 DNA has significantly higher methylation at the NEP promoter than either MCF-7 or HMEC DNA (Figure 4a; Supplementary Figure 5). Here, ACTB is linked to breast cancer.