**7.9 Methylation-specific PCR (MSP)**

It is a variant of PCR used to identify promoter hyper-methylation at CpG islands in cell lines and clinical samples, including fresh/frozen tissues. The target DNA is first treated with sodium bisulfite, which transforms the unmethylated cytosine bases in to uracil, which pair with adenosine of the PCR primers. The modified DNA is then amplified using two types of primers that only differ at their CpG islands. One primer set anneals to DNA with cytosine (corresponding to methylated cytosine), while the other anneals to DNA with uracil (corresponding to unmethylated cytosine). The MSP technique provides quantitative information about the methylation when used in quantitative PCR [3, 4, 7, 49, 50].
