Suppression of thymidine phosphorylase expression by promoter methylation in human cancer cells lacking enzyme activity

PurposeThymidine phosphorylase (TP, EC 2.4.2.4) activity varies in different human cancer cell lines. Nevertheless, little is known about the regulatory mechanisms of TP expression in such cancers. Promoter methylation of dinucleotide cytosine–guanine (CpG) sites is a known mechanism of reversible gene expression silencing.