TP53 and neoplasm: Oncogene (e.g. HRAS) promoter regions are frequently hypomethylated (Feinberg and Vogelstein, 1983), while tumour suppressor loci such as TP53, APC and VHL are commonly hypermethylated in association with transcriptional silencing (Herman and Baylin, 2003), suggesting that DNA methylation alterations at specific loci can influence tumour progression.