Among the tumour suppressor genes with frequent promoter hypermethylation in melanomas, causing repression of transcription, are CDKN2A [143,144], Ras association domain family member 1 (RASSF1A) [145], and PTEN [146,147], with the latter two particularly becoming hypermethylated in later stages of the disease. The gene discussed is PTEN; the disease is melanoma.