CDKN2A and prostate carcinoma: CpG island methylation of p16 gene, which has been observed in prostate cell lines, appears rare in prostate cancer tissues (Herman et al. 1995; Jarrard et al. 1997; Gu et al. 1998; Nguyen et al. 2000; Konishi et al. 2002; Maruyama et al. 2002).