CDKN2A and neoplasm: Some degree of methylation was detectable in the mucosa of neoplasia-free patients for all the genes assayed, although the levels varied considerably for different genes, from approximately 0.1% for DKK1 to approximately 20% in the case of N33. For APC and p16, we observed significantly higher levels of methylation in cancer patients compared with neoplasia-free patients, with intermediate levels in the adenoma patients after adjusting for age and gender.