DKK1 and neoplasm: Here we observed a significant age-related increase in methylation levels of Dkk1, Sfrp1, Slc5a8, Hoxd1, and Socs1 CGIs but not of Mlh1, which was still well-expressed at tp1, suggesting that expression decreases of the other genes precede the involvement of Mlh1. Although Mlh1 methylation levels have been reported to increase with age in normal colonic mucosa (characteristic of ‘type A’ genes) [5,7,35-37], our results rather comply with studies [37,38] classifying Mlh1 as a ‘type C’ gene, with methylation specificity for neoplasia.