Influencing epigenetic information with a hydrolytically stable carbocyclic 5-aza-2’-deoxycytidine

5-Aza-2’-deoxycytidine (AzadC) is an antimetabolite in clinical use, which reduces the level of the epigenetic modification 5-methyl-2’-deoxycytidine (mdC). AzadC is incorporated into the genome of proliferating cells, where it inhibits the DNA methyltransferases (DNMTs) in a suicide process leading to a reduction of mdC. The loss of mdC, which is a transcriptional silencer in promoters, leads to the reactivation of genes including tumor suppressor genes, which elicits a beneficial effect. The problem associated with AzadC is that the compound is hydrolytically unstable. It decomposes during treatment to a variety of poorly characterized hydrolysis products. After its incorporation into the genome, this hydrolytic instability generates abasic sites. It is consequently difficult to dissect if the activity of the compound is caused by DNMT inhibition or more generally by DNA lesion formation. We now discovered that a disarmed version of AzadC, in which the ribose oxygen was replaced by a CH2-group, is surprisingly stable under a variety of pH values while keeping the epigenetic activity against the DNMTs