Biochemistry of azacitidine: a review.

Azacitidine is a pyrimidine ring analog of cytidine that is incorporated into RNA causing alteration in RNA synthesis and processing and resulting in inhibition of protein synthesis. Azacitidine as the deoxynucleotide is also incorporated into DNA inhibiting its synthesis and blocking cytosine methylation by noncompetitive inhibition of DNA methyltransferase. The resulting hypomethylation of DNA is thought to induce gene activation and expression and cell differentiation. This may be an underlying factor in azacitidine's antileukemic activity and also contributes to its carcinogenic and tumor-promoting properties in experimental models.