The depletion of DNA methyltransferase-1 and the epigenetic effects of 5-aza-2'deoxycytidine (decitabine) are differentially regulated by cell cycle progression

• Published in: Epigenetics Vol. 6; no. 8; pp. 1021 - 1028
• Main Authors: Al-Salihi, Mazin, Yu, Margaret, Burnett, David M., Alexander, Amanda, Samlowski, Wolfram E., Fitzpatrick, Frank A.
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 01.08.2011
• Subjects: Antimetabolites, Antineoplastic - pharmacology; Azacitidine - analogs & derivatives; Azacitidine - pharmacology; Binding; Biology; Bioscience; Calcium; Cancer; Cell; Cell Cycle Checkpoints - drug effects; Cell Cycle Checkpoints - genetics; Cell Line, Tumor; CpG Islands - drug effects; Cycle; DNA (Cytosine-5-)-Methyltransferase 1; DNA (Cytosine-5-)-Methyltransferases - antagonists & inhibitors; DNA Damage; DNA Methylation; Epigenesis, Genetic - drug effects; Gene Expression Regulation, Neoplastic - drug effects; HCT116 Cells; Humans; Landes; Melanoma-Specific Antigens - genetics; Organogenesis; Proteins; S Phase; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Protein p53 - metabolism
• ISSN: 1559-2294; 1559-2308
• DOI: 10.4161/epi.6.8.16064

5-Aza-2'-deoxycytidine (decitabine) is a drug targeting the epigenetic abnormalities of tumors. The basis for its limited efficacy in solid tumors is unresolved, but may relate to their indolent growth, their p53 genotype or both. We report that the primary molecular mechanism of decitabine-depletion of DNA methyltransferase-1 following its "suicide" inactivation-is not absolutely associated with cell cycle progression in HCT 116 colon cancer cells, but is associated with their p53 genotype. Control experiments affirmed that the secondary molecular effects of decitabine on global and promoter-specific CpG methylation and MAGE-A1 mRNA expression were S-phase dependent, as expected. Secondary changes in CpG methylation occurred only in growing cells ~24-48 h after decitabine treatment; these epigenetic changes coincided with p53 accumulation, an index of DNA damage. Conversely, primary depletion of DNA methyltransferase-1 began immediately after a single exposure to 300 nM decitabine and it progressed to completion within ~8 h, even in confluent cells arrested in G 1 and G 2 /M. Our results suggest that DNA repair and remodeling activity in arrested, confluent cells may be sufficient to support the primary molecular action of decitabine, while its secondary, epigenetic effects require cell cycle progression through S-phase.