title: De novo DNA methyltransferases Dnmt3a and Dnmt3b primarily mediate the cytotoxic effect of 5-aza-2'-deoxycytidine.
abstract: The deoxycytidine analog 5-aza-2'-deoxycitidine (5-aza-dC) is a potent chemotherapeutic agent effective against selective types of cancer. The molecular mechanism by which 5-aza-dC induces cancer cell death, however, is not fully understood. It has been accepted that the mechanism of toxicity is due to the covalent binding between the DNA methyltransferase (Dnmt) and 5-aza-dC-substituted DNA. In order to define which member of the Dnmt family plays a dominant role in the cytotoxicity, we examined the effect of 5-aza-dC on cell growth and apoptosis in various Dnmt null mutant embryonic stem (ES) cells. Of interest, Dnmt3a-Dnmt3b double null ES cells were highly resistant to 5-aza-dC when compared to wild type, Dnmt3a null, Dnmt3b null, or Dnmt1 null ES cells. The cellular sensitivity to 5-aza-dC correlated well with the expression status of Dnmt3 in both undifferentiated and differentiated ES cells. When exogenous Dnmt3a or Dnmt3b was expressed in double null ES cells, the sensitivity to 5-aza-dC was partially restored. These results suggest that the cytotoxic effect of 5-aza-dC may be mediated primarily through Dnmt3a and Dnmt3b de novo DNA methyltransferases. Further, the ability to form Dnmt-DNA adducts was similar in Dnmt1 and Dnmt3, and the expression level of Dnmt3 was not higher than that of Dnmt1 in ES cells. Therefore, Dnmt3-DNA adducts may be more effective for inducing apoptosis than Dnmt1-DNA adducts. These results imply a therapeutic potential of 5-aza-dC to cancers expressing Dnmt3.
authors.affiliation: Department of Pathology, University of Florida College of Medicine, PO Box 100275, 1600 SW Archer Rd, Gainesville, FL 32610, USA.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Oka
authors.forename: Amy M
authors.initials: AM
authors.lastname: Meacham
authors.forename: Takashi
authors.initials: T
authors.lastname: Hamazaki
authors.forename: Nemanja
authors.initials: N
authors.lastname: Rodić
authors.forename: Lung-Ji
authors.initials: LJ
authors.lastname: Chang
authors.forename: Naohiro
authors.initials: N
authors.lastname: Terada
mesh_terms: D000818:Animals; D017209:Apoptosis; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D019556:COS Cells; D016923:Cell Death; D002454:Cell Differentiation; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism / Q000502:physiology*; D018736:DNA Adducts / Q000378:metabolism; D053938:DNA Fragmentation; D000090205:DNA Methyltransferase 3A; D015254:DNA Modification Methylases / Q000378:metabolism; D000077209:Decitabine; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian / Q000166:cytology; D015151:Immunoblotting; D016086:Lentivirus / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D009154:Mutation; D013234:Stem Cells / Q000166:cytology; D000097584:DNA Methyltransferase 3B
chemical_list: D001374:Azacitidine; D004247:DNA; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D018736:DNA Adducts; D000090205:DNA Methyltransferase 3A; D015254:DNA Modification Methylases; D000077209:Decitabine; D000097584:DNA Methyltransferase 3B; C000715535:Dnmt3a protein, mouse; C000619381:Dnmt1 protein, mouse