Decitabine activates specific caspases downstream of p73 in myeloid leukemia.
The demethylating effect of 5-aza-2' deoxycytidine (decitabine, DAC) has been well characterized. The molecular events downstream of methylation inhibition are less well known. Here, DAC was shown to induce apoptosis in acute myeloid leukemia (AML) cells (p53 mutant and wild type) but not in epithelial or normal peripheral blood mononuclear cells. Apoptosis was characterized by activation of the mitochondrial but not the receptor death pathway, as demonstrated by the release of cytochrome c and loss of mitochondrial membrane potential. Western blotting and enzyme assays showed that caspase-3, but not caspase-6 or caspase-8, were activated. Decitabine induced expression of the cell cycle inhibitor p21, arresting AML cell lines in G1 of the cell cycle. Expression of p21 was induced irrespective of the methylation status of its promoter, mediated instead via reexpression of the tumor suppressor p73, an upstream regulator of p21. The promoter of p73 was hypermethylated in AML cell lines in vitro and in primary AML cells ex vivo but not in DAC-resistant epithelial cells. In conclusion, DAC acts on leukemic myeloid cells via caspase activation, which may be dependent on demethylation of the hypermethylated p73 promoter and consequent reexpression of p73.
Tamm
Ingo
I
Department of Hematology and Oncology, Universitätsmedizin Berlin Charité, Campus Virchow, Berlin, Germany. ingo.tamm@charite.de
Wagner
Mandy
M
Schmelz
Karin
K
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D053148:Caspase 3 / Q000187:drug effects* / Q000378:metabolism; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000187:drug effects / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000187:drug effects* / Q000378:metabolism; D000077209:Decitabine; D004789:Enzyme Activation; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000187:drug effects* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins / Q000187:drug effects* / Q000378:metabolism
D000964:Antimetabolites, Antineoplastic; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C000606460:TP73 protein, human; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D000077209:Decitabine; D053148:Caspase 3; D001374:Azacitidine