title: RNA-dependent inhibition of ribonucleotide reductase is a major pathway for 5-azacytidine activity in acute myeloid leukemia.
abstract: 5-Azacytidine (5-azaC) is an azanucleoside approved for myelodysplastic syndrome. Approximately 80%-90% of 5-azaC is believed to be incorporated into RNA, which disrupts nucleic acid and protein metabolism leading to apoptosis. A smaller fraction (10%-20%) of 5-azaC inhibits DNA methylation and synthesis through conversion to decitabine triphosphate and subsequent DNA incorporation. However, its precise mechanism of action remains unclear. Ribonucleotide reductase (RR) is a highly regulated enzyme comprising 2 subunits, RRM1 and RRM2, that provides the deoxyribonucleotides required for DNA synthesis/repair. In the present study, we found for the first time that 5-azaC is a potent inhibitor of RRM2 in leukemia cell lines, in a mouse model, and in BM mononuclear cells from acute myeloid leukemia (AML) patients. 5-azaC-induced RRM2 gene expression inhibition involves its direct RNA incorporation and an attenuated RRM2 mRNA stability. Therefore, 5-azaC causes a major perturbation of deoxyribonucleotide pools. We also demonstrate herein that the initial RR-mediated 5-azaC conversion to decitabine is terminated through its own inhibition. In conclusion, we identify RRM2 as a novel molecular target of 5-azaC in AML. Our findings provide a basis for its more widespread clinical use either alone or in combination.
authors.affiliation: Division of Pharmaceutics, College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Josephine
authors.initials: J
authors.lastname: Aimiuwu
authors.forename: Hongyan
authors.initials: H
authors.lastname: Wang
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
authors.forename: Zhiliang
authors.initials: Z
authors.lastname: Xie
authors.forename: Jiang
authors.initials: J
authors.lastname: Wang
authors.forename: Shujun
authors.initials: S
authors.lastname: Liu
authors.forename: Rebecca
authors.initials: R
authors.lastname: Klisovic
authors.forename: Alice
authors.initials: A
authors.lastname: Mims
authors.forename: William
authors.initials: W
authors.lastname: Blum
authors.forename: Guido
authors.initials: G
authors.lastname: Marcucci
authors.forename: Kenneth K
authors.initials: KK
authors.lastname: Chan
mesh_terms: D001374:Azacitidine / Q000494:pharmacology* / Q000627:therapeutic use; D004273:DNA, Neoplasm / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D020014:K562 Cells; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000201:enzymology*; D008297:Male; D020871:RNA Stability / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000378:metabolism*; D012262:Ribonucleoside Diphosphate Reductase / Q000008:administration & dosage* / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D025521:Tumor Suppressor Proteins; C093713:ribonucleotide reductase M2; C475286:RRM1 protein, human; D012262:Ribonucleoside Diphosphate Reductase; D001374:Azacitidine