Thymoquinone exerts potent growth-suppressive activity on leukemia through DNA hypermethylation reversal in leukemia cells

• Published in: Oncotarget 2017-05, Vol.8 (21), p.34453-34467
• Main Authors: Pang, Jiuxia, Shen, Na, Yan, Fei, Zhao, Na, Dou, Liping, Wu, Lai-Chu, Seiler, Christopher L, Yu, Li, Yang, Ke, Bachanova, Veronika, Weaver, Eric, Tretyakova, Natalia Y, Liu, Shujun
• Format: Article
• Language: English
• Subjects: Animals; Benzoquinones - administration & dosage; Benzoquinones - pharmacology; Catalytic Domain - drug effects; Cell Line, Tumor; Cell Proliferation - drug effects; DNA (Cytosine-5-)-Methyltransferase 1 - antagonists & inhibitors; DNA (Cytosine-5-)-Methyltransferase 1 - chemistry; DNA (Cytosine-5-)-Methyltransferase 1 - metabolism; DNA Methylation - drug effects; Dose-Response Relationship, Drug; Down-Regulation; Gene Expression Regulation, Neoplastic - drug effects; Humans; Leukemia, Myeloid, Acute - drug therapy; Leukemia, Myeloid, Acute - genetics; Leukemia, Myeloid, Acute - metabolism; Mice; Molecular Docking Simulation; Research Paper; Xenograft Model Antitumor Assays
• ISSN: 1949-2553; 1949-2553
• DOI: 10.18632/oncotarget.16431

Thymoquinone (TQ), a bioactive constituent of the volatile oil of Monarda fistulosa and Nigella sativa, possesses cancer-specific growth inhibitory effects, but the underlying molecular mechanisms remain largely elusive. We propose that TQ curbs cancer cell growth through dysfunction of DNA methyltransferase 1 (DNMT1). Molecular docking analysis revealed that TQ might interact with the catalytic pocket of DNMT1 and compete with co-factor SAM/SAH for DNMT1 inhibition. In vitro inhibitory assays showed that TQ decreases DNMT1 methylation activity in a dose-dependent manner with an apparent IC50 of 30 nM. Further, exposure of leukemia cell lines and patient primary cells to TQ resulted in DNMT1 downregulation, mechanistically, through dissociation of Sp1/NFkB complex from DNMT1 promoter. This led to a reduction of DNA methylation, a decrease of colony formation and an increase of cell apoptosis via the activation of caspases. In addition, we developed and validated a sensitive and specific LC-MS/MS method and successfully detected a dynamic change of TQ in mouse plasma after administration of TQ through the tail vein, and determined a tolerable dose of TQ to be 15 mg/kg in mouse. TQ administration into leukemia-bearing mice induced leukemia regression, as indicated by the reversed splenomegaly and the inhibited leukemia cell growth in lungs and livers. Our study for the first time demonstrates that DNMT1-dependent DNA methylation mediates the anticancer actions of TQ, opening a window to develop TQ as a novel DNA hypomethylating agent for leukemia therapy.