title: Inhibition of DNA-dependent protein kinase catalytic subunit by small molecule inhibitor NU7026 sensitizes human leukemic K562 cells to benzene metabolite-induced apoptosis.
abstract: Benzene is an established leukotoxin and leukemogen in humans. We have previously reported that exposure of workers to benzene and to benzene metabolite hydroquinone in cultured cells induced DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to mediate the cellular response to DNA double strand break (DSB) caused by DNA-damaging metabolites. In this study, we used a new, small molecule, a selective inhibitor of DNA-PKcs, 2-(morpholin-4-yl)-benzo[h]chomen-4-one (NU7026), as a probe to analyze the molecular events and pathways in hydroquinone-induced DNA DSB repair and apoptosis. Inhibition of DNA-PKcs by NU7026 markedly potentiated the apoptotic and growth inhibitory effects of hydroquinone in proerythroid leukemic K562 cells in a dose-dependent manner. Treatment with NU7026 did not alter the production of reactive oxygen species and oxidative stress by hydroquinone but repressed the protein level of DNA-PKcs and blocked the induction of the kinase mRNA and protein expression by hydroquinone. Moreover, hydroquinone increased the phosphorylation of Akt to activate Akt, whereas co-treatment with NU7026 prevented the activation of Akt by hydroquinone. Lastly, hydroquinone and NU7026 exhibited synergistic effects on promoting apoptosis by increasing the protein levels of pro-apoptotic proteins Bax and caspase-3 but decreasing the protein expression of anti-apoptotic protein Bcl-2. Taken together, the findings reveal a central role of DNA-PKcs in hydroquinone-induced hematotoxicity in which it coordinates DNA DSB repair, cell cycle progression, and apoptosis to regulate the response to hydroquinone-induced DNA damage.
authors: School of Public Health, Wuhan University, Wuhan, 430071, China.|School of Medicine, Jianghan University, Wuhan, 430056, China.
authors: Hao
authors: H
authors: You
authors: School of Public Health, Wuhan University, Wuhan, 430071, China.
authors: Meng-Meng
authors: MM
authors: Kong
authors: School of Public Health, Wuhan University, Wuhan, 430071, China.
authors: Li-Ping
authors: LP
authors: Wang
authors: School of Public Health, Wuhan University, Wuhan, 430071, China.
authors: Xiao
authors: X
authors: Xiao
authors: School of Public Health, Wuhan University, Wuhan, 430071, China.
authors: Han-Lin
authors: HL
authors: Liao
authors: School of Pharmaceutical Science, Wuhan University, Wuhan, 430071, China.
authors: Zhuo-Yue
authors: ZY
authors: Bi
authors: School of Public Health, Wuhan University, Wuhan, 430071, China.
authors: Hong
authors: H
authors: Yan
authors: School of Public Health, Wuhan University, Wuhan, 430071, China.
authors: Hong
authors: H
authors: Wang
authors: School of Public Health, Wuhan University, Wuhan, 430071, China.
authors: Chun-Hong
authors: CH
authors: Wang
authors: Receptor Biology Laboratory, Toxicology and Molecular Biology Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV, 26505, USA.
authors: Qiang
authors: Q
authors: Ma
authors: School of Medicine, Jianghan University, Wuhan, 430056, China.
authors: Yan-Qun
authors: YQ
authors: Liu
authors: School of Public Health, Wuhan University, Wuhan, 430071, China. yongyib@yahoo.com.cn.
authors: Yong-Yi
authors: YY
authors: Bi
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001554:Benzene / Q000633:toxicity*; D002384:Catalysis; D002867:Chromones / Q000494:pharmacology*; D004249:DNA Damage / Q000187:drug effects* / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects / Q000502:physiology*; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells; D009025:Morpholines / Q000494:pharmacology*; D021122:Protein Subunits
chemical_list: C479235:2-(morpholin-4-yl)benzo(h)chromen-4-one; D002867:Chromones; D009025:Morpholines; D021122:Protein Subunits; D051747:DNA-Activated Protein Kinase; D001554:Benzene
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