Etoposide Quinone Is a Redox-Dependent Topoisomerase II Poison
Etoposide Quinone Is a Redox-Dependent Topoisomerase II Poison
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DOI：
10.1021/bi200438m
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发表时间：
2011-06-28
期刊：
影响因子：
2.9
通讯作者：
Deweese, Joseph E.
中科院分区：
文献类型：
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作者：
Jacob, David A.;Mercer, Susan L.;Deweese, Joseph E.
依托泊苷是一种拓扑异构酶II毒药，用于治疗多种人类癌症。不幸的是，2-3%的依托泊苷治疗的患者发展为治疗相关的白血病，其特征在于11 q23染色体重排。依托泊苷诱导白血病发生的分子基础尚不清楚，但与酶介导的DNA切割有关。依托泊苷经CYP 3A 4代谢为依托泊苷儿茶酚，后者可进一步氧化为依托泊苷醌。CYP 3A 4变异体与依托泊苷相关白血病风险降低相关，表明依托泊苷代谢产物可能参与白血病发生。尽管依托泊苷作用于酶-DNA界面，但几种醌类通过氧化还原依赖性蛋白加合作用毒害拓扑异构酶II。依托泊苷醌对拓扑异构酶II α介导的DNA切割的影响以前已经被检查过。尽管研究结果表明醌的活性略高于依托泊苷，但这些研究是在存在显著水平的还原剂（应将依托泊苷醌还原为儿茶酚）的情况下进行的。因此，我们研究了在不存在还原剂的情况下依托泊苷醌毒害人拓扑异构酶II α的能力。在这些条件下，依托泊苷醌在诱导酶介导的DNA切割方面的活性比依托泊苷高5倍。与其他氧化还原依赖性毒物一致，当在DNA之前与蛋白质孵育时，依托泊苷醌使拓扑异构酶II α失活，并且在二硫苏糖醇存在下失去活性。与依托泊苷不同，醌代谢物不需要ATP来获得最大活性，并诱导高比例的双链DNA断裂。我们的研究结果支持这一假设，依托泊苷醌有助于依托泊苷相关的白血病。
Etoposide is a topoisomerase II poison that is used to treat a variety of human cancers. Unfortunately, 2-3% of patients treated with etoposide develop treatment-related leukemias characterized by 11q23 chromosomal rearrangements. The molecular basis for etoposide-induced leukemogenesis is not understood but is associated with enzyme-mediated DNA cleavage. Etoposide is metabolized by CYP3A4 to etoposide catechol, which can be further oxidized to etoposide quinone. A CYP3A4 variant is associated with a lower risk of etoposide-related leukemias, suggesting that etoposide metabolites may be involved in leukemogenesis. Although etoposide acts at the enzyme-DNA interface, several quinones poison topoisomerase II via redox-dependent protein adduction. The effects of etoposide quinone on topoisomerase II alpha-mediated DNA cleavage have been examined previously. Although findings suggest that the activity of the quinone is slightly greater than that of etoposide, these studies were carried out in the presence of significant levels of reducing agents (which should reduce etoposide quinone to the catechol). Therefore, we examined the ability of etoposide quinone to poison human topoisomerase II alpha in the absence of reducing agents. Under these conditions, etoposide quinone was similar to 5-fold more active than etoposide at inducing enzyme-mediated DNA cleavage. Consistent with other redox-dependent poisons, etoposide quinone inactivated topoisomerase II alpha when incubated with the protein prior to DNA and lost activity in the presence of dithiothreitol. Unlike etoposide, the quinone metabolite did not require ATP for maximal activity and induced a high ratio of double-stranded DNA breaks. Our results support the hypothesis that etoposide quinone contributes to etoposide-related leukemogenesis.