Byl J A, Fortune J M, Burden D A, Nitiss J L, Utsugi T, Yamada Y, Osheroff N
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
Biochemistry. 1999 Nov 23;38(47):15573-9. doi: 10.1021/bi991791o.
TAS-103 is a novel antineoplastic agent that is active against in vivo tumor models [Utsugi, T., et al. (1997) Jpn. J. Cancer Res. 88, 992-1002]. This drug is believed to be a dual topoisomerase I/II-targeted agent, because it enhances both topoisomerase I- and topoisomerase II-mediated DNA cleavage in treated cells. However, the relative importance of these two enzymes for the cytotoxic actions of TAS-103 is not known. Therefore, the primary cellular target of the drug and its mode of action were determined. TAS-103 stimulated DNA cleavage mediated by mammalian topoisomerase I and human topoisomerase IIalpha and beta in vitro. The drug was less active than camptothecin against the type I enzyme but was equipotent to etoposide against topoisomerase IIalpha. A yeast genetic system that allowed manipulation of topoisomerase activity and drug sensitivity was used to determine the contributions of topoisomerase I and II to drug cytotoxicity. Results indicate that topoisomerase II is the primary cellular target of TAS-103. In addition, TAS-103 binds to human topoisomerase IIalpha in the absence of DNA, suggesting that enzyme-drug interactions play a role in formation of the ternary topoisomerase II.drug.DNA complex. TAS-103 induced topoisomerase II-mediated DNA cleavage at sites similar to those observed in the presence of etoposide. Like etoposide, it enhanced cleavage primarily by inhibiting the religation reaction of the enzyme. Based on these findings, it is suggested that TAS-103 be classified as a topoisomerase II-targeted drug.
TAS-103是一种新型抗肿瘤药物，对体内肿瘤模型具有活性[内木，T.等人（1997年）《日本癌症研究杂志》88卷，992 - 1002页]。这种药物被认为是一种双靶向拓扑异构酶I/II的药物，因为它能增强处理过的细胞中拓扑异构酶I和拓扑异构酶II介导的DNA切割。然而，这两种酶对TAS-103细胞毒性作用的相对重要性尚不清楚。因此，确定了该药物的主要细胞靶点及其作用方式。TAS-103在体外刺激了由哺乳动物拓扑异构酶I以及人拓扑异构酶IIα和IIβ介导的DNA切割。该药物对I型酶的活性低于喜树碱，但对拓扑异构酶IIα的活性与依托泊苷相当。利用一种允许操纵拓扑异构酶活性和药物敏感性的酵母遗传系统来确定拓扑异构酶I和II对药物细胞毒性的贡献。结果表明拓扑异构酶II是TAS-103的主要细胞靶点。此外，TAS-103在不存在DNA的情况下与人拓扑异构酶IIα结合，这表明酶 - 药物相互作用在三元拓扑异构酶II - 药物 - DNA复合物的形成中起作用。TAS-103在与依托泊苷存在时观察到的类似位点诱导拓扑异构酶II介导的DNA切割。与依托泊苷一样，它主要通过抑制酶的再连接反应来增强切割。基于这些发现，建议将TAS-103归类为一种靶向拓扑异构酶II的药物。
