Brabec V, Vrána O, Nováková O, Kleinwächter V, Intini F P, Coluccia M, Natile G
Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czech Republic.
Nucleic Acids Res. 1996 Jan 15;24(2):336-41. doi: 10.1093/nar/24.2.336.
It has been shown recently that some analogues of clinically ineffective trans-diamminedichloroplatinum (II) (transplatin) exhibit antitumor activity. This finding has inverted the empirical structure-antitumor activity relationships delineated for platinum(II) complexes, according to which only the cis geometry of leaving ligands in the bifunctional platinum complexes is therapeutically active. As a result, interactions of trans platinum compounds with DNA, which is the main pharmacological target of platinum anticancer drugs, are of great interest. The present paper describes the DNA binding of antitumor trans-[PtCl(2)(E-imino ether)(2)] complex (trans-EE) in a cell-free medium, which has been investigated using three experimental approaches. They involve thiourea as a probe of monofunctional DNA adducts of platinum (II) complexes with two leaving ligands in the trans configuration, ethidium bromide as a probe for distinguishing between monofunctional and bifunctional DNA adducts of platinum complexes and HPLC analysis of the platinated DNA enzymatically digested to nucleosides. The results show that bifunctional trans-EE preferentially forms monofunctional adducts at guanine residues in double-helical DNA even when DNA is incubated with the platinum complex for a relatively long time (48 h at 37 degrees C in 10 mM NaCIO(4). It implies that antitumor trans-EE modifies DNA in a different way than clinically ineffective transplatin, which forms prevalent amount of bifunctional DNA adducts after 48 h. This result has been interpreted to mean that the major adduct of trans-EE, occurring in DNA even after long reaction times, is a monofunctional adduct in which the reactivity of the second leaving group is markedly reduced. It has been suggested that the different properties of the adducts formed on DNA by transplatin and trans-EE are relevant to their distinct clinical efficacy.
最近研究表明，一些临床上无活性的反式二氯二氨合铂（II）（反铂）类似物具有抗肿瘤活性。这一发现颠覆了针对铂（II）配合物所描绘的经验性结构 - 抗肿瘤活性关系，根据该关系，只有双功能铂配合物中离去配体的顺式几何结构才具有治疗活性。因此，反式铂化合物与DNA（铂类抗癌药物的主要药理学靶点）的相互作用备受关注。本文描述了抗肿瘤反式 - [PtCl₂(E - 亚氨基醚)₂]配合物（反式 - EE）在无细胞培养基中的DNA结合情况，该研究采用了三种实验方法。它们包括使用硫脲作为铂（II）配合物单功能DNA加合物的探针，该配合物带有两个处于反式构型的离去配体；使用溴化乙锭作为区分铂配合物单功能和双功能DNA加合物的探针；以及对酶解为核苷的铂化DNA进行HPLC分析。结果表明，即使在DNA与铂配合物孵育较长时间（37℃下在10 mM NaClO₄中孵育48小时）时，双功能反式 - EE仍优先在双螺旋DNA的鸟嘌呤残基处形成单功能加合物。这意味着抗肿瘤反式 - EE修饰DNA的方式与临床上无活性的反铂不同，反铂在48小时后会形成大量的双功能DNA加合物。这一结果被解释为，即使经过长时间反应，反式 - EE在DNA中形成的主要加合物仍是单功能加合物，其中第二个离去基团的反应性明显降低。有人提出，反铂和反式 - EE在DNA上形成的加合物的不同性质与其截然不同的临床疗效相关。
