Increased DNA binding activity of cis-1,1-cyclobutanedicarboxylatodiammineplatinum(II) (Carboplatin) in the presence of nucleophiles and human breast cancer MCF-7 cell cytoplasmic extracts:: Activation theory revisited
Increased DNA binding activity of cis-1,1-cyclobutanedicarboxylatodiammineplatinum(II) (Carboplatin) in the presence of nucleophiles and human breast cancer MCF-7 cell cytoplasmic extracts:: Activation theory revisited
复制标题
DOI：
10.1016/s0006-2952(99)00250-6
复制
发表时间：
1999-11-15
影响因子：
5.8
通讯作者：
Holler, E
中科院分区：
文献类型：
--
作者：
Natarajan, G;Malathi, R;Holler, E
卡铂[cis-1，1-cyclobutanedicarboxylic atodiamminepatinum（II）]活化的分子机制仍不清楚。我们研究了在硫脲，谷胱甘肽和人乳腺癌MCF-7细胞胞质提取物的存在下，卡铂与小牛胸腺DNA的结合，通过测量DNA依赖性，溴化乙锭荧光和原子吸收光谱。反应96小时后，与不存在亲核试剂的对照相比，硫脲（6倍）和谷胱甘肽（3- 4倍）存在下，由于铂（Pt）-DNA加合物的形成，溴化乙锭的DNA依赖性荧光产率的降低显著增加。通过原子吸收光谱法测量，结合到DNA中的铂水平也显著升高（硫脲和谷胱甘肽分别为2至3倍和5至7倍）。更值得注意的是，在MCF-7人乳腺癌细胞的细胞质提取物存在下形成的Pt-DNA加合物也以剂量相关的方式显示出类似的结果。因此，在存在与顺铂[顺式二氨二氯铂（II）]的预期淬灭效应完全相同的含S亲核试剂的情况下，卡铂显示出DNA结合/损伤的特征性增加。我们提出了一个亲核试剂促进释放的活性物种的卡铂与DNA结合之前。(C)1999 Elsevier Science Inc.
The molecular mechanism of carboplatin [cis-1,1-cyclobutanedicarboxylatodiammineplatinum(II)] activation is still unresolved. We studied the binding of carboplatin to calf thymus DNA in the presence of thiourea, glutathione, and human breast cancer MCF-7 cell cytoplasmic extracts by measurement of DNA-dependent, ethidium bromide fluorescence and atomic absorption spectroscopy. After a 96-hr period of reaction, the decrease in the DNA-dependent fluorescence yield of ethidium bromide due to the formation of platinum (Pt)-DNA adducts increased significantly in the presence of thiourea (6-fold) and glutathione (3- to 4-fold) as compared to the controls in the absence of the nucleophiles. There was also a marked elevation in the levels of platinum incorporated into DNA, measured by atomic absorption spectroscopy (2- to 3-fold and 5- to 7-fold for thiourea and glutathione, respectively). More remarkably, the Pt-DNA adducts formed in the presence of cytoplasmic extracts of MCF-7 human breast cancer cells also showed similar results in a dose-related fashion. Carboplatin, therefore, displayed a characteristic increase in DNA binding/damaging in the presence of the very same S-containing nucleophiles that showed the expected quenching effects in the case of cisplatin [cis-diamminedichloroplatinum (II)]. We propose a nucleophile-facilitated release of the active species of carboplatin prior to binding with DNA. (C) 1999 Elsevier Science Inc.