Center for Cell Dynamics and Department of Physics, Korea University, Anam, Seongbuk, Seoul, 136-713, Korea.
Phys Chem Chem Phys. 2012 Mar 7;14(9):3128-33. doi: 10.1039/c2cp23551j. Epub 2012 Jan 30.
Platinum-based anti-cancer drugs form a major family of cancer chemotherapeutic agents. Cisplatin, the first member of the family, remains a potent anti-cancer drug and exhibits its clinical effect by inducing local DNA kinks and subsequently interfering with DNA metabolism. Although its mechanism is reasonably well understood, effects of intracellular ions on cisplatin activity are left to be elucidated because cisplatin binding to DNA, thus its drug efficacy, is modified by various ions. One such issue is the effect of carbonate ions: cisplatin binding to DNA is suppressed under physiological carbonate conditions. Here, we examined the role of common cellular ions (carbonate and chloride) by measuring cisplatin binding in relevant physiological buffers via a DNA micromanipulation technique. Using two orthogonal single-molecule methods, we succeeded in detecting hidden monofunctional adducts (kink-free, presumably clinically inactive form) and clearly showed that the major effect of carbonates was to form such adducts and to prevent them from converting to bifunctional adducts (kinked, clinically active). The chloride-rich environment also led to the formation of monofunctional adducts. Our approach is widely applicable to the study of the transient behaviours of various drugs and proteins that bind to DNA in different modes depending on various physical and chemical factors such as tension, torsion, ligands, and ions.
铂类抗癌药物形成了一类主要的癌症化疗药物。顺铂是该家族的第一个成员，仍然是一种有效的抗癌药物，通过诱导局部 DNA 扭曲，进而干扰 DNA 代谢来发挥其临床效果。尽管其作用机制已被很好地理解，但细胞内离子对顺铂活性的影响仍有待阐明，因为顺铂与 DNA 的结合，从而影响其药效，受到各种离子的修饰。其中一个问题是碳酸根离子的影响：在生理碳酸条件下，顺铂与 DNA 的结合受到抑制。在这里，我们通过 DNA 微操作技术在相关生理缓冲液中测量顺铂的结合，研究了常见细胞内离子（碳酸根离子和氯离子）的作用。我们使用两种正交的单分子方法，成功地检测到隐藏的单功能加合物（无扭曲，推测临床上无活性的形式），并清楚地表明，碳酸根的主要作用是形成这种加合物，并阻止它们转化为双功能加合物（扭曲，临床上有活性）。富含氯离子的环境也导致了单功能加合物的形成。我们的方法广泛适用于研究各种药物和蛋白质与 DNA 的结合的瞬态行为，这些药物和蛋白质根据各种物理和化学因素（如张力、扭转、配体和离子）以不同的模式与 DNA 结合。
