Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India.
Department of Biochemistry, Ballygunge Science College, University of Calcutta, Kolkata, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2014 Mar 25;122:690-7. doi: 10.1016/j.saa.2013.11.078. Epub 2013 Dec 1.
Drugs belonging to the Non-steroidal anti-inflammatory (NSAID) group are not only used as anti-inflammatory, analgesic and anti-pyretic agents, but also show anti-cancer effects. Complexing them with a bioactive metal like copper, show an enhancement in their anti-cancer effects compared to the bare drugs, whose exact mechanism of action is not yet fully understood. For the first time, it was shown by our group that Cu(II)-NSAIDs can directly bind to the DNA backbone. The ability of the copper complexes of NSAIDs namely meloxicam and piroxicam to bind to the DNA backbone could be a possible molecular mechanism behind their enhanced anticancer effects. Elucidating base sequence specific interaction of Cu(II)-NSAIDs to the DNA will provide information on their possible binding sites in the genome sequence. In this work, we present how these complexes respond to differences in structure and hydration pattern of GC rich sequences. For this, binding studies of Cu(II) complexes of piroxicam [Cu(II)-(Px)2 (L)2] and meloxicam [Cu(II)-(Mx)2 (L)] with alternating GC (polydG-dC) and homopolymeric GC (polydG-polydC) sequences were carried out using a combination of spectroscopic techniques that include UV-Vis absorption, fluorescence and circular dichroism (CD) spectroscopy. The Cu(II)-NSAIDs show strong binding affinity to both polydG-dC and polydG-polydC. The role reversal of Cu(II)-meloxicam from a strong binder of polydG-dC (Kb=11.5×10(3) M(-1)) to a weak binder of polydG-polydC (Kb=5.02×10(3) M(-1)), while Cu(II)-piroxicam changes from a strong binder of polydG-polydC (Kb=8.18×10(3) M(-1)) to a weak one of polydG-dC (Kb=2.18×10(3) M(-1)), point to the sensitivity of these complexes to changes in the backbone structures/hydration. Changes in the profiles of UV absorption band and CD difference spectra, upon complex binding to polynucleotides and the results of competitive binding assay using ethidium bromide (EtBr) fluorescence indicate different binding modes in each case.
非甾体抗炎药（NSAID）不仅具有抗炎、镇痛和退热作用，而且还表现出抗癌作用。将它们与生物活性金属如铜复合，可以增强其抗癌作用，而其确切的作用机制尚不完全清楚。我们小组首次表明，Cu(II)-NSAIDs 可以直接与 DNA 骨架结合。NSAIDs 即美洛昔康和吡罗昔康的铜配合物能够与 DNA 骨架结合，这可能是其增强抗癌作用的一种分子机制。阐明 Cu(II)-NSAIDs 与 DNA 的碱基序列特异性相互作用将为它们在基因组序列中的可能结合位点提供信息。在这项工作中，我们展示了这些配合物如何响应富含 GC 序列的结构和水合模式的差异。为此，使用包括紫外可见吸收光谱、荧光和圆二色性（CD）光谱在内的光谱技术组合，研究了吡罗昔康[Cu(II)-(Px)2(L)2]和美洛昔康[Cu(II)-(Mx)2(L)]的 Cu(II)配合物与交替 GC（聚 dG-dC）和同聚 GC（聚 dG-聚 dC）序列的结合。Cu(II)-NSAIDs 对聚 dG-dC 和聚 dG-聚 dC 均具有很强的结合亲和力。Cu(II)-美洛昔康从聚 dG-dC 的强结合物（Kb=11.5×10(3)M(-1)）转变为聚 dG-聚 dC 的弱结合物（Kb=5.02×10(3)M(-1)），而 Cu(II)-吡罗昔康则从聚 dG-聚 dC 的强结合物（Kb=8.18×10(3)M(-1)）转变为聚 dG-dC 的弱结合物（Kb=2.18×10(3)M(-1)），这表明这些配合物对骨架结构/水合的变化很敏感。在配合物与多核苷酸结合后，紫外吸收带和 CD 差谱的轮廓发生变化，以及使用溴化乙锭（EtBr）荧光进行的竞争结合实验的结果表明，在每种情况下都存在不同的结合模式。
