Bourassa P, Thomas T J, Tajmir-Riahi H A
Department of Chemistry-Physics, University of Québec in Trois-Rivières, C. P. 500, Trois-Rivières, Québec G9A 5H7, Canada.
Department of Medicine, Rutgers Robert Wood Johnson Medical School, and Rutgers Cancer Institute of New Jersey, New Brunswick, NJ 08901, USA.
J Pharm Biomed Anal. 2014 Jul;95:193-9. doi: 10.1016/j.jpba.2014.02.028. Epub 2014 Mar 12.
We located the binding sites of antitumor drugs tamoxifen, 4-hydroxytamoxifen and endoxifen with calf-thymus DNA. FTIR, CD, UV-vis and fluorescence spectroscopic methods as well as molecular modeling were used to characterize the drug binding sites, binding constant and the effect of drug binding on DNA stability and conformation. Structural analysis showed that tamoxifen and its metabolites bind DNA via hydrophobic and hydrophilic interactions with overall binding constants of K(tam-DNA)=3.5 (±0.2)×10⁴ M⁻¹, K(4-hydroxytam-DNA)=3.3 (±0.4) × 10⁴ M⁻¹ and K(endox)-DNA=2.8 (±0.8)×10⁴ M⁻¹. The number of binding sites occupied by drug is 1 (tamoxifen), 0.8 (4-hydroxitamoxifen) and 1.2 (endoxifen). Docking showed the participation of several nucleobases in drug-DNA complexes with the free binding energy of -3.85 (tamoxifen), -4.18 (4-hydroxtamoxifen) and -3.74 kcal/mol (endoxifen). The order of binding is 4-hydroxy-tamoxen>tamoxifen>endoxifen. Drug binding did not alter DNA conformation from B-family structure, while major biopolymer aggregation occurred at high drug concentrations. The drug binding mode is correlated with the mechanism of action of antitumor activity of tamoxifen and its metabolites.
我们确定了抗肿瘤药物他莫昔芬、4-羟基他莫昔芬和恩杂鲁胺与小牛胸腺DNA的结合位点。使用傅里叶变换红外光谱（FTIR）、圆二色光谱（CD）、紫外可见光谱（UV-vis）和荧光光谱方法以及分子模拟来表征药物结合位点、结合常数以及药物结合对DNA稳定性和构象的影响。结构分析表明，他莫昔芬及其代谢产物通过疏水和亲水相互作用与DNA结合，其总结合常数分别为K（他莫昔芬-DNA）=3.5（±0.2）×10⁴ M⁻¹、K（4-羟基他莫昔芬-DNA）=3.3（±0.4）×10⁴ M⁻¹和K（恩杂鲁胺-DNA）=2.8（±0.8）×10⁴ M⁻¹。药物占据的结合位点数分别为1（他莫昔芬）、0.8（4-羟基他莫昔芬）和1.2（恩杂鲁胺）。对接显示几种核碱基参与了药物-DNA复合物的形成，其自由结合能分别为-3.85（他莫昔芬）、-4.18（4-羟基他莫昔芬）和-3.74 kcal/mol（恩杂鲁胺）。结合顺序为4-羟基他莫昔芬>他莫昔芬>恩杂鲁胺。药物结合未改变DNA从B族结构的构象，而在高药物浓度下发生了主要生物聚合物聚集。药物结合模式与他莫昔芬及其代谢产物的抗肿瘤活性作用机制相关。
