Gastpar R, Goldbrunner M, Marko D, von Angerer E
Institut für Pharmazie, Universität Regensburg, D-93040 Regensburg, Germany.
J Med Chem. 1998 Dec 3;41(25):4965-72. doi: 10.1021/jm980228l.
The aim of this study was the identification of the essential structural elements in the 12-formyl-5,6-dihydroindolo[2, 1-a]isoquinoline system required for the inhibition of tubulin polymerization which is understood to be the predominant mode of action of this class of cytostatics. Since 2-phenylindole forms the main fragment of this tetracycle, it was used as the basic structure and modified with respect to the number and positions of the oxygen functions in the aromatic rings. Further modifications related to the nitrogen, which was both replaced by oxygen and sulfur and alkylated. All derivatives were tested for cytostatic activity in human breast cancer cells (MDA-MB 231, MCF-7) and inhibition of tubulin polymerization. The spectrum of activity ranged from inactive to IC50 values of 35 nM (cell growth inhibition) and 1.5 microM (tubulin polymerization), respectively, for the most active derivative 3e (3-formyl-6-methoxy-2-(4-methoxyphenyl)indole). Although the correlation between antiproliferative activity and inhibition of tubulin polymerization was not very pronounced, all of the potent cytostatic agents in this study disrupted microtubule assembly completely at the standard concentration of 40 microM. By fluorescence microscopy it was demonstrated that the derivative 3e degrades the cytoskeleton in a similar fashion as colchicine does leading to the condensation of the microtubules around the nucleus after treatment. The comparison between hydroxy and methoxy derivatives revealed a striking difference between the 2-phenylindole derivatives and the indoloisoquinolines. In the 2-phenylindole series, the methoxy compounds were much more effective than the free phenols, whereas in the tetracyclic system the effect of the hydroxy derivatives exceeded that of the methylated compounds by 1 order of magnitude. Preliminary studies on the binding mode showed that both the 2-phenylindole derivatives and the indoloisoquinolines bind to the colchicine site on tubulin.
本研究的目的是确定12-甲酰基-5,6-二氢吲哚并[2,1-a]异喹啉系统中抑制微管蛋白聚合所需的基本结构元素，据了解，这是这类细胞抑制剂的主要作用方式。由于2-苯基吲哚构成了该四环的主要片段，因此将其用作基本结构，并对芳香环中氧官能团的数量和位置进行了修饰。还对氮进行了进一步修饰，氮既被氧和硫取代，又进行了烷基化。所有衍生物均在人乳腺癌细胞（MDA-MB 231、MCF-7）中测试了细胞抑制活性以及对微管蛋白聚合的抑制作用。活性范围从无活性到最具活性的衍生物3e（3-甲酰基-6-甲氧基-2-(4-甲氧基苯基)吲哚）的IC50值分别为35 nM（细胞生长抑制）和1.5 μM（微管蛋白聚合抑制）。尽管抗增殖活性与微管蛋白聚合抑制之间的相关性不是很明显，但本研究中所有有效的细胞抑制剂在40 μM的标准浓度下都能完全破坏微管组装。通过荧光显微镜证明，衍生物3e以与秋水仙碱类似的方式降解细胞骨架，导致处理后细胞核周围的微管凝聚。羟基衍生物和甲氧基衍生物之间的比较揭示了2-苯基吲哚衍生物和吲哚并异喹啉之间的显著差异。在2-苯基吲哚系列中，甲氧基化合物比游离酚更有效，而在四环系统中，羟基衍生物的效果比甲基化化合物高出1个数量级。关于结合模式的初步研究表明，2-苯基吲哚衍生物和吲哚并异喹啉都与微管蛋白上的秋水仙碱位点结合。
