Photoinduced in situ generation of DNA-targeting ligands: Novel approaches towards cytotoxic DNA-binding and DNA-damaging agents

有机配体与DNA之间的相互作用是药物开发中鉴定铅结构的范例，因为这种相互作用可能影响核酸的生理功能。事实上，传统肿瘤靶向药物的作用模式涉及它们与肿瘤细胞DNA的关联或化学反应。然而，这种化疗方法的一个主要缺点仍然是药物对健康组织产生严重的副作用。这些不良反应可以通过具有空间和时间控制的药物来减轻。为此，需要一种化合物，它能通过外部刺激触发与DNA的结合。在本研究项目中，我们希望通过光生成DNA结合剂的开发，为探索时间和空间可控的DNA配体做出贡献。基于我们之前的合作工作，苯乙烯基苯并噻唑和邻苯乙烯基取代的n -杂环将不与DNA结合。然而，在DNA存在的照射下，这些底物在原位形成阳离子七烷，然后对DNA具有高亲和力。该计划的重点是对原位光生成DNA配体的基础研究，主要侧重于改善底物的光化学性质，增加配体对特定DNA形式的选择性，以及底物在体内的应用。在基础光化学研究中，将研究苯乙烯基底物的取代模式对配体形成光反应的影响，以确定在溶解度、吸收特性的生物相容性、光反应性、底物与DNA结合的不情愿以及所产生的光产物与核酸的亲和力方面的最佳发色团结构。此外，将测试结构变化，通过形成双插层体来提高对DNA的亲和力，或完成原位形成的配体与不规则或非规范DNA形式的选择性结合，如四重DNA或含有基本位点的DNA。后一种核酸结构在生物相关过程中起着至关重要的作用，因此与它们结合的光可控配体是药物设计中有吸引力的靶标。另一个子项目旨在合成苯乙烯基底物，这种底物附着在DNA损伤功能上，可以对DNA进行化学修饰，即对DNA结构和活性进行更持久的改变。根据主要原理，只有在光诱导形成DNA插层后，DNA损伤功能才能有效地传递到DNA附近，从而诱导DNA病变的形成。最后，底物和光产物的细胞毒性将在细胞中进行测试，以评估体内的一般方法。

The interactions between organic ligands and DNA are a paradigm for the identification of lead structures in drug development, because such interactions may affect the physiological functions of the nucleic acid. Indeed, the mode of action of traditional tumor-targeting drugs involves their association or chemical reaction with the DNA of tumor cells. Nevertheless, a major drawback of this chemotherapeutic approach still is the occurrence of severe side effects of the drug on the healthy tissue. These adverse effects may be diminished by drugs that can be applied with spatial and temporal control. For that purpose, chemical compounds are required whose association with DNA can be triggered by an external stimulus. In this research project, we wish to contribute to the quest for time- and space-controllable DNA ligands with the development of photo-generated DNA binders. Based on our previous collaborative work, styrylbenzothiazoles and ortho-styryl-substituted N-heterocycles will be made available that do not bind to DNA. Upon irradiation in the presence of DNA, however, these substrates form cationic hetarenes in situ, which then have a high affinity to DNA. The proposed project is focused on the fundamental investigation of in situ photo-generated DNA ligands with a main emphasis on improved photochemical properties of the substrates, on increased selectivity of the ligands towards particular DNA forms, and on the application of the substrates in vivo.In basic photochemical studies, the influence of the substitution pattern of the styryl substrate on the ligand-forming photoreaction will be examined to identify the optimal structure of the chromophore with regard to solubility, bio-compatibility of the absorption properties, photoreactivity, reluctance of the substrate to bind to DNA, and affinity of the resulting photoproduct to the nucleic acid. In addition, structure variations will be tested that shall enable higher affinity to the DNA by the formation of bis-intercalators, or that accomplish selective binding of the in situ formed ligand to irregular or non-canonical DNA forms, such as quadruplex DNA or abasic site-containing DNA. The latter nucleic-acid structures play essential roles in biologically relevant processes, so that photo-controllable ligands which bind to them are attractive targets in drug design. Another sub-project aims at the synthesis of styryl substrates that are attached to a DNA-damaging functionality, which enables the chemical modification of DNA, i.e. a more sustaining change of the DNA structure and activity. According to the main principle, only after the photoinduced formation of the DNA intercalator the DNA-damaging functionality is efficiently delivered into the close vicinity of DNA, where it can subsequently induce the formation of DNA lesions. Finally, the cytotoxicity of the substrates and photoproducts will be tested in cells to assess the general approach in vivo.