特异性靶向多聚端粒G-四链体小分子配体的发现及其抗肿瘤分子机制研究

Telomere is considered to be a life clock for cells, because of its progressive loss that universally accompanies cell division, which is critical for preventing cancer. However, about 85–90% of cancers use telomerase for maintenance of telomere, while 10–15% use an alternative lengthening of telomeres (ALT) mechanism. Thus, inhibiting either telomerase or ALT will be a wonderful anticancer strategy but can induce drug resistance in cancer. The 3′-terminal overhang of telomere has a high propensity to fold into G-quadruplex. Stabilization of such structures can inhibit the lengthening of telomere by the two pathways, leading to effective anticancer activity. Nevertheless, large quantities of G-quadruplexes are present in the genome, predominantly in regulatory regions. Hence, non-specific targeting by ligands might alter many genes modulated by G-quadruplexes, leading to unexpected side effects. Notably, only telomeric DNA has the capacity to form multimeric G-quadruplexes in the human genome. Thus, it is believed that small molecules that specifically target telomeric multimeric G-quadruplexes might be more promising anticancer agents. In the previous work, we have discovered a multimeric telomeric G-quadruplex specific ligand called IZNP-1. In this study, on the basis of IZNP-1, we will synthesize serials of new compounds and then evaluate their properties as multimeric telomeric G-quadruplex ligands. Afterward, we will summarize the structure-function relationship, providing design ideas for compounds targeting such distinct structures. We will also probe the binding mode of the optimal compound, and deeply investigate its anticancer activity and molecular mechanism in the telomerase-positive or ALT cancer cells, offering new insights for the development of selective anticancer drugs targeting telomeric multimeric G-quadruplexes.

端粒随有丝分裂而逐渐缩短，是细胞的生命时钟。癌细胞却能通过激活端粒酶或ALT来延长端粒而实现永生化，因此抑制端粒延长是一种重要的抗癌策略。目前，靶向端粒酶的抗癌疗法对ALT肿瘤无效，且能代偿性激活ALT，使肿瘤耐药。稳定端粒G-四链体的化合物具有同时抑制端粒酶及ALT活性的潜力，其应用前景广阔。然而，G-四链体参与众多调控过程，无差别稳定该结构则会带来许多副作用。因此，以端粒区域唯一存在的多聚G-四链体结构为靶点发展特异性配体具有重要意义。在前期工作中，我们筛选到了靶向多聚端粒G-四链体的化合物IZNP-1。本项目将以IZNP-1为先导结构，通过设计、合成与筛选，获得性能更优的特异性配体，总结构效关系，为多聚端粒G-四链体小分子配体的设计提供思路；同时也将阐明优选化合物的结合模式，探究其在端粒酶阳性肿瘤细胞与ALT肿瘤细胞中的抗癌活性及分子机制，为以端粒为靶点的抗癌药物研发提供实验基础。

端粒是位于染色体末端的特殊复合物结构，主要由4−15 kb的富含鸟嘌呤的TTAGGG双链重复序列和末端一段约200 nt 的单链悬垂序列（3'-overhang）以及端粒结合蛋白构成，能够保护染色体的完整性。端粒的维持在肿瘤的发生发展中起着重要的作用。而对端粒维持功能的干预则是目前有效的一种抗肿瘤策略。. 研究表明，端粒单链悬垂序列在生理条件下可以形成稳定的G-四链体结构。小分子配体通过稳定端粒G-四链体可以破坏端粒末端的完整结构，导致端粒功能的紊乱，进而抑制肿瘤细胞生长。值得一提的是，端粒末端重复的富G序列具有同时形成多个G-四链体结构单元的潜力，这些结构单元可以通过串联堆叠等作用形成特殊的多聚G-四链体结构，而G-四链体之间的结合部位能够给小分子配体提供独特的结合空腔。由于多聚G-四链体只存在于端粒区域，那么发展选择性作用于多聚端粒G-四链体的小分子配体在肿瘤治疗方面将具有很大的应用前景。本项目以前期发展的IZNP-1为先导结构，通过设计、合成与筛选，获得性能更优的特异性配体DIZ系列化合物，总结构效关系，为多聚端粒G-四链体小分子配体的设计提供思路；同时也阐明优选化合物DIZ3的结合模式，探究其抗癌活性及分子机制，为以端粒为靶点的抗癌药物研发提供实验基础。