Bcl-2拮抗剂对Hedgehog依赖性肿瘤的生长抑制作用及其机制研究

Many efforts have been devoted to develop molecular targeted anti-cancer drugs targeting Smoothened (Smo), a critical component of hedgehog (Hh) signaling pathway. Our pilot studies revealed that AT-101, a pan-Bcl-2 inhibitor, may suppress the Hh signaling pathway activity by likely targeting Smo. Similar to other molecular targeted anti-cancer drugs, acquired resistance is easily emerged for Smo inhibitors. Until now, the strategy to circumvent the acquired resistance of Smo inhibitors is to develop the second generation of Smo inhibitors. However, this is only effective for reversing the resistance caused by mutation of Smo, while lacking effects against resistance caused by other mechanisms. Due to the aberrant Hh pathway activity in all tumors resistant to Smo inhibitos, the expression of Bcl-2, one of the transcriptional target genes of transcriptional factor Gli of Hh pathway, must be consequently upregulated. We hypothesize that targeting Bcl-2 may circumvent the resistance of Smo inhibitors caused by the majority (or all) the resistance mechanisms, and we have preliminarily demonstrated that AT-101 may circumvent the resistance of Smo inhibitors caused by two of all the resistant mechanisms, Smo mutation and Gli2 amplification. Hence, this proposal is aimed to elucidate: 1), whether AT-101 may inhibit the growth of Hh-dependent tumors by targeting Smo; 2) Compared to other Smo inhibitors only targeting Smo, whether it takes longer time for the emergence of resistance to AT-101, when AT-101 is used for treating tumors addiction to Hh; 3) whether targeting Bcl-2 by Bcl-2 antagonists AT-101, ABT-737, and ABT-199, may circumvent the resistance of Smo inhibitors caused by the majority (or all) of the resistant mechanisms. Our study will demonstrate that AT-101 is a novel Smo inhibitors, also possessing advantage against other Smo inhibitors; meanwhile, this study will discover a novel and better strategy for combating acquired resistance of Smo inhibitors by targeting Bcl-2.

靶向hedgehog(Hh)通路中Smoothened (Smo)抗肿瘤药物是当前研究热点之一。我们前期发现，Bcl-2抑制剂AT-101能显著抑制Hh活性，为潜在Smo抑制剂。Smo抑制剂极易产生耐药，目前主要克服策略为开发二代Smo抑制剂，但其只针对Smo点突变耐药，对其它机制导致的耐药无效。由于Smo抑制剂耐药肿瘤中Hh依旧异常激活，则Hh转录靶基因Bcl-2肯定高表达，故靶向Bcl-2或可抑制大部分（或所有）耐药机制导致的Smo抑制剂耐药肿瘤生长。本项目拟阐明在Hh依赖性肿瘤中，AT-101能否靶向Smo，抑制Hh活性，进而抑制其生长；相对其它Smo抑制剂，潜在双靶向Smo及Bcl-2的AT-101对Hh依赖性肿瘤是否更不容易产生耐药；以Bcl-2拮抗剂AT-101、ABT-737及ABT-199为分子探针，阐明靶向Bcl-2能否克服大部分（或所有）耐药机制导致的Smo抑制剂耐药。

Hedgehog(Hh)信号通路对众多肿瘤的发生和发展起着重要作用。靶向其受体Smoothened（Smo）的抗肿瘤药物已经成功上市，但其原发性及继发性耐药严重影响了其临床疗效。本项目研究发现Bcl-2抑制剂ABT-199、ABT-263能显著抑制Hh信号通路活性，其机制分别为通过靶向Smo、Gli进而抑制其活性。进一步研究发现ABT-199、ABT-263具有克服Smo抑制剂耐药的潜能。体内实验发现ABT-199、ABT-263能显著抑制Hh依赖性的髓母细胞瘤的生长并且能克服Smo突变、对Smo抑制剂耐药的髓母细胞瘤的生长。本项目同时与药物化学实验室合作，新开发了一系列具有高活性、高选择性的Bcl-2抑制剂。本项目的研究成果为开发新型Hh抑制剂，特别是具有克服耐药潜能的新型Hh抑制剂提供了一种新策略。