Mechanisms of mutant p53 reactivation

项目摘要 肿瘤抑制蛋白p53是人类癌症中最常见的突变蛋白。约60万 在美国，每年都有新的癌症患者被诊断出患有表达突变的p53的肿瘤。最 的突变是错义突变，影响p53 DNA结合域中的六个热点位点之一。 这些癌症表达全长p53，其已失去肿瘤抑制活性，但已获得功能获得性表达。 肿瘤形态学特性为癌细胞提供选择性优势。 大量受影响的癌症使p53成为癌症治疗的一个精致靶点。然而，治疗 方法需要突变的p53的再活化。开发“再激活或校正药物”是具有挑战性的， 但由于在制药、生物技术和这一领域的学术界经验非常有限，情况更加复杂。 通过开发p53校正剂药物来探索新的治疗方法的这些挑战导致了 非常缓慢，并且在使用所提出的p53再活化剂化合物的临床试验中成功有限。最近出现了 几种报道的化合物可能在体内不作用于突变型p53，而是利用氧化还原- 表达p53突变体的细胞的敏感性。结合p53的真正p53突变校正剂药物的开发 并在p53癌症突变体中恢复野生型样构象/活性，因此仍然是一个中心目标， 潜在的巨大影响。为了实现这一目标，对p53癌症突变体的机制理解 重新激活过程是必不可少的，但目前大多缺乏由于缺乏真正的p53校正 除了为相对罕见的p53-Y220 C等位基因开发的化合物之外， 我们已经广泛研究了遗传和药理学p53再激活。我们发现基因内拯救 我们正在开发的突变和小分子诱导类似的构象变化，并稳定 p53热点突变体的活性构象。虽然再激活突变没有直接的治疗作用， 潜在的，他们帮助我们理解p53突变再激活机制，并可以指导纠正药物 发展利用从重新激活第二位点突变中获得的信息，我们开发了一种工具， 本发明涉及结合突变型p53并由此恢复重构的细胞中突变型p53的DNA结合活性的化合物， 纯化的体外系统。当暴露含有p53热点突变体的细胞时，p53靶基因被诱导 这些化合物。此外，在p53突变体中，细胞增殖停止，并诱导凋亡 依赖的方式。重要的是，携带p53突变体的肿瘤的生长被这种化合物系列阻断， 动物模型缺乏p53或表达野生型p53的肿瘤不受这种治疗的影响。这些 化合物为开发作为真正的p53突变体的药物样分子的可行性提供了强有力的支持 校正器。我们现在建议使用这些工具化合物以及充分表征的拯救突变， 对p53热点突变体的再激活过程进行详细的分子理解。的结果 这些研究对于启动化学多样性p53校正剂药物的开发至关重要。

PROJECT SUMMARY The tumor suppressor protein p53 is the most frequently mutated protein in human cancers. About 600,000 new cancer patients in the United States are diagnosed each year with tumors expressing mutated p53. Most of the mutations are missense mutations that affect one of six hotspot sites in the p53 DNA binding domain. These cancers express full length p53 that has lost tumor suppressor activity, but has acquired gain-of-function oncomorphic properties that provide selective advantage to cancer cells. The large number of affected cancers make p53 an exquisite target for cancer therapy. However, therapeutic approaches require reactivation of mutated p53. Developing “reactivation or corrector drugs” is challenging in itself, but further complicated by very limited experience in pharma, biotech, and academia in this domain. These challenges in exploring novel therapeutic approaches by developing p53 corrector drugs have led to very slow, and limited success in clinical trials with proposed p53 reactivator compounds. It recently emerged that several of the reported compounds are likely not acting on mutant p53 in vivo, but rather exploit redox- sensitivity of cells expressing p53 mutants. Development of bona fide p53 mutant corrector drugs that bind p53 and restore a wild-type like conformation/activity in p53 cancer mutants, thus remains a central goal with potentially very high impact. To achieve this goal mechanistic understanding of the p53 cancer mutant reactivation process is essential, but currently mostly lacking due to the lack of genuine p53 corrector molecules with the exception of compounds developed specifically for the relatively rare p53-Y220C allele. We have extensively studied genetic and pharmacological p53 reactivation. We found that Intragenic rescue mutations and small molecules we are developing induce a similar conformational change and stabilize an active conformation of p53 hotspot mutants. Although reactivation mutations have no direct therapeutic potential, they help in our understanding of p53 mutant reactivation mechanisms and can guide corrector drug development. Using information obtained from reactivating second-site mutations, we have developed tool compounds that bind mutant p53 and thereby restore DNA binding activity of mutant p53 in a reconstituted purified in vitro system. p53 target genes are induced when cells harboring p53 hotspot mutants are exposed to these compounds. Furthermore, cell proliferation is halted and apoptosis is induced in a p53 mutant dependent manner. Importantly, growth of tumors carrying p53 mutants is blocked by this compound series in animal models. Tumors lacking p53 or expressing wild-type p53 are not affected by such treatment. These compounds provide strong support for feasibility to develop drug-like molecules that act as genuine p53 mutant correctors. We now propose to use these tool compounds as well as well-characterized rescue mutations to develop detailed molecular understanding of the reactivation process for p53 hotspot mutants. Findings from these studies will be essential to jump start the development of chemically diverse p53 corrector drugs.