Potentials of reactivated mutant p53

描述（由申请人提供）：近50%的癌症病例中发生p53基因内的突变，导致非功能性缺陷蛋白的积累。p53功能的丧失导致产生遗传稳定性和内在抗癌防御的自杀程序的废除，为癌细胞的不受控制的增殖和恶性进展开辟了道路。同时，在p53基因内含有结构缺陷的细胞中，p53途径的其他组分通常保持完整，使肿瘤细胞对重新引入的野生型p53高度敏感。从理论上讲，突变型p53蛋白的活性受损可以通过小分子来纠正，从而诱导治疗效果。在初步研究中，通过在基于细胞的读出中对化学文库进行高通量筛选，获得了一组恢复His273 p53突变体转录活性的小分子。一些化合物显示出His273 p53突变体依赖性生长抑制和促凋亡活性，以及裸鼠中A431细胞异种移植物的生长减少。 在目标1的拟议计划，我们将确定小分子，重新激活转录活性的几类p53突变体在人类肿瘤细胞的情况下，通过分析额外的正在进行的筛选结果。这些化合物将根据化学相似性、对不同类型的p53突变体的活性谱以及作用机制的差异进行分类。p53通路内由p53再活化化合物引起的变化及其作用机制的详细表征将在该计划的目标2中提出挑战。目的3：研究p53通路的修复对突变型p53肿瘤细胞的治疗作用。通过野生型p53的条件表达和在项目过程中获得的突变型p53的化学再激活剂，将实现p53途径的再激活。将发现恢复的p53活性与其他治疗性处理的最佳组合，以确保细胞毒性超过细胞抑制作用的流行。这些研究将在体外和肿瘤异种移植物中进行。将开发和实验测试用于调节人类肿瘤细胞中p53依赖性应答的方法。该项目完成后，将提出将突变型p53转化为治疗药物的新型潜在抗癌药物类别，并将评估恢复的突变型p53的治疗潜力。

DESCRIPTION (provided by applicant): Mutations within the p53 gene leading to accumulation of non-functional faulty protein occur in nearly 50% of cancer cases. Loss of p53 function results in abrogation of suicidal programs that produce genetic stability and intrinsic anticancer defense, opening the way for uncontrolled proliferation and malignant progression of cancer cells. Meanwhile, in the cells harboring structural defects within the p53 gene, the other components of the p53 pathway usually remain intact, leaving tumor cells highly sensitive to reintroduced wild-type p53. Theoretically, the impaired activity of mutant p53 protein could be pharmacologically corrected by small molecules, which induce a therapeutic effect. In a preliminary study, a set of small molecules that restore transcriptional activity of the His273 p53 mutant was obtained by high throughput screening of a chemical library in a cell-based readout. Some of the compounds show His273 p53 mutant-dependent growth suppressing and pro-apoptotic activity, and reduced growth of xenografts of A431 cell in nude mice. In Aim 1 of the proposed program, we shall identify small molecules that reactivate transcriptional activity of several classes of p53 mutants in the context of human tumor cells by analyzing results of additional ongoing screenings. These compounds will be classified according to chemical similarity, spectrum of activity toward different classes of p53 mutants, and differences in the mechanisms of action. Detailed characterization of changes within the p53 pathway, caused by the p53-reactivating compounds, and their mechanisms of action will be challenged in Aim 2 of the program. Aim 3 is designed to evaluate therapeutic potentials of restored p53 pathways in human tumor cells bearing mutant p53. Reactivation of p53 pathways will be achieved both by conditional expression of the wild-type p53, and by chemical reactivators of mutant p53 obtained in the course of the project. Optimal combinations of restored p53 activity with other therapeutic treatments will be found to ensure prevalence of cytotoxicity over cytostatic effects. These studies will be conducted both in vitro and in tumor xenografts. Approaches for modulation of the p53-dependnet response in human tumor cells will be developed and experimentally tested. Upon the completion of the project, novel potential classes of anticancer drugs that convert mutant p53 into a therapeutic will be suggested, and therapeutic potentials of restored mutant p53 will be evaluated.