NOVEL DNA DOUBLE STRAND BREAK REPAIR TARGETING THERAPEUTICS FOR CANCER TREATMENT

产品说明：癌细胞经常破坏DNA双链断裂（DSB）修复蛋白，导致基因组不稳定和肿瘤的遗传进化。由于代偿性修复途径的活性，这些蛋白质的失活通常不会引起DNA DSB修复的明显缺陷。我们的理由是，识别削弱这些补偿途径的化合物将是开发治疗药物的第一步，这些药物可以使肿瘤细胞而不是正常组织对遗传毒性癌症疗法敏感。DNA损伤反应组蛋白H2 AX是一种剂量依赖性肿瘤抑制因子，在许多癌症中表达减少。H2 AX缺陷导致基因组不稳定性，但不会导致通过非同源末端连接（NHEJ）进行的DNA DSB修复中的明显缺陷。NHEJ因子XLF的缺乏也不会导致NHEJ中可证实的缺陷。然而，H2 AX和XLF的组合缺陷导致NHEJ对DSB修复的严重阻断。这些发现表明，H2 AX和XLF在代偿性DSB修复途径中，并且在缺乏另一种途径的细胞中抑制一种途径将导致NHEJ的深度阻断。与新墨西哥州大学分子发现中心（UNMCMD）合作，我们开发了一种用于抑制NHEJ的化合物的流式细胞术高通量筛选。该筛选已被优化并用于筛选实现Z'得分>0.6的化合物的小文库（1，500）。在这里，我们建议使用这种方法来筛选一个更大，更复杂的化学库，以确定化合物，抑制NHEJ特异性在H2 AX缺陷，但不是野生型细胞。我们将这些化合物称为NHEJ的H2 AX特异性合成抑制剂（SIN）。一个线性的，多步骤的方法来验证这些化合物的功能也将被开发。我们相信，开发选择性抑制癌细胞中NHEJ的药物将最终使我们能够利用DNA修复途径缺陷来治疗癌症。此外，这种方法与目前选择性抑制癌细胞中DSB修复的其他主要途径同源重组（HR）的努力相比具有显著优势。然而HR仅在分裂细胞中的DSB修复中起作用，NHEJ在细胞周期的G 0-G1期的所有细胞中的DSB修复中是必需的。因此，通过我们的筛选鉴定的抑制NHEJ的药物将有效治疗所有癌细胞，包括绝大多数不活跃分裂的癌细胞。重要的是，癌症干细胞被认为是许多癌症治疗后复发的基础，主要存在于G1期，也会被SIN敏化。除了鉴定H2 AX特异性SIN外，这些研究的完成将为未来鉴定SIN以治疗在广泛的DNA DSB修复蛋白中有缺陷的癌症建立线性管道。此外，他们还将确定正常细胞和癌细胞使用的新DSB修复途径。

DESCRIPTION: Cancer cells frequently inactivate DNA double strand break (DSB) repair proteins causing genomic instability and the genetic evolution of tumors. Inactivation of these proteins usually does not cause overt defects in DNA DSB repair due to the activity of compensatory repair pathways. We reason that identifying compounds that cripple these compensatory pathways will be the first step in developing therapeutic agents that can sensitize tumor cells, but not normal tissues to genotoxic cancer therapies. The DNA damage response histone protein H2AX is a dosage-dependent tumor suppressor that exhibits reduced expression in many cancers. H2AX deficiency leads to genomic instability, but not to overt defects in DNA DSB repair by non-homologous end joining (NHEJ). Deficiency in the NHEJ factor XLF also does not lead to demonstrable defects in NHEJ. However, the combined deficiency of H2AX and XLF leads to a severe block in DSB repair by NHEJ. These findings demonstrate that H2AX and XLF are in compensatory DSB repair pathways and that inhibition of one pathway in cells deficient in the other will lead to a profound block in NHEJ. In conjunction with the University of New Mexico Center for Molecular Discover (UNMCMD), we have developed a flow cytometric high throughput screen for chemical compounds that inhibit NHEJ. This screen has been optimized and used to screen a small library of compounds (1,500) achieving Z' scores of >0.6. Here, we propose to use this approach to screen a larger, more complex chemical library to identify compounds that inhibit NHEJ specifically in H2AX-deficient, but not wild type cells. We refer to these compounds as H2AX-specific Synthetic Inhibitors of NHEJ (SINs). A linear, multistep approach to validate the function of these compounds will also be developed. We believe that developing agents that selectively inhibit NHEJ in cancer cells will ultimately enable us to exploit DNA repair pathway defects to treat cancers. Moreover, this approach has significant advantages over current efforts to selectively inhibit the other major pathway of DSB repair, homologous recombination (HR) in cancer cells. Whereas HR only functions in DSB repair in dividing cells, NHEJ is required for DSB repair in all cells in the G0-G1 phases of the cell cycle. Thus, agents identified by our screen, which inhibit NHEJ will be effective in treating all cancer cells including the vast majority that are not actively dividing. Importantly, cancer stem cells, which are thought to be the basis for relapse of many cancers after treatment, exist primarily in G1 and would also be sensitized by SINs. In addition to identifying H2AX-specific SINs, completion of these studies will establish a linear pipeline for th future identification of SINs for treating cancers defective in a broad range of DNA DSB repair proteins. Moreover, they will also identify novel DSB repair pathways used by normal cells and cancer cells.