Defining the role of proteostasis pathways in cancer drug resistance

描述（由申请人提供）：对癌症生存所必需的蛋白质靶向药物的获得性耐药是有效治疗癌症的主要障碍。在大多数情况下，驱动耐药性进化和维持的分子成分尚未得到很好的定义，但在癌症亚型中可能是保守的。因此，确定对癌症耐药重要的细胞通路对于开发新的治疗策略至关重要。癌症人群中耐药性进化的一个明显例子是brca2缺陷癌症中对聚adp -核糖聚合酶（PARP）抑制剂（PARPi）的耐药性。乳腺癌2易感蛋白（BRCA2）和PARP1都在DNA修复中起作用。任何一个基因的功能丧失都不是致命的，然而，两个基因的丧失都会导致双链断裂的积累和细胞死亡。这种合成的致死性相互作用使PARPi成为治疗brca2缺陷乳腺癌、前列腺癌和卵巢癌的有吸引力的药物；然而，PARPi耐药源于编码突变但功能良好的BRCA2蛋白的BRCA2逆转等位基因的表达。逆转录BRCA2蛋白缺失了野生型蛋白的大部分，可能增加了不稳定性和对分子伴侣的依赖。此外，parpi抗性细胞中来自多个等位基因的BRCA2突变版本的表达可能会对存在的用于感知和响应细胞蛋白质折叠需求变化的蛋白质静止机制造成重大负担。由此可见，为了维持该突变蛋白的表达并减轻对细胞蛋白质折叠能力的挑战，PARPi施加了一种选择性压力，导致依赖于改变的蛋白质静止途径来生存。我建议通过解决以下目标来验证这一假设：1)表征BRCA2逆转蛋白表达对蛋白质质量控制和应激反应途径的依赖性和影响。2)确定具有BRCA2逆转等位基因的parpi耐药癌细胞是否依赖于蛋白酶抑制途径存活。3)使用无偏基因组宽RNA干扰筛选，鉴定具有BRCA2逆转等位基因的parpi耐药癌细胞存活和/或维持耐药所需的基因。我们期望通过完成这些研究，我们将确定蛋白质质量控制和应激反应途径的组成部分，这些组成部分对于通过逆转突变重新获得功能性BRCA2蛋白的parpi耐药肿瘤的生存和/或耐药性维持至关重要。这项工作确定的成分和途径将提供概念验证机制，可能用于开发新的治疗策略，以防止耐药癌细胞群的逃逸。！

DESCRIPTION (provided by applicant): Acquired resistance to drugs targeting proteins essential for cancer survival is a major hurdle for the effective treatment of cancer. In most cases the molecular components that drive the evolution and maintenance of drug resistance are not well defined, but are likely to be conserved amongst cancer subtypes. Thus, the identification of cellular pathways important for cancer drug resistance is critical for the development of new treatment strategies. A clear example of the evolution of drug resistance in a cancer population is resistance to Poly ADP-Ribose Polymerase (PARP) inhibitors (PARPi) in BRCA2-deficient cancers. Both Breast Cancer 2 susceptibility protein (BRCA2) and PARP1 function in DNA repair. Loss-of-function of either gene is not lethal, however, loss of both leads to an accumulation of double-strand breaks and cell death. This synthetic lethal interaction has made PARPi an attractive drug therapy for BRCA2-deficient cancers of the breast, prostate, and ovary; however, PARPi resistance arises from the expression of BRCA2 reversion alleles encoding a mutated, but functional, BRCA2 protein. The revertant BRCA2 protein is missing large parts of the wild-type protein and likely has increased instability and dependence on molecular chaperones. Additionally, the expression of mutated versions of BRCA2 from multiple alleles in PARPi-resistant cells likely places a significant burden on the proteostatic machinery that exists to sense and respond to changes in cellular protein folding requirements. It follows that to maintain the expression of this mutant protein and to alleviate challenges to the cells protein folding capacity, PARPi exerts a selective pressure resulting in dependence on altered proteostasis pathways for survival. I propose to test this hypothesis by addressing the following aims: 1) Characterize the dependence and effects of BRCA2 revertant protein expression on protein quality control and stress response pathways. 2) Determine whether PARPi-resistant cancer cells with BRCA2 reversion alleles rely on proteostasis pathways for survival. 3) Use an unbiased genome wide RNA interference screen to identify genes required for the survival and/or maintenance of drug resistance of PARPi-resistant cancer cells with BRCA2 reversion alleles. We expect that by the completion of these proposed studies, we will have identified the components of protein quality control and stress response pathways that are critical for the survival and/or maintenance of drug resistance in PARPi-resistant tumors that re-acquire functional BRCA2 proteins through reversion mutations. The components and pathways identified by this work will provide proof- of-concept mechanisms that may be exploited in developing new treatment strategies to prevent the escape of drug resistant populations of cancer cells. !