Optimizing PARP inhibitor therapy through novel approaches to resolve the molecular mechanisms of response

多聚(ADP-核糖)聚合酶(PARP)是一个涉及多方面的酶家族。 细胞功能，包括DNA损伤修复(DDR)和染色质稳定性等 它们才刚刚被发现。PARP在DDR中的重要性，特别是非同源性 末端连接，使其成为DDR缺乏的癌症的理想治疗靶点 很突出。PARP的临床靶向首先在携带BRCA突变的患者中进行， 因此，在同源重组中存在缺陷，其中抑制PARP是合成致命的。 虽然有效，但PARP抑制剂(PARPI)并没有像希望的那样具有开创性，因为 几种抗性机制和DDR的复杂性。目前已批准的有3家 PARP抑制剂治疗卵巢癌及两种晚期临床应用 审判。然而，我们对PARP疗效背后的分子生物学的理解仍然 有限的。有趣的是，敲除PARP并不会产生与PARP相同的细胞致命性 抑制剂，这是最近通过发现PARP抑制剂将PARP捕获到位点来解释的 DNA损伤的可能性。然而，即使它们结合在相同的蛋白质口袋中，并具有相似的 亲和力，一些PARP抑制剂是更有效的诱捕剂，原因尚不清楚。 因此，PARP抑制剂通过捕获和酶抑制发挥作用。我们的 对细胞系反应数据库的初步分析表明，细胞系之间存在很大差异 对不同PARP抑制剂的敏感性，某些细胞系对低陷阱更敏感 抑制剂和其他对高诱捕作用更敏感的抑制剂。确定其作用机制 不同的PARP抑制剂敏感性将为临床选择 PARP抑制剂，以推动更有效的治疗。在这里，我们将解决三个具体目标 通过单细胞蛋白表达和动力学的新方法：1)确定PARPI- 细胞反应的特定驱动因素以选择最佳的PARPI治疗，2)阐明 PARPI敏感性优化联合治疗的分子机制；3)最佳配对 PARPI，以提高疗效并将毒性降至最低。解析PARP抑制剂的作用机制 疗效将使最佳的临床使用和组合试验设计成为可能。我们预计将确定 每种临床PARP抑制剂的反应生物标志物将指导临床选择 PARPI治疗。

Poly(ADP-ribose) polymerases (PARP) are a family of enzymes involved with multiple facets of cellular function including DNA damage repair (DDR) and chromatin stability, along with others that are just being discovered. The importance of PARP in DDR, specifically non-homologous end joining, makes it an ideal therapeutic target in cancer where DDR deficiencies are prominent. Clinical targeting of PARP was first performed in patients harboring BRCA mutations, and thus defects in homologous recombination, where PARP inhibition is synthetically lethal. Although effective, PARP inhibitors (PARPi) did not prove as ground breaking as hoped due to several resistance mechanisms and the complexity of DDR. Currently there are 3 approved PARP inhibitors for treatment of patient with ovarian cancer and two more in late stage clinical trials. However, our understanding of molecular biology underlying PARP efficacy remains limited. Intriguingly, knocking out PARP does not produce the cellular lethality found with PARP inhibitor, which was recently explained by the discovery that PARP inhibitors trap PARP to sites of DNA damage. However, even though they bind into the same protein pocket and have similar affinities, some PARP inhibitors are much more potent trappers, the reason remains unknown. Thus, PARP inhibitors function through both trapping and and enzymatic inhibition. Our preliminary analysis of cell line response databases demonstrates wide differences in cell line susceptibility to different PARP inhibitors, with some cell lines more sensitive to low trapping inhibitors and other more sensitive to high trapping inhibitors. Determining the mechanisms of differential PARP inhibitor sensitivity would provide insight into clinical selection among the PARP inhibitors to drive more effective therapies. Here we will address three specific aims through novel approaches of single cell protein expression and dynamics: 1) determine PARPi- specific drivers of cellular response to select optimal PARPi treatment, 2) elucidate the molecular mechanism of PARPi sensitivity to optimize combination therapy, and 3) optimally pair PARPi to increase efficacy and minimize toxicity. Resolving the mechanisms of PARP inhibitor efficacy will enable optimal clinical use and combination trial design. We expect to determine biomarkers of response for each of the clinical PARP inhibitors that will guide clinical selection of PARPi treatment.