Targeting nucleotide excision repair in combination cancer therapy

描述（由申请方提供）：卵巢癌的一线治疗包括与铂类药物（Pt）联合治疗，顺铂或卡铂（1）。成功治疗上皮性卵巢癌（EOC）的一个主要障碍是对铂基化疗药物的耐药性（3）。即使在最初对治疗有反应的EOC中，大多数也会复发并对铂耐药;由于二线治疗基本无效，预后极差。提供有效治疗EOC的困难突出了基于个体疾病的生物学定制治疗的重要性。我们对乳腺癌和卵巢癌中的同源重组（HR）/BRCA途径（4;5）以及这些癌症中HR的常见改变的理解的最新进展已经导致通过利用合成致死性的概念靶向聚ADP-核糖聚合酶（PARP）。虽然PARP抑制剂在BRCA突变型癌症的单药研究中取得了一些成功，但PARP抑制剂与Pt治疗的组合效果要差得多。铂剂通过形成Pt-DNA加合物来赋予其治疗效果，所述加合物阻断DNA复制和转录。Pt-DNA加合物的修复降低了基于铂的治疗的功效，并有助于细胞耐药性。重要的是，Pt-DNA损伤的修复由PARP非依赖性途径、核苷酸切除修复（NER）和同源重组修复（HRR）催化。因此，在HRR缺陷型癌症中，靶向NER预期会对Pt治疗的敏感性产生显著影响。BRCA 1或2的生殖系突变使女性易患HRR缺陷的遗传性乳腺癌和卵巢癌。因此，我们将解决这样的假设，即在HRR缺陷的癌症中，可以利用合成的致死相互作用靶向NER途径与小分子，并且当与顺铂组合时，将以最小的毒性提供增加的功效。顺铂治疗与NER抑制剂组合将根据不同细胞的HRR状态差异性地改变不同细胞的修复能力。非癌性的HRR熟练细胞可以通过HRR修复或耐受顺铂损伤，因此与不能通过任一途径修复顺铂损伤的HRR缺陷癌细胞相比具有降低的毒性。为了解决我们的假设，我们将在两个特定目标中使用我们最近发现的靶向着色性干皮病A组（XPA）蛋白（6）和复制蛋白A（RPA）（7-9）的NER抑制剂。目的1将开发和表征XPA蛋白的新型抑制剂，并评估与顺铂组合在HRR熟练和缺乏的人卵巢癌和乳腺癌的细胞培养模型中的功效。然后，我们将确定XPA抑制与顺铂治疗组合对细胞毒性、DNA损伤信号传导和乳腺癌和卵巢癌的细胞培养物和异种移植模型中顺铂-DNA损伤的修复的影响。在目标2中，我们将确定靶向RPA蛋白的小分子抑制RPA-DNA结合相互作用的机制，实现单药活性，并与顺铂和依托泊苷在BRCA 1缺陷型癌症中协同作用。我们以前的数据确定了两类RPA抑制剂，它们都降低了

DESCRIPTION (provided by applicant): First line treatment of ovarian cancer includes combination therapy with a platinum drug (Pt), either cisplatin or carboplatin (1). A major impediment to the successful treatment of epithelial ovarian cancer (EOC) is resistance to Pt-based chemotherapeutic agents (3). Even in EOCs that initially respond to treatment, most will recur and will be Pt resistant; with an extremely poor prognosis as second line therapies are largely ineffective. The difficulties in providing effective treatment of EOC highlights the importance of tailoring therapies based on the biology of the individual disease. Recent advances in our understanding of the homologous recombination (HR)/BRCA pathway in breast and ovarian cancer (4;5) and the common alteration of HR in these cancers has led to targeting poly-ADP-ribose polymerase (PARP) by exploiting the concept of synthetic lethality. While PARP inhibitors have had some success in single agent studies in BRCA mutant cancers, combination of PARP inhibitors with Pt therapy has been considerably less effective. Pt agents impart their therapeutic effect by the formation of Pt-DNA adducts, which block DNA replication and transcription. Repair of Pt-DNA adducts reduces the efficacy of platinum-based treatment and contributes to cellular resistance. Importantly, repair of Pt-DNA damage is catalyzed by the PARP-independent pathways, nucleotide excision repair (NER) and homologous recombination repair (HRR). Thus, in HRR deficient cancers, targeting NER would be expected to have a significant impact on sensitivity to Pt therapy. Germ line mutations in BRCA1 or 2 predispose women to hereditary breast and ovarian cancer which are HRR deficient. Therefore we will address the hypothesis that synthetic lethal interactions can be exploited targeting the NER pathway with small molecules in HRR deficient cancers and, when combined with cisplatin will provide increased efficacy with minimal toxicity. Cisplatin treatment, in combination with an NER inhibitor, will differentially alter the repair capacity of different cells dependent on their HRR status. Non-cancerous, HRR proficient cells can repair or tolerate the cisplatin damage via HRR and thus will have reduced toxicity compared to the HRR deficient cancer cells which are unable to repair the cisplatin damage via either pathway. To address our hypothesis we will employ our recently discovered NER inhibitors targeting the xeroderma pigmentosum group A (XPA) protein (6) and replication protein A (RPA) (7-9) in two specific aims. Aim 1 will develop and characterize novel inhibitors of the XPA protein and assess efficacy in combination with cisplatin in cell culture models of HRR proficient and deficient human ovarian and breast cancers. We will then determine the impact of XPA inhibition in combination with cisplatin therapy on cytotoxicity, DNA damage signaling and repair of cisplatin-DNA damage in cell culture and xenograft models of breast and ovarian cancer. In aim 2 we will determine the mechanism by which small molecules targeting the RPA protein inhibit the RPA-DNA binding interaction, achieve single agent activity and synergize with cisplatin and etoposide in BRCA1 deficient cancers. Our previous data identified two classes of RPA inhibitors, both of which decrease