Cell Cycle Blockade and Therapeutic Sensitization

顺铂和卡铂在临床上被广泛用于治疗各种癌症，如肺癌。 卵巢、非小细胞肺(NSCLC)、睾丸、头颈和膀胱起源。这些药物证明了 良好的活性，但在大多数情况下，这种活性是短暂的，因为肿瘤在发病时变得不敏感 抵抗。有几种选择可以使肿瘤细胞对铂类药物敏感。由于铂类药物 与DNA相互作用形成DNA加合物作为其作用机制，抑制DNA修复可使 由于DNA加合物的持久性，肿瘤细胞高度敏感。通过核苷酸修复这些加合物 睾丸癌的切除修复(NER)较低，这使得这些癌症对铂类药物和 导致约90%的治愈率。最近的数据表明，这些加合物的修复是复杂的，涉及 NER介导的伤口作为中间体导致双链断裂，然后通过以下方式修复 同源重组(HR)。碱基切除修复(BER)途径也与顺铂有关 修理。有趣的是，临床上铂的活性范围已经扩大到包括三阴性乳房 含有BRCA1突变或低BRCA1表达的癌症(BRCAness肿瘤)。高灵敏度还具有 已在遗传性或低表达BRCA1卵巢癌中观察到。BRCA1缺失引起的敏化作用是 由于由此产生的HR缺陷，当与抑制多(ADP-核糖)-聚合酶(PARP)时， 奥拉帕利的BER途径会产生合成致命性。因此，奥拉帕利可进一步增加铂的敏感性。 BRCAness表型的肿瘤。然而，这种致敏作用仅限于少量的BRCA1 患者，但在我们的建议中，我们将测试诱导细胞周期阻断的小分子将 抑制BRCA1基因在卵巢癌和乳腺癌中的表达以增强肿瘤细胞的敏感性 到铂类药物和PARP抑制剂。我们将通过三个具体目标来解决这一假设：1)建立 细胞周期阻断与BRCA1表达的关系及细胞周期机制的初步探讨 导致BRCA1抑制的封锁；2)定义下游机制，从而下调BRCA1 以及3)确定协同活性的合理组合，并证明- 异种移植/PDX系统中的概念。据独立报道，有几种药物可以诱导细胞周期停滞，并 我们将利用药理学工具前瞻性地建立BRCA1抑制的新关系 定义抗肿瘤活性、生化和分子工具，以确定细胞周期阻断的潜在基础 和BRCA1抑制，并使用Bliss和Chou-Talalay数学模型来识别协同作用 顺铂和奥拉帕利与BRCAness的最佳诱导剂的组合。这个项目有可能 使顺铂难治性癌症敏感，并扩大可合理治疗的癌症基础 BRCA1介导的HR缺陷的已证实的基于治疗的原则。人们对这些研究抱有很高的期望 该研究的提出将改变大量BRCA1阳性癌症患者的生存结局。

Cisplatin and carboplatin (Pt) are used heavily in the clinic against a variety of cancers, such as those of ovarian, non-small cell lung (NSCLC), testicular, head & neck, and bladder origin. These drugs demonstrate good activity, but in most cases, the activity is short-lived as tumors become desensitized by the onset of resistance. Several options are available to sensitize tumor cells to platinum-based therapy. Since Pt drugs interact with DNA to form DNA adducts as a mechanism of their action, inhibition of DNA repair can make tumor cells highly sensitive through persistence of the DNA adduct. Repair of these adducts by nucleotide excision repair (NER) in testicular cancers is low, which makes these cancers highly sensitive to Pt drugs and leads to about 90% cure rate. Recent data suggests that repair of these adducts is complex, and involves NER-mediated incisions that induce double strand breaks as intermediates, which are then repaired by homologous recombination (HR). The base excision repair (BER) pathway has also been implicated in cisplatin repair. Interestingly, the spectrum of Pt activity in the clinic has broadened to include triple-negative breast cancers that harbor BRCA1 mutation or low BRCA1 expression (BRCAness tumors). High sensitivity has also been observed in hereditary or low-expressing BRCA1 ovarian cancers. Sensitization from loss of BRCA1 is due to resultant HR defect, which when combined with inhibition of poly-(ADP-ribose)-polymerase (PARP) in the BER pathway by olaparib produces synthetic lethality. Thus, olaparib further augments Pt sensitivity in tumors with the BRCAness phenotype. This sensitization, however, is limited to the small number of BRCA1 patients, but in our proposal we will test the hypothesis that small molecules inducing cell cycle blockade will suppress BRCA1 expression in BRCA1-proficient ovarian and breast cancers to enhance tumor cell sensitivity to Pt drugs and PARP inhibitors. We will address this hypothesis through three specific aims: 1) Establish the relationship between cell cycle blockade and BRCA1 expression and delineate the mechanism of cell cycle blockade causing BRCA1 suppression; 2) Define downstream mechanisms downregulating BRCA1 as a result of cell cycle blockade; and 3) Identify rational combinations for synergistic activity and demonstrate proof-of- concept in xenograft/PDX systems. Several agents are reported independently to induce cell cycle arrest and we will prospectively establish the novel relationship with BRCA1 suppression utilizing pharmacologic tools to define antitumor activity, biochemical and molecular tools to define the underlying basis of cell cycle blockade and of BRCA1 suppression, and use the Bliss and Chou-Talalay mathematical models to identify synergistic combinations of cisplatin and olaparib with an optimal inducer of BRCAness. This project has the potential to sensitize cisplatin refractory cancers and also broaden the cancer base that could be treated rationally on a proven therapy-based principal of BRCA1-mediated defect in HR. There is high expectation that the studies proposed will change the trajectory of survival outcomes in large numbers of BRCA1-proficient cancers.