Cell Cycle Blockade and Therapeutic Sensitization

顺铂和卡铂（Pt）在临床上大量用于对抗多种癌症，例如， 卵巢、非小细胞肺（NSCLC）、睾丸、头颈部和膀胱来源。这些药物证明 良好的活性，但在大多数情况下，活性是短暂的，因为肿瘤变得脱敏的发病， 阻力有几种选择可用于使肿瘤细胞对基于铂的治疗敏感。由于PT药物 与DNA相互作用形成DNA加合物作为其作用机制，抑制DNA修复可以使 肿瘤细胞通过DNA加合物的持久性高度敏感。核苷酸对这些加合物的修复 睾丸癌的切除修复（NER）较低，这使得这些癌症对铂类药物高度敏感， 治愈率高达90%最近的数据表明，这些加合物的修复是复杂的， NER介导的切口诱导双链断裂作为中间体，然后通过 同源重组（HR）。碱基切除修复（BER）途径也与顺铂有关 修复.有趣的是，临床上铂活性的范围已经扩大到包括三阴性乳腺癌。 携带BRCA 1突变或BRCA 1低表达的癌症（BRCAness肿瘤）。高灵敏度也 在遗传性或低表达BRCA 1的卵巢癌中观察到。BRCA 1缺失的致敏性是 由于由此产生的HR缺陷，当与聚（ADP-核糖）聚合酶（PARP）的抑制相结合时， 奥拉帕尼的BER途径产生合成致死性。因此，奥拉帕尼进一步增加了Pt敏感性， 具有BRCAness表型的肿瘤。然而，这种致敏作用仅限于少数BRCA 1 患者，但在我们的建议，我们将测试的假设，小分子诱导细胞周期阻滞， 抑制BRCA 1基因型卵巢癌和乳腺癌中BRCA 1表达以增强肿瘤细胞敏感性 铂类药物和PARP抑制剂。我们将通过三个具体目标来解决这个假设：1）建立 细胞周期阻滞与BRCA 1表达的关系及细胞周期阻滞机制的探讨 阻断导致BRCA 1抑制; 2）定义下游机制下调BRCA 1的结果 细胞周期阻滞;和3）确定合理的组合协同活性，并证明- 异种移植/PDX系统的概念。据报道，几种药物独立地诱导细胞周期停滞， 我们将利用药理学工具前瞻性地建立与BRCA 1抑制的新关系， 定义抗肿瘤活性，生物化学和分子工具，以确定细胞周期阻滞的潜在基础 和BRCA 1抑制，并使用布利斯和Chou-Talalay数学模型，以确定协同 顺铂和奥拉帕尼与BRCAness的最佳诱导剂的组合。该项目有可能 敏感顺铂难治性癌症，也扩大了癌症的基础，可以合理地治疗， BRCA 1介导的HR缺陷的基于治疗的原则。 这项研究将改变大量BRCA 1阳性癌症的生存结局轨迹。

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.