Exploiting synthetic-lethal interactions to target triple-negative breast cancers

项目摘要/摘要 目前还没有针对三阴性(TN)乳腺癌的靶向治疗策略， 最难治疗的乳腺癌，不过度表达人类表皮生长因子 受体2(HER2)，缺乏雌激素和孕激素受体的表达。因此，有一个 迫切需要加深我们对这种侵袭性乳腺癌亚型的了解并确定 治疗干预的临床相关靶点。我们最近发现一种致癌基因 转录因子MYC以及依赖于MYC的信号通路在 原发人类三阴性乳腺肿瘤。此外，我们发现MYC的激活与 患者ʼ预后较差，提示MYC通路可能在推动 这些侵袭性肿瘤的形成。 我们如何才能杀死MYC驱动的TN肿瘤？因为MYC是一种转录因子，经过合理设计 可以直接抑制其活性的小分子抑制剂不能用于临床。另一种选择 选择性杀伤MYC驱动的肿瘤的方法是利用“合成-致死”相互作用的存在。 我们小组之前采取了一种偏向细胞周期的方法，发现对有丝分裂激酶的抑制 细胞周期蛋白依赖性激酶(CDK)1诱导MYC过表达的细胞发生凋亡。这个 这种细胞死亡的机制包括促进凋亡的bcl2家族成员BIM的上调。我们 随后使用这种方法治疗MYC表达升高的TN细胞系和异种移植瘤。 这些观察表明，依赖于MYC的合成-致死相互作用是存在的，而且重要的是，可以是 靶向选择性地杀死MYC驱动的肿瘤。 这项拟议研究的目标1将进一步研究小分子CDK的临床潜力 对MYC驱动的TN癌的抑制作用，特别是与临床抗细胞凋亡抑制剂联合使用 BCL-2成员。这是基于我们的新假设，因为CDK抑制上调了BIM和 激活线粒体内源性通路，联合使用CDK和抗凋亡抑制剂 BCL-2家族成员可显著提高细胞死亡率。目标2将描述一个新的 发现了MYC激活和Pim1抑制之间的合成致死相互作用，Pim1是一种非必需的， 先前显示的与MYC基因相互作用的激酶。Aim 3将进行一场贯穿始终的小型 分子筛查识别能够诱导MYC依赖的合成致死性的潜在先导分子 在乳腺细胞中。我们将使用人体乳房模型进行这些实验 上皮细胞，基因定义的癌细胞系，以及一组新的人-鼠原位肿瘤 移植模特。如果成功，这项拟议的研究不仅将扩大我们对MYC生物学的了解，而且 还将提供新的治疗概念，供患有TN肿瘤的患者再次测试。

PROJECT SUMMARY/ABSTRACT No targeted therapeutic strategies are currently available against triple-negative (TN) breast cancer, the most difficult-to-treat form of breast cancer, which does not overexpress human epidermal growth factor receptor 2 (HER2) and lacks the expression of the estrogen and progesterone receptors. Thus, there is an urgent need in deepening our understanding of this aggressive breast cancer subtype and identifying clinically relevant targets for therapeutic intervention. We have recently discovered that an oncogenic transcription factor MYC as well as the MYC-dependent signaling pathways are significantly up-regulated in primary human triple-negative breast tumors. In addition, we found that MYC activation is associated with patientsʼ poor prognosis suggesting that the MYC pathways may play a fundamental role in driving the formation of these aggressive tumors. How can we kill MYC-driven TN tumors? Because MYC is a transcription factor, rationally designed small molecule inhibitors that can directly inhibit its activity are not available for clinical use. An alternative approach in selectively killing MYC-driven tumors is to exploit the existence of “synthetic-lethal” interactions. Our group previously took a cell cycle-biased approach and discovered that inhibition of the mitotic kinase cyclin-dependent kinase (CDK) 1 resulted in apoptosis in cells engineered to overexpress MYC. The mechanism of such cell death involved an up-regulation of a pro-apoptotic BCL-2 family member BIM. We subsequently used this approach to treat TN cell lines and xenograft tumors with elevated MYC expression. These observations suggest that MYC-dependent synthetic-lethal interactions exist, and importantly, can be targeted to selectively kill MYC-driven tumors. Aim 1 of this proposed research will further study the clinical potential of small molecule CDK inhibition against MYC-driven TN cancers particularly in combination with clinical inhibitors of anti-apoptotic BCL-2 members. This is based on our novel hypothesis that, because CDK inhibition up-regulates BIM and activates mitochondrial intrinsic pathway, the combined use of the inhibitors for CDK and anti-apoptotic BCL-2 family members may significantly enhance the rate of cell death. Aim 2 will characterize a newly discovered synthetic-lethal interaction between MYC activation and inhibition of Pim1, a non-essential, kinase previously shown to genetically interact with MYC. Aim 3 will conduct a high-throughout small molecule screen to identify potential lead molecules capable of inducing MYC-dependent synthetic lethality in mammary cells. We will carry out these experiments using a combination of model human mammary epithelial cells, genetically defined cancer cell lines, and a panel of novel human-in-mouse orthotopic tumor grafts models. If successful, the proposed research will not only expand our knowledge on MYC biology but will also provide novel therapeutic concepts to be tested again patients with TN tumors.