(PQC2) Plasticity Of The.PI3K Network In Early Dormancy

描述(申请人提供)：尽管分子疗法有望为癌症患者带来持久的缓解，但大多数“靶向”药物没有达到这一期望，由于出现转移疾病，只能提供有限的、在大多数情况下是短暂的益处。尽管许多研究都集中在耐药机制上，但分子疗法实际上可能对肿瘤重新编程，并选择对疾病进展或肿瘤可塑性重要的新的癌症表型的可能性还没有被广泛考虑。我们通过检测肿瘤对靶向抑制磷脂酰肌醇-3激酶(PI3K)网络的反应来测试这一概念，PI3K网络是几乎每个人的疾病驱动因素 人类癌症和重要的治疗靶点。我们的初步数据显示，PI3K的小分子抑制剂在肿瘤中诱导了全球转录和代谢重新编程。这种适应性反应赋予了一种新的癌症表型，它结合了长期增殖和生物能量学静止、出现衰老、提高细胞存活率和增加肿瘤细胞侵袭的矛盾特征。这些都是休眠的关键特征，休眠是一种难以捉摸的过程，在这个过程中，肿瘤细胞从原发灶早期扩散，抵抗凋亡，种植转移部位，并保持长时间的静止，直到再次苏醒为复发(和不可治愈的)疾病。从机制上讲，PI3K抑制诱导的肿瘤可塑性包括胞浆和线粒体中Akt的重新激活，以及Akt依赖的亲环素D(CypD)的磷酸化，CypD是线粒体生物能量学和细胞凋亡的多功能调节因子。相反，当与线粒体完整性的小分子拮抗剂Gamitrinib、PI3K抑制剂联合使用时，不再触发适应性肿瘤重新编程、抑制侵袭并发挥显著增强的抗癌活性。因此，可以提出这样的假设，即肿瘤休眠可以被诱导为对分子治疗的适应性反应，并通过线粒体重新编程来协调，这将构成本应用的重点。第一个特定目的的实验将概括已建立的休眠模型中PI3K抑制素的表型，并剖析这一途径与细胞周期停滞、衰老和细胞侵袭的激酶级联(S)相关的机制要求。在第二个特定目标中，我们将定义休眠中Akt重新激活的机制(S)，描述线粒体中CypD-Akt复合体的特征，并剖析CypD的Akt磷酸化在线粒体功能重新定位中的作用，包括细胞凋亡、生物能学和自噬。第三个具体目标是研究PI3K抑制剂和线粒体质量控制拮抗剂Gamitrinib在体内血管生成、转移和肿瘤休眠模型中的合理组合，在肿瘤细胞杀伤、适应性表型逆转和临床前活性方面的作用。总体而言，实验计划将把肿瘤休眠的新机制描述为对分子治疗的适应性反应。这一结果将证明新的治疗策略，以消除休眠和消除肿瘤的转移能力。

DESCRIPTION (provided by applicant): Despite the promise, and hope, that molecular therapies could bring durable remissions to cancer patients, most "targeted" drugs did not live up to this expectation, providing only limited, and, in most cases, short-lived benefit due to the emergence of metastatic disease. Although much effort has focused on mechanisms of drug resistance, the possibility that molecular therapies may actually reprogram tumors, and select new cancer phenotypes important for disease progression, or tumor plasticity, has not been widely considered. We tested this concept by examining the response of tumors to targeted inhibition of the phosphatidylinositol-3 kinase (PI3K) network, a disease driver in virtually every human cancer and important therapeutic target. Our preliminary data show that small molecule inhibitors of PI3K induce a global transcriptional and metabolic reprogramming in tumors. This adaptive response imparts a new cancer phenotype that combines paradoxical traits of protracted proliferative and bioenergetics quiescence, appearance of senescence, heightened cell survival and increased tumor cell invasion. These are pivotal hallmarks of dormancy, an elusive process in which tumor cells disseminate early from a primary lesion, resist apoptosis, seed metastatic sites, and remain quiescent for long periods of time only to re-awaken as recurrent (and incurable) disease. Mechanistically, tumor plasticity induced by PI3K inhibition involves reactivation of Akt in cytosol and mitochondria, and Akt- dependent phosphorylation of cyclophilin D (CypD), a multifunctional regulator of mitochondrial bioenergetics and apoptosis. Conversely, when combined with a small molecule antagonist of mitochondrial integrity, Gamitrinib, PI3K inhibitors no longer trigger adaptive tumor reprogramming, suppress invasion and exert considerably enhanced anticancer activity. Therefore, the hypothesis that tumor dormancy can be induced as an adaptive response to molecular therapy and coordinated by mitochondrial reprogramming can be formulated, and will constitute the focus of the present application. Experiments in the first specific aim will recapitulate the phenotype of PI3K inhibitin in established dormancy models, and dissect the mechanistic requirements of this pathway with respect to cell cycle quiescence, senescence, and kinase cascade(s) of cell invasion. In the second specific aim, we will define the mechanism(s) of Akt reactivation in dormancy, characterize a CypD-Akt complex in mitochondria, and dissect the role of Akt phosphorylation of CypD in repurposing of mitochondrial functions in apoptosis, bioenergetics, and autophagy. The third specific aim will examine the rational combination of PI3K inhibitors plus an antagonist of mitochondrial quality control, Gamitrinib, in tumor cell killing, reversal of the adaptive phenotyp, and preclinical activity in models of angiogenesis, metastasis, and tumor dormancy, in vivo. Overall, the experimental plan will characterize a new mechanism of tumor dormancy as an adaptive response to molecular therapy. The results will credential novel therapeutic strategies to obliterate dormancy and eradicate metastatic competency of tumors.