Investigating the Role of Emergent Oscillations of Hypoxia Inducible Factor-1 alpha Activity in Cancer Growth and Progression

摘要 缺氧几乎影响到转移级联的所有步骤，并且是癌症的一个独立的不利指标。 预后。细胞对低氧的反应受到严格的调控，并由低氧诱导因子介导。 (HIF)，其中HIF-1是普遍表达的同源物。对缺氧的典型反应包括 作为关键转录因子的缺氧诱导因子-1α的稳定作用，调节超过1000个基因的表达 基因产物间接影响癌症进展的关键步骤。然而，我们发现， 种群对低氧的反应比经典理解的反应更复杂，只有很小的 乳酸依赖型缺氧诱导因子-1α稳定性和转录活性的亚群振荡 举止。乳酸是糖酵解的副产物，由于缺氧诱导因子-1α活性增加，可导致 伴侣介导的自噬，驱动振荡，降解低氧诱导因子-1α。由于HIF的中心性- 1α在缺氧肿瘤的转录调控中，HIF-1α在一组细胞中的振荡可能具有深远的意义 对基因表达和癌症进展的影响。我们的初步数据显示，振荡低氧 输入可以驱动大规模的转录变化，导致代谢活动增加，细胞增殖， 以及与昼夜节律和入侵相关的通路调节的改变。这些数据表明 HIF-1α活性可能出现的振荡可能为这些细胞提供了一种选择性的逃逸优势 低氧诱导应激反应。 我们的初步数据为研究癌症人群中的这种新出现的表型提供了强有力的理论基础。 驱动这些振荡的机制和这些振荡的表型后果。此外， 许多基因对振荡低氧的反应是一种性质不同的信号，表明存在 调节基序，不连贯的前馈回路(IFFL)，可以区分振荡和 持续的HIF-1α信号。使用一种涉及计算建模、生物信息学和 实验，我们将系统地识别和验证这些IFFL，以及必要的辅助因素 与HIF-1α一起形成这些IFFL。我们的目标不仅将阐明基本的监管 在癌症中解码振荡信号的机制，但也提供了一种靶向策略来遏制 新出现的HIF-1α振荡的表型后果。最后，我们将测试紧急事件的后果 在乳腺癌发生的小鼠模型中HIF-1α的体内振荡，并测试振荡的HIF-1α是否与 提高肿瘤的致瘤性、增殖性和存活率。我们建议的方法将从机械上促进 了解振荡的起源，癌症表型异质性的产生，以及 了解并针对这一新出现的亚群影响癌症进展的后果。

ABSTRACT Hypoxia influences nearly all steps in the metastatic cascade, and is an independent adverse indicator for cancer prognosis. Cellular response to hypoxia is tightly regulated, and is mediated by hypoxia-inducible factors (HIFs), with HIF-1 being the ubiquitously expressed homologue. Canonical response to hypoxia involves stabilization of HIF-1α, which acts as a key transcriptional factor, regulating the expression of more than 1000 gene products indirectly, influencing key steps in cancer progression. However, we discovered that the population response to hypoxia is more complex than the canonically understood response, with a small subpopulation displaying oscillations in HIF-1α stabilization and transcriptional activity in a lactate dependent manner. Lactate is a byproduct of glycolysis, which is itself increased due to HIF-1α activity, and can cause degradation of HIF-1α by chaperone mediated autophagy, driving oscillations. Owing to the centrality of HIF- 1α in transcriptional regulation in hypoxic tumors, oscillations in HIF-1α in a subset of cells could have profound consequences in gene expression, and cancer progression. Our preliminary data show that oscillatory hypoxic input can drive large scale transcriptomic changes, resulting in increased metabolic activity, cell proliferation, as well as altered regulation of pathways related to circadian rhythms, and invasion. These data suggest that possibly emergent oscillations in HIF-1α activity may provide a selective advantage to these cells to escape hypoxia induced stress response. Our preliminary data present a strong rationale to investigate this emergent phenotype in cancer populations, the mechanisms driving these oscillations and the phenotypic consequence of these oscillations. Furthermore, many of the genes responded to oscillating hypoxia as a qualitatively different signal, suggesting presence of regulatory motifs, incoherent feedforward loops (IFFLs) which could distinguish between oscillatory and sustained HIF-1α signal. Using an integrated approach involving computational modeling, bioinformatics, and experimentation, we will systematically identify and validate these IFFLs, as well as the co-factors necessary to form these IFFLs along with HIF-1α. Our aim will not only shed light on the fundamental regulatory mechanisms of decoding of oscillatory signaling in cancer, but also provide a targeting strategy to contain the phenotypic consequences of emergent HIF-1α oscillations. Finally, we will test the consequence of emergent HIF-1α oscillations in vivo in a mouse model of breast cancer tumorigenesis, and test if oscillating HIF-1α confers increased tumorigenicity, proliferation, and survival. Our proposed method will facilitate mechanistically understanding the genesis of oscillations, generation of phenotypic heterogeneity in cancer, as well as understand and target the consequence of this emergent subpopulation in influencing cancer progression.