Molecular Imaging of Pyruvate Kinase M2

抽象的。 葡萄糖动态平衡在多种细胞过程中起着关键作用，葡萄糖受损或改变。 新陈代谢与多种病理状态有关。葡萄糖代谢的一个关键步骤是催化 由糖酵解酶丙酮酸激酶产生。增殖细胞几乎普遍表达丙酮酸激酶M2 (PKM2)亚型，可呈现激活或非激活状态。PKM2处于细胞新陈代谢的连接点， 并决定细胞是将葡萄糖代谢成三磷酸腺苷，还是用它来制造更多必要的建筑 用于细胞分裂的块。多项研究表明，PKM2表达的动态变化对 在不同的环境中改变葡萄糖代谢。能够非侵入性地可视化和跟踪动态 PKM2表达的变化将有助于更好地理解糖代谢变化和 多种疾病状态下糖酵解的下游介体。在脑内缺乏PKM2的表达和 心肌成像使这一成像策略在神经学和心血管领域具有很高的应用前景。 我们最近报道了第一个临床相关的[18F]DASA-23的开发和人工翻译 以及使用正电子发射断层扫描来检测、定位和量化PKM2的特定放射性药物 (宠物)成像。我们已经确定了[18F]DASA-的生物分布、辐射剂量学和脑分布。 23名健康志愿者，并在一个潜在的应用中探索了其可视化PKM2表达的能力 原发脑瘤患者的比例。尽管我们的结果突出了对PKM2、[18F]DASA进行成像的潜力- 23有几个限制，阻碍了广泛的使用，以及研究PKM2介导的糖酵解的能力 在更广泛的应用中重新编程。这包括对胆囊壁的高辐射剂量，高度 脑白质内的非特异性结合，在放射性示踪剂制剂载体中的溶解性差。 这项提议将开发新的PKM2放射性示踪剂，以克服[18F]DASA-23的限制。发展 一种安全可靠的PKM2放射性示踪剂将能够重复评估血糖的动态变化 在多种不同的应用和患者群体中的新陈代谢。我们将建立合成和氟- 18放射性标记两个物理化学性质相对于DASA-的候选小分子 23、PKM2的药理活性和特异性，以及放射性标记的可能性。我们将自动执行 放射合成和表征细胞培养中的摄取和特异性(目标1)，确定生物分布和 辐射剂量学(目标2)，并评估在一个潜在的应用中可视化PKM2表达的能力 原发脑肿瘤(目标3)。这一提议的成功将开发用于可视化标记的新型放射性示踪剂 新陈代谢。这将对研究多发性硬化症中糖代谢的改变具有重要的意义。 应用，并可能提高我们对疾病中代谢适应的集体理解。重要的是 这项技术将在不同的临床前和临床研究中被广泛的用户采用。

ABSTRACT. Glucose homeostasis plays a critical role in multiple cellular processes, and impaired or altered glucose metabolism is associated with a wide range of pathological states. A key step in glucose metabolism is catalyzed by the glycolytic enzyme pyruvate kinase. Proliferating cells almost universally express the pyruvate kinase M2 (PKM2) isoform, which can assume either an active or inactive state. PKM2 is at the nexus of cellular metabolism, and determines whether cells metabolize glucose into ATP or use it to make more of the necessary building blocks for cell division. Multiple studies have demonstrated how dynamic changes in PKM2 expression contribute to altered glucose metabolism in different contexts. The ability to non-invasively visualize and track dynamic changes in PKM2 expression will enable improved understanding of altered glucose metabolism and the downstream mediators of glycolysis in multiple disease states. The lack of PKM2 expression within the brain and myocardium make this imaging strategy highly promising for neurological and cardiovascular applications. We have recently reported the development and human translation of [18F]DASA-23, the first clinically-relevant and specific radiopharmaceutical to detect, localize, and quantify PKM2 using positron emission tomography (PET) imaging. We have determined the biodistribution, radiation dosimetry, and brain distribution of [18F]DASA- 23 in healthy volunteers, and have explored its ability to visualize PKM2 expression in one potential application of patients with primary brain tumors. Although our results highlight the potential of imaging PKM2, [18F]DASA- 23 has several limitations that impedes widespread use, and the ability to study PKM2-mediated glycolytic reprogramming in broader applications. This includes high radiation dose to the gallbladder wall, a high degree of non-specific binding within white matter in the brain, and poor solubility in radiotracer formulation vehicle. This proposal will develop novel PKM2 radiotracers to overcome the limitations of [18F]DASA-23. Development of a safe and reliable PKM2 radiotracer will enable repeat assessment of the dynamic alterations in glucose metabolism in multiple different applications and patient populations. We will establish the synthesis and fluorine- 18 radiolabeling of two candidate small molecules with improved physicochemical properties relative to DASA- 23, pharmacological activity and specificity for PKM2, and the potential for radiolabeling. We will automate the radiosyntheses and characterize uptake and specificity in cell culture (Aim 1), determine biodistribution and radiation dosimetry (Aim 2), and assess the ability to visualize PKM2 expression in one potential application of primary brain tumors (Aim 3). Success of this proposal will develop novel radiotracers for visualizing a hallmark of metabolism. This will have important ramifications for studying altered glucose metabolism in multiple applications and could improve our collective understanding of metabolic adaptations in disease. Importantly, this technology will be adopted by a wide range of users in different pre-clinical and clinical studies.