Exploiting Altered Porphyrin Synthesis for Metabolic Imaging of Glioblastoma

为了与NIH的使命保持一致，支持“关于病因、诊断、预防， 和治疗癌症”（NCI）和“新的生物医学成像和生物工程技术和设备， 从根本上改善疾病的检测、治疗和预防”（NIBIB）， 该建议是利用癌细胞中的代谢改变进行非侵入性诊断， 胶质母细胞瘤（GBM）是成人中最致命和最常见的原发性脑癌。GBM 每年在美国夺走超过13，000条生命，并由多种复杂的基因亚型定义， 肿瘤侵入邻近脑组织。GBM患者管理中出现的困境包括 表征随时间推移和响应于治疗而发生的肿瘤特异性改变。一个策略是 使用获得的分子水平上的实时信息来定义和分析这些改变， 先进的成像技术。该策略具有区分遗传性肿瘤和局部区域肿瘤的潜力 变化以及评估和监测治疗反应。具体地，肿瘤的体内可视化- 特定的代谢途径可能会大大增加用于有效管理的诊断信息， GBM患者一种这样的途径是5-氨基乙酰丙酸（5-ALA，一种天然存在的乙酰丙酸）的转化。 在血红素生物合成过程中，底物）转化为原卟啉IX（PpIX，荧光产物）。该途径 在90%的GBM中高度和选择性地上调，并且已经在GBM中鉴定了增加的PpIX水平。 肿瘤分级增加的区域。超极化~（13）C磁共振研究进展 MRS首次实现了对关键动态的实时非侵入性测量 体内代谢过程。在这里，我们建议开发一种基于超极化13 C MRS的方法， 通过利用癌细胞改变的卟啉代谢对GBM进行非侵入性评估。首先，我们将 合成特定位置的5-ALA 13 C-取代，并优化底物配方， 最大偏振，当用作成像剂时，其直接转化为更高的信号放大 (Aim 1）。其次，我们将评估超极化13 C-5-ALA作为分子成像的可行性 试剂来测量GBM中改变的卟啉代谢，这是一系列体外细胞实验中的第一次， 然后在大鼠GBM模型中（目的2）。 考虑到超极化13 C MRS正在患有多种疾病的患者中进行积极研究， 成功完成这一高风险/高回报的项目有可能提供一种非侵入性的方法 用于GBM患者的诊断、监测和治疗评价。

In keeping with the mission of the NIH to support research “with respect to the cause, diagnosis, prevention, and treatment of cancer” (NCI) and “of new biomedical imaging and bioengineering techniques and devices to fundamentally improve the detection, treatment, and prevention of disease” (NIBIB), the overarching goal of this proposal is to leverage metabolic alterations in cancer cells for the noninvasive diagnosis and characterization of glioblastoma (GBM), the most deadly and common primary brain cancer in adults. GBM takes more than 13,000 lives in the USA each year and is defined by multiple, complex genetic subtypes and tumor invasion into adjacent brain tissue. Emerging dilemmas in the management of patients with GBM include characterizing the tumor-specific alterations that occur over time and in response to therapies. One strategy is to define and analyze these alterations using real-time information on the molecular level acquired with advanced imaging techniques. This strategy has the potential to differentiate genetic and loco-regional tumor variations as well as evaluate and monitor treatment responses. Specifically, the in vivo visualization of tumor- specific metabolic pathways is likely to add greatly to the diagnostic information used to effectively manage patients with GBM. One such pathway is the conversion of 5-aminolevulinic acid (5-ALA, a naturally occurring substrate) to protoporphyrin IX (PpIX, the fluorescent product) during heme biosynthesis. This pathway is highly and selectively upregulated in 90% of GBMs and increasing levels of PpIX have been identified within regions of increasing tumor grade. The recent development of hyperpolarized 13C magnetic resonance spectroscopy (MRS) enables for the first time the real-time non-invasive measurement of critical dynamic metabolic processes in vivo. Here, we propose to develop a hyperpolarized 13C MRS-based approach for noninvasive assessment of GBM by exploiting the altered porphyrin metabolism of cancer cells. Firstly, we will synthesize 5-ALA 13C-substituted in specific positions and optimize the substrate formulation to achieve maximum polarization, which directly translates into higher signal amplification when used as an imaging agent (Aim 1). Secondly, we will evaluate the feasibility of using hyperpolarized 13C-5-ALA as molecular imaging agent to measure the altered porphyrin metabolism in GBM, first in a series of in vitro cell experiments and then in a rat model of GBM (Aim 2). Given that hyperpolarized 13C MRS is being actively investigated in patients with numerous diseases, the successful completion of this high-risk/high-reward project has the potential to provide a noninvasive approach for the diagnosis, monitoring, and therapeutic evaluation of GBM patients.