Using [6-13C,6-15N3]-L-Arginine for the molecular imaging of in vivo tumor arginase flux, and towards understanding the role of arginase isoforms in cancer metabolism.

项目摘要(&A) 肿瘤微环境的各种细胞成分经历代谢变化以支持 肿瘤的生长和转移。癌症代谢是一个临床相关和令人兴奋的研究领域，因为它 为这种疾病的发生和发展提供了更多的机械洞察力。一种改进的 对这一高度复杂的过程的理解可以导致新疗法的开发，并且 肿瘤代谢表型的特征可能为决定预后提供额外的标准 以及治疗方案的选择。对于后者，超极化核磁共振领域已经出现，目标是 建立一种非侵入性测量体内酶通量的成像模式。 癌症代谢改变的一种方式涉及精氨酸的利用，精氨酸源于 多种精氨酸酶亚型在癌细胞和肿瘤相关巨噬细胞(TAMs)中的过度表达 被认为能促进细胞增殖和免疫抑制。血浆精氨酸酶活性升高 癌症患者与日益激进的组织学分级和非侵入性量化有关 超极化MRI检测肿瘤内精氨酸酶活性可能是一项更好的预后指标。此外， 随着耗竭免疫疗法人数的增加，治疗前后精氨酸酶流量的差异 泻下疗法的启动可能与渗透的变化相关，并提供对 治疗效果，这是该模式的另一个潜在应用。 此外，还存在两种不同的精氨酸酶亚型(精氨酸酶-1，A1和-2，A2)，它们在细胞类型上是不同的 表达和亚细胞定位。胞质A1在TAMs中表达良好，而线粒体则表达良好 A2在包括癌细胞在内的大多数细胞类型中都有一定程度的表达。人口和 下游酶的浓度在细胞质和线粒体之间也不同，导致 A1和A2在TAM和癌症中具有不同的细胞类型特异性促肿瘤功能的假说 细胞。A1和A2对细胞代谢和增殖的个体细胞类型特异性贡献有 尚未在癌症背景下进行研究。针对精氨酸代谢的治疗目前处于I期 和II临床试验，这一知识将支持这类疗法未来迭代的发展。 我优化了[6-13C，6-15N3]-L-精氨酸作为一种两用探针的合成，用于1)用途 用于体内精氨酸酶活性测量的超极化MRI探针以及2)基于LC/MS的同位素示踪 代谢组学实验来验证工作假说。从这个项目中获得的信息可能会产生新的 用于患者分层的工具和指标，并将增加对癌症新陈代谢和 它在癌细胞增殖中的作用，共同为改善患者护理和 为这种疾病提供了更多的机械洞察力。此外，从这一过程中获得的技能和知识 研究计划和培训计划将为我实现成为一名内科科学家的目标做好准备。

Project Summary & Abstract The various cellular components of the tumor microenvironment undergo metabolic changes to support tumor growth and metastasis. Cancer metabolism is a clinically relevant and exciting field of study, as it provides additional mechanistic insight into the onset and progression of this disease. An improved understanding of this highly complex process can lead to the development of novel therapies, and characterization of a tumor's metabolic phenotype may provide additional criteria for determining prognosis and therapy selection. Towards the latter, the field of hyperpolarized MRI has emerged with the goal of establishing an imaging modality that can non-invasively measure enzymatic flux in vivo. One way in which cancer metabolism is altered involves arginine utilization, stemming from the overexpression of various arginase isoforms in cancer cells and tumor associated macrophages (TAMs), which is thought to promote cellular proliferation and immunosuppression. Elevated arginase activity in the plasma of cancer patients is associated with increasingly aggressive histological grading, and non-invasive quantification of intratumoral arginase activity with hyperpolarized MRI may be an improved prognostic metric. Furthermore, with the rising population of TAM-depleting immunotherapies, differences in arginase flux before and after the initiation of TAM-depleting therapies may correlate to changes in TAM infiltration and provide insight into therapeutic efficacy, which is another potential application of this modality. In addition, two arginase isoforms exist (arginase-1, A1, and -2, A2) which differ in cell-type-specific expression and subcellular localization. Cytosolic A1 is favorably expressed in TAMs, whereas mitochondrial A2 is expressed to some degree across most cell types, including cancer cells. The population and concentrations of downstream enzymes also differs between the cytoplasm and mitochondrion, leading to the hypothesis that A1 and A2 have different, cell-type-specific, pro-tumor functions in TAMs and cancer cells. The individual cell-type-specific contributions of A1 and A2 to cellular metabolism and proliferation have yet to be studied in the setting of cancer. With therapies that target arginine metabolism currently in Phase I and II clinical trails, this knowledge will support the development of the future iterations of this class of therapy. I have optimized the synthesis of [6-13C,6-15N3]-L-arginine as a dual purpose probe for 1) use as a hyperpolarized MRI probe for in vivo arginase activity measurements, and 2) LC/MS-based isotopic tracing metabolomics experiments to test the working hypothesis. Information gained from this project may yield new tools and metrics for patient stratification, and will add to the general understanding of cancer metabolism and its role in cancer cell proliferation, collectively contributing towards the improvement of patient care and providing additional mechanistic insight into this disease. In addition, the skills and knowledge gained from this research proposal and training plan will prepare me to achieve my goal of becoming a physician scientist.