Detection of in vivo enzyme activities with CEST MRI

描述（由申请人提供）：酶活性是癌症诊断和评估化疗的重要生物标志物。我们已经开发了通过化学交换饱和转移（CEST）检测的MRI造影剂，并且对酶活性有反应。我们还开发了CEST MRI方法，可以在人类癌症小鼠模型的体内肿瘤组织中检测这些药物。重要的是，我们可以在同一研究中在同一组织位置选择性地检测酶反应剂和无反应的“对照”剂，这提高了我们对小鼠模型中酶活性的评估。正如多个荧光团在体外和离体研究中彻底改变了酶活性的评估一样，CEST试剂和CEST MRI有可能彻底改变体内酶活性的评估。我们建议在我们最近的研究成果的基础上，通过连接酶反应剂和对照剂来创建二聚体剂，通过比较顺磁性和抗磁性CEST剂，并通过优化CEST MRI采集方案的饱和期来提高CEST MRI的检测灵敏度。我们还建议开发酶反应性CEST试剂，以半定量检测胰腺癌小鼠模型中的尿激酶纤溶酶原激活物（uPA）、前列腺癌小鼠模型中的前列腺特异性膜抗原（PSMA）和乳腺癌小鼠模型中的转谷氨酰胺酶（TG2）的活性。我们建议使用这些CEST药物和我们的体内CEST MRI方法来研究三个生物医学目标：A)在给药小鼠模型之前预测化疗的效果；B)评估对化疗的早期反应；C)验证我们的假设，即在预测和评估治疗效果方面，酶活性是比酶表达更准确的生物标志物。总之，这些研究解决了我们的总体目标，即最终使用CEST药物和CEST MRI为每个患者量身定制化疗和治疗方案的选择，以支持个性化医疗的范例。

DESCRIPTION (provided by applicant): Enzyme activities are important biomarkers for cancer diagnoses and assessing chemotherapies. We have developed MRI contrast agents that are detected via Chemical Exchange Saturation Transfer (CEST) and that are responsive to enzyme activity. We have also developed CEST MRI methods that can detect these agents within in vivo tumor tissues in mouse models of human cancers. Importantly, we can selectively detect an enzyme-responsive agent and an unresponsive "control" agent during the same study in the same tissue location, which improves our evaluation of enzyme activity within the mouse model. Just as multiple fluorophores have revolutionized the evaluation of enzyme activities during in vitro and ex vivo studies, CEST agents and CEST MRI has potential to revolutionize the evaluation of enzyme activities in vivo. We propose to build on our recent research successes by linking enzyme-responsive and control agents to create a dimeric agent, by comparing paramagnetic and diamagnetic CEST agents, and by optimizing the saturation period of the CEST MRI acquisition protocol in order to improve the detection sensitivity of CEST MRI. We also propose to develop enzyme-responsive CEST agents that semi-quantitatively detect the activities of urokinase Plasminogen Activator (uPA) in mouse models of pancreatic cancer, Prostate Specific Membrane Antigen (PSMA) in mouse models of prostate cancer, and transglutaminase (TG2) in mouse models of breast cancer. We propose to use these CEST agents and our in vivo CEST MRI methodology to investigate three biomedical aims: A) to predict the effect of chemotherapies before they are administered to mouse models; B) to evaluate early response to chemotherapies; C) to investigate our hypothesis that enzyme activity is a more accurate biomarker than enzyme expression for predicting and evaluating therapeutic effects. Together, these studies address our overarching goal of eventually using CEST agents and CEST MRI to tailor the choice of chemotherapy and treatment regimen for each individual patient, in order to support the paradigm of personalized medicine. PUBLIC HEALTH RELEVANCE: We propose to continue to develop CEST agents and CEST MRI methods that detect enzyme activities within in vivo mouse models of cancer. We propose to use our CEST agents and CEST MRI methods to evaluate chemotherapies and to assess whether enzyme activity is a better biomarker than enzyme expression.