MRI of tumor-infiltrating lymphocytes using MRI-cytometry

项目总结 这项提议寻求进一步开发和验证一种基于细胞大小的磁共振成像方法，称为 核磁共振细胞术作为一种新的肿瘤浸润性淋巴细胞成像方法及其评价 作为替代成像生物标志物预测免疫检查点阻断(ICB)治疗反应的可能性 免疫疗法。ICB是最广泛使用的免疫疗法，但它对评估提出了新的挑战 肿瘤治疗反应。ICB诱导TIL渗入肿瘤以杀灭癌症，但这种增加 TIL的数量可能导致一过性肿瘤增大，这是目前肿瘤进展的指标，即， 无回应者。因此，对ICB的有效反应可能被误诊为肿瘤进展，即， 伪级数。通常比传统治疗方法需要更长的等待时间来验证 肿瘤体积持续变化，这阻碍了治疗计划的及时调整，特别是在 无反应患者，造成不必要的治疗延误、成本和毒性风险。当前主流 成像方法需要外源性试剂来标记TIL，这显著增加了成本和风险 毒性。为了克服这些限制，该应用程序提出了一种新颖的、无外源代理的方法 成像磁贴。因为淋巴细胞(直径5-10μm，激活和不激活)明显较小 与大多数癌细胞(10-20微米)相比，细胞大小可以作为内源性对比来区分“小”TIL 来自“大”癌细胞。TILs的显著增加预计将导致一些独特的微观结构 变化，例如，平均细胞大小减小，“小”细胞的细胞比例增加。为了检测这些变化， 我们最近开发了一种基于细胞大小的MRI方法，称为MRI-细胞术，用于成像细胞大小分布 以及体内的细胞内体积分数。根据我们的初步数据，我们假设核磁共振细胞仪能 作为TIL的特异性成像生物标志物，因此可以预测ICB免疫治疗的治疗反应。 为了验证我们的假设，我们提出了三个具体目标：目标1[发展]：进一步发展核磁共振细胞术 成像，以克服潜在的混杂效应，以准确估计微观结构参数。目标2 [验证]：验证核磁共振细胞仪成像以确定ICB后淋巴细胞浸润的特征 使用临床前动物模型进行免疫治疗。目的3[评价]：评价核磁共振细胞术预测肿瘤的价值 对ICB免疫治疗和放射治疗的联合反应。这个项目的成功完成将 建立一种新的无外源性试剂的MRI工具用于肿瘤浸润性淋巴细胞的成像 免疫检查点封锁免疫疗法。它可以作为临床MRI的一个附加组件，以降低成本和 与这些淋巴细胞标记方法相比，毒性风险更高。此外，建议的方法是 预计可以轻松地转换到诊所，允许临床医生对有反应和无反应的患者进行分层 及早以个体化用药方式调整治疗方案。

PROJECT SUMMARY This proposal seeks to further develop and validate a cell-size-based MR imaging method dubbed MRI-cytometry as a novel approach for imaging tumor-infiltrating lymphocytes (TILs), and to evaluate its potential as a surrogate imaging biomarker to predict treatment response to immune-checkpoint blockade (ICB) immunotherapy. ICB is the most widespread class of immunotherapies but it poses a new challenge to assess tumor therapeutic response. ICB induces infiltrations of TILs into tumors to kill cancer, but such increased numbers of TILs may lead to transient tumor enlargement, which is the current indicator of tumor progression i.e., non-responders. Therefore, effective response to ICB could be misdiagnosed as tumor progression i.e., pseudo-progression. There is often a much longer waiting period than conventional treatments to verify the persistence of tumor volume changes, which prevents timely adjustments of treatment plans particularly in non-responder patients, causing unwanted treatment delays, costs, and risks of toxicity. Current mainstream imaging methods require exogenous agents for labeling TILs, which significantly increases cost and risks of toxicity. To overcome these limitations, this application proposes a novel, exogenous-agent-free approach for imaging TILs. Because lymphocytes (5-10 μm in diameter with and without activation) are significantly smaller than most cancer cells (10-20 µm), cell size could be used as an endogenous contrast to distinguish “small” TILs from “large” cancer cells. The significantly increased TILs are expected to cause some unique microstructural changes e.g., decreased mean cell sizes and increased cell fractions of “small” cells. To detect these changes, we recently developed a cell-size-based MRI method dubbed MRI-cytometry for imaging cell size distribution and intracellular volume fractions in vivo. Based on our preliminary data, we hypothesize that MRI-cytometry can serve as a specific imaging biomarker of TILs, and hence can predict treatment response to ICB immunotherapy. To test our hypothesis, we propose three specific aims: Aim 1 [development]: To further develop MRI-cytometry imaging to overcome potentially confounding effects for accurate estimation of microstructural parameters. Aim 2 [validation]: To validate MRI-cytometry imaging to characterize lymphocyte infiltration following ICB immunotherapy using preclinical animal models. Aim 3 [evaluation]: To evaluate MRI-cytometry to predict tumor response to combinations of ICB immunotherapy and radiotherapy. Successful completion of this project will establish a new exogenous-agent-free MRI tool for imaging tumor-infiltrating lymphocytes following immune-checkpoint blockade immunotherapy. It can be used as an “add-on” to clinical MRI to reduce cost and risks of toxicity compared with those lymphocyte labeling methods. Moreover, the proposed approach is expected to be translated to the clinic easily, allowing clinicians to stratify responder and non-responder patients early to adjust treatment plans in the manner of personalized medicine.