MRI of tumor-infiltrating lymphocytes using MRI-cytometry

项目摘要 该提案旨在进一步开发和验证一种基于细胞大小的MR成像方法， MRI-细胞术作为一种新的方法成像肿瘤浸润淋巴细胞（TIL），并评估其 有可能作为替代成像生物标志物来预测对免疫检查点阻断（ICB）的治疗反应 免疫疗法ICB是最广泛的一类免疫疗法，但它提出了一个新的挑战， 肿瘤治疗反应。ICB诱导TIL浸润到肿瘤中以杀死癌症，但这增加了肿瘤细胞的增殖。 TIL的数量可能导致短暂的肿瘤扩大，这是肿瘤进展的当前指标，即， 无应答者。因此，对ICB的有效应答可能被误诊为肿瘤进展，即， 伪级数通常有一个比传统治疗更长的等待期来验证 肿瘤体积变化的持续性，这妨碍了治疗计划的及时调整，特别是在 无应答患者，导致不必要的治疗延迟、成本和毒性风险。目前主流 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，本申请提出了一种新颖的、无外源代理的方法， 成像TILs。因为淋巴细胞（活化和未活化时直径为5-10 μm）明显较小， 与大多数癌细胞（10-20 µm）相比，细胞大小可用作区分“小”TIL的内源性对比 “大”癌细胞。预期显著增加的TILs会导致一些独特的微观结构 改变例如，平均细胞尺寸减小，“小”细胞的细胞分数增加。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细胞计数法，用于成像细胞大小分布 和体内细胞内体积分数。基于我们的初步数据，我们假设MRI细胞计数可以 作为TIL的特异性成像生物标志物，因此可以预测对ICB免疫疗法的治疗反应。 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MRI细胞术 成像以克服潜在的混淆效应，从而精确估计微观结构参数。目的2 [验证]：验证MRI细胞计数成像以表征ICB后淋巴细胞浸润 使用临床前动物模型进行免疫治疗。目的3 [评价]：评价MRI-细胞术预测肿瘤 ICB免疫疗法和放射疗法的组合的反应。该项目的成功完成将 建立一种新的无外源性试剂的MRI工具，用于成像肿瘤浸润淋巴细胞， 免疫检查点阻断免疫疗法。它可以用作临床MRI的“附加”，以降低成本， 与这些淋巴细胞标记方法相比，存在毒性风险。此外，建议的方法是 预计将很容易被翻译到诊所，使临床医生分层反应和非反应患者 及早调整治疗方案，以个性化用药的方式。

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.