Mechanisms of PD-1 and Tim-3 crosstalk in tumor-infiltrating lymphocytes

项目摘要 在过去的二十年里，许多类型的癌症的治疗发生了翻天覆地的变化，免疫疗法- 包括检查点阻断和过继性细胞治疗在内的方法，在一些疾病中取得了显著的效果。 患者到目前为止，无法在更多患者中实现更完全的反应已经引发了广泛的 努力确定改善缓解率和缓解持续时间的新靶点，无论是作为单药还是联合用药 第一代免疫疗法，如PD-1/PD-L1阻断。第二代检查点之一 包括我们自己在内的许多组织都注意到了Tim-3蛋白。到目前为止，mAb 靶向Tim-3的药物在实体瘤的临床试验中表现不佳，部分原因可能是， Tim-3在耗尽的T细胞上以高水平表达，它在TpEx细胞上不表达。获得更好的 了解Tim-3在这些不同细胞类型中的功能可能会导致更具选择性和有效性的Tim-3。 靶向治疗，无论是作为单一药物，或关键的是，与PD-1通路阻断剂组合。 我们的团队和其他人的工作表明，Tim-3似乎对人类特别重要。 肿瘤中大量存在的调节性T细胞（Treg）的抑制功能，特别是“效应细胞” Treg（eTreg），是Treg的一个特别抑制性的子集。这些细胞在实体瘤中富集， 相对于它们在正常外周组织中的比例，这表明它们可能是更有吸引力的靶点。 肿瘤内免疫反应的特异性增强。由于Treg表达Tim的比例很大， 3，该分子在体内的功能仍在阐明，我们产生了一个敲除模型来研究Tim- 3、这些细胞因此，我们发现，诱导型Treg特异性Tim-3缺失导致细胞凋亡显著减少。 同源肿瘤的生长和浸润这些肿瘤的Treg的数量。然而，Treg特异性 Tim-3缺失在稳态条件下未可检测地影响Treg发育或免疫耐受性。 基于已发表的和初步的数据，我们假设Tim-3是肿瘤细胞中效应Treg的关键调节因子。 肿瘤微环境我们将用三个具体目标来检验这一假设。在目标1中，我们将确定 为什么Treg特异性Tim-3 KO小鼠的肿瘤中eTreg较少。在目标2中，我们将定义 肿瘤微环境中Treg Tim-3的缺失。最后，在目标3中，我们将确定Tim-3的损失 在两种小鼠模型中，Treg的表达影响了对PD-1检查点阻断的反应， 相互作用在头颈癌患者对PD-1阻断治疗反应中的作用。 总之，这些研究将为更合理地将Tim-3作为治疗靶点提供基础 在现有的检查点靶点（如PD-1）的背景下，因此，这些研究代表了一种逻辑 延长了该供资项目上一周期开展的工作。

PROJECT SUMMARY The past twenty years have seen a sea change in the treatment of many types of cancer, with immunotherapy- based approaches, including checkpoint blockade and adoptive cell therapy, yielding remarkable results in some patients. The inability, thus far, to achieve more complete responses in more patients has set off a widespread effort to identify novel targets for improving rates and duration of response, either as single agents or together with first-generation immunotherapies, like PD-1/PD-L1 blockade. One of the second-generation checkpoint targets that has attracted attention from many groups, including our own, is the protein Tim-3. Thus far, mAb’s targeting Tim-3 have under-performed in clinical trials for solid tumors, likely due in part to the fact that while Tim-3 is expressed at high levels on exhausted T cells, it is not expressed on the TpEx cells. Obtaining a better understanding of Tim-3 function in these various cell types may lead to more selective and efficacious Tim3- targeting therapies, either as single agents or, critically, in combination with PD-1 pathway blockade. Work from our groups and others have revealed that Tim-3 appears to be particularly important for the suppressive function of regulatory T cells (Treg) that are present in high numbers in tumors, in particular “effector” Treg (eTreg), which are a particularly suppressive subset of Treg. These cells are enriched within solid tumors, relative to their proportions in normal peripheral tissues, suggesting that they could be attractive targets for more specific augmentation of immune responses within tumors. Since a significant proportion of Treg express Tim- 3, and the function of this molecule in vivo is still being elucidated, we generated a knockout model to study Tim- 3 on these cells. Thus, we found that inducible Treg-specific Tim-3 deletion results in a dramatic decrease in both the growth of syngeneic tumors and the number of Treg infiltrating those tumors. However, Treg-specific Tim-3 deletion did not detectably impact Treg development or immune tolerance under homeostatic conditions. Based on published and preliminary data, we hypothesize that Tim-3 is a critical regulator of effector Treg in the tumor microenvironment. We will test this hypothesis with three Specific Aims. In Aim 1, we will determine why there are fewer eTreg in the tumors of mice with Treg-specific Tim-3 KO. In Aim 2, we will define the effects of loss of Treg Tim-3 on the tumor microenvironment. Finally, in Aim 3, we will determine how the loss of Tim-3 on Treg impacts the response to PD-1 checkpoint blockade, in both mouse models, with an extension toward the role of the interaction in the response to PD-1 blockade therapy in patients with head and neck cancer. Together, these studies will provide the basis for more rational translation of Tim-3 as a target in the treatment of solid tumors, in the context of existing checkpoint targets like PD-1. As such, these studies represent a logical extension of work carried out in the previous cycle of this funded project.