Modulation of the anti-tumor immune response by Major Histocompatibility Class-II expression on tumor cells

项目总结/摘要 免疫检查点抑制（ICI）改善了许多转移性癌症患者的前景。但是，在这方面， 对ICI的耐药性仍然知之甚少，目前还没有批准的治疗策略来克服 阻力对ICI的抗性的一种可能机制是T细胞对肿瘤的无效识别， 主要组织相容性复合物（MHC）-T细胞受体相互作用介导。大多数肿瘤表达MHC I类，其向CD8 + T细胞呈递抗原，所述CD8 + T细胞被认为是主要的细胞毒性效应细胞。 有趣的是，一个肿瘤亚群也表达MHC II类，其将抗原呈递给CD4 + T细胞， 通常认为其仅存在于免疫系统的"专职"抗原呈递细胞上。CD4 + t 细胞是一个多样化的群体，包括辅助细胞亚群，这些亚群对产生和维持有效的免疫应答至关重要。 免疫反应我们的实验室已经表明，肿瘤特异性MHC-II（tsMHC-II）表达是一个积极的预后， ICI治疗的黑色素瘤患者的指标。此外，我们的初步数据显示， II类主要组织相容性复合物反式激活因子（CIITA）的表达，其驱动MHC-1的表达。 II和相关机制，增强免疫活性小鼠的肿瘤排斥。额外的初步共培养 实验表明，当用MHC-II+刺激时，CD4 + T细胞产生更多的促炎细胞因子。 与MHC-II肿瘤细胞相比。这些数据，在小鼠和人类，表明tsMHC-II可以增强抗- 通过激活辅助性T细胞的肿瘤免疫。因此，我们假设tsMHC-II可以被 来自CD4 + T细胞的T细胞受体（TCR）激活CD4 + T细胞中的信号传导，并偏向于抗肿瘤 CD4 + T细胞的极化。这一提议概述了检验这一假设的两个详细的具体目标。 提出的实验包括肿瘤细胞和T细胞的体外共培养，以分离表型特异性T细胞。 tsMHC-II参与后CD4 + T细胞的变化。体内鼠模型和基于质谱的细胞计数 人类肿瘤的表征将进一步确定tsMHC-II如何改变免疫微环境。 此外，我们将从浸润tsMHC-II+肿瘤的CD4 + T细胞产生溶解的TCR（sTCR）， 测试这些sTCR结合自体tsMHC-II+肿瘤细胞的能力。我们还将对这些TCR进行 进入永生化T细胞系以测试tsMHC-II接合诱导T细胞中信号传导变化的能力。 该项目的完成将产生关于tsMHC-II如何被自体浸润识别的新见解。 CD4 + T细胞以及tsMHC-II如何影响抗肿瘤CD4 + T细胞应答。总的来说，该项目将提高 了解抗肿瘤免疫，并可能提出新的翻译方法，以规避 通过tsMHC-II上调剂在临床中对ICI的抗性。

PROJECT SUMMARY/ABSTRACT Immune checkpoint inhibition (ICI) has improved the outlook for many patients with metastatic cancer. However, resistance to ICI remains poorly understood, with no currently approved therapeutic strategies to overcome resistance. A possible mechanism of resistance to ICI is ineffective recognition of a tumor by a T cell, which is mediated by Major Histocompatibility Complex (MHC)-T cell receptor interactions. Most tumors express MHC class I, which presents antigen to CD8+ T cells, which are thought to be the main cytotoxic effector cells. Interestingly, a subset of tumors also express MHC class II, which presents antigen to CD4+ T cells and is canonically thought to only be present on “professional” antigen presenting cells of the immune system. CD4+ T cells are a diverse population and include helper subsets that are crucial generating and maintaining an effective immune response. Our lab has shown that tumor-specific MHC-II (tsMHC-II) expression is a positive prognostic indicator for melanoma patients treated with ICI. Additionally, our preliminary data show that enforced tumor cell expression of Class II Major Histocompatibility Complex Transactivator (CIITA), which drives expression of MHC- II and related machinery, enhances tumor rejection in immunocompetent mice. Additional preliminary co-culture experiments suggest that CD4+ T cells produce more pro-inflammatory cytokine when stimulated with MHC-II+ compared to MHC-II- tumor cells. These data, in mouse and human, suggest that tsMHC-II may enhance anti- tumor immunity through activation of helper T cells. Thus, we hypothesize that tsMHC-II can be recognized by T cell receptors (TCRs) from CD4+ T cells, activates signaling in CD4+ T cells, and skews toward anti-tumor polarization of CD4+ T cells. This proposal outlines two detailed specific aims for testing this hypothesis. Proposed experiments include in vitro co-culture of tumor cells and T cells in order to isolate the phenotypic change in CD4+T cells following engagement of tsMHC-II. In vivo murine models and mass cytometry-based characterization of human tumors will further define how tsMHC-II alters the immune microenvironment. Furthermore, we will generate solubilized TCRs (sTCRs) from CD4+ T cells infiltrating tsMHC-II+ tumors and test the ability of these sTCRs to bind to autologous tsMHC-II+ tumor cells. We will also transduce these TCRs into an immortalized T cell line to test the ability of tsMHC-II engagement to induce signaling changes in T cells. Completion of this project will yield new insights regarding how tsMHC-II is recognized by autologous infiltrating CD4+ T cells and how tsMHC-II influences anti-tumor CD4+ T cell responses. Overall, this project will enhance understanding of anti-tumor immunity and may suggest novel translational approaches to circumventing resistance to ICI in the clinic through tsMHC-II upregulating agents.