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

项目摘要/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。然而， 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 抵抗。抵抗ICI的一种可能机制是T细胞对肿瘤的识别无效，这是 由主要组织相容性复合体(MHC)-T细胞受体相互作用介导。大多数肿瘤表达MHC I类，它向CD8 T细胞递呈抗原，CD8 T细胞被认为是主要的细胞毒效应细胞。 有趣的是，肿瘤的一个亚群也表达MHC II类，它是CD4T细胞的抗原，是 通常认为只存在于免疫系统的“专业”抗原提呈细胞上。CD4T 细胞是一个多样化的群体，包括对生成和维护有效的 免疫反应。我们的实验室表明，肿瘤特异性MHC-II(tsMHC-II)的表达是一个积极的预后指标 ICI治疗黑色素瘤患者的指标。此外，我们的初步数据显示，强制肿瘤细胞 推动MHC-2表达的第二类主要组织相容性复合体反式活化子(CIITA) II和相关机制，增强免疫活性小鼠的肿瘤排斥反应。额外的初步共培养 实验表明，在MHC-II刺激下，CD4T细胞产生更多的促炎细胞因子 与MHC-II-肿瘤细胞相比。这些在小鼠和人类身上的数据表明，tsMHC-II可能会增强抗 通过激活辅助性T细胞实现肿瘤免疫。因此，我们假设tsMHC-II可以被 来自CD4T细胞的T细胞受体(TCR)，激活CD4T细胞中的信号，并向抗肿瘤倾斜 CD4T细胞的极化。这项提案概述了检验这一假说的两个详细的具体目标。 建议的实验包括肿瘤细胞和T细胞的体外共培养，以分离表型 与tsMHC-II结合后CD4T细胞的变化小鼠体内模型及基于质量细胞术的研究 人类肿瘤的特征将进一步定义tsMHC-II如何改变免疫微环境。 此外，我们将从浸润性TMHC-II肿瘤的CD4T细胞中产生可溶性TCRs(STCRs) 测试这些sTCRs与自体tsMHC-II肿瘤细胞结合的能力。我们还将转换这些TCR 转化为永生化T细胞系，以测试tsMHC-II参与诱导T细胞信号变化的能力。 该项目的完成将产生关于自体渗透如何识别tsMHC-II的新见解 CD4T细胞和tsMHC-II如何影响抗肿瘤的CD4T细胞反应。总体而言，该项目将增强 了解抗肿瘤免疫，并可能提出新的翻译方法来规避 临床上通过tsMHC-II上调药物对ICI的耐药性。

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.