Interrogating the Fgl2-FcgRIIB axis: A novel mechanism mediating apoptosis of tumor-specific memory CD8+ T cells

项目总结 每50个美国人中就有一个会在一生中被诊断出患有黑色素瘤，而皮肤黑色素瘤是 最致命的皮肤癌。肿瘤免疫治疗是治疗该病的突破性方法，具有细胞毒性。 CD8+T细胞肿瘤的侵袭是免疫治疗成功的关键因素。因此，确定有效的 提高患者肿瘤特异性CD8+T细胞反应的大小和功能的策略 仍然是一个重要的目标。CD8+T细胞上的抑制分子对T细胞信号转导和免疫是必不可少的 动态平衡。然而，这些分子的表达增加与抗肿瘤效应减弱有关。 反应以及较差的患者存活率。FcγRIIB是最近在一个亚群上发现的抑制性Fc受体 CD8+T细胞。FcγRIIB+CD8+T细胞活化标志物表达增加，增殖能力增强 能力，并分泌更多的促炎细胞因子比他们的FcγRIIB-在小鼠和人类， 使它们成为抗肿瘤反应的必需品。最近，我们发现一种免疫抑制剂 细胞因子纤维蛋白原样蛋白2(FGL2)是一种与CD8+T细胞表面的FcγRIIB结合并诱导FcγRIIB- 介导CD8+T细胞的凋亡。本研究的目的是探讨Fgl2的作用机制。 通过以下目的使用同基因小鼠模型调节肿瘤特异性的FcγRIIB+CD8+T细胞。目标1 (F99)：确定Fgl2关键调控肿瘤特异性的细胞和分子机制 CD8+T细胞。我们的研究表明，Foxp3+调节性T细胞和CD8+T细胞在肿瘤中都表达Fgl2 老鼠和人类。因此，我们将确定这些细胞类型分泌的Fgl2是否必要和/或充分 对于FcγRIIb介导的CD8+T细胞凋亡，这一发现将为后续研究提供动力 靶向这种细胞类型的治疗靶点。此外，我们已经发现，FcγRIIB-FGL2结合诱导 细胞凋亡，即细胞凋亡的上游要求(例如，T细胞受体刺激、募集到 FcγRIIB的胞内结构域)是目标1的后半部分的最近端研究项目。 FcγRIIb通过Fgl2诱导细胞凋亡的途径很容易发现一条新的CD8+T细胞途径 用于未来的免疫疗法。目标2(K00)：识别T细胞抵抗新的机制 癌症免疫疗法。在F99阶段之后，我打算过渡到K00阶段，开始博士后研究。 大量研究强调了检查点分子表达升高(PD-1，TIM-3)的作用以及 促炎症细胞因子(干扰素γ、肿瘤坏死因子)的产生减少在介导ICB耐药中的作用。海流 癌症免疫治疗的范式围绕着肿瘤微环境对 T细胞，但效应CD8+T细胞自身分泌的免疫抑制因子的存在及其影响 是不完全理解的。拟议目标的影响是相当大的，因为它们将确定新的目标， 这可能会挽救一群对肿瘤免疫反应至关重要的记忆CD8+T细胞。

PROJECT SUMMARY One in fifty Americans will be diagnosed with melanoma in their lifetime and skin cutaneous melanoma is the deadliest skin cancer. Cancer immunotherapy is a breakthrough approach to treat this disease and cytotoxic CD8+ T-cell tumor infiltration is a critical factor to immunotherapeutic success. As such, identifying effective strategies to increase the magnitude and functionality of the patient’s tumor-specific CD8+ T-cell response remains an important goal. Inhibitory molecules on CD8+ T cells are imperative to T-cell signaling and immune homeostasis. However, elevated expression of these molecules is correlated with dampened antitumor effector response as well as poorer patient survival. FcγRIIB is an inhibitory Fc receptor recently discovered on a subset of CD8+ T cells. FcγRIIB+ CD8+ T cells exhibit increased expression of activation markers, higher proliferative ability, and secrete more proinflammatory cytokines than their FcγRIIB- counterparts in mice and humans, making them imperative to the antitumor response. Recently, we discovered that an immunosuppressive cytokine, fibrinogen-like protein 2 (Fgl2), is a ligand that binds FcγRIIB on CD8+ T cells and induces FcγRIIB- mediated apoptosis of CD8+ T cells. The goal of this research is to interrogate the mechanism by which Fgl2 regulates tumor-specific FcγRIIB+ CD8+ T cells using syngeneic mouse models via the following aim. AIM 1 (F99): Determine the cellular and molecular mechanism by which Fgl2 critically regulates tumor-specific CD8+ T cells. Our studies show that both Foxp3+ regulatory T cells and CD8+ T cells express Fgl2 at the tumors of mice and humans. Thus, we will determine if Fgl2 secreted by these cell types is necessary and/or sufficient for FcγRIIB-mediated CD8+ T-cell apoptosis, findings which would provide the impetus for subsequent therapeutic targeting of this cell type. Additionally, as we have discovered that FcγRIIB-Fgl2 binding induces apoptosis, the upstream requirements of apoptosis (e.g. T-cell receptor stimulation, proteins recruited to the intracellular domain of FcγRIIB) are proximal items of investigation in the latter part of Aim 1. Piecing together the pathway by which FcγRIIB induces apoptosis via Fgl2 could uncover a new CD8+ T cell pathway readily harnessed for future immunotherapies. AIM 2 (K00): Identify novel mechanisms of T cell resistance to cancer immunotherapy. After the F99 stage, I intend to transition to the K00 stage to begin postdoctoral studies. Numerous studies highlight the role of elevated checkpoint molecule expression (PD-1, TIM-3) as well as decreased proinflammatory cytokine production (IFNγ, TNF) in mediating resistance to ICB. The current paradigm in cancer immunotherapy revolves around the suppressive impact of the tumor microenvironment on T cells, but the existence and impact of immunosuppressive factors secreted by effector CD8+ T cells themselves is incompletely understood. The impact of the proposed aims is considerable as they will identify novel targets, that could rescue a population of memory CD8+ T cells that are crucial to the immune response to tumor.