Augmenting T cell activity to weak tumor antigens and reversing myeloid cell-mediated T cell inhibition

我们的长期目标是开发一种新的方法来治疗已建立的黑色素瘤， 针对弱免疫原性和低表达的肿瘤抗原（TAg）的细胞毒性T细胞应答，包括 新抗原，同时赋予T细胞对髓源性抑制细胞（MDSC）的抗性- 介导的抑制。在临床试验中，基于T细胞的免疫疗法已证明肿瘤消退 提高了存活率。然而，尽管这些令人鼓舞的临床结果，持久的抗肿瘤反应是不可能的。 仅在一部分晚期黑色素瘤患者中观察到。这种差异强调了需要更多的 有效的治疗策略。基于T细胞的疗法部分受到低T细胞受体（TCR）亲和力的阻碍 和/或亲合力以及肿瘤细胞表面TAg的低表达。此外， MDSC对产生有效和长寿命的抗肿瘤T细胞应答构成主要障碍。在我们 已发表和初步研究，通过Toll样受体接合激活T细胞中的MyD 88信号传导， 增强的T细胞应答和延长的T细胞存活。通过将CD 8 α（细胞外）与MyD 88融合， （细胞内; CD 8 α：MyD 88）分子或通过将黑素瘤反应性TCR连接至MyD 88（TCR：MyD 88），我们获得了 开发了一种新的平台，在TLR-独立的，严格的TCR- 依赖的方式。CD 8 α：MyD 88在T细胞中的表达显著增强了对弱免疫应答的反应， TAg的次优水平和TCR依赖性的方式，并在初步研究中已经证明， 将MDSC分化为可以增强T细胞反应的细胞的非凡特性。重要的是 CD 8 α的使用提供了独特的特征，因为它代表了一种“通用”的方法来增强T细胞 无论患者的HLA类型如何。我们的中心假设是，T细胞工程化， 表达CD 8 α：MyD 88（或TCR：MyD 88）将放大TCR信号， 免疫原性或低表达的TAG包括新抗原，并逆转免疫原性或低表达的TAG的抑制活性。 骨髓细胞抑制，导致有效和长期的抗肿瘤反应。目标1： 确定T细胞中MyD 88激活增强TCR信号的分子机制。通过在 在人类和小鼠细胞的体外研究中，我们将定义MyD 88 信号传导增强TCR对不同亲和力的肿瘤抗原的应答。目的二是决定命运， 在具有已建立的皮下或皮下移植模型的小鼠中， 颅内黑素瘤目的3是确定在体内的意义和定义的机制 通过T细胞中的MyD 88信号转导逆转髓系细胞的抑制功能。这些研究 具有临床意义，因为它们有可能提供有关TCR反应如何发生的机制见解 扩增和抑制和/或逆转MDSC功能的新策略。

Our long term goal is to develop a novel approach for treating established melanoma tumors by enhancing cytotoxic T cell responses towards weakly immunogenic and lowly expressed tumor antigens (TAgs) including neoantigens while simultaneously conferring T cells resistance to myeloid-derived suppressor cell (MDSC)– mediated suppression. In clinical trials, T cell-based immunotherapies have demonstrated tumor regression and increased survival rates. Yet despite these encouraging clinical results, durable antitumor responses are observed in only a subset of patients with advanced melanoma. This discrepancy stresses the need for more effective treatment strategies. T cell-based therapies are hindered in part by low T cell receptor (TCR) affinity and/or avidity and by the low expression of TAg on the tumor cell's surface. Additionally, the presence of MDSCs poses a major obstacle to generating effective and long-lived antitumor T cell responses. In our published and preliminary studies, activating MyD88 signaling in T cells, via toll like receptor engagement, augmented T cell responses and prolonged T cell survival. By fusing the CD8α (extracellular) to MyD88 (intracellular; CD8α:MyD88) molecule or by linking melanoma-reactive TCRs to MyD88 (TCR:MyD88) we have developed a novel platform that strongly activates MyD88 signaling in a TLR-independent, strictly TCR- dependent fashion. CD8α:MyD88 expression in T cells considerably amplifies responses to weak and suboptimal levels of TAg and in a TCR-dependent manner, and in preliminary studies has demonstrated the extraordinary property of differentiating MDSC's into cells that can enhance T cell responses. Importantly, the use of CD8α offers the unique feature in that it represents a `universal' approach to potentiating T cell responses, regardless of the patient's HLA type. Our central hypothesis is that T cells engineered to express a CD8α:MyD88 (or TCR:MyD88) will amplify TCR signals against a variety of weakly immunogenic or lowly expressed TAgs including neoantigens and reverse the suppressive activity of myeloid cell suppression, resulting in effective and long-lived antitumor responses. Aim 1 is to determine the molecular mechanisms by which MyD88 activation in T cells augments TCR signals. Through in vitro studies of human and mouse cells, we will define the molecular interactions through which MyD88 signaling augments TCR responses to tumor antigens of varying affinities. Aim 2 is determine the fate and antitumor efficacy of each CD8α:MyD88 and TCR:MyD88 T cells in mice with an established subcutaneous or intracranial melanoma tumor. Aim 3 is to ascertain the in vivo significance and define the mechanism(s) through which MyD88 signaling in T cells reverses myeloid cell's suppressive function. These studies are clinically significant as they have the potential to offer mechanistic insights as to how TCR responses can be amplified and, novel strategies for inhibiting and/or reversing MDSC function.