Role of cDC2 subsets in host protection and CD4T cell responses in melanoma

项目摘要 尽管最近取得了成功，但许多黑色素瘤患者仍然对免疫治疗没有反应，而且有一种 迫切需要确定新的治疗靶点。免疫治疗的主要目标是激活肿瘤- 特异性免疫反应，其中肿瘤特异性T细胞起着至关重要的作用。尽管细胞毒CD8T细胞 长期以来一直是肿瘤特异性免疫研究的主要焦点，越来越多的证据表明 CD4T细胞在肿瘤排斥反应中的作用，特别是在接受免疫原治疗的肿瘤中。然而， 与CD8T细胞相比，CD4T细胞在黑色素瘤中的激活机制尚不清楚。 2型常规树突状细胞(CDC2)具有很高的抗原提呈能力，能够激活抗原特异性 CD4T细胞，但其在肿瘤免疫中的作用尚未完全了解，部分原因是表型 这种细胞类型中的异质性。我们先前确定CD301b+DC是主要的CDC2人群 小鼠皮肤，并表明它们将抗原从皮肤转移到引流淋巴结，并有效地 抗原特异性CD4T细胞。本提案侧重于了解它们在宿主保护和保护中的作用 小鼠实验性黑色素瘤模型中CD4T细胞的激活。为了了解cDC2细胞如何对 在分子水平的肿瘤微环境中，我们使用了一种新的单细胞RNA测序技术来 确定在黑色素瘤进展过程中cDC2亚群中特定亚群基因表达的变化。同时， 我们使用有针对性的细胞耗竭方法来确定cDC2耗竭宿主的细胞机制。 对未经治疗的黑色素瘤和接受免疫原性治疗的黑色素瘤均有保护作用。这些 实验将共同提供对cDC2亚群在黑色素瘤中作用的全面理解 并有可能揭示导致黑色素瘤特异性CD4T细胞激活的新的细胞途径。

Project Summary Despite recent successes, many melanoma patients still fail to respond to immunotherapy and there is a pressing need for identifying novel therapeutic targets. The primary goal of immunotherapy is to activate tumor- specific immune responses, in which tumor-specific T cells play a crucial role. Although cytotoxic CD8T cells have long been the main focus of research on tumor-specific immunity, growing evidence shows the contribution of CD4T cells to tumor rejection, especially in tumors treated with immunogenic therapy. However, the mechanism of CD4T cell activation in melanoma is less well understood compared to that of CD8T cells. Type 2 conventional dendritic cells (cDC2s) have high antigen presenting capacity to activate antigen-specific CD4T cells, but their role in tumor immunity has not been fully understood due partially to the phenotypic heterogeneity within this cell type. We previously identified CD301b+ DCs as the major cDC2 population in the mouse skin and showed that they transport antigens from the skin to the draining lymph node and efficiently prime antigen-specific CD4T cells. This proposal focuses on understanding their role in host protection and CD4T cell activation in experimental melanoma models in mice. To understand how cDC2 cells respond to the tumor microenvironment at the molecular level, we employ a novel technique of single-cell RNA sequencing to identify subset-specific gene expression changes in cDC2 subsets during melanoma progression. In parallel, we use targeted cell depletion approaches to identify the cellular mechanisms of cDC2-depedent host protection in both untreated melanoma as well as in those treated with immunogenic therapy. These experiments will collectively provide comprehensive understanding on the role of cDC2 subsets in melanoma and potentially reveal new cellular pathways that lead to activation of melanoma-specific CD4T cells.