Metabolic Regulation ofPD-L1 in CD11c+ Cells

项目总结/摘要 长期目标是找到更好的干预方法来阻断癌症的发生、进展和发展， 转移PD-L1/PD-1信号通路是肿瘤利用的关键免疫检查点机制， 逃避抗肿瘤免疫反应。PD-L1与活化T细胞上的PD-1结合以介导抑制信号 通过表达PD-1的T细胞。相比之下，PD-L1表达在髓系细胞中的功能作用 车厢不太清楚。众所周知，CD 11 c + DC具有捕获肿瘤抗原的功能， 交叉呈递这些抗原给肿瘤引流淋巴结中的T细胞，导致产生 肿瘤特异性细胞毒性T淋巴细胞（CTL），有助于肿瘤排斥。有趣的是，我们发现 从溶酶体酸性脂肪酶（LAL）敲除（lal-/-）小鼠血液中分离的CD 11 c+细胞具有 在缺乏抗原呈递的情况下，免疫抑制，并在体外直接刺激肿瘤增殖， 体内肿瘤生长。与此同时，Ial-/-CD 11 c+细胞中PD-L1表达增加，这是 免疫抑制和肿瘤刺激。我们的观察表明，LAL缺陷诱导的代谢 转换导致CD 11 c+细胞赋予肿瘤刺激而不是排斥。根据这些观察， 该提案将重点关注Ial-/-CD 11 c+细胞中的PD-L1表达如何有助于免疫抑制和肿瘤 在LAL缺陷期间刺激。LAL是水解胆固醇酯和甘油三酯的关键酶， 细胞的溶酶体产生游离脂肪酸（FFA）和胆固醇。FFA的代谢物是以下物质的配体： 核转录因子过氧化物酶体增殖物激活受体（PPAR-A），一种负调节因子， 炎症由于LAL与脂肪酸代谢密切相关，因此拟定的研究将进一步阐明 lal-/-CD 11 c+细胞影响肿瘤免疫和刺激的潜在代谢机制 PD-L1的表达。RNAseq和流式细胞术证明PD-L1表达受以下因素调节： 葡萄糖/谷氨酰胺代谢过程和哺乳动物雷帕霉素靶蛋白（mTOR）， 是在过氧化物酶体增殖物激活受体的控制下。因此，本提案将检验一个中心假设， LAL/PPAR γ/mTOR轴调控PD-L1表达在lal-/-CD 11 c+细胞免疫抑制中起关键作用 以及通过代谢重编程刺激肿瘤。为了实现我们的目标，我们将使用独特的lal-/- 小鼠模型和条件性c-fms-rtTA/（TetO）7-CMV-hLAL; Ial-/-三联小鼠模型（c-fms-Tg/KO），其中 hLAL在Ial-/-小鼠的骨髓区室中特异性表达。制定了以下具体目标 为了检验中心假设：1）表征PD-L1表达的发育和代谢调节 2）表征CD 11 c+细胞的PD-L1表达在调节T细胞增殖中的作用， 功能; 3）表征肿瘤刺激中CD 11 c+细胞的PD-L1表达。成功的结果将 有助于设计更有效的方案，通过操纵PD-L1癌症免疫治疗的有效性， 代谢途径和免疫检查点途径。

Project Summary/Abstract The long-term goal is to find better intervening approaches to interdict cancer initiation, progression and metastasis. The PD-L1/PD-1 signaling pathway is a critical immune checkpoint mechanism utilized by tumor to escape antitumor immune responses. PD-L1 binds to PD-1 on activated T cells to mediate an inhibitory signal through PD-1-expressing T cells. In comparison, the functional roles of PD-L1 expression in the myeloid compartment are less clear. CD11c+ DCs are well known for their function to capture tumor antigens and cross-present these antigens to T cells in tumor-draining lymph nodes, resulting in the generation of tumor-specific cytotoxic T lymphocytes (CTLs) that contribute to tumor rejection. Interestingly, we have shown that CD11c+ cells isolated from the blood of lysosomal acid lipase (LAL) knockout (lal-/-) mice possess immunosuppression in the absence of antigen presentation, and directly stimulate tumor proliferation in vitro and tumor growth in vivo. Concomitantly, PD-L1 expression was increased in lal-/- CD11c+ cells, which is required for immunosuppression and tumor stimulation. Our observations suggest that the LAL deficiency-induced metabolic switch leads CD11c+ cells to confer tumor stimulation rather than rejection. Based on these observations, this proposal will focus on how PD-L1 expression in lal-/- CD11c+ cells contributes to immune suppression and tumor stimulation during LAL-deficiency. LAL is a key enzyme that hydrolyzes cholesteryl esters and triglycerides in the lysosome of cells to generate free fatty acids (FFAs) and cholesterol. The metabolites of FFAs are ligands for nuclear transcription factor peroxisome proliferator activated receptor  (PPAR), a negative regulator of inflammation. Since LAL is critically involved in fatty acid metabolism, the proposed study will further elucidate the underneath metabolic mechanism by which lal-/- CD11c+ cells influence tumor immunity and stimulation through PD-L1 expression. RNAseq and flow cytometry demonstrated that PD-L1 expression is regulated by glucose/glutamine metabolic processes and mammalian target of rapamycin (mTOR) in lal-/- CD11c+ cells, which is under the control of PPAR. Therefore, the current proposal will test a central hypothesis that LAL/PPAR/mTOR axis-regulated PD-L1 expression plays a key role in lal-/- CD11c+ cells’ immune suppression and tumor stimulation through metabolic reprogramming. To achieve our goals, we will use the unique lal-/- mouse model and the conditional c-fms-rtTA/(TetO)7-CMV-hLAL;lal-/- triple mouse model (c-fms-Tg/KO) in which hLAL is specifically expressed in the myeloid compartment of lal-/- mice. The following specific aims are designed to test the central hypothesis:1) Characterizing the developmental and metabolic regulation of PD-L1 expression in CD11c+ cells; 2) Characterizing PD-L1 expression of CD11c+ cells in regulating T cell proliferation and functions; 3) Characterizing PD-L1 expression of CD11c+ cells in tumor stimulation. The successful outcome will help to design a more efficient regimen to increase the efficacy of PD-L1 cancer immunotherapy by manipulating the metabolic pathway and the immune checkpoint pathway.