Fatty acid signaling in the pancreatic tumor microenvironment

项目概要/摘要 尽管近年来在精准医学方面取得了重大进展，但胰腺导管腺癌（PDAC）仍然存在 几乎一致致命虽然PDAC中最常见的基因组改变目前是不可药物化的， 常规疗法通常对这种疾病无效，免疫调节疗法有望 显著改善PDAC患者的预后。这种疗法的发展需要改进 了解表征PDAC微环境的免疫逃避机制，包括 频繁排除CD 4 T细胞和大量免疫抑制性骨髓细胞。我们最近 发现癌细胞内在的谷草转氨酶2（GOT 2）塑造了免疫 抑制抗肿瘤免疫的微环境。从机制上讲，我们发现GOT 2的功能超出了其 在苹果酸-天冬氨酸穿梭中起作用，并促进核受体的转录活性 PPARd，通过与PPARd配体花生四烯酸直接结合而促进。而PDAC细胞中的GOT 2是 对于体内癌细胞增殖，GOT 2缺失导致肿瘤生长的T细胞依赖性抑制， 遗传或药理学PPARd激活在GOT 2缺失的情况下恢复PDAC进展。这种癌症 细胞内在GOT 2-PPARd轴促进来自肿瘤的CD 4和CD 8 T细胞的空间限制 在某些实施方案中，所述免疫抑制剂可抑制肿瘤微环境，并促进肿瘤浸润性骨髓细胞的免疫抑制表型。我们的结果 到目前为止，证明了一个非典型的功能，为一个既定的线粒体酶的转录 调节免疫逃避，在这里，我们建议利用这种新的GOT 2-PPARd轴，以促进免疫逃避。 产生抗肿瘤免疫应答，具有以下特定目的。目的1：评估治疗效果 在已建立的PDAC中靶向GOT 2-PPARd轴的潜力。我们将进行临床前评价， GOT 2/PPARd通路抑制与旨在增加抗肿瘤T细胞活性的治疗方法 在不同的小鼠模型中，验证我们在具有已知临床结果和突变的患者标本中的发现。 状态，并评估患者人群中GOT 2 信号传导和T细胞空间调节。目的2：分析癌症驱动的免疫逃避机制 细胞内GOT 2。我们将应用体外共培养系统，体内试验测试一套GOT 2突变体 不同的脂肪酸信号传导能力，以及无偏的转录分析，以了解逐步的 介导免疫逃避的旁分泌调节的机制。目的3：探讨脂肪酸介导的基因 由GOT 2和PPARd调节。我们将分析PPARd的全基因组结合模式， GOT 2调节的免疫调节转录因子，并表征了细胞中的染色质状态。 脂肪酸信号转导干扰的背景下，防止或允许抗肿瘤免疫反应。这项工作将 利用我们最近在PDAC中发现的一种新的免疫抑制机制， 为临床转化提供新的治疗组合信息。

PROJECT SUMMARY/ABSTRACT Despite significant recent advances in precision medicine, pancreatic ductal adenocarcinoma (PDAC) remains near-uniformly lethal. While the most frequent genomic alterations in PDAC are not presently druggable and conventional therapies are often ineffective in this disease, immune-modulatory therapies hold promise to meaningfully improve outcomes for PDAC patients. Development of such therapies requires an improved understanding of the immune evasion mechanisms that characterize the PDAC microenvironment, including frequent exclusion of antineoplastic T cells and abundance of immune-suppressive myeloid cells. We recently found that cancer cell-intrinsic glutamic-oxaloacetic transaminase 2 (GOT2) shapes the immune microenvironment to suppress antitumor immunity. Mechanistically, we found that GOT2 functions beyond its established role in the malate-aspartate shuttle and promotes the transcriptional activity of nuclear receptor PPARd, facilitated by direct binding to PPARd ligand arachidonic acid. While GOT2 in PDAC cells is dispensable for cancer cell proliferation in vivo, GOT2 loss results in T cell-dependent suppression of tumor growth, and genetic or pharmacologic PPARd activation restores PDAC progression in the GOT2-null context. This cancer cell-intrinsic GOT2-PPARd axis promotes spatial restriction of both CD4 and CD8 T cells from the tumor microenvironment, and fosters the immune-suppressive phenotype of tumor-infiltrating myeloid cells. Our results to date demonstrate a non-canonical function for an established mitochondrial enzyme in transcriptional regulation of immune evasion, and here we propose to exploit this novel GOT2-PPARd axis to promote a productive antitumor immune response with the following specific aims. Aim 1: Assess the therapeutic potential of targeting the GOT2-PPARd axis in established PDAC. We will perform preclinical evaluation of GOT2/PPARd pathway inhibition together with therapeutic approaches aimed to increase antitumor T cell activity in diverse mouse models, validate our findings in patient specimens with known clinical outcomes and mutational status, and assess heterogeneity across the patient population with respect to the association between GOT2 signaling and T cell spatial regulation. Aim 2: Analyze the immune evasion mechanisms driven by cancer cell-intrinsic GOT2. We will apply in vitro co-culture systems, in vivo assays testing a suite of GOT2 mutants with varying fatty acid signaling capacity, and unbiased transcriptional analyses to understand the stepwise mechanisms mediating paracrine regulation of immune evasion. Aim 3: Interrogate fatty acid-mediated gene regulation by GOT2 and PPARd. We will analyze the genome-wide binding patterns of PPARd and additional immune-modulatory transcription factors putatively regulated by GOT2, and characterize chromatin states in the context of fatty acid signaling perturbations that prevent or permit antitumor immune responses. This work will leverage our recent identification of a novel immune suppression mechanism in PDAC, with the potential to inform on new therapeutic combinations poised for clinical translation.