Autophagy and mTORC1 signaling in lymphatic malformation and lymphangiosarcoma

摘要/摘要 摘要淋巴管肉瘤是一种淋巴管分化的血管肉瘤，起源于恶性肿瘤。 内皮细胞(ECs)的转化。LAS的病因很大程度上是未知的，尽管是淋巴性的。 畸形(例如，乳腺癌患者的慢性淋巴水肿)已被认为是 疾病。拟议研究的长期目标是了解分子和细胞机制。 淋巴管畸形和进展到LAS的研究，以开发有效治疗的新策略 这种致命的疾病。在上一个资助期，我们创建了一个具有诱导性EC特异性的小鼠模型 TSC1的缺失，它概括了人类LAS的显著特征，并表明过度激活 在LAS的启动和维持过程中，内皮细胞中mTORC1和增加的VEGF自分泌信号是必需的。 在进一步的初步研究中，我们发现在TSC缺乏的情况下，mTORC1超激活的维持 细胞在葡萄糖饥饿时需要自噬，但在氨基酸饥饿或正常情况下不需要。 此外，自噬特别是通过脂质分解代谢和生成 在这些能量胁迫条件下，脂肪酸是ATP的主要来源。此外，与临床一致 血管畸形向血管肉瘤恶变伴发 二次突变，初步研究采用来自我们的LAS样本的完整外显子组测序(WES) Tsc1IΔEC小鼠模型检测到几个基因的继发性突变，其中包括与细胞有关的CDK6 周期调节，并与其他癌症有关。基于这些强有力的初步研究，并利用我们的 独特的新的小鼠模型，我们建议1)确定自噬在调节 脂解作用产生脂肪酸作为ATP生产的替代燃料以维持mTORC1的超激活 在TSC1缺失的血管肿瘤细胞中；2)检测自噬介导的脂质分解代谢在维持 淋巴管畸形和LAS患者体内mTORC1的高激活及潜在治疗评价 靶向自噬介导的脂解在小鼠和PDX淋巴管畸形模型中的疗效 3)探讨CDK6等基因的继发性突变在肺癌发生发展中的作用和机制。 淋巴管畸形的发展和向LAS的进展。综上所述，拟议的研究将审查 通过新的脂代谢机制和自噬逆转mTORC1的调节 与mTORC1信号协同的次级突变将提供重要的机械性见解 这种疾病可能有助于为这种毁灭性疾病提供新的治疗方法。

Summary/Abstract Lymphangiosarcoma (LAS) is angiosarcoma with lymphatic differentiation that originates from the malignant transformation of endothelial cells (ECs). The etiology of LAS is largely unknown, although lymphatic malformation (e.g. chronic lymphedema in breast cancer patients) has been recognized as a risk factor for the disease. The long-term goal of the proposed studies is to understand the molecular and cellular mechanisms of lymphatic malformation and progression to LAS in order to develop new strategies for effective therapies of this deadly disease. In the previous funding period, we created a mouse model with inducible EC-specific deletion of Tsc1 which recapitulates salient features of human LAS, and showed that hyper-activation of mTORC1 and increased VEGF autocrine signaling in ECs were required for initiation and maintenance of LAS. In further preliminary studies, we discovered that maintenance of hyper-activation of mTORC1 in TSC-deficient cells required autophagy under glucose-starvation, but not amino acid-starvation or normal conditions. Moreover, autophagy maintains elevated levels of ATP specifically through lipid catabolism and generation of fatty acids as the main source of ATP under these energy stress conditions. In addition, consistent with clinical findings that malignant transformation of vascular malformation to angiosarcoma was accompanied with secondary mutations, preliminary studies employing whole exome sequencing (WES) of LAS samples from our Tsc1iΔEC mice model identified secondary mutations in several genes including Cdk6, which is involved in cell cycle regulation and implicated in other cancers. Based on these strong preliminary studies and using our unique novel mouse models, we propose to 1) determine the mechanisms of autophagy in the regulation of lipolysis to produce fatty acids as an alternative fuel for ATP production to maintain mTORC1 hyper-activation in Tsc1-null vascular tumor cells; 2) examine the role of autophagy-mediated lipid catabolism in maintaining mTORC1 hyper-activation in lymphatic malformation and LAS in vivo and evaluate potential therapeutic efficacy of targeting autophagy-mediated lipolysis in mouse and PDX models of lymphatic malformation and LAS; and 3) explore the roles and mechanisms of secondary mutations in Cdk6 and other genes in the development of lymphatic malformation and progression to LAS. Together, the proposed studies to examine reverse regulation of mTORC1 by autophagy through novel mechanisms of lipid metabolism as well as secondary mutations that synergizing with mTORC1 signaling will provide significant mechanistic insights into the disease, which may contribute to novel therapies for this devastating disease.