Mechanisms and Function of Autophagy in Cancer

自噬在肿瘤中的机制和作用 摘要 这项研究计划的总体目标是阐明自噬的分子机制和它的 在癌症中的作用。自噬是一种溶酶体介导的应激反应分解代谢途径，发挥着重要作用 在正常生物学和疾病中都扮演着重要的角色。尽管自噬的核心分子途径相对 描述得很清楚，这条途径是如何被精确调控以实现特定的、有时似乎是 违反直觉的功能并不明确。例如，是什么机制使“自噬上瘾”？ 癌细胞同时具有完整的mTOR活性和高水平的基础自噬，考虑到mTOR是一种 真正的自噬抑制剂？自噬在决定不同细胞命运中的作用是什么 死亡、衰老和茎干，这些都与肿瘤的发生有关？有什么治疗意义可以 我们从这些关于自噬的基本生物学问题的答案中学到了什么？在之前的资助中 周期，我们在细胞和小鼠模型中观察到自噬抑制的强大的抗癌作用。 多种癌症类型，包括胶质母细胞瘤(GBM)和胰腺导管腺癌(PDAC)。我们 发现一种特定的蛋白磷酸酶2A(PP2A)复合体可以被刺激以增强自噬 通过去磷酸化自噬启动的蛋白激酶复合体，ULK1复合体，从而 对抗mTOR的自噬抑制活性。重要的是，我们的初步结果表明 PP2A还参与TFEB转录因子的激活，TFEB转录因子是自噬基因的主要调节因子 表达与溶酶体的生物发生。因此，通过调节ULK1复合体和TFEB、PP2A 调节自噬的启动和效力。有趣的是，我们还发现自噬和TFEB 在临床相关条件下调节GBM细胞衰老。根据这些初步研究，在这方面 Grant，我们将进一步研究自噬的分子基础及其在癌症中的作用，重点是 以下两个目标：(1)蛋白磷酸酶调节TFEB的机制和功能 这种调节对自噬和依赖自噬的癌细胞的影响；以及(2)自噬的作用 和TFEB在癌细胞衰老中的作用。为了实现这些目标，我们将进行实验，使用一种 多种方法的结合，包括标准的细胞、分子和生化方法、动物 建模，以及更专业的技术，如定量质谱学和深度测序。 拟议研究的成功将导致从机制上深入理解监管和 自噬在正常生物学和癌症生物学中的作用，并可能为精确靶向 用于癌症治疗的自噬。该提案还将阐明自噬与 其他重要的生物过程，包括溶酶体的生物发生和衰老。

Mechanisms and Function of Autophagy in Cancer Summary The overall goal of this research proposal is to elucidate the molecular mechanisms of autophagy and its role in cancer. Autophagy is a lysosome-mediated, stress-responsive catabolic pathway that plays important role in both normal biology and disease. Although the core molecular pathway of autophagy has been relatively well delineated, how this pathway is precisely regulated to accomplish specific and sometime seemingly counterintuitive function is not clear. For example, what is the mechanism that enables “autophagy-addicted” cancer cells to possess both intact mTOR activity and high levels of basal autophagy, considering mTOR is a bona fide inhibitor of autophagy? What is the role of autophagy in determining various cell fates such as cell death, senescence, and stemness, which are all relevant to tumorigenesis? What therapeutic implication can we learn from the answers to these basic biological questions concerning autophagy? In the previous funding cycle, we have observed potent anticancer effect of autophagy-inhibition in cellular and mouse models for multiple cancer types, including glioblastoma (GBM) and pancreatic ductal adenocarcinoma (PDAC). We discovered that a specific protein phosphatase 2A (PP2A) complex can be stimulated to enhance autophagy initiation through dephosphorylating the autophagy-initiating protein kinase complex, the ULK1 complex, thus counteracting the autophagy-suppressing activity of mTOR. Importantly, our preliminary results indicate that PP2A is also involved in the activation of TFEB transcriptional factor, a master regulator of autophagy gene expression and lysosomal biogenesis. Therefore, via regulating the ULK1 complex and TFEB, PP2A modulates both initiation and potency of autophagy. Intriguingly, we also found that autophagy and TFEB regulate GBM cell senescence under clinically relevant conditions. Based on these preliminary studies, in this grant, we will further investigate the molecular basis of autophagy and its role in cancer, by focusing on the following two aims: (1) the mechanisms by which protein phosphatases regulate TFEB, and the functional impact of such regulation on autophagy and autophagy-addicted cancer cells; and (2) the role of autophagy and TFEB in cancer cell senescence. To achieve these aims, we will conduct experiments that employ a combination of approaches, including standard cellular, molecular and biochemical approaches, animal modeling, and more specialized technologies such as quantitative mass spectrometry and deep sequencing. Success of the proposed study will lead to an in-depth mechanistic understanding of the regulation and function of autophagy in normal biology and cancer biology, and might provide insights into precise targeting of autophagy for cancer treatment. The proposal will also shed light on the functional interplay of autophagy with other important biological processes, including lysosomal biogenesis and senescence.