Role of the UPR in myc-induced tumorigenesis

未折叠蛋白反应(UPR)是一种细胞内平衡程序，由过量的 内质网(ER)管腔中未折叠/错误折叠的客户蛋白，主要是 细胞保护作用。我们之前的研究表明，肿瘤细胞在低氧和营养剥夺的情况下存活 应激依赖于内质网驻留蛋白和UPR效应蛋白。除了肿瘤之外 微环境，癌基因也已知激活细胞应激反应，包括新陈代谢 应激、细胞凋亡和衰老。MYC是染色体易位或基因扩增的目标 在许多人类癌症的发展过程中。C-Myc的表达与健壮有关 上调细胞总蛋白质含量和蛋白质合成速率。这一发现提高了 C-Myc转化的细胞可能经历了比正常水平更高的内质网应激。在预赛中 研究中，我们使用了多种调节c-Myc激活的遗传模型来证明Myc 激活UPR的PERK/elF2a/ATF4臂。UPR的激活通过以下途径增加细胞存活率 细胞保护性自噬的诱导和内质网钙离子释放减少。Perk消融 显著减少Myc诱导的裸鼠自噬、细胞转化和肿瘤形成。 来自E)j，-Myc小鼠和人类淋巴瘤的样本显示出更高水平的UPR激活， 与相应的正常组织比较。我们认为细胞内蛋白质负荷的增加 过表达c-Myc导致内质网应激和UPR激活，从而缓和内质网应激和 促进转化和肿瘤生长。这一假设将在四个具体目标中进行检验：在目标1中， 我们将确定elF2a磷酸化、ATF4和CHOP诱导、Nrf2激活的需求 和miRNA211在c-Myc诱导的体内外转化中。在具体目标2中，我们将阐明 UPR激活在致癌转化中提供细胞保护的机制 MYC。在特定目标3下，我们将研究c-Myc过表达对细胞活化的影响 其他两条普遍定期审议的主要途径。在特定的目标4中，我们将确定PERK激活在c-Myc中的作用 使用转基因小鼠模型诱导淋巴肿大。成功完成这些研究 将首次确立Myc上调为普遍定期审议的细胞自主激活剂，并将 揭开抑制Myc依赖肿瘤发生的新靶点。 相关性(请参阅说明)： 主要癌基因c-Myc在恶性肿瘤中被激活，包括淋巴瘤、结直肠癌和 神经母细胞瘤。未折叠蛋白应答(UPR)作为一种机制越来越被人们所认识 肿瘤对应激的抵抗力和肿瘤形成的促进剂。我们的初步发现表明了一个新的角色 C-Myc作为肿瘤发生的增强子的UPR激活。我们建议的研究将调查 Myc在细胞系、动物肿瘤模型和人体样本中激活UPR的机制 有可能导致针对Myc依赖的恶性肿瘤的新疗法的开发。

The Unfolded Protein Response (UPR) is a cellular homeostatic program initiated by an excess of unfolded/misfolded client proteins in the Endoplasmic Reticulum (ER) lumen, with primarily a cytoprotective effect. We previously showed that tumor cell survival under hypoxic and nutrient deprivation stress is dependent on the ER resident protein and UPR effector PERK. In addition to the tumor microenvironment, oncogenes are also known to activate cellular stress responses, including metabolic stress, apoptosis, and senescence. MYC is the target of chromosomal translocation or gene amplification during the development of many human cancers. c-Myc expression has been associated with robust upregulation of both total cellular protein content and rates of protein synthesis. This finding raises the possibility that c-Myc-transformed cells experience a higher than normal level of ER stress. In preliminary studies, we have used multiple genetic models of regulated c-Myc activation, to demonstrate that Myc activates the PERK/elF2a/Atf4 arm of the UPR. Activation of the UPR leads to increased cell survival via the induction of cytoprotective autophagy and reduced release of Ca^* from the ER. PERK ablation significantly reduced Myc-induced autophagy, cell transformation and tumor formation in nude mice. Samples from E)j,-Myc mice and human lymphomas demonstrate higher levels of UPR activation, compared to corresponding normal tissues. We hvpothesize that the increase in protein burden in cells overexpressing c-Myc results in ER stress and activation of the UPR which tempers ER stress and facilitates transformation and tumor growth. This hypothesis will be tested in four specific aims: In Aim 1, we will determine the requirement for elF2a phosphorylation, ATF4 and Chop induction, Nrf2 activation and miRNA 211 in c-Myc-induced transformation in vitro and in vivo. In specific Aim 2, we will elucidate the mechanism of cytoprotection afforded by UPR activation in the context of oncogenic transformation by Myc. Under specific Aim 3, we will investigate the impact of c-Myc overexpression on the activation of the other two major UPR pathways. In specific Aim 4, we will determine the role of PERK activation in c-Myc induced lymphomagenesis using a transgenic mouse model. Successful completion of these studies would establish, for the first time, Myc upregulation as a cell-autonomous activator of UPR and would unveil novel targets for inhibiting Myc-dependent tumorigenesis. RELEVANCE (See instructions): The major oncogene c-Myc is activated in malignancies, including lymphomas, colorectal cancer and neuroblastomas. The Unfolded Protein Response (UPR) is increasingly been recognized as a mechanism of tumor resistance to stress and- promoter of tumorigenesis. Our preliminary findings suggest a novel role of UPR activation as an enhancer of tumorigenesis by c-Myc. Our proposed studies will investigate the mechanism of UPR activation by Myc in cell lines, animal tumor models and human samples and have the potential to lead to the development of novel therapeutics targeting Myc-dependent malignancies.