Regulatory non-Smad signaling in TGF-b-induced epithelial-mesenchymal transition

项目总结/摘要 随着上皮细胞向癌的发展，自分泌TGF-β信号的增加在肿瘤的发生发展中起着重要作用。 癌症进展，通过诱导上皮可塑性反应，可导致上皮-间充质 过渡（EMT）。EMT导致细胞去粘附并增加细胞运动性和侵袭性，这是EMT的先决条件。 癌细胞的扩散，并且越来越多地被视为癌干细胞的整体特性。作为TGF-β 信号传导驱动EMT，TGF-β反应有助于癌症进展，我们一直在研究 TGF-β信号的调节，因为它与上皮可塑性有关。 研究充分的Smad信号通路调节基因表达，以响应TGF-β，但TGF-β， 诱导的上皮可塑性反应不能仅仅用基因调控的变化来解释。因此，委员会认为， TGF-β诱导的非Smad信号转导受到越来越多的赞赏。在这笔资金的支持下， 一直在研究TGF-β诱导的Erk MAPK和PI 3 K-Akt-mTOR通路的激活，并已开始 在EMT中扮演的角色TGF-β诱导的上皮细胞中任一途径活化的特定作用 可塑性反应有待进一步确定。我们还发现，细胞调节其对TGF-β的反应性。 通过调节细胞内储存的细胞表面TGF-β受体水平。葡萄糖水平升高 和胰岛素激活细胞表面TGF-β受体的上调，这似乎是由Akt介导的 激活和Rab GT3激活蛋白AS 160，Akt磷酸化的直接靶标。我们 假设Akt激活增加，如在癌中常见的，或由Akt激活增加引起， 葡萄糖或胰岛素刺激，增强细胞的TGF-β反应性，以及敏感性和易感性， 癌细胞对EMT的反应性，因此可能通过增强TGF-β反应性促进癌症进展。 我们现在寻求继续我们的研究计划，旨在表征非Smad信号的作用， 控制细胞表面TGF-β受体水平的机制，以及由此产生的TGF-β反应性，以及 TGF-β诱导的EMT本研究的主要目的是：（1）研究 葡萄糖或胰岛素对TGF-β信号传导、上皮-间充质转化、癌症干细胞生成和 EMT依赖的癌症进展;（2）确定调节细胞表面的分子机制 TGF-β受体对Akt激活的反应;（3）确定TGF-β诱导的Erk的作用 MAPK和PI 3 K-Akt通路在上皮-间充质转化和癌症干细胞生成中的活化。 我们的研究应该为TGF-β反应性的调节和TGF-β受体的表达提供新的机制见解。 TGF-β诱导的非Smad信号在细胞TGF-β反应中的作用，特别是在EMT和癌症中 干细胞生成这些见解可能将高血糖或胰岛素治疗与癌症进展联系起来， 通过增加TGF-β反应性，并揭示了Akt信号增加的新作用， 常见于癌，因此通过增强TGF-β反应性促进癌症进展。

Project Summary/Abstract As epithelial cells progress to carcinomas, increased autocrine TGF-¿ signaling acquires a prominent role in cancer progression, by inducing an epithelial plasticity response that can lead to epithelial-mesenchymal transition (EMT). EMT results in cell de-adhesion and increased cell motility and invasion, a prerequisite of cancer cell dissemination, and is increasingly seen as an integral property of carcinoma stem cells. As TGF-¿ signaling drives EMT, and TGF-¿ responsiveness contributes to cancer progression, we have been studying the regulation of TGF-¿ signaling, as it pertains to epithelial plasticity. The well-studied Smad signaling pathway regulates gene expression in response to TGF-¿, but the TGF-¿- induced epithelial plasticity response cannot be explained merely by changes in gene regulation. Accordingly, TGF-¿-induced non-Smad signaling has received increasing appreciation. Supported by this grant, we have been studying the TGF-¿-induced activation of the Erk MAPK and PI3K-Akt-mTOR pathways, and have started addressing their roles in EMT. The specific roles of TGF-¿-induced activation of either pathway in the epithelial plasticity response remain to be further defined. We also found that cells regulate their responsiveness to TGF- ¿, by regulating the TGF-¿ receptor levels at the cell surface from intracellular stores. Increased glucose levels and insulin activate this upregulation of cell surface TGF-¿ receptors, which appears to be mediated by Akt activation and the Rab GTPase activating protein AS160, a direct target of Akt phosphorylation. We hypothesize that increased Akt activation, as commonly seen in carcinomas, or resulting from increased glucose or insulin stimulation, enhances the cell's TGF-¿ responsiveness, and the sensitivity and susceptibility of cancer cells to EMT, and thus may promote cancer progression by enhancing TGF-¿ responsiveness. We now seek to continue our research program aimed at characterizing the roles of non-Smad signaling mechanisms in the control of the cell surface TGF-¿ receptor levels, and resulting TGF-¿ responsiveness, and in TGF-¿-induced EMT. We organized our current and future research in three Aims: (1) To study the effects of glucose or insulin on TGF-¿ signaling, epithelial-mesenchymal transition, cancer stem cell generation and EMT-dependent cancer progression; (2) To define the molecular mechanisms regulating the cell surface presentation of the TGF-¿ receptors in response to Akt activation; (3) To define the roles of TGF-¿-induced Erk MAPK and PI3K-Akt pathway activation in epithelial-mesenchymal transition, and cancer stem cell generation. Our studies should provide novel mechanistic insights into the regulation of TGF-¿ responsiveness and the roles of TGF-¿-induced non-Smad signaling in the cellular TGF-¿ response, in particular in EMT and cancer stem cell generation. These insights may link hyperglycemia or insulin treatment with cancer progression, through increased TGF-¿ responsiveness, and reveal a new role for the increased Akt signaling that is commonly seen in carcinomas, thus contributing to cancer progression by enhancing TGF-¿ responsiveness.