Molecular and Cellular Mechanisms of Resistance to mTORC1 Inhibition in the Skin

 描述(申请人提供)：精确医学时代已经迎来了大量的靶向治疗，其中许多旨在抑制PI3K/AKT/mTOR信号通路，这是人类肿瘤中最常见的上调的致癌信号通路之一。然而，这些抑制剂在早期临床试验中的结果很大程度上令人失望。这些药物表现不佳的最令人信服的解释之一是缓解了许多调节致癌信号通路的负反馈通路。过去十年的研究表明，PI3K/AKT/mTOR信号的下调经常导致上游受体酪氨酸激酶(RTK)信号的反馈抑制丢失，包括ErbB受体信号。现在，关键的挑战是阐明这种作用的基本分子和细胞机制，以便制定合理的策略来规避肿瘤对这些抑制剂的耐药性。利用允许特定干扰mTORC1信号的新型小鼠模型，我们证明了mTORC1在体内调节小鼠皮肤的生理性EGFR水平和细胞与细胞之间的黏附方面发挥着关键作用。在这里，我们建议使用这些强大的遗传系统来梳理出相互关联的机制，通过这些机制，mTORC1抑制导致EGFR信号的矛盾上调和黏附连接成熟的抑制，这两个潜在的关键事件介导了肿瘤对PI3K/AKT/mTOR抑制剂的耐药性。目的1通过评估mTORC1干扰对角质形成细胞中EGFR运输和降解的影响，确定mTORC1反馈如何抑制上游EGFR水平和信号转导。目的2通过研究EGFR/PI3K/AKT和Rho家族GTPase信号在这一过程中的作用，并鉴定mTORC1调节连接形成下游的磷酸化蛋白质组，确定mTORC1信号是如何调控粘连连接成熟的。最后，目标3将探索mTORC1干扰对EGFR和细胞-细胞黏附的影响如何影响两阶段致癌模型中已建立的皮肤乳头状瘤的癌症进展。利用等基因和体内系统，这项工作阐明了几个基本的分子和细胞机制，通过这些机制，上皮性肿瘤可能会对mTORC1抑制产生耐药性。

 DESCRIPTION (provided by applicant): The era of precision medicine has ushered in a large number of targeted therapeutics, many aimed at inhibiting PI3K/AKT/mTOR signaling, one of the most commonly up-regulated oncogenic signaling pathways in human tumors. However, these inhibitors have had largely disappointing results in early clinical trials. One of the most compelling explanations for the poor performance of these drugs has been the relief of numerous negative feedback pathways that regulate oncogenic signaling circuits. The last decade of work has revealed that down-regulation of PI3K/AKT/mTOR signaling frequently results in loss of feedback inhibition of upstream receptor tyrosine kinase (RTK) signaling, including ErbB receptor signaling. Now, the key challenge is to elucidate the basic molecular and cellular mechanisms by which this works so that rational strategies can be devised to circumvent tumor resistance to these inhibitors. Using novel mouse models that allow specific perturbation of mTORC1 signaling, we demonstrate that mTORC1 plays a critical role in regulating physiologic EGFR levels and cell-cell adhesion in vivo in the murine skin. Here, we propose to use these powerful genetic systems to tease out the interconnected mechanisms by which mTORC1 inhibition leads to paradoxical up- regulation of EGFR signaling and suppression of adherens junction maturation, potentially key events mediating tumor resistance to PI3K/AKT/mTOR inhibitors. Aim 1 will determine how mTORC1 feedback inhibits upstream EGFR levels and signaling by assessing the effects of mTORC1 perturbation on EGFR trafficking and degradation in keratinocytes. Aim 2 will establish how mTORC1 signaling modulates adherens junction maturation by examining the role of EGFR/PI3K/AKT and Rho family GTPase signaling in this process, and identifying the mTORC1-regulated phospho-proteome downstream of junction formation. Finally, Aim 3 will explore how effects of mTORC1 perturbation on EGFR and cell-cell adhesion affect carcinoma progression of established skin papillomas in two-stage carcinogenesis models. Using isogenic and in vivo systems, this work clarify several basic molecular and cellular mechanisms by which epithelial tumors may develop resistance to mTORC1 inhibition.