The role of AKT signaling in NOTCH1 induced leukemias

描述（由申请人提供）：NOTCH1受体的激活突变导致NOTCH信号的异常激活在超过50%的人t淋巴细胞白血病（T-ALL）的发病机制中起关键作用。T-ALL病例NOTCH1突变的鉴定促使临床试验启动，以测试用？-分泌酶抑制剂（GSIs）在本病中的作用然而，GSI仅在一小部分NOTCH1突变的T-ALL中有活性，这表明GSI耐药的机制可能限制了GSI在T-ALL中的有效性。我们的初步数据显示：(i) NOTCH1上调T-ALL的PI3K/AKT通路；（ii） NOTCH1信号下调PTEN抑癌基因的表达；（iii） PTEN的缺失与GSIs对NOTCH1抑制的抗性有关。因此，我们的中心假设是，PI3K-AKT通路的活性至少在一定程度上介导了NOTCH1异常信号的致癌作用。我们进一步提出，PTEN的突变缺失导致PI3K-AKT的组成性激活促进细胞生长、增殖和存活，使T-ALL细胞对NOTCH1抑制不敏感。本研究的短期目标是确定NOTCH1与PI3K/AKT信号通路相互作用在t细胞转化和治疗反应中的意义。为实现这些目标，我们提出以下具体目标：目标一。分析NOTCH1与Pten-PI3K-AKT在t细胞转化过程中的相互作用。为此，我们将利用逆转录病毒癌基因转移在野生型和Pten敲除小鼠的造血祖细胞中表达活化的NOTCH1，以评估致癌NOTCH1和PI3K-Akt信号之间的相互作用在t淋巴细胞肿瘤发病机制中的相关性。目标2。分析NOTCH1与Pten在白血病干细胞中的功能关系。在本研究中，我们将分析NOTCH1和PI3K-Akt信号通路在表达活化NOTCH1的pten -野生型、pten -单倍不足型和pten -缺失型白血病干细胞稳态中的作用。目标3。分析NOTCH和Akt信号在T-ALL对分子靶向药物反应中的相互作用。pten缺失是否诱导对NOTCH1抑制剂的耐药？抑制AKT信号通路是否能逆转对NOTCH1抑制剂的耐药性？pten杂合子和/或pten缺失的T-ALL肿瘤是否对Akt抑制剂或靶向Akt信号下游效应物（如mTOR、NFKB和FOXO因子）的药物表现出更高的敏感性？公共卫生相关性：本项目旨在分析NOTCH1和PI3K-AKT通路在t淋巴细胞白血病（T-ALL）发病机制中的遗传相互作用，以及它们在肿瘤对靶向NOTCH1和AKT癌蛋白的新疗法的耐药性中的作用。这里概述的实验将为合理开发对抗T-ALL的新疗法奠定基础。

DESCRIPTION (provided by applicant): Aberrant activation of NOTCH signaling due to the presence of activating mutations in the NOTCH1 receptor play a critical role in the pathogenesis in more than 50% human T-cell lymphoblastic leukemias (T-ALL). The identification of NOTCH1 mutations of T-ALL cases has prompted the initiation of clinical trials to test the effectiveness of blocking NOTCH1 signaling with ?-secretase inhibitors (GSIs) in this disease. However, GSIs are active only in a small fraction of T-ALLs with NOTCH1 mutations, suggesting that mechanisms responsible for GSI resistance may limit the effectiveness of GSIs in T-ALL. Our preliminary data shows that: (i) NOTCH1 upregulates the PI3K/AKT pathway in T-ALL; (ii) NOTCH1 signaling downregulates the expression of the PTEN tumor suppressor gene; and (iii) loss of PTEN is associated with resistance to NOTCH1 inhibition with GSIs. Thus, our central hypothesis is that the activity of the PI3K-AKT pathway mediates, at least in part, the oncogenic effects of aberrant NOTCH1 signaling. We further propose that constitutive activation of PI3K-AKT due to mutational loss of PTEN promotes cell growth proliferation and survival rendering T-ALL cells insensitive to NOTCH1 inhibition. The short-term goals of this research are to establish the significance of the interaction between NOTCH1 and PI3K/AKT signaling pathways in T-cell transformation and therapy response. To achieve these objectives, we propose the following specific aims: Aim 1. To analyze the interaction between NOTCH1 and Pten-PI3K-AKT in T-cell transformation. In this aim we will use retroviral oncogene transfer to express activated NOTCH1 in hematopoietic progenitors from wild type and Pten knockout mice to assess the relevance of the interaction between oncogenic NOTCH1 and PI3K-Akt signaling in the pathogenesis of T-cell lymphoblastic tumors. Aim 2. To analyze the functional relationship between NOTCH1 and Pten in leukemia stem cells. In this aim we will analyze the role of the NOTCH1 and PI3K-Akt signaling pathways in the homeostasis of the leukemia stem cells from Pten-wild type, Pten-haploinsuficient and Pten-null tumors expressing activated NOTCH1. Aim 3. To analyze the interaction between NOTCH and Akt signaling in the response of T-ALL to molecularly targeted drugs. Does Pten-loss induce resistance to NOTCH1 inhibitors? Does inhibition of the AKT signaling pathway reverse resistance to NOTCH1 inhibitors? Do Pten-heterozygous and/or Pten-null T-ALL tumors show increased sensitivity to Akt inhibitors or to drugs targeting downstream effectors of Akt signaling such as mTOR, NFKB and FOXO factors? PUBLIC HEALTH RELEVANCE: This project aims to analyze the genetic interaction between NOTCH1 and PI3K-AKT pathways in the pathogenesis of T-cell lymphoblastic leukemias (T-ALL) and their role in tumor resistance to emerging therapies targeting the NOTCH1 and AKT oncoproteins. The experiments outlined here will set the basis for the rational development of new therapies against T-ALL.