The role of AKT signaling in NOTCH1 induced leukemias

描述（由申请人提供）：由于NOTCH 1受体中存在激活突变导致的NOTCH信号传导异常激活在超过50%的人T细胞淋巴母细胞白血病（T-ALL）的发病机制中起关键作用。T-ALL病例中NOTCH 1突变的鉴定促使临床试验的启动，以测试用？分泌酶抑制剂（GSI）在这种疾病中的作用。然而，GSI仅在一小部分具有NOTCH 1突变的T-ALL中具有活性，这表明GSI耐药机制可能限制GSI在T-ALL中的有效性。我们的初步数据表明：（i）NOTCH 1上调T-ALL中的PI 3 K/AKT通路;（ii）NOTCH 1信号转导下调PTEN肿瘤抑制基因的表达;（iii）PTEN的缺失与GSI对NOTCH 1抑制的抗性相关。因此，我们的中心假设是PI 3 K-AKT通路的活性至少部分地介导了异常NOTCH 1信号传导的致癌作用。我们进一步提出，由于PTEN的突变缺失导致的PI 3 K-AKT的组成性激活促进细胞生长、增殖和存活，使得T-ALL细胞对NOTCH 1抑制不敏感。本研究的短期目标是建立NOTCH 1和PI 3 K/AKT信号通路之间的相互作用在T细胞转化和治疗反应中的意义。为了实现这些目标，我们提出了以下具体目标：目标1。分析NOTCH 1与Pten-PI 3 K-AKT在T细胞转化中的相互作用。在这个目标中，我们将使用逆转录病毒癌基因转移表达激活的NOTCH 1在造血祖细胞从野生型和Pten基因敲除小鼠，以评估致癌NOTCH 1和PI 3 K-Akt信号之间的相互作用在T细胞淋巴母细胞肿瘤的发病机制的相关性。目标二。分析白血病干细胞中NOTCH 1和Pten的功能关系。在这个目标中，我们将分析NOTCH 1和PI 3 K-Akt信号通路在白血病干细胞的稳态中的作用，所述白血病干细胞来自表达活化的NOTCH 1的Pten-野生型、Pten-单倍不足和Pten-无效肿瘤。目标3。分析NOTCH和Akt信号在T-ALL对分子靶向药物应答中的相互作用。Pten丢失是否诱导对NOTCH 1抑制剂的耐药性？抑制AKT信号通路是否逆转对NOTCH 1抑制剂的耐药性？Pten杂合子和/或Pten缺失T-ALL肿瘤是否对Akt抑制剂或靶向Akt信号传导下游效应物（如mTOR、NF κ B和FOXO因子）的药物敏感性增加？ 公共卫生相关性：该项目旨在分析NOTCH 1和PI 3 K-AKT通路在T细胞淋巴母细胞白血病（T-ALL）发病机制中的遗传相互作用及其在肿瘤对靶向NOTCH 1和AKT癌蛋白的新兴疗法的耐药性中的作用。本文概述的实验将为合理开发针对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.