ROLE OF NOTCH-EGFR PATHWAY COOPERATIVITY IN BASAL-LIKE BREAST CANCER

基底细胞样乳腺癌(BLBC，或三阴性)是一种高度致命的疾病形式， 目前缺乏有效的治疗方法。这种致命性被认为部分是由于肿瘤数量的增加- 在BLBC中测量的起始(或干细胞)细胞。表皮生长因子受体(EGFR)是常见的 在这些肿瘤中表达，但针对该受体的抑制剂已显示出可测量但有限的活性 乳腺癌临床试验。相反，EGFR是多种其他实体肿瘤的有效靶点。连 尽管在乳腺癌中使用EGFR抑制剂的临床试验仍在继续，但这些药物在治疗乳腺癌方面缺乏疗效 人们对这种疾病仍然知之甚少。BLBC还表现出频繁的Notch受体过度激活，这是 乳腺中的致癌物质。这四个家族成员通常在乳腺癌细胞中共表达。 在那里他们可以扮演相反或多余的角色。它们的激活依赖于酶的活性 伽玛分泌酶复合体，其抑制剂(GSI)正在临床试验。这些药物在全球范围内抑制了 所有四种受体都可以产生显著的毒性，促使人们研究毒性较低的方法 阻止Notch信令。幸运的是，许多依赖Notch的过程对基因剂量很敏感 受体专一性。因此，完全和泛受体抑制可能不是所有治疗所必需的。 涉及Notch受体的应用。 我们最近报道了Notch和EGFR通路之间的合成致死关系 (董等人，癌症研究，2010年7月)。通过以下目标，我们将检验以下假设 Noch和EGFR受体作为BLBC细胞生存所需的协同癌蛋白发挥作用。 具体目的1.检测联合抑制Notch-EGFR通路对肿瘤发生的影响 BLBC肿瘤中的细胞存活。我们将评估联合途径抑制对根除的相对能力 乳腺癌细胞的启动肿瘤和分化程度较高的部分。我们还将开始确定 使用一种新技术联合抑制途径对人原发BLBC肿瘤的疗效 这些癌细胞被移植到免疫缺陷小鼠体内，并研究对功能Notch的需求。 在更广泛的BLBC细胞系中表现出可变的EGFR表达的EGFR通路。具体目标2. 确定部分Notch通路抑制在以下情况下诱导合成致死性的能力 联合应用EGFR阻断BLBC细胞。部分通路抑制将通过两个途径实现 策略、GSI的剂量修饰和受体特异性击倒。与EGFR封锁相结合， 我们将研究这些方法诱导细胞死亡的程度以及它们如何影响细胞的生存能力 肿瘤起始细胞和分化细胞。相反，通过强制表达激活的受体， 单个受体抑制细胞死亡和在存在的情况下扩大肿瘤启动群体的能力 将测量GSI和EGFR抑制剂治疗的比例。

Basal-like breast cancer (BLBC, or triple-negative) is a highly lethal form of the disease for which effective therapeutics are lacking. This lethality is though to be due in part to the increased numbers of tumor- initiating (or stem) cells measured in BLBCs. The epidermal growth factor receptor (EGFR) is commonly expressed in these tumors, but inhibitors against the receptor have shown measurable but limited activity in breast cancer clinical trials. In contrast, EGFR is an effective target in multiple other solid tumor types. Even though clinical trials using EGFR inhibitors continue in breast cancer, the lack of efficacy of these agents in this disease remains poorly understood. BLBCs also show frequent hyperactivation of Notch receptors, which are oncogenic in the mammary gland. The four family members are commonly co-expressed in breast cancer cells where they can play opposing or redundant roles. Their activation is dependent on the enzymatic activity of the gamma secretase complex, inhibitors of which (GSIs) are being trialed in the clinic. These drugs globally inhibit all four receptors and can produce significant toxicity, motivating investigation into less toxic approaches to blocking Notch signaling. Fortunately, many Notch-dependent processes are sensitive to gene dosage and are receptor specific. Therefore, complete and pan-receptor inhibition may not be necessary for all therapeutic applications involving Notch receptors. We have recently reported a synthetic lethal relationship between the Notch and EGFR pathways (Dong, et al., Cancer Research, July 2010). Through the following aims, we will test the hypothesis that Notch and EGFR receptors function as cooperating oncoproteins required for BLBC cell survival. Specific Aim 1. To examine the effect of combined Notch-EGFR pathway inhibition on tumor-initiating cell survival in BLBC tumors. We will assess the relative ability of combined pathway inhibition to eradicate the tumor-initiating and more differentiated fractions of breast cancer cells. We will also begin to determine the efficacy of combined pathway inhibition against primary human BLBC tumors using a novel technology wherein these cancers are grafted into immunodeficient mice, and investigate the requirement for functional Notch- EGFR pathways in a broader panel of BLBC cell lines that show variable EGFR expression. Specific Aim 2. To determine the ability of partial Notch pathway inhibition to induce synthetic lethality when combined with EGFR blockade in BLBC cells. Partial pathway inhibition will be achieved through two strategies, dose modifications of GSI and receptor-specific knockdowns. In combination with EGFR blockade, we will examine the extent to which these approaches induce cell death and how they affect the viability of tumor-initiating and differentiated cells. Conversely, through forced expression of activated receptors, the ability of individual receptors to suppress cell death and expand the tumor-initiating population in the presence of GSI and EGFR inhibitor treatment will be measured.