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

描述（由申请人提供）：基底样乳腺癌（BLBC，或三阴性）是一种高度致命的疾病形式，缺乏有效的治疗方法。这种致死性被认为部分是由于在BLBC中测量的肿瘤起始（或干）细胞数量增加。表皮生长因子受体（EGFR）通常在这些肿瘤中表达，但针对该受体的抑制剂在乳腺癌临床试验中显示出可测量但有限的活性。相反，EGFR是多种其他实体瘤类型的有效靶点。尽管使用EGFR抑制剂的临床试验仍在乳腺癌中进行，但这些药物在这种疾病中缺乏疗效仍然知之甚少。BLBC还显示Notch受体的频繁超活化，Notch受体在乳腺中是致癌的。这四个家族成员通常在乳腺癌细胞中共同表达，它们可以发挥相反或冗余的作用。它们的激活依赖于γ分泌酶复合物的酶活性，其抑制剂（GSI）正在临床试验中。这些药物在全球范围内抑制所有四种受体，并可能产生显著的毒性，从而促使人们研究毒性较小的方法来阻断Notch信号传导。幸运的是，许多Notch依赖性过程对基因剂量敏感，并且是受体特异性的。因此，对于涉及Notch受体的所有治疗应用，完全和泛受体抑制可能不是必需的。 我们最近报道了Notch和EGFR途径之间的合成致死关系（Dong等人，癌症研究，2010年7月）。通过以下目的，我们将测试Notch和EGFR受体作为BLBC细胞存活所需的协同癌蛋白发挥作用的假设。具体目标1。检测联合Notch-EGFR途径抑制对BLBC肿瘤中肿瘤起始细胞存活的影响。我们将评估联合途径抑制根除乳腺癌细胞的肿瘤起始部分和更分化部分的相对能力。我们还将开始确定联合途径抑制对原发性人BLBC肿瘤的疗效，使用一种新的技术，其中这些癌症被移植到免疫缺陷小鼠中，并在更广泛的BLBC细胞系中研究功能性Notch-EGFR途径的需求，这些细胞系显示可变的EGFR表达。具体目标2。确定在BLBC细胞中，部分Notch途径抑制与EGFR阻断联合诱导合成致死的能力。部分途径抑制将通过两种策略实现，GSI的剂量调整和受体特异性敲低。结合EGFR阻断，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肿瘤起始细胞和分化细胞的活力。相反，通过活化受体的强制表达，将测量在GSI和EGFR抑制剂治疗存在下个体受体抑制细胞死亡和扩增肿瘤起始群体的能力。 公共卫生相关性：这项研究的目的是为在基底细胞样乳腺癌中使用Notch和EGFR抑制剂的临床试验奠定基础。具体而言，这项工作的结果将有助于指导Notch-EGFR联合抑制早期或晚期乳腺癌的临床试验设计。它们还具有通过鉴定对组合途径抑制敏感的相关生物标志物来促进患者选择的潜力。

DESCRIPTION (provided by applicant): 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 thought 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. PUBLIC HEALTH RELEVANCE: The goal of this research is to lay the foundation for a clinical trial using Notch and EGFR inhibitors in basal-like breast cancer. Specifically, the results of this work will help direct the clinical trial design of combined Notch-EGFR inhibition towards early or late stage breast cancer. They also have the potential to facilitate patient selection through the identification of relevant biomarkers of sensitivity to combined pathway inhibition.