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

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。这种致命性部分是由于肿瘤数量的增加- 在BLBC中测量的起始（或干）细胞。表皮生长因子受体（EGFR）通常是 在这些肿瘤中表达，但针对该受体的抑制剂显示出可测量但有限的活性， 乳腺癌临床试验。相反，EGFR是多种其他实体瘤类型的有效靶点。甚至 尽管在乳腺癌中使用EGFR抑制剂的临床试验仍在继续，但这些药物在乳腺癌中缺乏疗效， 疾病仍然知之甚少。BLBC还显示Notch受体的频繁超活化， 在乳腺中致癌。这四个家族成员通常在乳腺癌细胞中共表达 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， γ分泌酶复合物，其抑制剂（GSI）正在临床试验中。这些药物全面抑制 所有四种受体，并可产生显着的毒性，激发研究毒性较小的方法， 阻断Notch信号。幸运的是，许多Notch依赖性过程对基因剂量敏感， 受体特异性因此，完全和泛受体抑制可能不是所有治疗药物所必需的。 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 (Dong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： Notch和EGFR受体作为BLBC细胞存活所需的协同癌蛋白发挥作用。 具体目标1。检查Notch-EGFR途径联合抑制对肿瘤启动的影响 BLBC肿瘤中的细胞存活率。我们将评估联合途径抑制根除 乳腺癌细胞的肿瘤起始和更分化的部分。我们还将开始确定 使用新技术的联合途径抑制对原发性人BLBC肿瘤的功效，其中 将这些癌症移植到免疫缺陷小鼠中，并研究功能性Notch的需求， 在一组更广泛的BLBC细胞系中显示EGFR表达可变的EGFR通路。具体目标2。 确定部分Notch途径抑制诱导合成致死率的能力， 在BLBC细胞中结合EGFR阻断。部分途径抑制将通过两个 策略、GSI的剂量调整和受体特异性敲减。与EGFR阻断剂联合， 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活力。 肿瘤起始细胞和分化细胞。相反，通过激活受体的强制表达， 单个受体抑制细胞死亡并在存在肿瘤细胞的情况下扩增肿瘤起始群体的能力 将测量GSI和EGFR抑制剂治疗。

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.