The Function of EGFL6 in Ovarian Cancer Cell Biology, Tumor Initiation, and Therapy

摘要：卵巢癌是一种致命性疾病，死亡率：发病率居所有癌症的第3位。 高级别浆液性癌(HGSC)是我们仅见过的最具侵袭性的卵巢癌亚型 患者存活率很少或没有改善。因此，有一种明显未得到满足的需求，即确定和开发新的 HGSC的治疗靶点。我们最近发现，干细胞调节因子EGFL6是一种关键的 ALDH HGSC肿瘤干细胞(CSC)的调节因子，与治疗耐药相关。EGFL6 促进ALDH HGSC的迁移和不对称分裂，而EGFL6在HGSC中被敲除 癌细胞会导致小鼠失去干性，并显著减少肿瘤的生长。因此，我们 假设EGFL6是HGSC的一个有前途的治疗靶点。了解治疗潜力 EGFl6导向的药物将需要更多地了解EGFl6在卵巢癌细胞生物学中的S角色。这个 癌细胞上的EGFL6受体尚不清楚。由于配体/受体信号的中断已被证明是非常重要的 在其他途径中有效的治疗机制，我们建议SA1：识别EGFL6受体和 描述EGFL6信号复合体的特征。除了调节HGSC CSC外，EGFL6还是一个重要的 正常干细胞的调节因子。突变的正常干细胞被认为是癌症启动细胞的来源。我们 假设EGFL6作为正常干细胞和HGSC CSC的调节因子可能是卵巢发育所必需的 癌症的发生和生长。因此，我们建议SA2：评估EGFL6在肿瘤发生中的作用。 我们将使用一种新的遗传性HGSC小鼠模型来评估(I)EGFL6基因敲除的影响或(Ii)影响 EGFL6中和抗体对HGSC启动和生长的影响。我们已经证明，小鼠的EGFL6 我们研制的中和抗体在小鼠体内对人癌细胞具有良好的治疗活性。 为了将这些研究转化为临床试验，我们开发了一组人源化的EGFL6阻断抗体 (hEGFL6-Ab)。我们建议SA3：验证hEGFL6-Ab，并确定患者的 肿瘤可以预测对抗EGFL6治疗的反应。使用体外实验和一种新的人源化基质- 患者来源的异种移植模型，我们将确定最有效的hEGFL6-Ab。我们假设病人 其肿瘤细胞表达EGFL6和/或表现出EGFL6途径激活将对此反应最大 心理治疗。利用hEGFL6-Ab反应性和非反应性肿瘤的表达分析，我们建议 生成一个算法来预测患者对抗EGFL6治疗的反应。 影响：这些研究将1)确定卵巢癌细胞中EGFL6信号级联反应，2)确定 HGSC启动和生长过程中对癌细胞EGFL6表达的要求，以及3)创建和验证 新的人源化抗EGFL6-Ab和伴随的识别/分层患者的算法 大多数人对这种治疗都有反应。最终，该项目将生产出一种很有前途的治疗剂。 定位于卵巢癌的首个人类临床试验。

ABSTRACT: Ovarian cancer is a deadly disease with the 3rd-highest mortality:incidence ratio of all cancers. High-grade serous cancer (HGSC) is the most aggressive ovarian cancer subtype for which we have seen only little or no improvement in patient survival. Thus there is a clear unmet need to identify and develop new therapeutic targets in HGSC. We recently showed that the stem cell regulatory factor EGFL6 is a critical regulator of ALDH+ HGSC cancer stem-like cells (CSC), cells associated with therapeutic resistance. EGFL6 promotes the migration and asymmetric division of ALDH+HGSC CSC, while EGFL6 knockdown in HGSC cancer cells leads to loss of stemness and dramatically reduced tumor growth in mice. We therefore hypothesize that EGFL6 is a promising therapeutic target for HGSC. Understanding the therapeutic potential EGFL6-directed agents will require greater understanding of EGFL6's roles in ovarian cancer cell biology. The EGFL6 receptor on cancer cells is unknown. As disruption of ligand/receptor signaling has proven a very effective therapeutic mechanism in other pathways, we propose SA1: To Identify the EGFL6 receptor and characterize the EGFL6 signaling complex. In addition to regulating HGSC CSC, EGFL6 is an important regulator of normal stem cells. Mutated normal stem cells are a proposed source of cancer initiating cells. We hypothesize EGFL6 as a regulator of both normal stem cells and HGSC CSC may be essential for ovarian cancer initiation and growth. We therefore propose SA2: To evaluate the role of EGFL6 in cancer initiation. We will use a novel genetic mouse model of HGSC to assess (i) the impact of EGFL6 knockout or (ii) the effect of EGFL6 neutralizing antibodies on HGSC initiation and growth. We have shown that the murine EGFL6 neutralizing antibody we developed has excellent therapeutic activity versus human cancer cell lines in mice. To translate these studies into clinical trials we developed a a panel of humanized EGFL6-blocking antibodies (hEGFL6-Ab). We propose SA3: To validate hEGFL6-Ab and determine if EGFL6 expression by patients' tumors predicts response to anti-EGFL6 therapy. Using in vitro assays and a novel humanized stroma- patient derived xenograft model we will identify the most effective hEGFL6-Ab. We hypothesize that patients whose tumor cells express EGFL6 and/or exhibit EGFL6 pathway activation will be most responsive to such therapy. Using expression analysis of hEGFL6-Ab responsive and non-responsive tumors, we propose to generate an algorithm to predict patients' responses to anti-EGFL6 therapy. IMPACT: These studies will 1) define the EGFL6 signaling cascade in ovarian cancer cells, 2) define requirements for cancer cell EGFL6 expression in HGSC initiation and growth, and 3) create and validate a novel humanized anti-EGFL6-Ab and an accompanying algorithm that identifies/stratifies patients who are most apt to respond to such therapy. Ultimately, the project will produce a promising therapeutic agent positioned for first-in-human clinical trials in ovarian cancer.