VEGF Signaling in Mammary Tumorigenesis

描述(申请人提供)：这项建议将检验一个新的假设，即血管内皮生长因子/神经匹林-2(NRP2)信号与致癌刺激合作，通过增强肿瘤启动细胞的功能来驱动乳腺癌的形成，特别是三阴性肿瘤的形成。可能的机制是，VEGF/NRP2信号促进整合素？6？1/粘着斑激酶(FAK)介导的Hedgehog效应Gli1的诱导，而Hedgehog效应Gli1通过促进Bmi-1和其他靶基因的转录激活而发挥肿瘤起始细胞的功能。为了验证这一机制，提出了三个具体目标。第一个目标将确定NRP2在三阴性肿瘤的形成、维持和治疗中的作用，并解决关于血管内皮生长因子/NRP2信号增强肿瘤起始细胞功能的假设。这一目标将涉及转基因和原位小鼠模型，以及 从新切除的肿瘤中分离出的肿瘤细胞。第二个目的是基于NRP2与整合素β6？1(CD49f)特异性相互作用的发现，整合素β6？1整合素是肿瘤起始细胞的功能标志。这一目标将检验一种假说，即VEGF/NRP2信号通过FAK依赖的机制参与BMI-1的调节，BMI-1是一种多梳状转录抑制因子，对肿瘤干细胞的功能至关重要。第三个目的是确定VEGF/NRP2信号促进肿瘤起始细胞中Hedgehog通路的激活，并且VEGF/NRP2在肿瘤发生中的作用依赖于Gli1。更具体地说，这一假设将被评估，即VEGF/NRP2信号诱导肿瘤起始细胞中Gli1和Gli1介导的BMI-1表达，并且NRP2的丢失可以通过Gli1表达来补偿。这项工作将为VEGF/NRP2信号、整合素？6？1和FAK如何与Hedgehog通路相互作用以调节肿瘤起始细胞的功能提供一个完整的机制。在翻译水平上，这些研究将强调将NRP2靶向肿瘤细胞用于治疗侵袭性乳腺癌的可行性。这个问题是及时的，因为FDA建议停止使用阿瓦斯丁(贝伐单抗)治疗乳腺癌，因为它没有被证明有效。阿瓦斯丁不能抑制VEGF/NRP2的相互作用。这些发现加强了直接靶向NRP2的理论基础，特别是考虑到NRP2在肿瘤启动细胞中的优先表达和关键功能。 公共卫生相关性：这项提案试图了解乳腺癌形成和发展的机制。我们建议研究与癌基因协同作用的分子网络，以启动乳腺肿瘤的形成，并评估这些分子是否为治疗这些肿瘤的潜在靶点。

DESCRIPTION (provided by applicant): This proposal will examine the novel hypothesis that VEGF/Neuropilin-2 (NRP2) signaling cooperates with oncogenic stimuli to drive the formation of mammary cancers, especially triple-negative tumors, by potentiating the function of tumor-initiating cells. The mechanism proposed is that VEGF/NRP2 signaling promotes integrin ?6?1/focal adhesion kinase (FAK)-mediated induction of the Hedgehog effector Gli1, which contributes to the function of tumor initiating cells by promoting the transcriptional activation o Bmi-1 and other target genes. To validate this mechanism, three specific aims are proposed. The first aim will define the role of NRP2 in the formation, maintenance and therapy of triple-negative tumors, and address the hypothesis that VEGF/NRP2 signaling enhances the function of tumor initiating cells. This aim will involve transgenic and orthotopic mouse models, as well as tumor cells isolated from freshly resected tumors. The second aim is based on the finding that NRP2 interacts specifically with the ?6?1 integrin (CD49f), which is a functional marker of tumor initiating cells. This aim will examine the hypothesis that VEGF/NRP2 signaling contributes to the regulation of Bmi-1, a polycomb group transcriptional repressor important for the function of tumor stem cells, by a FAK- dependent mechanism. The third aim will establish that VEGF/NRP2 signaling promotes activation of the Hedgehog pathway in tumor initiating cells, and that the contribution of VEGF/NRP2 to tumorigenesis is dependent on Gli1. More specifically, the hypothesis will be evaluated that VEGF/NRP2 signaling induces Gli1 and Gli1-mediated Bmi-1 expression in tumor initiating cells and that loss of NRP2 can be compensated for by Gli1 expression. The proposed work will provide an integrated mechanism for how VEGF/NRP2 signaling, integrin ?6?1 and FAK interface with the Hedgehog pathway to regulate the function of tumor initiating cells. At a translational level, these studies will highlight the feasibility of targeting NRP2 on tumor cells for therapy of aggressive breast cancers. This issue is timely because the FDA has recommended discontinuing the use of Avastin (bevacizumab), which does not inhibit the VEGF/NRP2 interaction, for treating breast cancer because it has not been shown to be effective. These findings strengthen the rationale for targeting NRP2 directly especially given the preferential expression and critical function of NRP2 in tumor-initiating cell. PUBLIC HEALTH RELEVANCE: This proposal seeks to understand mechanisms that contribute to the formation and growth of breast cancers. We propose to investigate a network of molecules that cooperate with oncogenes to initiate the formation of breast tumors, and evaluate whether these molecules are potential targets for the treatment of these tumors.