Modulation of VEGF signaling by extracellular matrix and neuropilins: impact on tumor progression, angiogenesis and anti-angiogenic therapy in prostate and pancreatic cancer

人们普遍认为，肿瘤微环境在调节肿瘤的扩张和转移过程中起着积极的作用。基质分子作为肿瘤细胞迁移的底物，也为新血管床的成熟和稳定提供分化线索。此外，通过与特定生长因子的结合和相互作用，细胞外基质(ECM)提供了生长调节信号的储存库。Iruela-Arispe教授以前的工作表明，基质结合的血管内皮生长因子(VEGF)容易被蛋白质降解，释放一个可溶性受体酪氨酸激酶激活片段(N-末端)和一个较小的C-末端基质结合肽。有趣的是，这种C端的血管内皮生长因子结合并激活肿瘤和血管内皮细胞中的神经粘连蛋白-1(Nrp1)，从而可能促进肿瘤的生长和转移。这项拟议的项目将检验这样一个假设：对血管内皮生长因子进行细胞外处理会产生生物活性多肽，这些活性多肽继续支持血管生成生长，更重要的是介导肿瘤的进展。此外，这种C-末端的血管内皮生长因子构成了一个未开发的生长因子储存库，不受可用的血管内皮生长因子拮抗剂贝伐单抗的影响。为了评估前面的假设，将使用前列腺癌和胰腺癌的模型和人体样本，两者都代表具有强烈间质/ECM反应的肿瘤实体。体外实验将探讨C-端血管内皮生长因子多肽的血管生成和肿瘤生物学作用，并揭示与C-端血管内皮生长因子结合后激活的Nrp1下游的分子信号通路。此外，在高表达C-末端血管内皮生长因子的前列腺癌和胰腺癌的异种移植模型中，将确定Nrp1对肿瘤生长、血管生成进展和转移扩张的影响。此外，C-末端和全长血管内皮生长因子的存在将在人类前列腺癌和胰腺肿瘤的样本中被确定，其水平与肿瘤进展和临床随访相关。预计该项目的实施将在调节前列腺癌和胰腺癌血管生成扩张的ECM相互作用的背景下，扩展和阐明由血管内皮生长因子驱动的信号通路。这可能揭示目前临床上贝伐单抗应答率低的原因，为更好地对现有的血管内皮生长因子指导的治疗方案的患者进行分层提供一条途径，并有可能为未来的治疗确定血管内皮生长因子信号的新靶点。

It is generally accepted that the tumor microenvironment plays an active role in regulating expansion and metastatic progression. Matrix molecules serve as substrate for migration of tumor cells, as well as, provide differentiation cues for the maturation and stabilization of new vascular beds. In addition, through binding and interactions with specific growth factors, the extracellular matrix (ECM) offers a reservoir of growth regulatory signals. Previous work by Prof. Iruela-Arispe indicates that matrix-bound vascular endothelial growth factor (VEGF) is susceptible to proteolysis releasing a soluble receptor tyrosine kinase-activating fragment (N-terminal) and a smaller C-terminal matrix-bound peptide. Interestingly, this C-terminal VEGF peptide binds and activates neuropilin-1 (NRP1) in tumor and in endothelial cells, thereby possibly facilitating tumor growth and metastasis. The proposed project will test the hypothesis that: ¿Extracellular processing of VEGF results in the generation of bioactive peptides that continue to support angiogenic growth and more importantly mediate tumor progression. Furthermore, this C-terminal VEGF constitutes an untapped reservoir of growth factor that is not affected by the available VEGF-antagonist bevacizumab¿. For evaluation of the preceding hypothesis, models and human samples of prostate and pancreatic cancer will be applied, both representing tumor entities with a strong stroma/ECM reaction. In vitro experiments will address the angiogenic and tumor biological role of the C-terminal VEGF peptide and reveal the molecular signaling pathways that are activated downstream of NRP1 upon binding to C-terminal VEGF. Furthermore the impact of NRP1 blockade on tumor growth, angiogenic progression and metastatic expansion will be determined in xenograft models of prostate and pancreatic cancer overexpressing C-terminal VEGF. In addition, the presence of C-terminal and full-length VEGF will be determined in samples of human prostate and pancreatic tumors and its levels correlated with tumor progression and clinical follow-up. It is anticipated the execution of this project will expand and clarify the signaling pathways driven by VEGF in the context of ECM interactions that regulate angiogenic expansion in prostate and pancreatic cancer. This may reveal causes of present low response rates to bevacizumab in the clinic, offer a path for better stratification of patients for existing VEGF-directed therapeutic options, and potentially identifies new targets of VEGF signaling for future therapies.