VEGF blockade and alternative angiogenic pathways in neuroblastoma

描述(申请人提供)：大多数在婴儿期后被诊断为神经母细胞瘤的儿童预后很差，尽管进行了密集的治疗，但很少能存活下来。迫切需要新的治疗方法。最近，阻止血管生长(血管生成)进入肿瘤的药物已经在成人中得到临床验证，可能会为这些患者带来希望。一个有效的抗血管生成靶点是血管内皮生长因子(VEGF)，它在几乎所有人类癌症中都有表达，包括神经母细胞瘤。血管内皮生长因子可与血管内皮生长因子受体-1(VEGFR1)和血管内皮生长因子受体2(VEGFR2)结合，但已有的研究表明，血管内皮生长因子主要通过VEGFR2刺激血管生成。因此，拮抗血管内皮生长因子/血管内皮生长因子2信号通路已成为抗实验性和人类肿瘤的主要途径。我们先前已经证明，阻断VEGF和VEGFR2的药物可以减少实验性早期神经母细胞瘤的血管生成和生长，这表明这种治疗方法可能对患有这种癌症的儿童有用。然而，我们的实验也表明，这些肿瘤最终会对血管内皮生长因子/血管内皮生长因子R2的阻断产生抵抗力。这些结果表明，当VEGF/VEGFR2信号通路被阻断时，另一种机制可能支持神经母细胞瘤的血管生成。在这些研究中，我们将确定VEGFR1和Notch通路在神经母细胞瘤肿瘤血管中的激活是否构成了这样一种选择。VEGFR1和Notch蛋白都被认为在疾病状态下对血管生成有贡献。此外，这两条通路中的每一条都可能刺激另一条通路。我们的初步实验支持这一概念，并证明了VEGFR1和Notch在神经母细胞瘤肿瘤的血管中激活，这些血管对抗血管内皮生长因子治疗具有抵抗力。这些观察结果使我们提出，神经母细胞瘤补偿抗血管内皮生长因子治疗的一个机制是通过激活血管系统中的这些替代通路来保护肿瘤的血液供应。利用我们特征良好的异种移植模型，在该模型中，NB细胞系被移植到裸鼠的肾脏中，以及NB的TH-MYCN遗传模型，在目标1中，我们将确定VEGFR1信号是否可以从VEGFR2阻断中拯救肿瘤血管；在目标2中，我们将确定血管中Notch的激活是否促进肿瘤对VEGFR2阻断的抵抗力。我们在这些研究中的总体目标是通过识别并克服这些肿瘤逃避血管内皮生长因子抑制的机制来开发有效的治疗神经母细胞瘤的新方法。公共卫生相关性：患有转移性神经母细胞瘤的儿童预后很差，尽管接受了强化治疗，但只有30-35%的存活率。阻止血管生长(血管生成)进入肿瘤的药物已经在成年人身上得到临床验证，可能会为这些患者带来希望。我们在这些研究中的总体目标是通过识别并克服这些肿瘤逃避血管内皮生长因子阻断治疗的机制，为神经母细胞瘤儿童开发一种有效的抗血管生成疗法。

DESCRIPTION (provided by applicant): Most children diagnosed with neuroblastoma after infancy have a poor prognosis, and few will survive despite intensive therapy. New treatments are urgently needed. Recently, drugs which block blood vessel growth (angiogenesis) into tumors have been clinically validated in adults, and may offer promise for these patients. One validated anti-angiogenic target is vascular endothelial growth factor (VEGF), which is expressed in essentially all human cancers, including neuroblastoma. VEGF can bind to both VEGF-receptor-1 (VEGFR1) and VEGFR2, but much prior work indicates that VEGF stimulates angiogenesis primarily via VEGFR2. Therefore, antagonism of VEGF/VEGFR2 signaling has been the principal approach tested against experimental and human cancers. We have previously demonstrated that drugs which block VEGF and VEGFR2 lessen angiogenesis and growth of experimental early-stage neuroblastoma tumors, suggesting that this therapy may be therapeutically useful in children with this cancer. However, our experiments also demonstrate that these tumors ultimately become resistant to VEGF/VEGFR2 blockade. These results suggest that an alternative mechanism may support angiogenesis in neuroblastoma when VEGF/ VEGFR2 signaling is blocked. In these studies, we will determine if activation of VEGFR1 and Notch pathways in neuroblastoma tumor vessels constitutes one such alternative. Both VEGFR1 and Notch proteins are known to contribute to angiogenesis in disease states. In addition, activation of each of these two pathways may stimulate the other. Our initial experiments support this concept, and demonstrate VEGFR1 and Notch activation in the vessels of neuroblastoma tumors that are resistant to anti-VEGF treatment. These observations lead us to propose that one mechanism by which neuroblastomas compensate for anti-VEGF treatment is to preserve tumor blood supply by activating these alternative pathways in vasculature. Utilizing our well-characterized xenograft model, in which NB cell lines are implanted in the kidney of athymic mice, and the TH-MYCN genetic model of NB, we will, in Aim 1, determine whether VEGFR1 signaling can rescue tumor vasculature from VEGFR2 blockade; and in Aim 2, we will determine whether Notch activation in vessels promotes tumor resistance to VEGFR2 blockade. Our overall goal in these studies is to develop effective new treatments children with neuroblastoma by identifying and then overcoming the mechanisms by which these tumors evade inhibition of VEGF. PUBLIC HEALTH RELEVANCE: Children with metastatic neuroblastoma have a poor prognosis with only 30-35% surviving despite intensive therapy. Drugs which block blood vessel growth (angiogenesis) into tumors have been clinically validated in adults, and may offer promise for these patients. Our overall goal in these studies is to develop an effective anti-angiogenic therapy for children with neuroblastoma by identifying and then overcoming the mechanisms by which these tumors evade VEGF-blocking therapies.