The lymph node microenvionment in tumor metastasis

描述（由申请人提供）：淋巴结是大多数实体瘤（包括乳腺癌和黑色素瘤）转移的起始部位。临床记录表明，从淋巴结转移进展为远处转移，因为切除肿瘤，引流淋巴结可以改善许多肿瘤类型的临床结局。令人惊讶的是，淋巴结微环境中可能导致肿瘤转移的因素知之甚少。我们的初步数据表明，原发性肿瘤的先决条件引流以及远端淋巴结肿瘤转移诱导整合素？四个？1和VEGF-R3介导的淋巴管生成，而不是淋巴结血管生成。淋巴结淋巴管生成是肿瘤转移到淋巴结所必需的。选择性抑制整合素？四个？1或VEGF-R3在淋巴结中阻断淋巴结淋巴管生成并防止肿瘤转移到淋巴结。相比之下，通过注射VEGF-C刺激淋巴结淋巴管生成加速了向受刺激淋巴结的转移。在正常小鼠中刺激淋巴结淋巴管生成也促进肿瘤细胞归巢和外渗到刺激的淋巴结中，即使在没有原发性肿瘤的情况下，当肿瘤细胞直接注射到淋巴系统中时。这种归巢可以通过用整合素拮抗剂抑制淋巴管生成来阻断。四个？1或VEGF-R3。这些研究表明，淋巴结淋巴管生成通过增强肿瘤细胞粘附和外渗到淋巴结中直接促进淋巴结转移。为了进一步了解淋巴结微环境在肿瘤转移中的作用，我们将检验整合素？四个？1介导的信号通过桩蛋白促进淋巴管内皮细胞迁移和整合素？四个？1介导的信号传导通过蛋白激酶A，Raf和半胱天冬酶8促进淋巴管生成和随后的肿瘤转移过程中的淋巴管内皮细胞的存活;淋巴结淋巴管内皮细胞通过表达关键的肿瘤细胞化学引诱物如CCL 21以及肿瘤细胞粘附配体/受体，如整合素？四个？1，VCAM和E-选择素;以及淋巴结内的炎症介质和骨髓来源的细胞在促进肿瘤转移中起作用。这项建议的目的是：1）确定整合素的作用？四个？1-2）确定蛋白激酶A、Raf和caspase 8在整合素？四个？1介导的淋巴管内皮细胞存活; 3）评估特异性趋化因子和粘附受体在肿瘤转移过程中促进肿瘤细胞与淋巴管内皮细胞的吸引和粘附中的作用; 4）确定炎症介质和细胞在淋巴结淋巴管生成和转移中的作用。重要的是，我们对淋巴结淋巴管生成在肿瘤转移中的作用的初步研究结果表明，淋巴结淋巴管生成的检测可能有助于预测尚未形成的转移灶的部位，从而促进癌症诊断。这些结果还表明，淋巴结淋巴管生成抑制剂可能在癌症治疗中发挥重要作用。本申请中提出的研究可能导致诊断和预防或治疗转移性癌症的新试剂的开发和测试。

DESCRIPTION (provided by applicant): Lymph nodes are the initial sites of metastasis for most solid tumors, including breast carcinoma and melanoma. Progression from lymph node metastases to distant metastases is suggested by the clinical record as excision of tumor-bearing, draining lymph nodes can improve clinical outcome for many tumor types. Surprisingly, little is known about the factors in the lymph node microenvironment that may contribute to tumor metastasis. Our preliminary data show that primary tumors precondition draining as well as distal lymph nodes for tumor metastasis by inducing integrin ?4?1 and VEGF-R3-mediated lymphangiogenesis but not hemangiogenesis in lymph nodes. Lymph node lymphangiogenesis is then required for tumor metastasis to lymph nodes. Selective inhibition of integrin ?4?1 or VEGF-R3 in lymph nodes blocks lymph node lymphangiogenesis and prevents tumor metastasis to lymph nodes. In contrast, stimulation of lymph node lymphangiogenesis by injections of VEGF-C accelerates metastasis to stimulated lymph nodes. Stimulation of lymph node lymphangiogenesis in normal mice also promoted tumor cell homing to and extravasation into stimulated lymph nodes even in the absence of a primary tumor when tumor cells were injected directly into the lymphatic system. This homing could be blocked by suppressing lymphangiogenesis with antagonists of integrin ?4?1 or VEGF-R3. These studies suggest that lymph node lymphangiogenesis directly promotes lymph node metastasis by enhancing tumor cell adhesion and extravasation into the node. To further our understanding of the role of the lymph node microenvironment in tumor metastasis, we will test the hypotheses that integrin ?4?1 mediated signaling via paxillin promotes lymphatic endothelial cell migration and that integrin ?4?1 mediated signaling via Protein Kinase A, Raf and caspase 8 promote lymphatic endothelial cell survival during lymphangiogenesis and subsequent tumor metastasis; that lymph node lymphatic endothelium promotes the homing, adhesion and extravasation of tumor cells by expressing key tumor cell chemoattractants such as CCL21 as well as tumor cell adhesion ligands/receptors, such as integrin ?4?1, VCAM and E-Selectin; and that inflammatory mediators and bone marrow derived cells within the lymph node play roles in promoting tumor metastasis. The aims of this proposal are: 1) To determine the role of integrin ?4?1-paxillin interaction during lymphatic endothelial cell migration; 2) To determine the roles of protein kinase A, Raf and caspase 8 in integrin ?4?1 mediated lymphatic endothelial cell survival during lymphangiogenesis; 3) To evaluate the roles of specific chemokine and adhesion receptors in promoting tumor cell attraction and adhesion to lymphatic endothelium during tumor metastases; 4) To determine the contributions of inflammatory mediators and cells in lymph node lymphangiogenesis and metastasis. Importantly, our preliminary findings on the role of lymph node lymphangiogenesis in tumor metastasis indicate that detection of lymph node lymphangiogenesis may facilitate cancer diagnosis by helping to predict the sites of metastatic lesions yet to form. These results also suggest that inhibitors of lymph node lymphangiogenesis may play important roles in cancer therapeutics. The studies proposed in this application are likely to lead to the development and testing of new agents to diagnose and prevent or treat metastatic cancer.