The lymph node microenvionment in tumor metastasis

描述(申请人提供)：淋巴结是大多数实体肿瘤的初始转移部位，包括乳腺癌和黑色素瘤。从淋巴结转移到远处转移的临床记录表明，切除携带肿瘤的、引流的淋巴结可以改善许多肿瘤类型的临床预后。令人惊讶的是，人们对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，原发肿瘤通过诱导整合素-4？1和血管内皮生长因子-R3介导的淋巴管生成，而不是通过诱导淋巴管生成，从而使引流和远端淋巴结预调节肿瘤转移。然后，肿瘤转移到淋巴结需要淋巴结淋巴管生成。选择性抑制淋巴结中的整合素？4？1或血管内皮生长因子-R3，可阻断淋巴管生成，防止肿瘤向淋巴结转移。相反，注射血管内皮生长因子-C刺激淋巴结淋巴管生成可加速受刺激淋巴结的转移。当肿瘤细胞直接注入淋巴系统时，对正常小鼠淋巴结淋巴管生成的刺激也促进了肿瘤细胞归巢和渗入刺激的淋巴结，即使在没有原发肿瘤的情况下也是如此。这种归巢可被整合素？4？1或血管内皮生长因子-R3拮抗剂抑制淋巴管生成所阻断。这些研究表明，淋巴结淋巴管生成通过促进肿瘤细胞的黏附和渗入而直接促进淋巴转移。为了进一步了解淋巴结微环境在肿瘤转移中的作用，我们将验证以下假设：整合素？4？1介导的信号通过Paxlin促进淋巴管内皮细胞迁移，整合素？4？1通过蛋白激酶A、Raf和caspase 8介导的信号促进淋巴管内皮细胞在淋巴管生成和随后的肿瘤转移过程中存活；淋巴结淋巴管内皮细胞通过表达关键的肿瘤细胞趋化因子如CCL21以及肿瘤细胞黏附配体/受体，如整合素？4？1、VCAM和E-选择素，促进肿瘤细胞的归巢、黏附和外渗；淋巴结内的炎性介质和骨髓来源细胞在促进肿瘤转移中发挥作用。本研究的目的是：1)确定整合素β4？1-Paxlin相互作用在淋巴管内皮细胞迁移中的作用；2)确定蛋白激酶A、Raf和caspase 8在整合素？4？1介导的淋巴管生成过程中的作用；3)评价特定的趋化因子和黏附受体在肿瘤转移过程中促进肿瘤细胞吸引和黏附淋巴管内皮细胞的作用；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，我们关于淋巴结淋巴管生成在肿瘤转移中的作用的初步发现表明，检测淋巴结淋巴管生成可能有助于癌症诊断，因为它有助于预测尚未形成的转移灶的位置。这些结果还表明，淋巴结淋巴管生成的抑制物可能在癌症治疗中发挥重要作用。这项申请中提出的研究可能导致开发和测试新的药物来诊断和预防或治疗转移性癌症。

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.