The Six1/Eya Transcriptional complex as a mediator of lymphangiogenesis and lymph

描述（由申请人提供）：乳腺癌是女性癌症相关死亡的第二大原因，死亡是由于肿瘤细胞转移到远处器官。癌细胞的扩散是通过血管进行的，对乳腺癌来说尤其重要的是通过淋巴系统。尽管肿瘤经血液播散已被广泛研究，但导致淋巴播散的机制尚不清楚。本研究的重点是通过Six1/Eya2转录复合体控制VEGF-C水平，了解淋巴管生成和乳腺肿瘤转移扩散的新机制。需要验证的假设是Six1在乳腺癌中的过表达导致VEGF-C的上调，导致淋巴管生成增加，并增强肿瘤细胞的早期转移，包括淋巴传播。Six1激活VEGF-C和刺激淋巴转移的能力依赖于它与Eya2磷酸酶辅助因子的相互作用，以及Eya2的酶活性。如果这一假设是正确的，它将为乳腺癌转移机制提供重要的见解，并为通过抑制Six1/Eya相互作用和/或Eya2磷酸酶活性的“可药物”方法干扰Six1/Eya2功能来治疗淋巴转移的新策略提供理论依据。为了解决这一假设，我们将：1)验证VEGF-C是Six1/Eya2的直接转录靶点的假设，以及Six1和Eya2与VEGF-C和人类乳腺癌淋巴管生成相关的假设；2)利用小鼠体内转移模型验证VEGF-C是six1诱导的淋巴管生成和转移的关键介质的假设；3)在体内验证Six1诱导的淋巴管生成和转移需要Eya2的假设，重点研究Six1与Eya2的相互作用，以及Eya2磷酸酶活性的作用。靶向Six1/Eya2有可能在乳腺癌的早期（在本提案中研究）和晚期抑制乳腺癌。由于Six1/Eya2发育调节因子在大多数正常成人组织中缺乏表达，以及它们在癌症中的再表达，靶向该复合物的治疗药物应能抑制淋巴管生成和转移，且副作用有限。因此Six1/Eya2复合体是一种理想的乳腺癌治疗靶点，本研究将为该复合体的最终靶向治疗奠定基础。

DESCRIPTION (provided by applicant): Breast cancer is the second leading cause of cancer-related deaths among women, with deaths occurring due to the metastatic spread of tumor cells to distant organs. Spread of cancer cells occurs via blood vessels or, particularly important for breast cancer, via the lymphatic system. Although tumor dissemination via the blood has been extensively studied, the mechanisms that lead to lymphatic dissemination are poorly understood. This proposal focuses on understanding a new mechanism of lymphangiogenesis and breast tumor metastatic spread, via control of VEGF-C levels by the Six1/Eya2 transcriptional complex. The hypothesis to be tested is that Six1 overexpression in breast cancers leads to upregulation of VEGF-C, resulting in increased lymphangiogenesis and enhancing the early stages of metastasis including lymphatic dissemination of tumor cells. The ability of Six1 to activate VEGF-C and stimulate lymphatic metastasis is dependent on its interaction with the Eya2 phosphatase co-factor, and on the enzymatic activity of Eya2. If this hypothesis is correct, it will provide important insights into the mechanism of breast cancer metastasis and provide a rationale for a new strategy to therapeutically target lymphatic metastasis by interfering with Six1/Eya2 function through the "druggable" approaches of inhibiting Six1/Eya interaction and/or Eya2 phosphatase activity. To address this hypothesis, we will: 1) Test the hypothesis that VEGF-C is a direct transcriptional target of Six1/Eya2, and that Six1 and Eya2 correlate with VEGF-C and lymphangiogenesis in human breast cancer; 2) Test the hypothesis that VEGF-C is a critical mediator of Six1-induced lymphangiogenesis and metastasis using in vivo mouse metastasis models; and 3) Test the hypothesis that Eya2 is required for Six1-induced lymphangiogenesis and metastasis in vivo, with a specific emphasis on the interaction between Six1 and Eya2, as well as the role of the Eya2 phosphatase activity. Targeting Six1/Eya2 has the potential to inhibit breast cancer both at early (studied in this proposal) and later stages of the disease. Due to the paucity of expression of the Six1/Eya2 developmental regulators in most normal adult tissues, and their re-expression in cancers, therapeutic agents targeting this complex should inhibit lymphangiogenesis and metastasis with limited side effects. Thus the Six1/Eya2 complex is an ideal breast cancer therapeutic target, and work within this proposal will lay the foundation for eventual targeting of the complex.