Role of TbRIII in Regulating Motility and Invasion

描述（由申请人提供）：转化生长因子-b （TGF-b）在肿瘤发生中具有双重作用，最初作为肿瘤抑制因子，随后作为肿瘤促进因子。就TGF-b的二分功能机制而言，存在根本性的知识差距。III型TGF-b受体（TbRIII）在调节TGF-b信号传导和致癌作用中具有新兴但尚不清楚的作用。我们已经确定，TbRIII特异性地抑制癌细胞的迁移和侵袭，部分原因是通过外胞域脱落，释放可溶性TbRIII （sTbRIII）。为了探究TbRIII的作用机制，我们提出以下假设：细胞表面TbRIII通过激活Cdc42、破坏肌动蛋白细胞骨架、局灶黏着形成、极性和抑制定向迁移来减少卵巢表面上皮细胞和卵巢癌细胞的迁移，而sTbRIII通过MMP介导的外域脱落产生，通过新的Smad1途径抑制TGF-b信号和MMP的产生，TbRIII激活Cdc42抑制乳腺癌和卵巢癌细胞的侵袭性。这一假设将通过四个具体目标来解决。具体目标1：通过检查所涉及的蛋白酶，确定切割的位点以及如何调节该过程，将建立TbRIII经历外结构域脱落以产生sTbRIII的机制。具体目标2：通过检测TbRIII功能所需的功能元件，以及TbRIII介导的CDC42通路激活对极性、定向迁移、肌动蛋白细胞骨架和局灶复合物形成的影响，建立TbRIII抑制卵巢表面上皮细胞和卵巢癌细胞迁移的机制。特异性目的3：通过检测TbRIII功能所需的功能元件、sTbRIII对TGF-b细胞表面结合的影响、TGF-b通过Smad1和MMP产生的信号传导以及TbRIII介导的CDC42通路激活对侵袭的影响，建立TbRIII抑制乳腺癌和卵巢癌细胞侵袭的机制。特异性目的4：将探讨阻断TbRIII脱落和sTbRIII生成、直接降低细胞表面TbRIII和sTbRIII表达或表达TbRIII和/或sTbRIII对乳腺癌和卵巢癌细胞功能的影响，包括体外增殖、凋亡、侵袭和血管生成以及体内肿瘤形成和转移，以确定细胞表面TbRIII和sTbRIII是否协同作用以减少乳腺癌和卵巢癌的进展。这些研究将明确TbRIII抑制乳腺癌和卵巢癌细胞迁移和侵袭的机制，包括胞外结构域脱落的作用，明确TbRIII胞外结构域脱落在人类乳腺癌和卵巢癌中的生物学意义，并有助于设计特定的干预措施来预防和治疗人类乳腺癌和卵巢癌以及其他TbRIII有明确作用的人类癌症。公共卫生相关性：我们已经证明，转化生长因子-2 （TGF-b）的细胞表面受体，III型TGF-b受体（TbRIII），能够通过降低癌细胞迁移、侵袭和扩散到远处部位的能力，抑制多种人类癌症的癌症进展，包括乳腺癌、肺癌、卵巢癌、胰腺癌和前列腺癌。调控迁移和侵袭也是胚胎发育、组织修复和免疫应答的重要过程，在炎症和血管疾病中具有重要作用。因此，我们将研究TbRIII抑制迁移、侵袭和转移性扩散的机制，这些研究对于执行和与公共卫生相关，因为这些机制见解将定义TbRIII在人类乳腺癌和卵巢癌背景下的生物学功能。增加对TGF-b信号和TbRIII在调节迁移和侵袭中的作用的认识，并有助于靶向TGF-b信号通路，治疗这些癌症和其他迁移和侵袭或TGF-b信号通路具有突出作用的疾病。

DESCRIPTION (provided by applicant): Transforming growth factor-b (TGF-b has a dual role in tumorigenesis, initially functioning as a tumor suppressor and subsequently as a tumor promoter. A fundamental gap in knowledge exists in terms of mechanisms for the dichotomous function of TGF-b. The type III TGF-b receptor (TbRIII) has an emerging yet poorly understood role in regulating TGF-b signaling and carcinogenesis. We have establishing that TbRIII specifically inhibits cancer cell migration and invasion, in part by undergoing ectodomain shedding, releasing soluble TbRIII (sTbRIII). To investigate the mechanism of TbRIII function, the following hypothesis is proposed: Cell surface TbRIII decreases the migration of ovarian surface epithelial cells and ovarian cancer cells by activating Cdc42, disrupting the actin cytoskeleton, focal adhesion formation, polarity and inhibiting directional migration, while sTbRIII, generated through MMP-mediated ectodomain shedding, functions to inhibit TGF-b signaling and MMP production through a novel Smad1 pathway and TbRIII activates Cdc42 to inhibit the invasiveness of breast and ovarian cancer cells. This hypothesis will be addressed by four Specific Aims. Specific Aim 1: The mechanism by which TbRIII undergoes ectodomain shedding to produce sTbRIII will be established by examining the proteases involved, defining the site(s) of cleavage and how the process is regulated. Specific Aim 2: The mechanism by which TbRIII inhibits migration of ovarian surface epithelial cells and ovarian cancer cells will be established by examining the functional elements required for TbRIII function, and the effect of TbRIII-mediated activation of CDC42 pathways on polarity, directed migration, the actin cytoskeleton and focal complex formation. Specific Aim 3: The mechanism by which TbRIII inhibits invasion of breast and ovarian cancer cells will be established by examining the functional elements required for TbRIII function, the effect of sTbRIII on TGF-b cell surface binding, TGF-b signaling through Smad1 and MMP production and the effect of TbRIII-mediated activation of CDC42 pathways on invasion. Specific Aim 4: The effect of blocking TbRIII shedding and sTbRIII production, directly decreasing cell surface TbRIII and sTbRIII expression or expressing TbRIII and/or sTbRIII on both breast and ovarian cancer cell functions including proliferation, apoptosis, invasion and angiogenesis in vitro and tumor formation and metastasis in vivo will be explored to determine whether cell surface TbRIII and sTbRIII function in concert to decrease breast and ovarian cancer progression. These studies will define the mechanism by which TbRIII inhibits breast and ovarian cancer cell migration and invasion, including the role of ectodomain shedding, define the biological implications of ectodomain shedding of TbRIII in the context of human breast and ovarian cancers, and aid in the design of specific interventions for the prevention and treatment of human breast and ovarian cancers and other human cancers in which TbRIII has a defined role. PUBLIC HEALTH RELEVANCE: We have demonstrated that a cell surface receptor for the transforming growth factor-2 (TGF-b), the type III TGF-b receptor (TbRIII), is able to suppress cancer progression in a broad spectrum of human cancers, including cancers of the breast, lung, ovary, pancreas and prostate, by decreasing the ability of the cancer cells to migrate, invade and spread to distant sites. Regulating migration and invasion are also essential processes during embryonic development, tissue repair and in the immune response and have prominent roles in inflammatory and vascular diseases. Thus, these studies where we will investigate mechanisms by which TbRIII inhibits migration, invasion and metastatic spread are important to perform and relevant to public health as these mechanistic insights will define the biological functions of TbRIII in the context of human breast and ovarian cancers, increase understanding of the role of TGF-b signaling and of TbRIII in regulating migration and invasion and aid in targeting the TGF-b signaling pathway for the treatment of these cancers and other diseases in which migration and invasion or the TGF-b signaling pathway has a prominent role.