Role of Tissue Transglutaminase in Ovarian Cancer

描述（由申请人提供）： 摘要：该提议的总体假设是组织转谷氨酰胺酶 (TG2)，一种我们发现在卵巢癌 (OC) 中上调的蛋白质，通过增强 2-连环蛋白细胞信号传导来调节 OC 细胞的上皮间质转化 (EMT) 以及卵巢癌干细胞的存活。 TG2 是一种在多种上皮恶性肿瘤中过度表达的酶，可诱导钙依赖蛋白翻译后修饰和交联。我们首次报道了 TG2 在 OC 中上调，并且在当前资助期间我们实验室的工作表明该酶关键调节 OC 转移过程。我们发现，当腹膜内或裸鼠卵巢囊下注射时，与对照细胞相比，经改造表达降低水平的 TG2 的 OC 细胞诱导的腹膜播散明显减少。我们还表明，TG2 诱导 OC 细胞的 EMT 并调节 OC 细胞球状体的形成。这些发现使我们提出了一个假设，即 TG2 对于 EMT 过程和卵巢癌干细胞的存活至关重要，我们将通过实现三个目标来测试该假设： 目标 1：确定 TG2 调节 2-连环蛋白稳定性的机制并研究其对 2-连环蛋白依赖性基因转录的影响。我们将研究 TG2 敲低或抑制是否会改变 2-连环蛋白的细胞定位、磷酸化和响应 Wnt 信号的信号传导，从而有助于 OC 细胞的 EMT。目标 2：确定 TG2 诱导的 EMT 和转移是否受 2-catenin 信号传导调节。我们将研究 2-连环蛋白敲低是否抑制 TG2 诱导的 EMT 和转移，以及其稳定化是否会在表达低水平 TG2 的细胞中诱导 EMT。目标 3：确定 TG2 表达对卵巢癌干细胞存活和功能的影响。我们将测量并比较卵巢 CSC 与整个肿瘤中的 TG2 表达。我们将敲低 TG2 或抑制其酶活性，以阻断卵巢 CSC 的功能（例如存活、球体形成和致瘤性）。意义：我们是第一个研究TG2在卵巢癌中作用的小组，重点关注TG2调节的转移和EMT机制。这一提议是及时且高度相关的，因为 EMT 最近已与癌症干细胞表型联系起来。我们的小组已经提供了卵巢肿瘤中存在这种独特细胞群的证据。标准治疗后这些细胞的持续存在很可能是化疗未能消除癌症的原因。因此，证明 TG2 促进卵巢 CSC 的存活具有高度相关性，因为它将确定一条新的途径，可以针对根除治疗耐药干细胞和阻断 OC 转移的目标。

DESCRIPTION (provided by applicant): Abstract The overarching hypothesis for this proposal is that tissue transglutaminase (TG2), a protein we found to be up-regulated in ovarian cancer (OC) regulates epithelial to mesenchymal transition (EMT) in OC cells and the survival of ovarian cancer stem cells by enhancing 2-catenin cellular signaling. TG2, an enzyme overexpressed in several epithelial malignancies, induces Cadependent protein post-translational modifications and cross-linking. We reported for the first time that TG2 is up-regulated in OC and work in our laboratory during the current funding period demonstrated that the enzyme critically regulates the process of OC metastasis. We showed that when injected intraperitoneally or under the ovarian bursa of nude mice, OC cells engineered to express decreased levels of TG2 induced significantly less peritoneal dissemination compared to control cells. We also showed that TG2 induces EMT of OC cells and regulates formation of spheroids from OC cells. These discoveries led us to formulate the hypothesis that TG2 is critical to the process of EMT and the survival of ovarian cancer stem cells, which we will test by addressing three objectives: Aim 1: Identify the mechanisms by which TG2 regulates 2-catenin stability and study its effects on 2-catenin dependent gene transcription. We will study whether TG2 knockdown or inhibition alters 2-catenin cellular localization, phosphorylation and signaling in response to Wnt signals, contributing to EMT of OC cells. Aim 2: Determine whether TG2 induced EMT and metastasis are regulated by 2-catenin signaling. We will investigate whether 2-catenin knock-down inhibits TG2 induced-EMT and metastasis and whether its stabilization induces EMT in cells expressing low levels of TG2. Aim 3: Establish the effects of TG2 expression on the survival and functions of ovarian cancer stem cells. We will measure and compare TG2 expression in ovarian CSCs vs. whole tumors. We will knock-down TG2 or inhibit its enzymatic activity to block the functions of ovarian CSCs (e.g. survival, formation of spheroids and tumorigenicity). Significance: We are the first group studying the role of TG2 in ovarian cancer focusing on mechanisms of metastasis and EMT modulated by TG2. This proposal is timely and highly relevant as EMT has been recently linked to the cancer-stem cell phenotype. Our group has produced evidence for the presence of such a distinct population of cells in ovarian tumors. It is likely that persistence of these cells after standard treatment is responsible for the failure of chemotherapy to eliminate cancer. Therefore, demonstrating that TG2 facilitates the survival of ovarian CSCs is highly relevant, as it will identify a new pathway that can be targeted with the goal of eradicating treatment resistant stem cells and of blocking OC metastasis.