LPA Receptor Signaling in Colonic Epithelia

描述(由申请人提供)：生长因子信号通路的异常导致异常生长和分化，从而导致恶性转化。溶血磷脂酸(LPA)是最简单的磷脂之一，它介导的生长因子样效应能够调节肠上皮细胞的命运和天然免疫。LPA通过激活G蛋白偶联受体家族：LPA1R~LPA5R，介导多种生物学效应。发现LPA2受体(LPA2R)在人类结肠癌组织和细胞系中的表达水平升高，提示LPA与结肠癌之间存在病理联系。LPA在体外调节结肠癌细胞的增殖、存活和侵袭，但来自我们的研究的直接体内证据表明，在结肠癌啮齿动物模型中，LPA2R的缺失导致肿瘤负担降低。我们的研究表明，LPA2R介导的信号转导靶向多种癌基因和促炎蛋白，包括c-Myc、细胞周期蛋白D、低氧诱导因子-1、低氧诱导因子-2、环氧合酶-2和巨噬细胞移动抑制因子。然而，LPA如何调控这些致癌靶点的表达，以及这些基因和基因产物在LPA介导的发病机制中的作用在多大程度上尚未阐明。我们的目标是确定LPA2R介导的信号对HIF-1、HIF-2和MIF的调节机制，并验证LPA2R通过激活HIF和MIF刺激肿瘤生长、糖酵解和促炎细胞因子分泌的假说(特异性目标1)。LPA2R信号在一定程度上通过激活β-连环蛋白促进细胞增殖，我们将确定LPA诱导β-连环蛋白激活的潜在机制。我们将确定Kruppel-like factor5(KLF5)与-连环蛋白的相互作用，并确定KLF5在体内-连环蛋白核转位中的重要性。我们将确定选定的Wnt途径基因在LPA调节β-连环蛋白中的重要性(特异性目标2)。有证据表明，LPA2R的缺失减弱了结肠癌的发病机制。然而，仅LPA2R的过度表达是否足以导致肠癌的发生尚不清楚。我们将建立LPA2R转基因小鼠，以确定LPA2R过表达对肠道肿瘤发展的影响。此外，我们将确定NHERF2的缺失是否对于LPA在体内利用NHERF2缺陷的小鼠诱导结肠癌进展是必要的(特定目标3)。NHERF2与LPA2R相互作用以增强其细胞信号。这一建议的意义在于，更好地了解LPA2R介导的信号通路和机制，以及靶向LPA/LPA受体的可能性，将为癌症和炎症相关疾病等肠道疾病的治疗提供更好的治疗方式。

DESCRIPTION (provided by applicant): Aberration in the growth factor signaling pathways leads to abnormal growth and differentiation that contribute to malignant transformation. Lysophosphatidic acid (LPA), one of the simplest phospholipids, mediates growth factor-like effects that are capable of regulating the fate of intestinal epithelial cells and the innate immunity. LPA mediates diverse biological effects by activating a family of G protein-coupled receptors: LPA1R~LPA5R. The pathological link between LPA and colon cancer has been suggested by the finding that the expression level of LPA2 receptor (LPA2R) is elevated in human colon cancer tissues and cell lines. LPA regulates proliferation, survival, and invasion of colon cancer cells in vitro, but direct in vivo evidence came from our studies that the absence of LPA2R results in decreased tumor burden in rodent models of colon cancer. Our studies have shown that LPA2R-mediated signaling targets several oncogenes and pro-inflammatory proteins, including c-Myc, cyclin D, hypoxia-inducible factor (HIF)-1?, HIF-2?, cyclooxygenase-2, and macrophage migration inhibitory factor (MIF). However, how LPA regulates the expression of these oncogenic targets and to what extend these genes and gene products contribute to the pathogenesis mediated by LPA has not been elucidated. We aim to determine the mechanisms of the regulation of HIF-1?, HIF-2?, and MIF by LPA2R- mediated signaling and to test the hypothesis that LPA2R stimulates tumor growth, glycolysis, and secretion of pro-inflammatory cytokines through the activation of HIF and MIF (Specific Aim 1). LPA2R-signaling facilitates cell proliferation in part by activation of ?-catenin and we will determine the underlyng mechanism of LPA- induced activation of ?-catenin. We will determine the interaction between Kruppel-like factor 5 (KLF5) and ?- catenin and determine the importance of KLF5 in ?-catenin nuclear translocation in vivo. We will determine the importance of selected Wnt pathway genes in ?-catenin regulation by LPA (Specific Aim 2). Evidence shows the absence of LPA2R attenuates the pathogenesis of colon cancer. However, whether overexpression of LPA2R alone is sufficient for the development of cancer in the intestine is not known. We will generate LPA2R transgenic mice to determine the effects of LPA2R overexpression on tumor development in the intestine. In addition, we will determine whether the absence of NHERF2, which interacts with LPA2R to enhance its cellular signaling, is necessary for LPA-induced colon cancer progression in vivo using mice deficient in NHERF2 (Specific Aim 3). The significance of this proposal is that a better understanding of the LPA2R- mediated signaling pathways and mechanisms, together with the possibility of targeting LPA/LPA receptors, will provide better therapeutic modality for treatment of intestinal disorder, such as cancer and inflammation- associated diseases.