cPLA2alpha, COX-2 and TGF-beta in Liver Cancer

描述（申请人提供）：原发性肝癌是人类常见的恶性肿瘤，死亡率高，其发病率在世界范围内呈上升趋势，特别是在美国。它主要发生在预先存在的慢性炎症性肝病，包括慢性肝炎和肝硬化。本实验室最近的研究表明，前列腺素（PG）代谢在肝脏炎症和癌变中起着重要作用。在这项研究中，我们假设前列腺素信号的水平和激活状态是决定细胞对转化生长因子的反应的关键因素。(TGF-?).具体来说，我们假设增强的胞浆磷脂酶A2？（cPLA2？）环氧化酶-2（考克斯-2）控制的PG信号转导破坏TGF-β-介导的有丝分裂抑制，这一机制是至关重要的参与肝癌通过选择和扩大TGF-？耐药的发育异常和肿瘤上皮细胞更快地向恶性转化和肿瘤发展。因此，阻断PG信号可能恢复TGF-β 1的生长抑制作用。预防肝癌发生。本申请提出了一系列实验来评估上述假设。人肝癌细胞cPLA 2表达改变？和考克斯-2将用于确定其对TGF-？的反应。Smad 2/3的siRNA将被导入稳定表达反义cPLA 2的人肝癌细胞中。或考克斯-2，并在体外和SCID小鼠中分析这些细胞的增殖和凋亡。cPLA2？和考克斯- 2在肝脏将被开发和利用，以确定TGF-β-调节Smad激活、有丝分裂抑制、凋亡和肝癌发生。cPLA2？和考克斯-2转基因和敲除小鼠将与TGF-？受体II型敲除小鼠，以确定肝再生和DEN诱导的肝癌发生。最后，培养的肝星状细胞和实验动物模型将被用来评估我们的假设，TGF-？PG信号在肝星状细胞中的表达与肝纤维化和肝癌的发生密切相关。从拟议的研究结果，预计将提供重要的治疗意义的化学预防和治疗人类肝癌。公共卫生相关性：原发性肝癌是一种高度恶性的肿瘤，目前尚无有效的化学预防或系统治疗。这个应用程序提出了检查我们的假设，前列腺素信号的水平和激活状态代表了一个关键因素，决定细胞对TGF-？阻断前列腺素信号可能恢复生长抑制作用的TGF-？预防肝癌发生。将进行一系列实验来评估这一中心假设。拟议的实验结果预计将揭示TGF-？和前列腺素信号通路在肝癌发生中的作用，并提供了重要的治疗意义。

DESCRIPTION (provided by applicant): Primary liver cancer is the common malignant neoplasm in human with high mortality and its incidence is rising worldwide, especially in the United States. It occurs largely in the preexisting chronic inflammatory liver disorders, including chronic hepatitis and cirrhosis. Recent studies from our lab show that prostaglandin (PG) metabolism plays an important role in liver inflammation and carcinogenesis. In this grant we hypothesize that the level and activation status of prostaglandin signaling represents a key factor that determines the cellular response to transforming growth factor-? (TGF-?). Specifically, we postulate that enhanced cytosolic phospholipase A2? (cPLA2?) and cyclooxygenase-2 (COX-2) controlled PG signaling subverts TGF-?-mediated mitoinhibition and this mechanism is critically involved in liver carcinogenesis through selection and expansion of TGF-? resistant dysplastic and neoplastic epithelial cells that progress more rapidly toward malignant transformation and tumor development. Therefore, blocking PG signaling may restore the growth- inhibitory action of TGF-??and prevent hepatocarcinogenesis. This application proposes a series of experiments to evaluate the above hypotheses. Human liver cancer cells with altered expression of cPLA2? and COX-2 will be utilized to determine their response to TGF-?. siRNA for Smad2/3 will be introduced into human liver cancer cells stably expressing antisense cPLA2? or COX-2 and these cells will be analyzed for proliferation and apoptosis, in vitro and in SCID mice. Transgenic mice with targeted expression of cPLA2? and COX- 2 in the liver will be developed and utilized to determine TGF-?-regulated Smad activation, mitoinhibition, apoptosis, and hepatocarcinogenesis. The cPLA2? and COX-2 transgenic and knockout mice will be crossed with the TGF-?receptor type II knockout mice to determine liver regeneration and DEN-induced hepatocarcinogenesis. Finally, cultured hepatic stellate cells and experimental animal models will be utilized to evaluate our hypothesis that TGF-? and PG signaling in the fibrogenic hepatic stellate cells is critically involved in the pathogenesis of liver fibrosis and carcinogenesis. Results from the proposed studies are expected to provide important therapeutic implications for the chemoprevention and treatment of human liver cancer. PUBLIC HEALTH RELEVANCE: Primary liver cancer is a highly malignant neoplasm in human and currently there is no effective chemoprevention or systematic therapy. This application is proposed to examine our hypothesis that the level and activation status of prostaglandin signaling represents a key factor that determines the cellular response to TGF-? and that blocking prostaglandin signaling may restore the growth-inhibitory action of TGF-? and prevent hepatocarcinogenesis. A series of experiments will be performed to evaluate this central hypothesis. Results of the proposed experiments are expected to reveal an important link between TGF-? and prostaglandin signaling pathways in liver carcinogenesis and provide important therapeutic implications.