Colon Cancer Chemoprevention and COX-2 Suppression by Ursodeoxycholic Acid

熊去氧胆酸的结肠癌化学预防和 COX-2 抑制

• 批准号: 8601404
• 负责人: SHARAD KHARE
• 金额: --
• 依托单位: HARRY S. TRUMAN MEMORIAL VA HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8601404
• 关键词: Aberrant crypt foci; Adverse effects; Affect; Age; Apoptosis; Attention; Azoxymethane; Bile Acids; C-terminal; Cancer Cell Growth; Cancer Etiology; Cancer Patient; Cardiovascular system; Cell Culture Techniques; Cell Cycle Arrest; Cell Death; Cell Survival; Cells; Chemopreventive Agent; Cholic Acids; Clinical; Colon Carcinoma; Colonic Adenoma; Colonic Neoplasms; Colorectal Adenoma; Coupled; Data; Development; Diagnosis; Diet; Dysplasia; Ensure; Epithelial Cells; Foundations; Gastroenterology; Gene Expression; Goals; Growth; Guanosine Triphosphate Phosphohydrolases; Healthcare; Healthcare Systems; Human; In Vitro; Individual; Investigation; Lasers; Lesion; Liver diseases; Malignant Neoplasms; Modeling; Molecular; Mutagens; Nude Mice; PTGS2 gene; Patients; Phase; Premalignant; Preventive; Primary biliary cirrhosis; Protein Fragment; Proteins; Rattus; Recurrence; Regulation; Research; Risk; Rodent; Role; Sampling; Stromal Cells; Testing; Therapeutic; Therapeutic Intervention; Time; Treatment Cost; Treatment Efficacy; Tumor Promotion; Ulcerative Colitis; United States; Ursodeoxycholic Acid; Veterans; activated Protein C; adenoma; cancer cell; cancer chemoprevention; cancer prevention; carcinogenesis; double-blind placebo controlled trial; evidence base; high risk; human disease; improved; in vivo; inhibitor/antagonist; insight; mortality; novel; prevent; primary sclerosing cholangitis; protein expression; screening; tumor; tumor progression; tumor xenograft; tumorigenesis

DESCRIPTION (provided by applicant): Recent progress in Cox-2 selective inhibitors have shown promise to prevent colon cancer, but untoward cardiovascular side effects have dampened the enthusiasm for these agents. Since selective Cox-2 inhibitors appear problematic, increasing efforts are being made to identify other effective and safer chemopreventive agents. A large, phase III, double blind, placebo-controlled trial of Ursodeoxycholic acid (UDCA) to prevent the recurrence of colorectal adenoma was associated with a statistically significant reduction in recurrence of adenomas with high-grade dysplasia. My long-term research objectives are to elucidate the mechanisms by which UDCA exerts anticarcinogenic effects with respect to colon cancer. We have previously demonstrated that supplemental dietary cholic acid promoted the development of azoxymethane-induced rat colonic tumors. In contrast, dietary UDCA inhibited tumorigenesis and suppressed cholic acid-induced tumor promotion. To examine the mechanisms by which UDCA causes anticarcinogenic effects, studies in the proposal demonstrated that UDCA inhibited wild-type Ras activated tumors and generated RasGTPase activating protein (RasGAP) -N and -C terminal fragments. RasGAP C-terminal fragment sensitizes colon cancer cells towards UDCA-induced cell cycle arrest and suppresses Cox-2 expression in these cells. One of the major goals of this investigation is to provide proof of principle that RasGAP C-fragment protein will be useful in improving the efficacy of UDCA in colon cancer prevention. This will be achieved by investigating the growth of tumor xenografts in nude mice established with RasGAP C-transfectants and the effect of UDCA on regulators of G0/G1 cell cycle arrest in cell culture. Additionally, we will also investigate the effect of Intratumoral delivery of a permeable RasGAP C-fragment protein on tumor xenografts. Another goal of this investigation is to identify and characterize the transcriptional and post-transcriptional mechanisms by which RasGAP C-terminal fragment alters constitutive Cox-2 gene expression in colon cancer cells and UDCA suppresses Cox-2 in Aberrant Crypt Foci (ACF), the putative premalignant precursors of colon cancer. This will be achieved by investigating the stromal and epithelial cells of laser capture microdissected ACF in azoxymethane model of colonic carcinogenesis. We will extend our investigation to human samples by isolating ACFs from patients and study RasGAP fragments and Cox-2 regulators to ensure that regulatory components identified in vitro and in vivo are relevant to human disease. Studies in this proposal are, therefore, important for gaining insights into basic molecular regulation of Cox-2 by RasGAP C-fragments, a novel and unexplored mechanism. It will be useful in the development of better therapeutic interventions, as potential Cox-2 inhibitors are considered toxic for human use.

描述（由申请人提供）： Cox-2 选择性抑制剂的最新进展显示出预防结肠癌的希望，但不良的心血管副作用削弱了人们对这些药物的热情。由于选择性 Cox-2 抑制剂似乎存在问题，因此人们正在加大力度寻找其他有效且更安全的化学预防药物。一项用于预防结直肠腺瘤复发的熊去氧胆酸 (UDCA) 大型 III 期双盲安慰剂对照试验与重度不典型增生腺瘤复发率的统计学显着降低相关。我的长期研究目标是阐明 UDCA 对结肠癌发挥抗癌作用的机制。我们之前已经证明，补充膳食胆酸促进氧化偶氮甲烷诱导的大鼠结肠肿瘤的发展。相反，饮食中的UDCA可抑制肿瘤发生并抑制胆酸诱导的肿瘤生长。为了研究UDCA引起抗癌作用的机制，提案中的研究表明UDCA抑制野生型Ras激活的肿瘤并产生RasGTP酶激活蛋白（RasGAP）-N和-C末端片段。 RasGAP C 末端片段使结肠癌细胞对 UDCA 诱导的细胞周期停滞敏感，并抑制这些细胞中的 Cox-2 表达。这项研究的主要目标之一是提供原理证明，证明 RasGAP C 片段蛋白将有助于提高 UDCA 预防结肠癌的功效。这将通过研究 RasGAP C 转染子建立的裸鼠中肿瘤异种移植物的生长以及 UDCA 对细胞培养中 G0/G1 细胞周期停滞调节剂的影响来实现。此外，我们还将研究可渗透性 RasGAP C 片段蛋白的瘤内递送对肿瘤异种移植物的影响。这项研究的另一个目标是确定和表征 RasGAP C 末端片段改变结肠癌细胞中 Cox-2 基因表达的转录和转录后机制，以及 UDCA 抑制异常隐窝病灶 (ACF) 中的 Cox-2，ACF 是结肠癌的假定癌前前体。这将通过在结肠癌发生的氧化偶氮模型中研究激光捕获显微切割 ACF 的基质细胞和上皮细胞来实现。我们将通过从患者身上分离 ACF 来将研究范围扩展到人类样本，并研究 RasGAP 片段和 Cox-2 调节因子，以确保体外和体内鉴定的调节成分与人类疾病相关。因此，该提案中的研究对于深入了解 RasGAP C 片段（一种新颖且未经探索的机制）对 Cox-2 的基本分子调节非常重要。它将有助于开发更好的治疗干预措施，因为潜在的 Cox-2 抑制剂被认为对人类使用有毒。