Colon Cancer Chemoprevention

描述（由申请人提供）： 我们以前已经证明，补充膳食熊去氧胆酸（UDCA）抑制氧化偶氮甲烷诱导的大鼠结肠肿瘤的发展。为了检查UDCA引起抗癌作用的机制，申请中的研究表明UDCA可增加RasGT 3激活蛋白（RasGAP）活性，并产生半胱天冬酶-3依赖性RasGAP -N和-C末端片段。本申请的重要目的是确定RasGAP C端片段是否具有抑制和预防结肠癌的作用。在细胞培养研究中，我们已经证明RasGAP C-末端片段使结肠癌细胞对UDCA依赖性凋亡敏感。为了评估RasGAP C-末端片段对肿瘤进展的影响，将研究用该基因稳定转染的肿瘤异种移植物的生长。此外，将评估可渗透的RasGAP C片段蛋白的肿瘤内递送对肿瘤异种移植物的影响。为了确定该片段的化学预防功效，将研究通过脂质体灌肠引入RasGAP C-cDNA对直肠异常隐窝形成的影响。这将是首次尝试在小鼠模型中评价RasGAP C端片段的体内抗癌和化学预防功效。我们还利用创新技术分离了与HIV肽连接的RasGAP C片段蛋白，该肽允许其跨细胞膜转运和基于脂质体的小鼠结肠基因递送。我们进行这些研究的理由是，开发基于科学的证据来支持RasGAP C-末端片段的抗癌和预防益处，将为人类研究提供基础，以测试癌症患者和高危个体的潜在益处。希望通过该应用程序获得的信息可以被开发和应用于设计更有效的结肠癌预防抑制剂。

DESCRIPTION (provided by applicant): We have previously demonstrated that supplemental dietary Ursodeoxycholic Acid (UDCA) inhibited the development of azoxymethane-induced rat colonic tumors. To examine the mechanisms by which UDCA causes anticarcinogenic effects, studies in the application demonstrated that UDCA increased RasGTPase Activating Protein (RasGAP) activity and generated caspase-3 dependent RasGAP -N and -C terminal fragments. The important goal of this application is to determine whether RasGAP C-terminal fragment has a role in the inhibition and prevention of colon cancer. In cell culture studies we have demonstrated that RasGAP C-terminal fragment sensitizes colon cancer cells to UDCA dependent apoptosis. To evaluate the effect of RasGAP C-terminal fragment on tumor progression the growth of tumor xenografts stably transfected with this gene will be investigated. Further, the effect of Intratumoral delivery of permeable RasGAP C-fragment protein on tumor xenografts will be evaluated. To determine the chemopreventive efficacy of this fragment the effect of introduction of RasGAP C-cDNA through liposome enema on rectal aberrant crypt formation will be investigated. This will be the first attempt to evaluate in vivo the anti-cancer and chemopreventive efficacy of RasGAP C-terminal fragment in mouse models. We have also utilized innovative technologies in isolating RasGAP C-fragment protein attached to a HIV peptide, which permits its transport across cell membranes and liposome based gene delivery in mouse colon. Our rationale for these studies is that development of scientifically based evidence to support an anti-cancer and preventive benefit of RasGAP C-terminal fragment would provide a foundation for human studies to test potential benefits in cancer patients and high risk individuals. It is hoped that the information gained by this application can be exploited and applied toward the design of a more effective inhibitor for colon cancer prevention.