Colon Cancer Chemoprevention

描述(由申请人提供)： 我们先前已经证明，补充熊去氧胆酸(UDCA)可以抑制偶氮甲烷诱导的大鼠结肠肿瘤的发展。为了研究UDCA的抗癌作用机制，在应用中的研究表明，UDCA增加了RasGTP酶激活蛋白(RasGAP)的活性，并产生了依赖于caspase-3的RasGAP-N和-C末端片段。本应用的重要目的是确定RasGAP C-末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依赖的凋亡敏感。为了评价RasGAP C-末端片段对肿瘤进展的影响，我们将观察稳定转染该基因的肿瘤移植瘤的生长情况。此外，将评估瘤内注射可渗透的RasGAP C-片段蛋白对肿瘤移植瘤的影响。为了确定该片段的化学预防效果，我们将研究脂质体灌肠导入RasGAP C-cDNAs对直肠畸形隐窝形成的影响。这将是第一次尝试在体内评价RasGAP C-末端片段在小鼠模型中的抗癌和化学预防效果。我们还利用创新技术分离了附着在HIV多肽上的RasGAP C-片段蛋白，使其能够跨细胞膜转运，并在小鼠结肠内基于脂质体的基因输送。我们进行这些研究的理由是，发展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。希望通过这一应用获得的信息可以被开发并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.