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产生抗癌作用的机制，这项研究表明UDCA增加了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-末端片段是否在抑制结肠癌中发挥作用。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诱导的细胞凋亡敏感。为了研究RasGAP C-末端片段对肿瘤的抑制作用，我们将利用裸鼠模型进行体内实验。这将是首次尝试评价RasGAP C-末端片段在结肠癌中的抗癌活性。将过表达RasGAP C-片段蛋白的结肠癌细胞注射到小鼠体内，观察UDCA存在下的肿瘤生长特性。此外，我们还利用了一项创新技术来分离附着在HIV多肽上的RasGAP C-片段蛋白，这使得它能够跨细胞膜运输。为了评估治疗效果，这种蛋白质将直接注射到肿瘤中。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-末端片段的预防和治疗益处，将为人类研究测试癌症患者和高危个体的潜在益处提供基础。希望通过这一建议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和治疗抑制剂。

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 this proposal demonstrated that UDCA increased 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 of colon cancer. In cell culture studies we have demonstrated that RasGAP C-terminal fragment sensitizes colon cancer cells towards UDCA-induced apoptosis. To study tumor suppression by RasGAP C-terminal fragments, in vivo, we will utilize nude mouse model. This will be the first attempt to evaluate the anti-cancer activity of RasGAP C-terminal fragment in colon cancer. Colon cancer cells over-expressing RasGAP C-fragment protein will be injected into mice and tumor growth characteristics will be observed in the presence of UDCA. Further, we have also utilized an innovative technology in isolating RasGAP C-fragment protein attached to a HIV peptide, which permits its transport across cell membranes. To assess the therapeutic benefit, this protein will be injected directly in the tumor. Our rationale for these studies is that development of scientifically based evidence to support a preventive and therapeutic 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 proposal can be exploited and applied towards the design of a more effective inhibitor for colon cancer prevention and therapy.