COX-2 Inhibitor and N-3PUFA in Colon Cancer Prevention

描述(由申请人提供)：我们研究的长期目标是确定预防结肠癌的创新策略，并将临床前疗效研究的知识应用于结肠癌高危人群作为预防手段。目前的证据表明，富含n-3多不饱和脂肪酸(n-3 PUFAs)和环氧合酶(COX)-2抑制剂的饮食，如塞来昔布，可抑制偶氮甲烷(AOM)诱导的F344大鼠结肠癌的发生。虽然COX-2抑制剂对结肠癌的抑制作用比传统的非甾体抗炎药有效得多，但大剂量的COX-2抑制剂在人类身上也引起了一些副作用。本申请中提出的临床前实验将提供令人信服的证据，表明富含n-3PUFA的饮食与COX-2抑制剂塞来昔布的联合作用将是显著的，同时COX-2抑制剂引起的副作用将被降至最低。建议的研究将评估两种假说：a)COX-2抑制剂和n-3PUFAs的作用机制存在协同作用，前者通过调节二十烷类化合物的生成、血管生成和细胞凋亡来抑制癌变，而后者通过NO途径、细胞分化和细胞凋亡来抑制结肠癌的发生；b)富含n-3PUFAs的饮食与COX-2抑制剂相结合将通过协同调节上述分子参数来提高疗效。其具体目的是：1)确定低剂量塞来昔布在n-3多不饱和脂肪酸高脂饮食中的疗效，与高剂量塞来昔布在含有混合脂肪的高脂西式饮食中诱导F344大鼠结肠癌的效果进行比较。2)研究n-3PUFA饮食中塞来昔布对大鼠结肠癌相关基因表达的影响。我们将利用DNA微阵列、RT-PCR和Western Blot分析，重点研究凋亡基因Bcl2、NF1b和二十烷类和NO途径，包括COX-2、LOX和iNOS，以及它们与其他基因功能基团在结肠癌发生中的相互作用。明确描述临床前模型中的协同效应将使人类临床试验的合理设计成为可能。

DESCRIPTION (provided by applicant): The long-term objective of our research is to identify innovative strategies for colon cancer prevention and to apply the knowledge from preclinical efficacy studies to use with individuals at high-risk for colon cancer as a means of prevention. Current evidence suggests that a diet rich in n-3 polyunsaturated fatty acids (n-3 PUFAs) and cyclooxygenase (COX)-2 inhibitors, such as celecoxib suppress azoxymethane (AOM)-induced colon carcinogenesis in F344 rats. Although colon tumor inhibition by COX-2 inhibitors is much more effective than traditional NSAIDs, high doses of COX-2 inhibitors have caused some side effects in humans. The preclinical experiments proposed in this application will provide compelling evidence that the aggregate action of n-3 PUFA-rich diet in combination with a COX-2 inhibitor, celecoxib would be significant, while side effects induced by the COX-2 inhibitor would be minimized. The proposed studies will evaluate two hypothesis: a) There is synergism in the mechanisms of action of COX-2 inhibitors and n-3 PUFAs, the former inhibiting carcinogenesis through modulation of generation of eicosanoids, angiogenesis and apoptosis while the latter suppressing colon carcinogenesis through NO pathways, cell differentiation and apoptosis, b) the combination of a diet rich in n-3 PUFAs with a COX-2 inhibitor will increase the efficacy by modulating synergistically the above molecular parameters. The specific aims are: 1) Determine the efficacy of a low dose of celecoxib administered in n-3 PUFA rich diet as compared when a high dose of this agent administered in a high-fat, Western style diet containing mixed lipids in AOM-induced colon carcinogenesis in F344 rats. 2) Determine the combined effects of celecoxib administered in n-3 PUFA-rich diet on colon cancer-related genes in colonic mucosa and tumors of rats. We will focus on apoptotic genes, Bcl-2, NF?B and on the eicosanoid- and NO-pathways including COX-2, LOX, and iNOS and their interactions with other functional groups of genes in colon carcinogenesis using DNA microarrays, RT-PCR and Western Blot analysis. Clear delineation of the synergistic effects in preclinical models will allow the rational design of human clinical trials.