PREVENTION OF COLORECTAL CANCER BY iNOS AND COX-2 SELECTIVE INHIBITORS

描述（由申请人提供）：本提案的总体目标是开发诱导型一氧化氮合酶（iNOS）选择性抑制剂在结肠直肠癌化学预防中的用途，并了解这些药物抑制肿瘤的细胞和分子机制。此外，我们将设计通过同时应用iNOS-和考克斯-2选择性抑制剂来提高结肠癌预防和治疗效果的策略。结直肠癌是美国最常见的人类恶性肿瘤之一，预计2003年将有140，000例新发病例和约56，000例死亡。开发针对促进肿瘤细胞生长、不受控制的扩增和侵袭的特定分子靶点的治疗策略提供了合理的方法。一氧化氮，产生的NOS亚型，已牵连在几个病理生理条件，包括结肠癌的发生。我们的研究和其他人的研究表明，在结肠肿瘤中，与正常粘膜相比，iNOS活性上调了数倍，重要的是，一氧化氮或来自这些酶的反应分子在调节细胞凋亡和增殖中起着关键作用。我们实验室的最新证据表明，iNOS选择性抑制剂抑制化学诱导的结肠癌发生，也抑制转基因APC小鼠中的肿瘤形成。因此，重要的是系统地开发用于结肠癌预防/治疗的iNOS选择性抑制剂，并描述导致这些药剂抑制肿瘤发生的特定机制。 具体而言，我们将1）检查不同iNOS抑制剂[PBIT、NILT和BIPPA]对氧化偶氮甲烷（AOM）诱导的大鼠结肠癌发生的化学预防功效（最大耐受剂量选择;剂量反应效应;以及结肠癌发生促进/进展阶段的有效性; 2）建立通过组合考克斯-2-和iNOS-选择性抑制剂提高结肠癌预防和治疗功效的策略，和3）评估与iNOS抑制/考克斯-2抑制相关的细胞和分子生物标志物（细胞凋亡和增殖变化、一氧化氮、3-硝基酪氨酸以及NOS和考克斯亚型的表达和活性）并研究基因表达谱的调节以鉴定与细胞凋亡相关的基因的功能组的变化，细胞周期调节和iNOS和考克斯-2介导的信号; 4）了解iNOS和考克斯-2抑制剂调节结肠肿瘤细胞增殖和凋亡的机制。

DESCRIPTION (provided by applicant): The overall objective of this proposal is to develop the use of inducible nitric oxide synthase (iNOS)-selective inhibitors in the chemoprevention of colorectal cancer, and to gain an understanding of the cellular and molecular mechanism(s) of tumor inhibition by these agents. In addition, we will design the strategies for improving the efficacy of colon cancer prevention and treatment by concurrent application of iNOS- and COX-2 selective inhibitors. Colorectal cancer is one of the most common human malignancies in the United States, anticipated to account for 140,000 new cases and about 56,000 deaths in the year 2003. Developing treatment strategies, aimed at a specific molecular target that facilitate(s) tumor cell growth, uncontrolled expansion and invasion, provide a rational approach. Nitric oxide, produced by isoforms of NOS, has been implicated in several pathophysiological conditions including colon carcinogenesis. Our studies and those of others indicate that iNOS activities were up-regulated several-fold in colon tumors compared to normal mucosa and, importantly, nitric oxide or its reactive molecules derived from these enzymes play a pivotal role in modulation of apoptosis and proliferation. Recent evidence from our laboratory suggests that iNOS-selective inhibitors suppress chemically-induced colon carcinogenesis and also tumor formation in transgenic APC min mice. Thus, it is important to systematically develop iNOS-selective inhibitors for colon cancer prevention/treatment and delineate the specific mechanisms that lead to inhibition of tumorigenesis by these agents. Specifically, we will 1) examine the chemopreventive efficacy of different iNOS-inhibitors [PBIT, NILT and BIPPA] on azoxymethane (AOM)-induced colon carcinogenesis in rats (maximum tolerated dose selection; dose-response effects; and effectiveness during promotion/progression stages of colon carcinogenesis; 2) establish strategies to improve efficacy of colon cancer prevention and treatment by a combination of COX-2- and iNOS-selective inhibitors and 3) assess the cellular and molecular biomarkers associated with iNOS inhibition/COX-2 inhibition (apoptotic and proliferation changes, nitric oxide, 3-nitrotyrosine, and expression and activities of isoforms of NOS and COX) and study the modulation of gene expression profiles to identify changes in functional groups of genes associated with apoptosis, cell-cycle regulation and iNOS and COX-2 mediated signals and 4) understand the mechanisms by which inhibitors of iNOS and COX-2 modulate colon tumor cell proliferation and apoptosis.