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

描述(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选择性抑制剂在结直肠癌化学预防中的应用，并了解这些药物抑制肿瘤的细胞和分子机制(S)。此外，我们还将设计通过同时应用iNOS-和COX-2选择性抑制剂来提高结肠癌防治效果的策略。结直肠癌是美国最常见的人类恶性肿瘤之一，预计2003年新增病例14万例，死亡约5.6万例。制定治疗策略，针对特定的分子靶点，促进(S)肿瘤细胞的生长、不受控制的扩张和侵袭，提供了一种合理的方法。一氧化氮由一氧化氮合酶的亚型产生，与包括结肠癌发生在内的几种病理生理条件有关。我们和其他人的研究表明，iNOS活性在结肠肿瘤中上调了几倍，重要的是，来自这些酶的一氧化氮或其反应分子在调节细胞凋亡和增殖方面发挥了关键作用。来自我们实验室的最新证据表明，iNOS选择性抑制剂可以抑制化学诱导的结肠癌的发生，也可以抑制转基因APC min小鼠的肿瘤形成。因此，系统地开发iNOS选择性抑制剂用于结肠癌的预防/治疗，并阐明这些药物抑制肿瘤发生的具体机制是很重要的。 具体地说，我们将1)检测不同iNOS抑制剂[PBIT、NILT和BIPPA]对偶氮甲烷(AOM)诱导的大鼠结肠癌的化学预防效果(最大耐受剂量选择；剂量-反应效应；以及结肠癌发生的促进/进展阶段的有效性；2)建立通过联合应用COX-2和iNOS选择性抑制剂来提高结肠癌防治效果的策略；3)评估与iNOS抑制/COX-2抑制相关的细胞和分子生物标志物(细胞和增殖变化、一氧化氮、3-硝基酪氨酸以及NOS和COX异构体的表达和活性)，并研究基因表达谱的调控，以确定与细胞凋亡、细胞周期调控和iNOS和COX-2介导的信号相关的基因功能组的变化；4)了解iNOS和COX-2抑制剂调控结肠癌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.