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。此外，我们将设计通过iNOS-和COX-2选择性抑制剂同时应用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14万例新病例和约5.6万例死亡。针对促进肿瘤细胞生长、不受控制的扩张和侵袭的特定分子靶点制定治疗策略，提供了一种合理的方法。一氧化氮由一氧化氮的异构体产生，与多种病理生理条件有关，包括结肠癌的发生。我们和其他人的研究表明，与正常粘膜相比，iNOS活性在结肠肿瘤中上调了数倍，重要的是，一氧化氮或由这些酶衍生的活性分子在调节细胞凋亡和增殖中起着关键作用。我们实验室最近的证据表明，在转基因APC小鼠中，inos选择性抑制剂抑制化学诱导的结肠癌发生和肿瘤形成。因此，系统地开发用于结肠癌预防/治疗的inos选择性抑制剂，并描述这些药物抑制肿瘤发生的具体机制是很重要的。

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.