Role of Nitric Oxide in the Progression of Murine Cancer

游离氧自由基，一氧化氮（NO），在体外和体内的各种恶性肿瘤中升高。一氧化氮合酶（NOS）的三种同工酶在机体中负责从精氨酸合成一氧化氮：构成型神经元NOS (nNOS或NOS 1)，主要存在于神经元中；巨噬细胞和其他细胞中诱导的NOS (iNOS或NOS 2)；构成型内皮细胞NOS (eNOS、ecNOS或no3)，主要存在于内皮细胞中。在许多形式的癌症中，一氧化氮水平升高与肿瘤侵袭性增加有关。在大多数乳腺癌检查中发现一氧化氮水平升高，并与血管生成加速、细胞凋亡消除和肿瘤侵袭有关。在目前的R03应用中，我们建议阐明NO的产生在乳腺癌细胞侵袭特性中的作用。我们假设一氧化氮水平的增加（由一氧化氮活性增加产生）确实与肿瘤侵袭性增强有关。为了直接研究NOS在细胞中的作用，我们将在iNOS和eNOS敲除小鼠中研究致癌物7-12-二甲基苯(a)蒽（DMBA）诱导的小鼠乳腺癌。这些模型将使我们能够识别与肿瘤侵袭性最相关的NOS类型。我们还将通过使用NOS抑制剂化学改变细胞环境中NO的数量来验证我们的假设。ng -硝基- l-精氨酸甲酯（L-NAME）或ng -甲基- l-精氨酸（NMMA）对NOS活性的抑制应能减少肿瘤生长和转移，如果NO在这些过程中是一个重要的积极因素。最后，我们预计添加不需要NOS生成的外源性NO(例如，施用硝普钠或NOC-12[1 -羟基-2-氧-3- （n -乙基-2-氨基乙基）-3-乙基-1 -三嗪]将增加肿瘤侵袭性。我们期望从这些初步研究中获得的结果将为我们提供足够的数据，为随后的R01应用奠定基础，探索NO和NOS在乳腺癌中的作用机制，并最终转化为人类疾病，可能在生物标志物和治疗干预方面。

The free oxygen radical, nitric oxide (NO), is elevated in a variety of malignant tumors in vitro and in vivo. Three isoenzymes of nitric oxide synthase (NOS) are responsible for the synthesis of NO from arginine in the organism: constitutive neuronal NOS (nNOS or NOS 1), identified mainly in neurons; inducible NOS (iNOS or NOS 2), found in macrophages and other cells; and constitutive endothelial cell NOS (eNOS, ecNOS, or NOS 3), found predominantly in endothelial cells. Elevated levels of NO have been associated with increased tumor aggressiveness in many forms of cancer. Increased NO levels have been found in most breast cancers examined and are associated with accelerarion of angiogenesis, abrogation of apoptosis, and tumor invasion. In the present R03 application, we propose to elucidate the role of NO generation in the invasive characteristics of breast cancer cells. We hypothesize that increased levels of NO (produced by increased NOS activity) are, indeed, associated with enhanced tumor aggressiveness. To directly examine the role of NOS in cells, we will study murine mammary cancers induced by the carcinogen 7-12- dimethybenz(a)anthracene (DMBA) in iNOS and eNOS knockout mice. These models will enable us to identify the type of NOS that is most associated with tumor aggressiveness. We also will test our hypothesis by chemicall altering the amount of NO in the cellular environment using NOS inhibitors. Inhibition of NOS activity by NG-nitro-L- arginine methyl ester (L-NAME) or by NG-methyl-L-arginine (NMMA) should reduce tumor growth and metastases if NO is a significant positive factor in these processes. Finally, we anticipate that addition of exogenous NO that does not require NOS for its production (e.g., administration of sodium nitroprusside or NOC-12 [1hydroxy-2-oxo-3- (N-ethyl-2-aminoethyl)-3-ethyl-l-triazine] will increase tumor invasiveness. We anticipate that the results obtained from these preliminary studies will provide us with sufficient data to lay the foundation for a subsequent R01 application exploring the mechanisms involved in the actions of NO and NOS in breast cancer, with ultimate translation to human disease, potentially in terms of both biological markers and them therapeutic interventions.