Roles of Nitric Oxide and Oxyradicals in Cancer

一氧化氮和氧自由基在癌症中的作用

• 批准号: 6559111
• 负责人: CURTIS HARRIS
• 金额: --
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6559111
• 关键词: CpG islands; cancer risk; chemical structure function; clinical research; colon neoplasms; copper; free radical oxygen; gene expression; genetic polymorphism; genetic regulation; genetic susceptibility; hepatolenticular degeneration; human genetic material tag; human tissue; intermolecular interaction; iron; metal metabolism disorder; neoplasm /cancer; neoplasm /cancer genetics; nitric oxide; nitric oxide synthase; nucleic acid sequence; oxidative stress; p53 gene /protein

High concentrations of nitric oxide (NO) regulation of NO synthase (NOS) activity is essential for minimizing effects of cytotoxic and genotoxic nitrogen oxide species. We have shown previously, that NO-induced p53 protein accumulation, down-regulates basal and cytokine-modulated inducible NOS (NOS2) expression in human cells in vitro, and that p53-null mice have elevated NOS2 enzymatic activity. Our investigation of primary colon tumors establishes a strong positive relationship between the presence of NOS2 in tumors and the frequency of G:C to A:T transitions at CpG dinucleotides. These mutations also are common in lymphoid, esophageal, head and neck, stomach, brain and breast cancers. Increased NOS2 expression has been demonstrated in four of these cancers. Tumor-associated NO production may modify DNA directly, or may inhibit DNA repair activities, such as the recently described human thymine-DNA glycosylase, which has been shown to repair G:T mismatches at CpG dinucleotides. Because NO production also induces the accumulation of wild-type p53, the resulting growth inhibition can provide an additional strong selection pressure for nonfunctional, mutant p53. NO may, therefore, act as both an endogenous initiator and promoter in human colon carcinogenesis, and specific inhibitors of NOS2, as demonstrated recently in an animal tumor model, may have important chemopreventive potential in human colorectal cancer. Hemochromatosis and Wilson disease (WD), characterized by the excess hepatic deposition of iron and copper, respectively, produce oxidative stress and increase the risk of liver cancer. Because the frequency of p53 mutated alleles in nontumorous human tissue may be a biomarker of oxyradical damage and identify individuals at increased cancer risk, we have determined the frequency of p53 mutated alleles in nontumorous liver tissue from WD and hemochromatosis patients. When compared with the liver samples from normal controls, higher frequencies of G:C to T:A transversions at codon 249 (P < 0.001) and C:G to A:T transversions and C:G to T:A transitions at codon 250 (P < 0.001 and P < 0.005) were found in liver tissue from WD cases, a higher frequency of G:C to T:A transversions at codon 249 (P < 0.05) also was found in liver tissue from hemochromatosis cases. Sixty percent of the WD and 28% of hemochromatosis cases also showed a higher expression of inducible nitric oxide synthase in the liver, which suggests nitric oxide as a source of increased oxidative stress. A high level of etheno-DNA adducts, formed from oxyradical-induced lipid peroxidation, in liver from WD and hemochromatosis patients has been reported previously. Therefore, we exposed a wild-type p53 TK-6 lymphoblastoid cell line to 4-hydroxynonenal, an unsaturated aldehyde involved in lipid peroxidation, and observed an increase in G to T transversions at p53 codon 249 (AGG to AGT). These results are consistent with the hypothesis that the generation of oxygen/nitrogen species and unsaturated aldehydes from iron and copper overload in hemochromatosis and WD causes mutations in the p53 tumor suppressor gene.

高浓度的一氧化氮（NO）调节NO合酶（NOS）活性对于最小化细胞毒性和遗传毒性氮氧化物种类的影响是必不可少的。我们以前已经表明，NO诱导的p53蛋白的积累，下调基础和精氨酸调节诱导型NOS（NOS 2）在体外人类细胞的表达，和p53基因缺失小鼠有升高的NOS 2酶活性。 我们对原发性结肠肿瘤的研究建立了肿瘤中NOS 2的存在与CpG二核苷酸处G：C到A：T转换的频率之间的强正相关关系。这些突变在淋巴癌、食管癌、头颈癌、胃癌、脑癌和乳腺癌中也很常见。在这些癌症中的四种中已经证实了NOS 2表达增加。肿瘤相关的NO产生可以直接修饰DNA，或者可以抑制DNA修复活性，例如最近描述的人胸腺嘧啶-DNA糖基化酶，其已被证明可以修复CpG二核苷酸处的G：T错配。由于NO的产生也诱导野生型p53的积累，因此产生的生长抑制可以为无功能的突变型p53提供额外的强选择压力。因此，NO可能在人类结肠癌发生中充当内源性引发剂和促进剂，并且如最近在动物肿瘤模型中所证明的，NOS 2的特异性抑制剂可能在人类结肠直肠癌中具有重要的化学预防潜力。 血色素沉着症和威尔逊病（WD），其特征是过量的铁和铜的肝脏沉积，分别产生氧化应激和增加肝癌的风险。由于p53突变等位基因在非肿瘤性人体组织中的频率可能是氧自由基损伤的生物标志物，并识别癌症风险增加的个体，我们已经确定了WD和血色素沉着症患者的非肿瘤性肝组织中p53突变等位基因的频率。WD患者肝组织中249位密码子G：C → T：A颠换频率（P < 0.001）和250位密码子C：G → A：T颠换频率（P < 0.001和P < 0.005）均高于正常对照组，血色素沉着症患者肝组织中249位密码子G：C → T：A颠换频率（P < 0.05）也高于正常对照组。60%的WD和28%的血色素沉着症病例也显示出肝脏中诱导型一氧化氮合酶的较高表达，这表明一氧化氮是氧化应激增加的来源。在WD和血色素沉着症患者的肝脏中，由氧自由基诱导的脂质过氧化形成了高水平的乙烯基-DNA加合物。因此，我们将野生型p53 TK-6淋巴母细胞样细胞系暴露于4-羟基壬烯醛（一种参与脂质过氧化的不饱和醛），并观察到p53密码子249处的G至T颠换增加（AGG至AGT）。这些结果是一致的假设，即产生的氧/氮物种和不饱和醛从铁和铜过载血色素沉着症和WD导致突变的p53肿瘤抑制基因。