脂对泛醌细胞色素c还原酶的影响

用羟基磷灰石柱亲和层析法制备了高纯度的缺脂泛醌细胞色素c还原酶．脂的缺失使该酶活力丢失,部分细胞色素（约52.8％细胞色素b和82.5％细胞色素c₁）呈现还原状态．将缺脂泛醌细胞色素。还原酶与磷脂重组,可恢复其活性,同时那些呈还原状态的细胞色素也恢复到氧化态.此结果表明如此制备的缺脂泛醌细胞色素c还原酶仍保持着活力所必需的构象状态,细胞色素氧化还原状态随脂缺失的变化反映了脂与蛋白的相互作用.     

熊果酸对ox-LDL诱导的人脐静脉血管内皮细胞NQO1表达的影响(英文)

目的:研究熊果酸对经氧化性低密度脂蛋白(ox-LDL)干预后人脐静脉血管内皮细胞(human umbilical vein endothelial cells,HUVECs)醌还原氧化酶1表达的影响,以进一步探讨熊果酸抗动脉粥样硬化的机制。方法:体外培养人脐静脉内皮细胞,进行分组处理,每组n=5。对照组,不加任何处理;ox-LDL组,加入ox-LDL培养24h,终浓度为20mg/L;ox-LDL+低浓度熊果酸组,先加入ox-LDL(浓度20mg/L)孕育半小时,然后与熊果酸(浓度1.5μmlo/L)共同培养24h;ox-LDL+高浓度熊果酸组,先加入ox-LDL(浓度20mg/L)孕育半小时,然后与熊果酸(浓度4.5μmlo/L)共同培养24h;采用MTT试验测定细胞吸光度值,检测熊果酸对ox-LDL损伤的保护作用,采用RT-PCR法检测NQO1mRNA的表达,采用Western blot法检测NQO1蛋白的表达。结果:熊果酸减弱ox-LDL对HUVECs的损伤作用;ox-LDL组NQO1mRNA的表达量(0.624±0.009)明显高于对照组(0.521±0.007),P0.01。熊果酸呈浓度依赖性的提高NQO1mRNA的表达量(ox-LDL+低浓度熊果酸组vs ox-LDL组:0.722±0.058 vs 0.624±0.009,P0.01;ox-LDL+高浓度熊果酸组vs ox-LDL组:0.826±0.059 vs 0.624±0.009,P0.01)。ox-LDL组NQO1蛋白的表达量(0.624±0.009)明显高于对照组(0.521±0.007),P0.01。熊果酸呈浓度依赖性的提高NQO1蛋白的表达量(ox-LDL+低浓度熊果酸组vs ox-LDL组:0.710±0.058 vs 0.574±0.024,P0.01;ox-LDL+高浓度熊果酸组vs ox-LDL组:0.831±0.034 vs 0.574±0.024,P0.01)。结论:熊果酸可上调ox-LDL诱导的人脐静脉血管内皮细胞NQO1的表达,表明其可能具有抗氧化应激及抗动脉粥样硬化的作用。     

漏芦醇提取物对小鼠乳腺上皮细胞氧化损伤的缓解作用

摘要 目的：探讨漏芦乙醇提取物（RUEE）对脂多糖（LPS）诱导的小鼠乳腺上皮细胞氧化损伤发挥保护作用。方法：采用体外培养的小鼠乳腺上皮细胞系 HC11 为模型,首先利用MTT法筛选RUEE的最佳作用浓度及检测LPS和RUEE对细胞活力的影响,然后用1 μg?mL^-1 LPS单独处理,20、40、80 μg?mL^-1的RUEE与 1 μg?mL^-1 LPS 共处理 HC11细胞,检测氧化应激相关指标、抗氧化相关基因mRNA和蛋白表达的变化。结果：细胞活力实验确定20、40、80 μg?mL^-1的RUEE作为后续试验的添加浓度。LPS诱导可显著提高HC11细胞内丙二醛（MDA）含量、一氧化氮（NO）水平、一氧化氮合酶（iNOS）活性（P＜0.05）;明显降低超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GPx）、过氧化氢酶（CAT）的活性和总抗氧化能力（T-AOC）（P＜0.05）;显著抑制核因子E2相关因子2（Nrf2）、血红素氧合酶1（HO-1）、NAD(P)H醌氧化还原酶1（NQO1）的mRNA及蛋白表达（P＜0.05）。20、40、80 μg?mL^-1的RUEE预处理后可明显下调LPS诱导的HC11细胞内MDA含量、NO水平及iNOS活性（P＜0.05）;显著提高SOD、GPx、CAT的活性及T-AOC（P＜0.05）;显著上调Nrf2、HO-1、NQO1 mRNA和蛋白表达（P＜0.05）。结论：RUEE可以有效减轻LPS诱导的乳腺上皮细胞氧化损伤,这可能与RUEE能激活乳腺上皮细胞Nrf2进而促进抗氧化基因的表达有关。     

泥炭沼泽湿地土壤分解过程中可溶性有机质氧化还原能力变化特征及其影响机制

泥炭沼泽湿地土壤（泥炭土）分解过程是控制泥炭土碳排放的关键过程,其中可溶性有机质（DOM）是泥炭分解过程的主要输出物。DOM富含具有氧化还原活性的官能团,其中酚基具有抗氧化性质,是DOM氧化还原活性的重要组成部分,对驱动有氧和缺氧条件下的氧化还原过程意义重大。同时,酚基也可抑制泥炭的氧化降解,在泥炭土分解过程中起着重要作用。目前,关于泥炭分解过程中DOM氧化还原能力影响机制的相关研究较少。利用创新介导电化学方法、激发-发射荧光矩阵光谱法（EEM）,直接定量、定性评估DOM氧化还原变化程度,进而探讨（1）取自两个泥炭样地（OS/LB）的地表水、地下水、孔隙水样品中DOM的氧化还原性能;（2）来自泥炭样地OS的泥炭孔隙水剖面中DOM的氧化还原能力变化规律以及与泥炭分解的重要指标间的关系（如C/N和δ¹³C_DOC）。结果表明：选取电子转移能力（ETC）作为表征DOM氧化还原能力的指标,不同来源DOM的ETC值主要在2-4 mmole^-/gC之间;在泥炭土中DOM的ETC值与醌基和酚基的光谱性质参数存在强相关,这些基团对DOM氧化还原能力具有较大影响。具体表现为：在采样区OS,5-50 cm深度和0-210 cm深度的泥炭孔隙水剖面中,酚基在任意深度都是主导DOM氧化还原活性的重要组成部分,而醌基仅在没有淹水、有氧的近地表20 cm深度处时起到重要作用。在泥炭分解过程中,DOM氧化还原能力随深度的变化主要是受泥炭分解程度不同所致的泥炭自身酚基含量的变化所影响,特别是在未受地下水位波动影响的较大深度处。研究探讨泥炭分解过程中DOM氧化还原能力变化特征及其影响机制,为厘清有机质与泥炭沼泽湿地生物地球化学过程提供理论支撑。     

褐飞虱NADH泛醌氧化还原酶51kD亚基全长cDNA序列的克隆及分析

利用反转录聚合酶链式反应(RT-PCR)和快速扩增cDNA末端(RACE)技术克隆了褐飞虱NADH泛醌氧化还原酶51kD亚基(NQO)基因的全长cDNA片段,并进行了核苷酸序列测定.结果表明,该cDNA片段长度为1930 bp,所编码的蛋白与家牛、小家鼠、食蟹猴、人和蟾蜍的NADH泛醌氧化还原酶51kD亚基的氨基酸序列的同源性分别达到77%、76%、76%、75%和75%.Southern杂交分析表明,NQO基因在褐飞虱基因纽中以单拷贝形式存在.     

硫氧还蛋白在凋亡途径中的作用机制

硫氧还蛋白（Trx）是体内广泛存在的氧化还原蛋白,其家族中两种重要的硫氧还蛋白：硫氧还蛋白1（thioredoxin1,Trx1）和硫氧还蛋白2（thioredoxin2,Trx2）都含有保守的-Cys-Gly-Pro-Cys-还原序列。由于Trx具有调节细胞生长增殖和抗凋亡的作用,因此Trx在凋亡途径中的作用机制就成为了对抗肿瘤的研究热点。     

中国希瓦氏菌D14T的厌氧腐殖质呼吸

实验证明,希瓦氏菌新种（Shewanella cinicaD14T）在厌氧条件下可以利用多种有机酸盐和甲苯等环境有毒污染物作为电子供体,以腐殖质作为唯一末端电子受体进行厌氧呼吸（即醌呼吸）。电子在细胞膜呼吸链的传递过程中,偶联能量的产生来支持菌体的生长,1mmol/L AQDS可支持细胞增殖约60倍。电子供体的氧化和唯一电子受体腐殖质还原之间存在着动态的偶联过程,随着电子供体量的增加腐殖质还原的量也随之增加。典型呼吸链抑制剂诸如：抑制FeS中心的Cu2+ ,甲基萘醌类似物标桩菌素,抑制甲基萘醌氧化型向还原型转化的双香豆素和细胞色素P450的专一抑制物甲吡酮等对腐殖质的还原有着极为显著的抑制作用,为进一步证明希瓦氏菌（Shewanella cinica）D14T可利用腐殖质进行厌氧呼吸提供了有力的佐证。而D14T在进行腐殖质呼吸的同时,对于甲苯,苯胺等环境有毒物质的有效降解则具有着重要的环境学意义。     

硝基水杨酰胺抑制泛醌-细胞色素c还原酶的作用对氢醌的敏感性

泛醌－细胞色素ｃ还原酶（ＱＣＲ）是线粒体呼吸链的三个能量偶联部位之一,它起着将电子从还原型泛醌传递给细胞色素ｃ（Ｃｙｔ．ｃ）的作用,根据Ｋｉｎｇ和Ｙｕ提出的泛醌结合蛋白理论［１］,泛醌－细胞色素ｃ还原酶中含有泛醌结合蛋白ＱＰｃ．研究表明,泛醌－细胞色...     

吡咯喹啉醌及其生理功能

吡咯喹啉醌（ＰＱＱ）──一种新的氧化还原酶辅基,存在于一些微生物、植物和动物组织中,参与催化生物体内氧化还原反应。研究表明ＰＱＱ具有一些重要生理功能：刺激某些植物发育及微生物和人体细胞生长;作为动物体生长发育的必需因子;清除自由基保护机体免受自由基损害;防治肝损伤;促进神经生长因子合成等。因此,ＰＱＱ具有一定的医药应用前景。     

酚氧化酶及其酶原的研究进展(Ⅱ)——免疫学特性、细胞定位及其功能

酚氧化酶（Phenoloxidase,PO）又称为酪氨酸酶（tyrosinase,EC1．14．18．1）,是一种含铜的酶,能够催化单酚羟化成二酚（如多巴）,并把二酚氧化成醌;醌在非酶促条件下形成最终的反应产物黑色素。PO在脊椎动物和无脊椎动物中都广泛存在,而且被认为是一种参与免疫的重要因子。本文就酚氧化酶及其酶原的免疫学特性、细胞定位及其功能研究进展进行综述。     

NAD(P)H:Quinone Oxidoreductase 1 (NQO1) Localizes to the Mitotic Spindle in Human Cells

NAD(P)H:quinone oxidoreductase 1 (NQO1) is an FAD containing quinone reductase that catalyzes the 2-electron reduction of a broad range of quinones. The 2-electron reduction of quinones to hydroquinones by NQO1 is believed to be a detoxification process since this reaction bypasses the formation of the highly reactive semiquinone. NQO1 is expressed at high levels in normal epithelium, endothelium and adipocytes as well as in many human solid tumors. In addition to its function as a quinone reductase NQO1 has been shown to reduce superoxide and regulate the 20 S proteasomal degradation of proteins including p53. Biochemical studies have indicated that NQO1 is primarily located in the cytosol, however, lower levels of NQO1 have also been found in the nucleus. In these studies we demonstrate using immunocytochemistry and confocal imaging that NQO1 was found associated with mitotic spindles in cells undergoing division. The association of NQO1 with the mitotic spindles was observed in many different human cell lines including nontransformed cells (astrocytes, HUVEC) immortalized cell lines (HBMEC, 16HBE) and cancer (pancreatic adenocarcinoma, BXPC3). Confocal analysis of double-labeling experiments demonstrated co-localization of NQO1with alpha-tubulin in mitotic spindles. In studies with BxPc-3 human pancreatic cancer cells the association of NQO1 with mitotic spindles appeared to be unchanged in the presence of NQO1 inhibitors ES936 or dicoumarol suggesting that NQO1 can associate with the mitotic spindle and still retain catalytic activity. Analysis of archival human squamous lung carcinoma tissue immunostained for NQO1 demonstrated positive staining for NQO1 in the spindles of mitotic cells. The purpose of this study is to demonstrate for the first time the association of the quinone reductase NQO1 with the mitotic spindle in human cells.     

Characterization of the threshold for NAD(P)H:quinone oxidoreductase activity in intact sulforaphane-treated pulmonary arterial endothelial cells

Treatment of bovine pulmonary arterial endothelial cells in culture with the phase II enzyme inducer sulforaphane (5μM, 24h; sulf-treated) increased cell-lysate NAD(P)H:quinone oxidoreductase (NQO1) activity by 5.7 ± 0.6 (mean ± SEM)-fold, but intact-cell NQO1 activity by only 2.8 ± 0.1-fold compared to control cells. To evaluate the hypothesis that the threshold for sulforaphane-induced intact-cell NQO1 activity reflects a limitation in the capacity to supply NADPH at a sufficient rate to drive all the induced NQO1 to its maximum activity, total KOH-extractable pyridine nucleotides were measured in cells treated with duroquinone to stimulate maximal NQO1 activity. NQO1 activation increased NADP(+) in control and sulf-treated cells, with the effect more pronounced in the sulf-treated cells, in which the NADPH was also decreased. Glucose-6-phosphate dehydrogenase (G-6-PDH) inhibition partially blocked NQO1 activity in control and sulf-treated cells, but G-6-PDH overexpression via transient transfection with the human cDNA alleviated neither the restriction on intact sulf-treated cell NQO1 activity nor the impact on the NADPH/NADP(+) ratios. Intracellular ATP levels were not affected by NQO1 activation in control or sulf-treated cells. An increased dependence on extracellular glucose and a rightward shift in the K(m) for extracellular glucose were observed in NQO1-stimulated sulf-treated vs control cells. The data suggest that glucose transport in the sulf-treated cells may be insufficient to support the increased metabolic demand for pentose phosphate pathway-generated NADPH as an explanation for the NQO1 threshold.     

Expression of NAD(P)H:quinone oxidoreductase 1 in HeLa cells: role of hydrogen peroxide and growth phase

The aim of this work was to study the role of H(2)O(2) in the regulation of NAD(P)H:quinone oxidoreductase 1 (NQO1, DT-diaphorase, EC ) with relation to cell density of HeLa cells cultures and the function played by NQO1 in these cells. Levels of NQO1 activity were much higher (40-fold) in confluent HeLa cells than in sparse cells, the former cells being much more resistant to H(2)O(2). Addition of sublethal concentrations of H(2)O(2) (up to 24 microm) produced a significant increase of NQO1 (up to 16-fold at 12 microm) in sparse cells but had no effect in confluent cells. When cells reached confluency in the presence of pyruvate, a H(2)O(2) scavenger, NQO1 activity was decreased compared with cultures grown to confluency without pyruvate. Inhibition of quinone reductases by dicumarol substantially decreased viability of confluent cells in serum-free medium. This is the first demonstration that regulation of NQO1 expression by H(2)O(2) is dependent on the cell density in HeLa cells and that endogenous generation of H(2)O(2) participates in the increase of NQO1 activity as cell density is higher. This enzyme is required to promote survival of confluent cells.     

Nucleotide and deduced amino acid sequence of a human cDNA (NQO2) corresponding to a second member of the NAD(P)H:quinone oxidoreductase gene family. Extensive polymorphism at the NQO2 gene locus on chromosome 6.

NAD(P)H:quinone oxidoreductases (NQOs) are flavoproteins that catalyze the oxidation of NADH or NADPH by various quinones and oxidation-reduction dyes. We have previously described a complementary DNA that encodes a dioxin-inducible cytosolic form of human NAD(P)H:quinone oxidoreductase (NQO1). In the present report we describe the nucleotide sequence and deduced amino acid sequence for a cDNA clone that is likely to encode a second form of NAD(P)H:quinone oxidoreductase (NQO2) which was isolated by screening a human liver cDNA library by hybridization with a NQO1 cDNA probe. The NQO2 cDNA is 976 nucleotides long and encodes a protein of 231 amino acids (Mr = 25,956). The human NQO2 cDNA and protein are 54% and 49% similar to human liver cytosolic NQO1 cDNA and protein, respectively. COS1 cells transfected with NQO2 cDNA showed a 5-7-fold increase in NAD(P)H:quinone oxidoreductase activity as compared to nontransfected cells when either 2,6-dichlorophenolindophenol or menadione was used as substrate. Western blot analysis of the expressed NQO1 and NQO2 cDNA proteins showed cross-reactivity with rat NQO1 antiserum, indicating that NQO1 and NQO2 proteins are immunologically related. Northern blot analysis shows the presence of one NQO2 mRNA of 1.2 kb in control and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) treated human hepatoblastoma Hep-G2 cells and that TCDD treatment does not lead to enhanced levels of NQO2 mRNA as it does for NQO1 mRNA. Southern blot analysis of human genomic DNA suggests the presence of a single gene approximately 14-17 kb in length. The NQO2 gene locus is highly polymorphic as indicated by several restriction fragment length polymorphisms detected with five different restriction enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)     

NQO1-activated phenothiazinium redox cyclers for the targeted bioreductive induction of cancer cell apoptosis

Altered redox signaling and regulation in cancer cells represent a chemical vulnerability that can be targeted by selective chemotherapeutic intervention. Here, we demonstrate that 3,7-diaminophenothiazinium-based redox cyclers (PRC) induce selective cancer cell apoptosis by NAD(P)H:quinone oxidoreductase (NQO1)-dependent bioreductive generation of cellular oxidative stress. Using PRC lead compounds including toluidine blue against human metastatic G361 melanoma cells, apoptosis occurred with phosphatidylserine externalization, loss of mitochondrial transmembrane potential, cytochrome c release, caspase-3 activation, and massive ROS production. Consistent with reductive activation and subsequent redox cycling as the mechanism of PRC cytotoxicity, coincubation with catalase achieved cell protection, whereas reductive antioxidants enhanced PRC cytotoxicity. Unexpectedly, human A375 melanoma cells were resistant to PRC-induced apoptosis, and PRC-sensitive G361 cells were protected by preincubation with the NQO1 inhibitor dicoumarol. Indeed, NQO1 specific enzymatic activity was 9-fold higher in G361 than in A375 cells. The critical role of NQO1 in PRC bioactivation and cytotoxicity was confirmed, when NQO1-transfected breast cancer cells (MCF7-DT15) stably overexpressing active NQO1 displayed strongly enhanced PRC sensitivity as compared to vector control-transfected cells with baseline NQO1 activity. Based on the known overexpression of NQO1 in various tumors these findings suggest the feasibility of developing PRC lead compounds into tumor-selective bioreductive chemotherapeutics.     

Synthesis of cryptolepine analogues as potential bioreducible anticancer agents

A series of 10 novel nitro-analogues of cryptolepine (1) has been synthesised and these compounds were evaluated for their in-vitro cytotoxic properties as well as their potential for reductive activation by the cytosolic reductase enzymes NQO1 and NQO2. Molecular modelling studies suggest that cryptolepine is able to fit into the active site of NQO2 and thus raising the possibility that nitro-analogues of 1 could act as bioreductive prodrugs and be selectively reduced by NQO1 and NQO2 to more toxic species in cancer cells in which these enzymes are over-expressed. Analogues were screened against the RT112 cell line (high in NQO2), in the presence and absence of the essential cofactor dihydronicotinamide riboside (NRH), whereby all analogues were shown to be cytotoxic (IC50<2microM) in the absence of NRH. With the addition of NRH, one analogue, 2-fluoro-7,9-dinitrocryptolepine (7), exhibited a 2.4-fold increase in cytotoxic activity. Several nitro-derivatives were also evaluated as substrates for purified human NQO1 and analogues that were found to be substrates were subsequently tested against the H460 (high NQO1) and BE (low NQO1) cell lines to detect in-vitro activation by NQO1. The analogue 8-chloro-9-nitrocryptolepine (9) was found to be the best substrate for NQO1 but it was not more toxic to H460 than to BE cells. Fluorescence laser confocal microscopy of 1 and several analogues showed that in contrast to 1 the analogues were not localised into the nucleus suggesting that their cytotoxic mode(s) of action are different. This study has identified novel substrates for both NQO1 and NQO2 and further work on nitrocryptolepine derivatives as a lead towards novel anticancer agents would be worthwhile.     

An NQO1-Initiated and p53-Independent Apoptotic Pathway Determines the Anti-Tumor Effect of Tanshinone IIA against Non-Small Cell Lung Cancer

NQO1 is an emerging and promising therapeutic target in cancer therapy. This study was to determine whether the anti-tumor effect of tanshinone IIA (TSA) is NQO1 dependent and to elucidate the underlying apoptotic cell death pathways. NQO1(+) A549 cells and isogenically matched NQO1 transfected and negative H596 cells were used to test the properties and mechanisms of TSA induced cell death. The in vivo anti-tumor efficacy and the tissue distribution properties of TSA were tested in tumor xenografted nude mice. We observed that TSA induced an excessive generation of ROS, DNA damage, and dramatic apoptotic cell death in NQO1(+) A549 cells and H596-NQO1 cells, but not in NQO1(-) H596 cells. Inhibition or silence of NQO1 as well as the antioxidant NAC markedly reversed TSA induced apoptotic effects. TSA treatment significantly retarded the tumor growth of A549 tumor xenografts, which was significantly antagonized by dicoumarol co-treatment in spite of the increased and prolonged TSA accumulations in tumor tissues. TSA activated a ROS triggered, p53 independent and caspase dependent mitochondria apoptotic cell death pathway that is characterized with increased ratio of Bax to Bcl-xl, mitochondrial membrane potential disruption, cytochrome c release, and subsequent caspase activation and PARP-1 cleavage. The results of these findings suggest that TSA is a highly specific NQO1 target agent and is promising in developing as an effective drug in the therapy of NQO1 positive NSCLC.     

Mouse NRH:quinone oxidoreductase (NQO2): cloning of cDNA and gene- and tissue-specific expression

The mouse NQO2 cDNA and gene with flanking regions were cloned and sequenced. Analysis of the primary structure of the mouse NQO2 protein revealed the presence of glycosylation, myristylation, protein kinase C and caseine kinase II phosphorylation sites. These sites are conserved in the human NQO2 protein. The mouse NQO2 gene promoter contains several important cis-elements, including the antioxidant response element (ARE), the xenobiotic response element (XRE), and an Sp1 binding site. Northern analysis of eight mouse tissues indicated wide variations in the expression of the NQO2 and NQO1 genes. NQO2 gene expression was higher in liver and testis compared with the NQO1 gene, which was highest in the heart. NQO1 gene expression was undetectable in the testis. Mouse kidney showed significantly higher expression levels of NQO1 compared with NQO2. Brain, spleen, lung, and skeletal muscle showed undetectable levels of NQO2 and NQO1 gene expression. NQO2 activity followed a more or less similar pattern of tissue-specific expression as NQO2 RNA. Interestingly, the NQO2 activity remained unchanged in the NQO1-/-mice tissues compared with NQO1+/+ mice, with the exception of the liver. The livers from NQO1-/-mice showed a 45% increase in NQO2 activity compared with the NQO1+/+ mice. The mouse NQO2 cDNA was subcloned into the pMT2 eukaryotic expression vector which, upon transfection in monkey kidney COS1 cells, produced a significant increase in NQO2 activity. Deletion of 54 amino acids from the N-terminus of the mouse NQO2 protein resulted in the loss of NQO2 expression and activity in transfected COS1 cells. This indicates that deletion of exon(s) encoding the N-terminus of NQO2 from the endogenous gene in mouse embryonic (ES) stem cells should result in NQO2-null mice.     

Genetic deletion of NAD(P)H:quinone oxidoreductase 1 abrogates activation of nuclear factor-kappaB, IkappaBalpha kinase, c-Jun N-terminal kinase, Akt, p38, and p44/42 mitogen-activated protein kinases and potentiates apoptosis

The NAD(P)H:quinone oxidoreductase 1 (NQO1) is a phase II enzyme that reduces and detoxifies quinones and their derivatives. Although overexpressed in tumor cells, the NQO1 has been linked with the suppression of carcinogenesis, and the effect of NQO1 on tumor necrosis factor (TNF), a cytokine that mediates tumorigenesis through proliferation, invasion, angiogenesis, and metastasis of tumors, is currently unknown. The purpose of our study was to determine the role of NQO1 in TNF cell signaling by using keratinocytes derived from wild-type and NQO1 gene-deleted mice. TNF induced nuclear factor (NF)-kappaB activation in wild-type but not in NQO1-deleted cells. The treatment of wild-type cells with dicoumarol, a known inhibitor of NQO1, also abolished TNF-induced NF-kappaB activation. NF-kappaB activation induced by lipopolysaccharide, phorbol ester, and cigarette smoke, was also abolished in NQO1-deleted cells. The suppression of NF-kappaB activation was mediated through the inhibition of IkappaBalpha kinase activation, IkappaBalpha phosphorylation, and IkappaBalpha degradation. Further, the deletion of NQO1 abolished TNF-induced c-Jun N-terminal kinase, Akt, p38, and p44/p42 mitogen-activated protein kinase activation. TNF also induced the expression of various NF-kappaB-regulated gene products involved in cell proliferation, antiapoptosis, and invasion in wild-type NQO1 keratinocytes but not in NQO1-deleted cells. The suppression of these antiapoptotic gene products increased TNF-induced apoptosis in NQO1-deleted cells. We also found that TNF activated NQO1, and NQO1-specific small interfering RNA abolished the TNF-induced NQO1 activity and NF-kappaB activation. Overall, our results indicate that NQO1 plays a pivotal role in signaling activated by TNF and other inflammatory stimuli and that its suppression is a potential therapeutic strategy to inhibit the proliferation, survival, invasion, and metastasis of tumor cells.