NAD(P)H:Quinone Oxidoreductase 1 and NRH:Quinone Oxidoreductase 2 Activity and Expression in Bladder and Ovarian Cancer and Lower NRH:Quinone Oxidoreductase 2 Activity Associated with an NQO2 Exon 3 Single-Nucleotide Polymorphism

Polymorphisms and Pharmacogenomics of NQO2: The Past and the Future

The flavoenzyme N-ribosyldihydronicotinamide (NRH):quinone oxidoreductase 2 (NQO2) catalyzes two-electron reductions of quinones. NQO2 contributes to the metabolism of biogenic and xenobiotic quinones, including a wide range of antitumor drugs, with both toxifying and detoxifying functions. Moreover, NQO2 activity can be inhibited by several compounds, including drugs and phytochemicals such as flavonoids. NQO2 may play important roles that go beyond quinone metabolism and include the regulation of oxidative stress, inflammation, and autophagy, with implications in carcinogenesis and neurodegeneration. NQO2 is a highly polymorphic gene with several allelic variants, including insertions (I), deletions (D) and single-nucleotide (SNP) polymorphisms located mainly in the promoter, but also in other regulatory regions and exons. This is the first systematic review of the literature reporting on NQO2 gene variants as risk factors in degenerative diseases or drug adverse effects. In particular, hypomorphic 29 bp I alleles have been linked to breast and other solid cancer susceptibility as well as to interindividual variability in response to chemotherapy. On the other hand, hypermorphic polymorphisms were associated with Parkinson's and Alzheimer's disease. The I and D promoter variants and other NQO2 polymorphisms may impact cognitive decline, alcoholism and toxicity of several nervous system drugs. Future studies are required to fill several gaps in NQO2 research.

Single Nucleotide Polymorphisms Associated with Prostate Cancer Progression: A Systematic Review

BACKGROUND

New biomarkers of progression in patients with prostate cancer (PCa) are needed to improve their classification and clinical management. This systematic review investigated the relationship between single nucleotide polymorphisms (SNPs) and PCa progression.

METHODS

A keyword search was performed in Pubmed, EMBASE, Scopus, Web of Science, and Cochrane for publications between 2007 and 2022. We included articles with adjusted and significant associations, a median follow-up greater than or equal to 24 months, patients taken to radical prostatectomy (RP) as a first therapeutic option, and results presented based on biochemical recurrence (BCR).

RESULTS

In the 27 articles selected, 73 SNPs were identified in 39 genes, organized in seven functional groups. Of these, 50 and 23 SNPs were significantly associated with a higher and lower risk of PCa progression, respectively. Likewise, four haplotypes were found to have a significant association with PCa progression.

CONCLUSION

This article highlights the importance of SNPs as potential markers of PCa progression and their possible functional relationship with some genes relevant to its development and progression. However, most variants were identified only in cohorts from two countries; no additional studies reproduce these findings.

Elucidation of Protonation Cooperativity of a STING-Activating Polymer

Stimuli-responsive nanomaterials have the potential to improve the performance and overcome existing barriers of conventional nanotherapeutics. Molecular cooperativity design in stimuli-responsive nanomedicine can amplify physiological signals, enabling a cooperative response for improved diagnostic and therapeutic precision. Previously, this work reported an ultra-pH-sensitive polymer, PEG-b-PC7A, that possesses innate immune activating properties by binding to the stimulator of interferon genes (STING) through polyvalent phase condensation. This interaction enhances STING activation and synergizes with the endogenous STING ligand for robust cancer immunotherapy. Despite its successes in innate immune activation, the fundamental physicochemical and pH-responsive properties of PC7A require further investigation. Here, this study elucidates the protonation cooperativity driven by the phase transition of PC7A copolymer. The highly cooperative system displays an "all-or-nothing" proton distribution between highly charged unimer (all) and neutral micelle (nothing) states without gradually protonated intermediates. The binary protonation behavior is further illustrated in pH-precision-controlled release of a representative anticancer drug, β-lapachone, by PC7A micelles over a noncooperative PE5A polymer. Furthermore, the bimodal distribution of protons is represented by a high Hill coefficient (nH  > 9), featuring strong positive cooperativity. This study highlights the nanoscale pH cooperativity of an immune activating polymer, providing insights into the physicochemical characterization and design parameters for future nanotherapeutics development.

Chemical and Biochemical Reactivity of the Reduced Forms of Nicotinamide Riboside

All life forms require nicotinamide adenine dinucleotide, NAD⁺, and its reduced form NADH. They are redox partners in hundreds of cellular enzymatic reactions. Changes in the intracellular levels of total NAD (NAD⁺ + NADH) and the (NAD⁺/NADH) ratio can cause cellular dysfunction. When not present in protein complexes, NADH and its phosphorylated form NADPH degrade through intricate mechanisms. Replenishment of a declining total NAD pool can be achieved with biosynthetic precursors that include one of the reduced forms of nicotinamide riboside (NR⁺), NRH. NRH, like NADH and NADPH, is prone to degradation via oxidation, hydration, and isomerization and, as such, is an excellent model compound to rationalize the nonenzymatic metabolism of NAD(P)H in a biological context. Here, we report on the stability of NRH and its propensity to isomerize and irreversibly degrade. We also report the preparation of two of its naturally occurring isomers, their chemical stability, their reactivity toward NRH-processing enzymes, and their cell-specific cytotoxicity. Furthermore, we identify a mechanism by which NRH degradation causes covalent peptide modifications, a process that could expose a novel type of NADH-protein modifications and correlate NADH accumulation with "protein aging." This work highlights the current limitations in detecting NADH's endogenous catabolites and in establishing the capacity for inducing cellular dysfunction.

Cyclic Changes in Active Site Polarization and Dynamics Drive the 'Ping-pong' Kinetics in NRH:Quinone Oxidoreductase 2: An Insight from QM/MM Simulations

Quinone reductases belong to the family of flavin-dependent oxidoreductases. With the redox active cofactor, flavin adenine dinucleotide, quinone reductases are known to utilize a 'ping-pong' kinetic mechanism during catalysis in which a hydride is bounced back and forth between flavin and its two substrates. However, the continuation of this catalytic cycle requires product displacement steps, where the product of one redox half-cycle is displaced by the substrate of the next half-cycle. Using improved hybrid quantum mechanical/molecular mechanical simulations, both the catalytic hydride transfer and the product displacement reactions were studied in NRH:quinone oxidoreductase 2. Initially, the self-consistent charge-density functional tight binding theory was used to describe flavin ring and the substrate atoms, while embedded in the molecular mechanically-treated solvated active site. Then, for each step of the catalytic cycle, a further improvement of energetics was made using density functional theory-based corrections. The present study showcases an integrated interplay of solvation, protonation, and protein matrix-induced polarization as the driving force behind the thermodynamic wheel of the 'ping-pong' kinetics. Reported here is the first-principles model of the 'ping-pong' kinetics that portrays how cyclic changes in the active site polarization and dynamics govern the oscillatory hydride transfer and product displacement in this enzyme.

Oxidative stress index is increased in children exposed to industrial discharges and is inversely correlated with metabolite excretion of voc

Although the Atoyac River has been classified as highly polluted by environmental authorities, several communities are settled on its banks, affecting around 1.5 million persons, as well as farmland, due to an environmental distribution of toxics in the area. Our aim was to demonstrate that this environment affects important physiological processes that have an impact in health, so we conducted a study of schoolchildren from small communities on the banks of the river and in another similar town located far from it. 91 and 93 students, boys and girls, were studied from each site for oxidative stress index (OSI), calculated from the total antioxidant capacity and the total oxidative status, BTEX metabolite excretion and relevant metabolic polymorphisms participating in the bioactivation-detoxification of most VOC: CYP2E1 RsaI, NQO1 C609T, and null polymorphisms of GSTT1 and GSTM1. Results showed that OSI was significantly higher in children living by the river (5.23 ± 3.4 vs 2.59 ± 1.46, 95% C.I.). At this site, OSI was correlated with diminished metabolite excretion and a diminished antioxidant capacity; an association with genotypes CYP2E1RsaI (c2c2), GSTT1 present and NQO1*2 (CC) was also observed. Furthermore, boys at this site exhibited a diminished BMI compared to boys from the other community who were younger.

IN CONCLUSION

children living at polluted sites like this, show early biological effects that might lead to health problems in their adult life. Environmental protection should be enforced to protect people's health in these sites where not even environmental monitoring is done. Environ. Mol. Mutagen. 59:639-652, 2018. © 2018 Wiley Periodicals, Inc.

Reduction and Scavenging of Chemically Reactive Drug Metabolites by NAD(P)H:Quinone Oxidoreductase 1 and NRH:Quinone Oxidoreductase 2 and Variability in Hepatic Concentrations

Detoxicating enzymes NAD(P)H:quinone oxidoreductase 1 (NQO1) and NRH:quinone oxidoreductase 2 (NQO2) catalyze the two-electron reduction of quinone-like compounds. The protective role of the polymorphic NQO1 and NQO2 enzymes is especially of interest in the liver as the major site of drug bioactivation to chemically reactive drug metabolites. In the current study, we quantified the concentrations of NQO1 and NQO2 in 20 human liver donors and NQO1 and NQO2 activities with quinone-like drug metabolites. Hepatic NQO1 concentrations ranged from 8 to 213 nM. Using recombinant NQO1, we showed that low nM concentrations of NQO1 are sufficient to reduce synthetic amodiaquine and carbamazepine quinone-like metabolites in vitro. Hepatic NQO2 concentrations ranged from 2 to 31 μM. NQO2 catalyzed the reduction of quinone-like metabolites derived from acetaminophen, clozapine, 4′-hydroxydiclofenac, mefenamic acid, amodiaquine, and carbamazepine. The reduction of the clozapine nitrenium ion supports association studies showing that NQO2 is a genetic risk factor for clozapine-induced agranulocytosis. The 5-hydroxydiclofenac quinone imine, which was previously shown to be reduced by NQO1, was not reduced by NQO2. Tacrine was identified as a potent NQO2 inhibitor and was applied to further confirm the catalytic activity of NQO2 in these assays. While the in vivo relevance of NQO2-catalyzed reduction of quinone-like metabolites remains to be established by identification of the physiologically relevant co-substrates, our results suggest an additional protective role of the NQO2 protein by non-enzymatic scavenging of quinone-like metabolites. Hepatic NQO1 activity in detoxication of quinone-like metabolites becomes especially important when other detoxication pathways are exhausted and NQO1 levels are induced.

The ontogeny and population variability of human hepatic dihydronicotinamide riboside:quinone oxidoreductase (NQO2)

Dihydronicotinamide riboside:quinone oxidoreductase (NQO2) is an enzyme that performs reduction reactions involved in antioxidant defense. We hypothesized that NQO2 hepatic drug clearance would develop in children over time, similar to NQO1. Using human liver cytosol (n = 117), the effects of age, sex, ethnicity, and weight on NQO2 expression and activity were probed. No significant correlations were observed. Biochemical activity of NQO2 was as high at birth as in adults (0.23 ± 0.04 nmol/min/mg protein, mean ± SEM, range 0-1.83). In contrast, modeled hepatic clearance through the NQO2 pathway was up to 10% of adult levels at birth, reaching predicted adult levels (0.3 ± 0.03 L/h) at 14 years of age. Comparisons between NQO1 and NQO2 in the same livers showed that neither protein (P = 0.32) nor activity (P = 0.23) correlated, confirming both orthologs are independently regulated. Because hepatic clearance through NQO2 does not mature until teenage years, compounds detoxified by this enzyme may be more deleterious in children.

The two common polymorphic forms of human NRH-quinone oxidoreductase 2 (NQO2) have different biochemical properties

There are two common forms of NRH-quinone oxidoreductase 2 (NQO2) in the human population resulting from SNP rs1143684. One has phenylalanine at position 47 (NQO2-F47) and the other leucine (NQO2-L47). Using recombinant proteins, we show that these variants have similar steady state kinetic parameters, although NQO2-L47 has a slightly lower specificity constant. NQO2-L47 is less stable towards proteolytic digestion and thermal denaturation than NQO2-F47. Both forms are inhibited by resveratrol, but NQO2-F47 shows negative cooperativity with this inhibitor. Thus these data demonstrate, for the first time, clear biochemical differences between the variants which help explain previous biomedical and epidemiological findings.

Design of optimized hypoxia-activated prodrugs using pharmacokinetic/pharmacodynamic modeling

Hypoxia contributes to resistance of tumors to some cytotoxic drugs and to radiotherapy, but can in principle be exploited with hypoxia-activated prodrugs (HAP). HAP in clinical development fall into two broad groups. Class I HAP (like the benzotriazine N-oxides tirapazamine and SN30000), are activated under relatively mild hypoxia. In contrast, Class II HAP (such as the nitro compounds PR-104A or TH-302) are maximally activated only under extreme hypoxia, but their active metabolites (effectors) diffuse to cells at intermediate O2 and thus also eliminate moderately hypoxic cells. Here, we use a spatially resolved pharmacokinetic/pharmacodynamic (SR-PK/PD) model to compare these two strategies and to identify the features required in an optimal Class II HAP. The model uses a Green's function approach to calculate spatial and longitudinal gradients of O2, prodrug, and effector concentrations, and resulting killing in a digitized 3D tumor microregion to estimate activity as monotherapy and in combination with radiotherapy. An analogous model for a normal tissue with mild hypoxia and short intervessel distances (based on a cremaster muscle microvessel network) was used to estimate tumor selectivity of cell killing. This showed that Class II HAP offer advantages over Class I including higher tumor selectivity and greater freedom to vary prodrug diffusibility and rate of metabolic activation. The model suggests that the largest gains in class II HAP antitumor activity could be realized by optimizing effector stability and prodrug activation rates. We also use the model to show that diffusion of effector into blood vessels is unlikely to materially increase systemic exposure for realistic tumor burdens and effector clearances. However, we show that the tumor selectivity achievable by hypoxia-dependent prodrug activation alone is limited if dose-limiting normal tissues are even mildly hypoxic.

Indigofera suffruticosa Mill extracts up-regulate the expression of the π class of glutathione S-transferase and NAD(P)H: quinone oxidoreductase 1 in rat Clone 9 liver cells

Because induction of phase II detoxification enzyme is important for chemoprevention, we study the effects of Indigofera suffruticosa Mill, a medicinal herb, on the expression of π class of glutathione S-transferase (GSTP) and NAD(P)H: quinone oxidoreductase 1 (NQO1) in rat Clone 9 liver cells. Both water and ethanolic extracts of I. suffruticosa significantly increased the expression and enzyme activities of GSTP and NQO1. I. suffruticosa extracts up-regulated GSTP promoter activity and the binding affinity of nuclear factor erythroid 2-related factor 2 (Nrf2) with the GSTP enhancer I oligonucleotide. Moreover, I. suffruticosa extracts increased nuclear Nrf2 accumulation as well as ARE transcriptional activity. The level of phospho-ERK was augmented by I. suffruticosa extracts, and the ERK inhibitor PD98059 abolished the I. suffruticosa extract-induced ERK activation and GSTP and NQO-1 expression. Moreover, I. suffruticosa extracts, especially the ethanolic extract increased the glutathione level in mouse liver and red blood cells as well as Clone 9 liver cells. The efficacy of I. suffruticosa extracts in induction of phase II detoxification enzymes and glutathione content implies that I. suffruticosa could be considered as a potential chemopreventive agent.

Genetic variants in metabolizing genes NQO1, NQO2, MTHFR and risk of prostate cancer: a study from North India

Quinone oxidoreductases (NAD(P)H): quinone oxidoreductase 1 (NQO1) and NRH: quinone oxidoreductase 2 (NQO2) are an antioxidant enzyme, important in the detoxification of environmental carcinogens. Methylene-tetra-hydrofolate reductase (MTHFR), plays a role in folate metabolism and may have oncogenic role through disruption of normal DNA methylation pattern, synthesis, and impaired DNA repair. In a case-control study, genotyping was done in 195 PCa and 250 age matched unrelated healthy controls of similar ethnicity to determine variants in NQO1 exon 4 (C > T, rs4986998), exon 6 (C > T, rs1800566), NQO2 -3423 (G > A, rs2070999) and MTHFR exon 4 (C > T, rs1801133) by PCR-RFLP methods. Heterozygous genotype CT and variant allele career genotype (CT + TT) of NQO1 exon 4 showed increased risk of PCa (OR = 2.06, p = 0.033; OR = 2.02, p = 0.027). Variant allele T also revealed increased risk (OR = 1.87, p = 0.029). Similarly variant genotype TT (OR = 2.71, p = 0.009), combined genotype (CT + TT) (OR = 1.59, p = 0.019) and T allele (OR = 1.63, p = 0.002) of NQO1 exon 6 demonstrated significant risk for PCa. Diplotypes of NQO1 (exon 4 and 6), C-T (OR = 1.56, Pc = 0.007) and T-T (OR = 0.011, Pc = 3.86) was associated with an increased risk for PCa. NQO2 and MTHFR did not show any risk with PCa. Our results strongly support that common sequence variants and diplotypes of NQO1 exon 4 and 6 genes may have role in PCa risk in the North Indian population, indicating the importance of genes involved in metabolism with respect to PCa risk. Additional studies on larger populations are needed to clarify the role of variation in these genes in PCa carcinogenesis.

Human NAD(P)H:quinone oxidoreductase type I (hNQO1) activation of quinone propionic acid trigger groups

NAD(P)H:quinone oxidoreductase type I (NQO1) is a target enzyme for triggered delivery of drugs at inflamed tissue and tumor sites, particularly those that challenge traditional therapies. Prodrugs, macromolecules, and molecular assemblies possessing trigger groups that can be cleaved by environmental stimuli are vehicles with the potential to yield active drug only at prescribed sites. Furthermore, quinone propionic acids (QPAs) covalently attached to prodrugs or liposome surfaces can be removed by application of a reductive trigger stimulus, such as that from NQO1; their rates of reductive activation should be tunable via QPA structure. We explored in detail the recombinant human NAD(P)H:quinone oxidoreductase type I (rhNQO1)-catalyzed NADH reduction of a family of substituted QPAs and obtained high precision kinetic parameters. It is found that small changes in QPA structure-in particular, single atom and function group substitutions on the quinone ring at R(1)-lead to significant impacts on the Michaelis constant (K(m)), maximum velocity (V(max)), catalytic constant (k(cat)), and catalytic efficiency (k(cat)/K(m)). Molecular docking simulations demonstrate that alterations in QPA structure result in large changes in QPA alignment and placement with respect to the flavin isoalloxazine ring in the active site of rhNQO1; a qualitative relationship exists between the kinetic parameters and the depth of QPA penetration into the rhNQO1 active site. From a quantitative perspective, a very good correlation is observed between log(k(cat)/K(m)) and the molecular-docking-derived distance between the flavin hydride donor site and quinone hydride acceptor site in the QPAs, an observation that is in agreement with developing theories. The comprehensive kinetic and molecular modeling knowledge obtained for the interaction of recombinant human NQO1 with the quinone propionic acid analogues provides insight into the design and implementation of the QPA trigger groups for drug delivery applications.

Institutional Profile: Pharmacogenomics research at Newcastle University

Newcastle University has been active in the field of pharmacogenomics/pharmacogenetics research since 1988. Research activity is based at the Faculty of Medical Sciences and is led by four professors within two separate research institutes. This article describes the various ongoing research projects and the teams involved together with our teaching activities in the subject.

Chemotherapy-induced toxicity is highly heritable in Drosophila melanogaster

OBJECTIVES

Identification of the genes responsible for chemotherapy toxicity in Drosophila melanogaster may allow for the identification of human orthologs that similarly mediate toxicity in humans. To develop D. melanogaster as a model of dissecting chemotoxicity, we first need to develop standardized high-throughput toxicity assays and prove that the interindividual variation in toxicity as measured by such assays is highly heritable.

METHODS

We developed a method for the oral delivery of commonly used chemotherapy drugs to Drosophila. Post-treatment female fecundity displayed a dose-dependent response to varying levels of the chemotherapy drug delivered. We fixed the dose for each drug at a level that resulted in a 50% reduction in fecundity and used a paternal half-sibling heritability design to calculate the heritability attributable to chemotherapy toxicity assayed by a decrease in female fecundity. The chemotherapy agents tested were carboplatin, floxuridine, gemcitabine hydrochloride, methotrexate, mitomycin C, and topotecan hydrochloride.

RESULTS

We found that six currently widely prescribed chemotherapeutic agents lowered fecundity in D. melanogaster in both a dose-dependent and a highly heritable manner. The following heritability estimates were found: carboplatin, 0.72; floxuridine, 0.52; gemcitabine hydrochloride, 0.72; methotrexate, 0.99; mitomycin C, 0.64; and topotecan hydrochloride, 0.63.

CONCLUSION

The high heritability estimates observed in this study, irrespective of the particular class of drug examined, suggest that human toxicity may also have a sizable genetic component.

Null association of NQO1 609C>T and NQO2 -3423G>A polymorphisms with susceptibility and prognosis of Esophageal cancer in north Indian population and meta-analysis

INTRODUCTION

NAD(P)H:quinone oxidoreductase 1 (NQO1) and NRH:quinone oxidoreductase 2 (NQO2), involved in detoxification of environmental carcinogens and activation of chemotherapeutic agents, are supposed to play critical role in carcinogenesis. So, we aimed to investigate the association of NQO1 609C>T and NQO2 -3423G>A polymorphisms with susceptibility and prognosis of Esophageal cancer (EC) in north Indian population. We also performed Meta analysis of published literatures on NQO1 609C>T polymorphism to systematically evaluate its association with EC.

METHODS

We genotyped NQO1 609C>T and NQO2 -3423G>A polymorphisms in 200 incident EC cases (including 150 follow-up cases) and 200 controls using PCR RFLP based methods. Binary logistic regression was applied for risk estimation, while Kaplan Meier and Cox regression tests were applied for survival analysis. All Meta analysis tests were performed using MIX 2.0 software.

RESULTS

The present study did not find any significant association of NQO1 609C>T and NQO2 -3423G>A polymorphisms with susceptibility to EC or its clinical phenotypes (histopathology, tumor location or lymph node metastasis) or interactions with lifestyle risk factors (tobacco usage, smoking, alcohol habit and occupational exposures). Meta analysis of NQO1 polymorphism also indicated null association of the polymorphism with EC overall or with cancer cases stratified by tumor histopathology/ethnicity. Moreover, no prognostic implication of both polymorphisms was observed in EC.

CONCLUSION

NQO1 609C>T and NQO2 -3423G>A polymorphisms do not seem to play any significant role in susceptibility or prognosis of EC in north Indian population and results of Meta-analysis further reinforces null association of NQO1 609C>T polymorphism with EC susceptibility.

Role of NQO1 609C>T and NQO2 -3423G>A gene polymorphisms in esophageal cancer risk in Kashmir valley and meta analysis

Esophageal cancer (EC) is a complex multifactorial disorder, where environmental and genetic factors play major role. NADPH:quinone oxidoreductase 1 (NQO1) and NRH:quinone oxidoreductase 2 (NQO2) are phase II cytosolic enzymes that catalyze metabolism of quinones, important in the detoxification of environmental carcinogens. A case-control study was performed to investigated the associations of NQO1 609C>T and NQO2 -3423G>A polymorphisms with susceptibility to EC in a high-risk Kashmiri population of India in 135 EC patients and 195 unrelated healthy controls using PCR-RFLP. We also performed a meta analysis of nine published studies (1,224 cases and 1,740 controls) on NQO1 609C>T and evaluated the association between the NQO1 609C>T polymorphisms and esophageal cancer risk. A significant difference in NQO1 609C>T and NQO2 -3423G>A genotype distribution between EC cases and corresponding controls groups was observed (OR = 2.65; 95 % CI = 1.29-5.42 and OR = 1.88; 95 % CI = 1.02-3.49 respectively). Further, gene-gene interaction showed significantly increased risk for esophageal adenocarcinoma with variant genotypes of NQO1 609C>T and NQO2 -3423G>A polymorphisms and interaction with environmental risk factors revealed pronounced risk of EC with NQO1 609C>T TT genotype in high salted tea users of Kashmir valley (OR = 3.72, 95 % CI = 0.98-14.19). Meta analysis of NQO 609C>T polymorphism also suggested association of the polymorphism with EC in Asians as well as Europeans. In conclusion, NQO1 609C>T and NQO2 -3423G>A genetic variations modulate risk of EC in high-risk Kashmir population.

Two minor NQO1 and NQO2 alleles predict poor response of breast cancer patients to adjuvant doxorubicin and cyclophosphamide therapy

OBJECTIVE

A SNP in the NQO1 gene has been implicated in the response of patients with breast cancer to anthracycline containing regimens. NQO1, and its homologue NQO2, share many substrates yet retain distinct functional differences, with NQO2 being a more permissive molecule for electron accepting substrates. We aimed to determine whether functional NQO2 variants are associated with altered response to adjuvant doxorubicin and cyclophosphamide therapy, with or without tamoxifen, in the treatment of breast cancer.

METHODS

Genomic DNA samples from 227 women with early breast cancer were genotyped for NQO1 and NQO2 polymorphisms. All participants were treated with an AC adjuvant therapy regimen. The functional implications of NQO2 polymorphisms were validated in in-vitro ectopic expression models.

RESULTS

The NQO1 SNP (rs1800566) was associated with a poorer outcome and a lower likelihood of having a treatment delay. Patients who had ER and PR negative disease and were wild type for both the NQO1 and an NQO2 SNP (rs1143684) had 100% 5-year overall survival compared with 88% for carriers of one minor allele and 70% for carriers of two or more minor alleles (P=0.018, log rank). Carriers of minor alleles of a triallelic NQO2 promoter polymorphism were more likely to be withdrawn from tamoxifen therapy prematurely due to intolerance (P=0.009, log rank). MCF-7 cells were sensitized to growth inhibition by doxorubicin and 4OH tamoxifen, but not cyclophosphamide, by ectopic expression of NQO2.

CONCLUSION

This study suggests that both NQO1 and NQO2 modulate the efficacy of AC therapy and that NQO2 is associated with tamoxifen toxicity.

Carnosic acid induces the NAD(P)H: quinone oxidoreductase 1 expression in rat clone 9 cells through the p38/nuclear factor erythroid-2 related factor 2 pathway

The anticarcinogenic effect of rosemary has been partly attributed to the modulation of the activity and expression of phase II detoxification enzymes. Here we compared the effects of phenolic diterpenes from rosemary on the expression of NAD(P)H: quinone oxidoreductase 1 (NQO1) in rat Clone 9 liver cells. Cells were treated with 1-20 μmol/L of carnosic acid (CA) or carnosol (CS) for 24 h. Both CA and CS dose dependently increased NQO1 enzyme activity and protein expression, and the induction potency of CA was stronger than that of CS. The increase in NQO1 enzyme activity in cells treated with 10 μmol/L CA and CS was 4.1- and 1.9-fold, respectively (P < 0.05). RT-PCR showed that CA and CS induced NQO1 mRNA in a dose-dependent manner. Furthermore, CA dose dependently induced transcription of nuclear factor erythroid-2 related factor 2 (Nrf2) and antioxidant response element (ARE)-luciferase reporter activity. Silencing of Nrf2 expression alleviated NQO1 protein expression and ARE-luciferase activity by CA. Moreover, the phosphorylation of p38 was mainly stimulated in the presence of CA. Pretreatment with SB203580 or silencing of p38 expression inhibited Nrf2 activation and NQO1 induction. These results suggest that the increased NQO1 expression by CA is likely related to the p38-Nrf2 pathway and help to clarify the possible molecular mechanism of action of rosemary phenolic compounds in drug metabolism and cancer prevention.

Association between genetic variants in the Coenzyme Q10 metabolism and Coenzyme Q10 status in humans

BACKGROUND

Coenzyme Q10 (CoQ10) is essential for mitochondrial energy production and serves as an antioxidants in extra mitochondrial membranes. The genetics of primary CoQ10 deficiency has been described in several studies, whereas the influence of common genetic variants on CoQ10 status is largely unknown. Here we tested for non-synonymous single-nucleotidepolymorphisms (SNP) in genes involved in the biosynthesis (CoQ3G272S , CoQ6M406V, CoQ7M103T), reduction (NQO1P187S, NQO2L47F) and metabolism (apoE3/4) of CoQ10 and their association with CoQ10 status. For this purpose, CoQ10 serum levels of 54 healthy male volunteers were determined before (T0) and after a 14 days supplementation (T14) with 150 mg/d of the reduced form of CoQ10.

FINDINGS

At T0, the CoQ10 level of heterozygous NQO1P187S carriers were significantly lower than homozygous S/S carriers (0.93 ± 0.25 μM versus 1.34 ± 0.42 μM, p = 0.044). For this polymorphism a structure homology-based method (PolyPhen) revealed a possibly damaging effect on NQO1 protein activity. Furthermore, CoQ10 plasma levels were significantly increased in apoE4/E4 genotype after supplementation in comparison to apoE2/E3 genotype (5.93 ± 0.151 μM versus 4.38 ± 0.792 μM, p = 0.034). Likewise heterozygous CoQ3G272S carriers had higher CoQ10 plasma levels at T14 compared to G/G carriers but this difference did not reach significance (5.30 ± 0.96 μM versus 4.42 ± 1.67 μM, p = 0.082).

CONCLUSIONS

In conclusion, our pilot study provides evidence that NQO1P187S and apoE polymorphisms influence CoQ10 status in humans.

Association of superoxide dismutases and NAD(P)H quinone oxidoreductases with prognosis of patients with breast carcinomas

Associations of transcript levels of oxidative stress-modifying genes SOD2, SOD3, NQO1 and NQO2 and their functional single nucleotide polymorphisms (SNPs) rs4880, rs1799895, rs2536512, rs699473, rs1800566 and rs1143684 with prognosis of breast cancer patients were studied. SNPs were assessed by allelic discrimination in a cohort of 321 breast cancer patients from the Czech Republic. Transcript levels were determined by real-time polymerase chain reaction (PCR) with absolute quantification in tumor and adjacent non-neoplastic control tissues. Both genotypes and transcript levels were then compared with available clinical data on patients. Patients carrying low activity allele Leu in NQO2 rs1143684 had a greater incidence of stage 0 or I disease (i.e., better prognosis) than patients with the Phe/Phe genotype. This association was more evident in patients without expression of progesterone receptors (p = 0.031). Patients carrying the Thr allele in SOD3 rs2536512 SNP had a significantly greater incidence of tumors expressing estrogen receptors than patients carrying the Ala/Ala genotype (p = 0.007). SOD3 transcript level was significantly higher in grade 1 or 2 tumors than in grade 3 tumors (p = 0.006). Patients carrying T allele in SOD3 rs699473 SNP had significantly poorer progression-free survival (PFS) than patients carrying the CC genotype (p = 0.038). The same applied to the subgroup of patients treated by hormonal regimens (p = 0.021). Patients carrying the high activity Ala/Ala genotype in SOD2 (rs4880) had significantly poorer PFS than Val allele carriers in the group treated by cyclophosphamide but not hormonal regimens (p = 0.004). Our results suggest that NQO2, SOD2 and SOD3 may significantly modify prognosis of breast cancer patients and that their significance should be further characterized.

Interplay of flavin's redox states and protein dynamics: an insight from QM/MM simulations of dihydronicotinamide riboside quinone oxidoreductase 2

Dihydronicotinamide riboside quinone oxidoreductase 2 is known to catalyze a two-electron reduction of quinone to hydroquinone using its cofactor, flavin adenine dinucleotide. Using quantum mechanical/molecular mechanical simulations, we have computed the reorganization free energies of the electron and proton transfer processes of flavin in the free state as well as when it is bound in the active site of the enzyme. The calculated energetics for electron transfer processes demonstrate that the enzyme active site lowers the reorganization energy for the redox process as compared to the enzyme-free aqueous state. This is most apparent in the two electron reduction step, which eliminates the possibility of flavosemiquinone generation. In addition, essential dynamics study of the simulated motions revealed spectacular changes in the principal components of atomic fluctuations upon reduction of flavin. This alteration of active site dynamics provides an insight into the "ping-pong" kinetics exhibited by the enzyme upon a change in the redox state of the enzyme-bound flavin. A charge perturbation analysis provides further support that the observed change in dynamics is correlated with the change in energetics due to the altered electrostatic interactions between the flavin ring and the active site residues. This study shows that the effect of electrostatic preorganization goes beyond the chemical catalysis as it strongly impacts the postcatalytic intrinsic protein dynamics.

Genetic polymorphism in metabolism and host defense enzymes: implications for human health risk assessment

Genetic polymorphisms in xenobiotic metabolizing enzymes can have profound influence on enzyme function, with implications for chemical clearance and internal dose. The effects of polymorphisms have been evaluated for certain therapeutic drugs but there has been relatively little investigation with environmental toxicants. Polymorphisms can also affect the function of host defense mechanisms and thus modify the pharmacodynamic response. This review and analysis explores the feasibility of using polymorphism data in human health risk assessment for four enzymes, two involved in conjugation (uridine diphosphoglucuronosyltransferases [UGTs], sulfotransferases [SULTs]), and two involved in detoxification (microsomal epoxide hydrolase [EPHX1], NADPH quinone oxidoreductase I [NQO1]). This set of evaluations complements our previous analyses with oxidative and conjugating enzymes. Of the numerous UGT and SULT enzymes, the greatest likelihood for polymorphism effect on conjugation function are for SULT1A1 (*2 polymorphism), UGT1A1 (*6, *7, *28 polymorphisms), UGT1A7 (*3 polymorphism), UGT2B15 (*2 polymorphism), and UGT2B17 (null polymorphism). The null polymorphism in NQO1 has the potential to impair host defense. These highlighted polymorphisms are of sufficient frequency to be prioritized for consideration in chemical risk assessments. In contrast, SNPs in EPHX1 are not sufficiently influential or defined for inclusion in risk models. The current analysis is an important first step in bringing the highlighted polymorphisms into a physiologically based pharmacokinetic (PBPK) modeling framework.

Superoxide dismutase and nicotinamide adenine dinucleotide phosphate: quinone oxidoreductase polymorphisms and pancreatic cancer risk

OBJECTIVES

Pancreatic carcinoma etiology and molecular pathogenesis is weakly understood. According to the assumption that genetic variation in carcinogen metabolism further modifies the risk of exposure-related cancers, an association of functional polymorphisms in oxidative stress-modifying genes superoxide dismutase 2 (SOD2 [Ala16Val, rs4880]), SOD3 (Arg231Gly, rs1799895), nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase (NQO1 [Pro187Ser, rs1800566], and NQO2 (Phe47Leu, rs1143684) with pancreatic cancer risk was studied.

METHODS

Polymorphisms were studied by allelic discrimination.

RESULTS

In a hospital-based case-control study on 500 individuals (235 cases and 265 controls) of Czech white origin, SOD2, SOD3, NQO1, and NQO2 polymorphisms showed no significant association with pancreatic cancer risk. Major lifestyle factors such as smoking and alcohol, coffee, or tea consumption did not modify the effect of the studied polymorphisms.

CONCLUSIONS

The first European study of the SOD2, SOD3, NQO1, and NQO2 roles in pancreatic cancer etiology did not find significant associations. Despite this observation, other populations with different lifestyle(s) may be at risk and should be further studied.

Sulforaphane and alpha-lipoic acid upregulate the expression of the pi class of glutathione S-transferase through c-jun and Nrf2 activation

The anticarcinogenic effect of dietary organosulfur compounds has been partly attributed to their modulation of the activity and expression of phase II detoxification enzymes. Our previous studies indicated that garlic allyl sulfides upregulate the expression of the pi class of glutathione S-transferase (GSTP) through the activator protein-1 pathway. Here, we examined the modulatory effect of sulforaphane (SFN) and alpha-lipoic acid (LA) or dihydrolipoic acid (DHLA) on GSTP expression in rat Clone 9 liver cells. Cells were treated with LA or DHLA (50-600 micromol/L) or SFN (0.2-5 micromol/L) for 24 h. Immunoblots and real-time PCR showed that SFN, LA, and DHLA dose dependently induced GSTP protein and mRNA expression. Compared with the induction by the garlic organosulfur compound diallyl trisulfide (DATS), the effectiveness was in the order of SFN > DATS > LA = DHLA. The increase in GSTP enzyme activity in cells treated with 5 micromol/L SFN, 50 micromol/L DATS, and 600 micromol/L LA and DHLA was 172, 75, 122, and 117%, respectively (P < 0.05). A reporter assay showed that the GSTP enhancer I (GPEI) was required for GSTP induction by the organosulfur compounds. Electromobility gel shift assays showed that the DNA binding of GPEI to nuclear proteins reached a maximum at 0.5-1 h after SFN, LA, and DHLA treatment. Super-shift assay revealed that the transcription factors c-jun and nuclear factor erythroid-2 related factor 2 (Nrf2) were bound to GPEI. These results suggest that SFN and LA in either its oxidized or reduced form upregulate the transcription of the GSTP gene by activating c-jun and Nrf2 binding to the enhancer element GPEI.

Association of disease-predisposition polymorphisms of the melatonin receptors and sunshine duration in the global human populations

Melatonin is predominantly involved in signaling circadian and seasonal rhythms, and its synthesis is regulated by the environmental light/dark cycle. The selection pressure by geographically different environmental light/dark cycles, which is predominantly determined by sunshine duration, on the global distribution of genetic polymorphisms in the melatonin pathway is not well understood. Recent genetic association studies identified various disease-predisposition polymorphisms in this pathway. We investigated the correlations between the prevalence of these clinically important single nucleotide polymorphisms (SNPs) and sunshine duration among worldwide human populations from twelve regions in the CEPH-HGDP database rs4753426, a recently reported predisposition SNP for type 2 diabetes in the promoter of the MT(2) melatonin receptor gene (MTNR1B), which was not included in the CEPH-HGDP genotyping array, was additionally genotyped. This SNP showed a marginally significant correlation in 760 CEPH-HGDP DNA samples (r = -0.5346, P = 0.0733), and it showed the most prominent association among the candidate melatonin pathway SNPs examined. To control for population structure, which may lead to a false positive correlation, we genotyped this SNP in a replication set of 1792 subjects from China. The correlation was confirmed among Chinese populations (r = -0.8694, P = 0.0002), and was also statistically significant after correction of other climatic and geographical covariants in multiple regression analysis (beta = -0.907, P = 1.94 x 10(-5)). Taken together, it suggests that the human melatonin signaling pathway, particularly MT(2) melatonin receptor may have undergone a selective pressure in response to global variation in sunshine duration.

Drug metabolism by tumours: its nature, relevance and therapeutic implications

Drug-metabolising enzymes (DMEs) are present in tumours and are capable of biotransforming a variety of antineoplastics. Tumoural drug metabolism is both a potential mechanism of resistance and a means of achieving optimal therapy. This review addresses the classes of DMEs, their cytotoxic substrates and distribution in specific malignancies. The limitations of preclinical and clinical studies are highlighted. Their role in predicting therapeutic response, the activation of prodrugs and the potential for their modulation for gain is also addressed. The contribution of tumoural DMEs to cancer therapy can only be ascertained through large prospective studies and supported by new technologies. Only then can efforts be concentrated in the design of better prodrugs or combination therapy to optimise individual therapy.

Deficiency of NRH:quinone oxidoreductase 2 differentially regulates TNF signaling in keratinocytes: up-regulation of apoptosis correlates with down-regulation of cell survival kinases

NRH:quinone oxidoreductase 2 (NQO2) is a cytosolic flavoprotein that catalyzes the two-electron reduction of quinones and quinoid compounds to hydroquinones. Although the role of a homologue, NAD(P)H:quinone oxidoreductase 1 (NQO1), is well defined in oxidative stress, neoplasia, and carcinogenesis, little is known about the mechanism of actions of NQO2 in these cellular responses. Whether NQO2 has any role in tumor necrosis factor (TNF) signaling was investigated using keratinocytes derived from wild-type and NQO2 knockout (NQO2-/-) mice. Although exposure of wild-type cells to TNF led to activation of nuclear factor-kappaB (NF-kappaB) and IkappaBalpha kinase, IkappaBalpha degradation, p65 phosphorylation, and p65 nuclear translocation, this cytokine had no effect on NQO2-/- cells. Deletion of NQO2 also abolished TNF-induced c-Jun NH2-terminal kinase, Akt, p38, and p44/p42 mitogen-activated protein kinase activation. The induction of various antiapoptotic gene products (MMP-9, cyclin D1, COX-2, IAP1, IAP2, Bcl-2, cFLIP, and XIAP) by TNF was also abolished in NQO2-/- cells. This correlated with potentiation of TNF-induced apoptosis as indicated by cell viability, Annexin V staining, and caspase activation. In agreement with this, we also found that TNF activated NQO2, and NQO2-specific small interfering RNA abrogated the TNF-induced NQO2 activity and NF-kappaB activation. Overall, our results indicate that deletion of NQO2 plays a differential role in TNF signaling pathway: by suppressing cell survival signals and potentiating TNF-induced apoptosis.