The role of glutathione S-transferase P in signaling pathways and S-glutathionylation in cancer

The Diagnostic Value of Nuclear Matrix Proteins in Bladder Cancer in the Aspect of Environmental Risk from Carcinogens

BACKGROUND

The interaction of environmental factors with genetic susceptibility and detoxification level seems to be an important causative factor in bladder cancer (BC). The aim of this study was to look for a BC marker panel which reflects the environmental risk. The nuclear matrix protein 22 (NMP22), bladder cancer-4 (BLCA-4), and total level proteins NMP22 and BLCA-4 (NMBL) in BC patients with genetic predisposition NAT2 (classified as slow acetylators, SA), DNA damage (8-OHdG), and detoxification by isoenzyme GSTπ activity were measured.

MATERIALS AND METHODS

The urine and blood from 91 BC patients and controls were examined, also according to tumor stage (T) and grade (G). The participants completed a questionnaire in order to evaluate environmental risk.

RESULTS

Most patients (75.3%) were previous or actual smokers. The levels of 8-OHdG, NMP22, BLCA-4, NMBL, and GSTπ were significantly higher in BC (p ≤ 0.001). The majority of patients (59.3%) were slow acetylators (SA). The highest BLCA-4/8-OHdG correlation was observed in total BC and SA smokers.

CONCLUSIONS

The total pool of nuclear matrix proteins in the urine (NMBL) has a higher diagnostic value in bladder cancer than single proteins. The particular value of BLCA-4 and GSTπ in the aspect of environmental risk was noted.

Solution structure of the TLR adaptor MAL/TIRAP reveals an intact BB loop and supports MAL Cys91 glutathionylation for signaling

MyD88 adaptor-like (MAL) is a critical protein in innate immunity, involved in signaling by several Toll-like receptors (TLRs), key pattern recognition receptors (PRRs). Crystal structures of MAL revealed a nontypical Toll/interleukin-1 receptor (TIR)-domain fold stabilized by two disulfide bridges. We therefore undertook a structural and functional analysis of the role of reactive cysteine residues in the protein. Under reducing conditions, the cysteines do not form disulfides, but under oxidizing conditions they are highly amenable to modification. The solution structure of the reduced form of the MAL TIR domain, determined by NMR spectroscopy, reveals a remarkable structural rearrangement compared with the disulfide-bonded structure, which includes the relocation of a β-strand and repositioning of the functionally important "BB-loop" region to a location more typical for TIR domains. Redox measurements by NMR further reveal that C91 has the highest redox potential of all cysteines in MAL. Indeed, mass spectrometry revealed that C91 undergoes glutathionylation in macrophages activated with the TLR4 ligand lipopolysaccharide (LPS). The C91A mutation limits MAL glutathionylation and acts as a dominant negative, blocking the interaction of MAL with its downstream target MyD88. The H92P mutation mimics the dominant-negative effects of the C91A mutation, presumably by preventing C91 glutathionylation. The MAL C91A and H92P mutants also display diminished degradation and interaction with interleukin-1 receptor-associated kinase 4 (IRAK4). We conclude that in the cell, MAL is not disulfide-bonded and requires glutathionylation of C91 for signaling.

Concluding the trilogy: The interaction of 2,2'-dihydroxy-benzophenones and their carbonyl N-analogues with human glutathione transferase M1-1 face to face with the P1-1 and A1-1 isoenzymes involved in MDR

A series of 2,2'-dihydroxybenzophenones and their carbonyl N-analogues were studied as potential inhibitors against human glutathione transferase M1-1 (hGSTM1-1) purified from recombinant E. coli. Their screening revealed an inhibition against hGSTM1-1 within a range of 0-42% (25 μM). The IC₅₀ values for the two stronger ones, 16 and 13, were 53.5 ± 5.6 μΜ and 28.5 ± 2.5 μΜ, respectively. The results were compared with earlier ones for isoenzymes hGSTP1-1 and hGSTA1-1 involved in MDR. All but one bind more strongly to A1-1, than M1-1 and P1-1, the latter being a poor binder. An order of potency A1-1 > > M1-1 >  P1-1 meritted 13, 14 and 16 as the most potent inhibitors with hGSTM1-1. Enzyme kinetics with hGSTM1-1 (K_m(CDNB) 213 ± 10 μΜ and K_m(GSH) 303 ± 11 μΜ) revealed a competitive modality for 16 (K_i(16)  = 22.3 ± 1.1 μΜ) and a mixed one for 13 versus CDNB (K_i(13)  = 33.3 ± 1.6 μM for the free enzyme and K_i(13) ' = 17.7 ± 1.7 μM for the enzyme-CDNB complex). 5- or 5'-Bromo- or phenyl-substituted (but not in combination) inhibitors, having a H-bonded oxime weakly acidic group of a small volume, are optimal candidates for binding hGSTM1-1. The outcome of the isoenzyme trilogy identified good binder leads for the investigated GSTs involved in MDR.

Store-operated Ca2+ entry controls ameloblast cell function and enamel development

Loss-of-function mutations in stromal interaction molecule 1 (STIM1) impair the activation of Ca²⁺ release-activated Ca²⁺ (CRAC) channels and store-operated Ca²⁺ entry (SOCE), resulting in a disease syndrome called CRAC channelopathy that is characterized by severe dental enamel defects. The cause of these enamel defects has remained unclear given a lack of animal models. We generated Stim1/2^K14cre mice to delete STIM1 and its homolog STIM2 in enamel cells. These mice showed impaired SOCE in enamel cells. Enamel in Stim1/2^K14cre mice was hypomineralized with decreased Ca content, mechanically weak, and thinner. The morphology of SOCE-deficient ameloblasts was altered, showing loss of the typical ruffled border, resulting in mislocalized mitochondria. Global gene expression analysis of SOCE-deficient ameloblasts revealed strong dysregulation of several pathways. ER stress genes associated with the unfolded protein response were increased in Stim1/2-deficient cells, whereas the expression of components of the glutathione system were decreased. Consistent with increased oxidative stress, we found increased ROS production, decreased mitochondrial function, and abnormal mitochondrial morphology in ameloblasts of Stim1/2^K14cre mice. Collectively, these data show that loss of SOCE in enamel cells has substantial detrimental effects on gene expression, cell function, and the mineralization of dental enamel.

Upregulated glutathione transferase omega-1 correlates with progression of urinary bladder carcinoma

OBJECTIVES

Newly discovered glutathione transferase omega 1 (GSTO1-1) plays an important role in the glutathionylation cycle, a significant mechanism of protein function regulation. GSTO1-1 expression pattern has not been studied in transitional cell carcinoma (TCC), as yet.

METHODS

A total of 56 TCC tumor and corresponding non-tumor specimens were investigated. Glutathione content and thioltransferase activity were measured spectrophotometrically. Protein-glutathione mixed disulfides were measured fluorimetrically. GSTO1-1 expression was determined by immunoblot and qPCR. Immunoprecipitation with GSTO1-1 antibody was followed by immunoblot using anti-GSTO1, GSTP1, c-Jun, JNK, Akt, phospho-Akt, and ASK1 antibody, while for the total S-glutathionylation levels non-reducing electrophoresis was performed.

RESULTS

The contents of reduced glutathione and thioltransferase activity were significantly increased in tumor compared to non-tumor tissue. The increased GSTO1 expression in tumor tissue showed clear correlation with grade and stage. However, decreased total protein glutathionylation level in tumor compared to non-tumor samples was found. Immunoprecipitation has shown an association of GSTO1-1 with GSTP1, Akt, phospho-Akt, and ASK1 proteins.

CONCLUSIONS

GSTO1 deglutathionylase activity suggests its potential important role in redox perturbations present in TCC. Increased GSTO1-1 expression might contribute to TCC development and/or progression supporting the notion that GSTO1-1 may be a promising novel cancer target.

Selenocompounds in Cancer Therapy: An Overview

In vitro and in vivo experimental models clearly demonstrate the efficacy of Se compounds as anticancer agents, contingent upon chemical structures and concentrations of test molecules, as well as on the experimental model under investigation that together influence cellular availability of compounds, their molecular dynamics and mechanism of action. The latter includes direct and indirect redox effects on cellular targets by the activation and altered compartmentalization of molecular oxygen, and the interaction with protein thiols and Se proteins. As such, Se compounds interfere with the redox homeostasis and signaling of cancer cells to produce anticancer effects that include alterations in key regulatory elements of energy metabolism and cell cycle checkpoints that ultimately influence differentiation, proliferation, senescence, and death pathways. Cys-containing proteins and Se proteins involved in the response to Se compounds as sensors and transducers of anticancer signals, i.e., the pharmacoproteome of Se compounds, are described and include critical elements in the different phases of cancer onset and progression from initiation and escape of immune surveillance to tumor growth, angiogenesis, and metastasis. The efficacy and mode of action on these compounds vary depending on the inorganic and organic form of Se used as either supplement or pharmacological agent. In this regard, differences in experimental/clinical protocols provide options for either chemoprevention or therapy in different human cancers.

Gene polymorphism profiles of drug-metabolising enzymes GSTM1, GSTT1 and GSTP1 in an Argentinian population

BACKGROUND

Glutathione S-transferases (GSTs) are drug-metabolising enzymes involved in biotransformation of carcinogens, drugs, xenobiotics and oxygen free radicals. Polymorphisms of GST genes contribute to inter-individual and population variability in the susceptibility to environmental risk factors, cancer predisposition and pharmacotherapy responses. However, data about GST variability in Argentina are lacking.

AIM

The purpose was to determine the prevalence of GSTM1, GSTT1 and GSTP1 polymorphisms in the general population from a central region of Argentina and to perform inter-population comparisons.

SUBJECTS AND METHODS

GSTM1 and GSTT1 gene deletions and GSTP1 c.313A > G were genotyped by PCR assays in 609 healthy and unrelated Argentinians.

RESULTS

The frequencies of variant genotypes in Argentinians were GSTM1-null (45%), GSTT1-null (17%) and GSTP1-GG (11%). GSTM1-present genotype was significantly associated with GSTP1-AG or GSTP1-GG variants (p = 0.037; p = 0.034, respectively). Comparison with worldwide populations demonstrated that the GST distributions in Argentina are similar to those reported for Italy and Spain, whereas significant differences were observed regarding Asian and African populations (p < 0.001).

CONCLUSION

This study has determined, for the first time, the normative profile of three pharmacogenetically relevant polymorphisms (GSTM1, GSTT1 and GSTP1) in the largest Argentinian cohort described to date, providing the basis for further epidemiological and pharmacogenetic studies in this country.

Phosphoramide mustard induces autophagy markers and mTOR inhibition prevents follicle loss due to phosphoramide mustard exposure

Phosphoramide mustard (PM) is an ovotoxic metabolite of cyclophosphamide. Postnatal day 4 Fisher 344 rat ovaries were exposed to vehicle control (1% DMSO) or PM (60μM)±LY294002 or rapamycin for 2 or 4 d. Transmission election microscopy revealed abnormally large golgi apparatus and electron dense mitochondria in PM-exposed ovaries prior to and at the time of follicle depletion. PM exposure increased (P<0.05) mRNA abundance of Bbc3, Cdkn1a, Ctfr, Edn1, Gstp1, Nqo1, Tlr4, Tnfrsfla, Txnrd1 and decreased (P<0.05) Casp1 and Il1b after 4d. PM exposure increased (P<0.1) BECN1 and LAMP, decreased (P<0.1) ABCB1 and did not alter ABCC1 protein. LY294002 did not impact PM-induced ovotoxicity, but decreased ABCC1 and ABCB1 protein. Rapamycin prevented PM-induced follicle loss. These data suggest that the mammalian target of rapamycin, mTOR, may be a gatekeeper of PM-induced follicle loss.

Glutathionylation of chikungunya nsP2 protein affects protease activity

BACKGROUND

Chikungunya fever is an emerging disease caused by the chikungunya virus and is now being spread worldwide by the mosquito Aedes albopictus. The infection can cause a persistent severe joint pain and recent reports link high levels of viremia to neuropathologies and fatalities. The viral protein nsP2 is a multifunctional enzyme that plays several critical roles in virus replication. Virus infection induces oxidative stress in host cells which the virus utilizes to aid viral propagation. Cellular oxidative stress also triggers glutathionylation which is a post-translational protein modification that can modulate physiological roles of affected proteins.

METHODS

The nsP2 protease is necessary for processing of the virus nonstructural polyprotein generated during replication. We use the recombinant nsP2 protein to measure protease activity before and after glutathionylation. Mass spectrometry allowed the identification of the glutathione-modified cysteines. Using immunoblots, we show that the glutathionylation of nsP2 occurs in virus-infected cells.

RESULTS

We show that in virus-infected cells, the chikungunya nsP2 can be glutathionylated and we show this modification can impact on the protease activity. We also identify 6 cysteine residues that are glutathionylated of the 20 cysteines in the protein.

CONCLUSIONS

The virus-induced oxidative stress causes modification of viral proteins which appears to modulate virus protein function.

GENERAL SIGNIFICANCE

Viruses generate oxidative stress to regulate and hijack host cell systems and this environment also appears to modulate virus protein function. This may be a general target for intervention in viral pathogenesis.

The Bioavailability of Soluble Cigarette Smoke Extract Is Reduced through Interactions with Cells and Affects the Cellular Response to CSE Exposure

Cellular exposure to cigarette smoke leads to an array of complex responses including apoptosis, cellular senescence, telomere dysfunction, cellular aging, and neoplastic transformation. To study the cellular response to cigarette smoke, a common in vitro model exposes cultured cells to a nominal concentration (i.e. initial concentration) of soluble cigarette smoke extract (CSE). However, we report that use of the nominal concentration of CSE as the only measure of cellular exposure is inadequate. Instead, we demonstrate that cellular response to CSE exposure is dependent not only on the nominal concentration of CSE, but also on specific experimental variables, including the total cell number, and the volume of CSE solution used. As found in other similar xenobiotic assays, our work suggests that the effective dose of CSE is more accurately related to the amount of bioavailable chemicals per cell. In particular, interactions of CSE components both with cells and other physical factors limit CSE bioavailability, as demonstrated by a quantifiably reduced cellular response to CSE that is first modified by such interactions. This has broad implications for the nature of cellular response to CSE exposure, and for the design of in vitro assays using CSE.

Mixed results with mixed disulfides

A period of research with Helmut Sies in the 1980s is recalled. Our experiments aimed at an in-depth understanding of metabolic changes due to oxidative challenges under near-physiological conditions, i.e. perfused organs. A major focus were alterations of the glutathione and the NADPH/NADP(+) system by different kinds of oxidants, in particular formation of glutathione mixed disulfides with proteins. To analyze mixed disulfides, a test was adapted which is widely used until today. The observations in perfused rat livers let us believe that glutathione-6-phosphate dehydrogenase (G6PDH), i.a. might be activated by glutathionylation. Although we did not succeed to verify this hypothesis for the special case of G6PDH, the regulation of enzyme/protein activities by glutathionylation today is an accepted posttranslational mechanism in redox biology in general. Our early experimental approaches are discussed in the context of present knowledge.

The influence of glutathion S-transferase P-1 polymorphism A313G rs1695 on the susceptibility to cyclophosphamide hematologic toxicity in Indonesian patients

Background: Chemotherapy often causes side effects such as hematologic toxicity. The degree of toxicity is often associated with genetic polymorphism. This study aims to determine the influence of GSTP1 A313G polymorphism, an enzyme responsible for detoxifying cyclophosphamid, on incidence and severity of cyclophosphamid hematologic toxicity.Methods: 91 Indonesian females diagnosed with breast cancer at Haji Adam Malik Central General Hospital, Medan, receiving cyclophosphamide, doxorubicin/epirubicin and 5-FU were included in this retrospective cohort study. DNA was extracted from peripheral leukocytes and GSTP1 A313G genotyping was analyzed using polymerase chain reaction-restriction length fragment polymorphism (PCR-RFLP). Genotype deviation and allele frequencies were also determined by Hardy-Weinberg Equilibrium. The degrees of hematologic toxicity (leucopenia and neutropenia data after chemotherapy cycles 1 and 3) were collected from the patient medical records. The data were analyzed using chi-square test.Results: 60.4% of the patients had the wildtype (A/A), while 29.7% were heterozygous (A/G), and 9.9% were homozygous mutant (G/G). There was no significant deviation of allele and genotype frequency from Hardy-Weinberg Equilibrium. The G allele (A/G & G/G) contributes to more severe degree of leukopenia compared to patients with wild type allele (A/A)  (p<0.05) after the 3rd chemotherapy cycles.Conclusion: There was association between GSTP1 polymorphism with the degree of hematologic toxicity in breast cancer patients receiving cyclophosphamide chemotherapy regimen.

Attenuation of lung fibrosis in mice with a clinically relevant inhibitor of glutathione-S-transferase π

Idiopathic pulmonary fibrosis (IPF) is a debilitating lung disease characterized by excessive collagen production and fibrogenesis. Apoptosis in lung epithelial cells is critical in IPF pathogenesis, as heightened loss of these cells promotes fibroblast activation and remodeling. Changes in glutathione redox status have been reported in IPF patients. S-glutathionylation, the conjugation of glutathione to reactive cysteines, is catalyzed in part by glutathione-S-transferase π (GSTP). To date, no published information exists linking GSTP and IPF to our knowledge. We hypothesized that GSTP mediates lung fibrogenesis in part through FAS S-glutathionylation, a critical event in epithelial cell apoptosis. Our results demonstrate that GSTP immunoreactivity is increased in the lungs of IPF patients, notably within type II epithelial cells. The FAS-GSTP interaction was also increased in IPF lungs. Bleomycin- and AdTGFβ-induced increases in collagen content, α-SMA, FAS S-glutathionylation, and total protein S-glutathionylation were strongly attenuated in Gstp-/- mice. Oropharyngeal administration of the GSTP inhibitor, TLK117, at a time when fibrosis was already apparent, attenuated bleomycin- and AdTGFβ-induced remodeling, α-SMA, caspase activation, FAS S-glutathionylation, and total protein S-glutathionylation. GSTP is an important driver of protein S-glutathionylation and lung fibrosis, and GSTP inhibition via the airways may be a novel therapeutic strategy for the treatment of IPF.

Association of polymorphisms in glutathione S-transferase genes (GSTM1, GSTT1, GSTP1) with idiopathic azoospermia or oligospermia in Sichuan, China

The reported effects of the glutathione S-transferase (GSTs) genes (GSTM1, GSTT1, and GSTP1) on male factor infertility have been inconsistent and even contradictory. Here, we conducted a case-control study to investigate the association between functionally important polymorphisms in GST genes and idiopathic male infertility. The study group consisted of 361 men with idiopathic azoospermia, 118 men with idiopathic oligospermia, and 234 age-matched healthy fertile male controls. Genomic DNA was extracted from the peripheral blood, and analyzed by polymerase chain reaction and restriction fragment length polymorphism analysis. There was a significant association between the GSTP1 variant genotype (Ile/Val + Val/Val) with idiopathic infertility risk (odds ratio [OR]: 1.53; 95% confidence interval [CI]: 1.11–2.11; P = 0.009). Similarly, a higher risk of infertility was noted in individuals carrying a genotype combination of GSTT1-null and GSTP1 (Ile/Val + Val/Val) (OR: 2.17; 95% CI: 1.43–3.31; P = 0.0002). These results suggest an increased risk of the GSTP1 variant genotype (Ile/Val + Val/Val) for developing male factor infertility. Our findings also underrate the significance of the effect of GSTM1 and/or GSTT1 (especially the former) in modulating the risk of male infertility in males from Sichuan, southwest China.

Nuclear Multidrug Resistance-Related Protein 1 Is Highly Associated with Better Prognosis of Human Mucoepidermoid Carcinoma through the Suppression of Cell Proliferation, Migration and Invasion

Objectives

Multidrug resistance-related protein 1 (MRP1) overexpression is a well acknowledged predictor of poor response to chemotherapy, but MRP1 also correlated to better prognosis in some reports, especially for patients not pretreated with chemotherapy. In our previous study, we found nuclear translocation of MRP1 in mucoepidermoid carcinoma (MEC) for the first time. The purpose of this study was to further investigate the function of nuclear MRP1 in MEC.

Materials and Methods

Human MEC tissue samples of 125 patients were selected and stained using immunohistochemistry. The expression level of total MRP1/nuclear MRP1 of each sample was evaluated by expression index (EI) which was scored using both qualitative and quantitative analysis. The correlations between the clinicopathologic parameters and the EI of nuclear MRP1 were analyzed using Spearman’s rank correlation analysis, respectively. The effects of RNAi-mediated downregulation of nuclear MRP1 on MEC cells were assessed using flow cytometric analysis, MTT assay, plate colony formation assay, transwell invasion assay and monolayer wound healing assay.

Results

In this study, we found the EI of nuclear MRP1 was negatively correlated to the pathologic grading (r = -0.498, P<0.01) / clinical staging (r = -0.41, P<0.01) / tumor stage (r = -0.28, P = 0.02) / nodal stage (r = -0.29, P<0.01) of MEC patients. The RNAi-mediated downregulation of nuclear MRP1 further proved that the downregulation of nuclear MRP1 could increase the cell replication, growth speed, colony formation efficiency, migration and invasion ability of MEC cells.

Conclusion

Our results suggested that nuclear MRP1 is highly associated with better prognosis of human mucoepidermoid carcinoma and further study of its function mechanism would provide clues in developing new treatment modalities of MEC.

GSTP1 Loss results in accumulation of oxidative DNA base damage and promotes prostate cancer cell survival following exposure to protracted oxidative stress

BACKGROUND

Epigenetic silencing of glutathione S-transferase π (GSTP1) is a hallmark of transformation from normal prostatic epithelium to adenocarcinoma of the prostate. The functional significance of this loss is incompletely understood. The present study explores the effects of restored GSTP1 expression on glutathione levels, accumulation of oxidative DNA damage, and prostate cancer cell survival following oxidative stress induced by protracted, low dose rate ionizing radiation (LDR).

METHODS

GSTP1 protein expression was stably restored in LNCaP prostate cancer cells. The effect of GSTP1 restoration on protracted LDR-induced oxidative DNA damage was measured by GC-MS quantitation of modified bases. Reduced and oxidized glutathione levels were measured in control and GSTP1 expressing populations. Clonogenic survival studies of GSTP1- transfected LNCaP cells after exposure to protracted LDR were performed. Global gene expression profiling and pathway analysis were performed.

RESULTS

GSTP1 expressing cells accumulated less oxidized DNA base damage and exhibited decreased survival compared to control LNCaP-Neo cells following oxidative injury induced by protracted LDR. Restoration of GSTP1 expression resulted in changes in modified glutathione levels that correlated with GSTP1 protein levels in response to protracted LDR-induced oxidative stress. Survival differences were not attributable to depletion of cellular glutathione stores. Gene expression profiling and pathway analysis following GSTP1 restoration suggests this protein plays a key role in regulating prostate cancer cell survival.

CONCLUSIONS

The ubiquitous epigenetic silencing of GSTP1 in prostate cancer results in enhanced survival and accumulation of potentially promutagenic DNA adducts following exposure of cells to protracted oxidative injury suggesting a protective, anti-neoplastic function of GSTP1. The present work provides mechanistic backing to the tumor suppressor function of GSTP1 and its role in prostate carcinogenesis.

Glutathione S-transferase pi expression regulates the Nrf2-dependent response to hormetic diselenides

Glutathione S-transferase pi (GSTP), a phase II gene downstream of the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant-responsive element (ARE)/electrophile response element (EpRE) transcription pathway, plays a key role in both the signaling and detoxification response to Se-organic compounds with thiol peroxidase activity. We here investigated the role of GSTP on the Nrf2 activation response of cells challenged with a new class of diselenides derived from the basic structure of diphenyl diselenide [(PhSe)2]. These diselenides, and particularly 2,2'-diselenyl dibenzoic acid (DSBA), behave as mild thiol peroxidases leading to a moderate generation of H2O2 and NOx, and signaling of stress-activated and survival-promoting MAPKs, which ultimately control the mitochondrial pathway of apoptosis. Used in murine embryonic fibroblasts (MEFs) and HepG2 human hepatocarcinoma cells to produce submaximal conditions of stress, the diselenide compounds stimulated Nrf2 nuclear translocation and then the transcription of the same Nrf2 gene as well as of GSTP and other phase II genes. This resulted in a higher degree of protection against H2O2 cytotoxicity (hormetic effect). Diselenide toxicity increased in GSTP knockout MEFs by a higher generation of NOx and stress activated protein kinase (SAPK)/JNK activation. A lowered hormetic potential of these cells was observed in association with an abnormal expression and nuclear translocation of Nrf2 protein. Immunoprecipitation and affinity purification experiments revealed the existence of an Nrf2/GSTP complex in MEFs and HepG2 cells. Covalent oligomers of GSTP subunits were observed in DSBA-treated HepG2 cells. In conclusion, GSTP gene expression influences the Nrf2-dependent response to hormetic diselenides. Mechanistic interpretation for this GSTP-dependent effect may include a direct and redox-sensitive interaction of GSTP with Nrf2 protein.

S-Glutathionylation and Redox Protein Signaling in Drug Addiction

Drug addiction is a chronic relapsing disorder that comes at a high cost to individuals and society. Therefore understanding the mechanisms by which drugs exert their effects is of prime importance. Drugs of abuse increase the production of reactive oxygen and nitrogen species resulting in oxidative stress. This change in redox homeostasis increases the conjugation of glutathione to protein cysteine residues; a process called S-glutathionylation. Although traditionally regarded as a protective mechanism against irreversible protein oxidation, accumulated evidence suggests a more nuanced role for S-glutathionylation, namely as a mediator in redox-sensitive protein signaling. The reversible modification of protein thiols leading to alteration in function under different physiologic/pathologic conditions provides a mechanism whereby change in redox status can be translated into a functional response. As such, S-glutathionylation represents an understudied means of post-translational protein modification that may be important in the mechanisms underlying drug addiction. This review will discuss the evidence for S-glutathionylation as a redox-sensing mechanism and how this may be involved in the response to drug-induced oxidative stress. The function of S-glutathionylated proteins involved in neurotransmission, dendritic spine structure, and drug-induced behavioral outputs will be reviewed with specific reference to alcohol, cocaine, and heroin.

Role of glutathione, glutathione transferase, and glutaredoxin in regulation of redox-dependent processes

Over the last decade fundamentally new features have been revealed for the participation of glutathione and glutathione-dependent enzymes (glutathione transferase and glutaredoxin) in cell proliferation, apoptosis, protein folding, and cell signaling. Reduced glutathione (GSH) plays an important role in maintaining cellular redox status by participating in thiol-disulfide exchange, which regulates a number of cell functions including gene expression and the activity of individual enzymes and enzyme systems. Maintaining optimum GSH/GSSG ratio is essential to cell viability. Decrease in the ratio can serve as an indicator of damage to the cell redox status and of changes in redox-dependent gene regulation. Disturbance of intracellular GSH balance is observed in a number of pathologies including cancer. Consequences of inappropriate GSH/GSSG ratio include significant changes in the mechanism of cellular redox-dependent signaling controlled both nonenzymatically and enzymatically with the participation of isoforms of glutathione transferase and glutaredoxin. This review summarizes recent data on the role of glutathione, glutathione transferase, and glutaredoxin in the regulation of cellular redox-dependent processes.

Immunohistochemical biomarkers and FDG uptake on PET/CT in head and neck squamous cell carcinoma

BACKGROUND

There is an exciting complementarity between the spatial resolution provided by molecular imaging of a single, often unspecific, biomarker on one hand and the more detailed biological profile achievable from a diagnostic biopsy using a panel of immunohistochemical (IHC) markers on the other. A number of previous studies have shown a relationship between glucose transport protein expression and 18F-Fludeoxyglucose (FDG) PET uptake. Here, FDG uptake is analyzed in relation to expression of a selected panel of IHC cancer biomarkers in head and neck squamous cell carcinomas (HNSCC).

MATERIAL AND METHODS

IHC staining for Bcl-2, β-tubulin-1 and 2, p53, EGFR, Ki-67, glutathione-S-transferase-π and p16 was performed on formalin-fixed paraffin embedded diagnostic biopsies from 102 HNSCC cases treated at Rigshospitalet during 2005-2009. The proportion of positive cells was used for analyses, except p16, which was scored according to EORTC guidelines. In all cases, maximal FDG standardized uptake value (SUV) metrics were extracted for the primary tumor, TSUVmax. Univariate linear regression and multiple linear regression of TSUVmax versus IHC markers were performed.

RESULTS

In univariate analyses, TSUVmax showed negative associations with Bcl-2 (p = 0.002) and p16 (p = 0.005) indices and positive association with β-tubulin-1 index (p = 0.003). On multivariate analysis, TSUVmax remained associated with β-tubulin-1 (p = 0.009), Bcl-2 (p = 0.03) and p16 (p = 0.03). All correlations had r-squared < 0.3.

CONCLUSION

Statistically significant correlations were observed between the expression of IHC biomarkers and maximum FDG uptake in the primary tumor.

Genetic variation and gastric cancer risk: a field synopsis and meta-analysis

BACKGROUND

Data on genetic susceptibility to sporadic gastric carcinoma have been published at a growing pace, but to date no comprehensive overview and quantitative summary has been available.

METHODS

We conducted a systematic review and meta-analysis of the evidence on the association between DNA variation and risk of developing stomach cancer. To assess result credibility, summary evidence was graded according to the Venice criteria and false positive report probability (FPRP) was calculated to further validate result noteworthiness. Meta-analysis was also conducted for subgroups, which were defined by ethnicity (Asian vs Caucasian), tumour histology (intestinal vs diffuse), tumour site (cardia vs non-cardia) and Helicobacter pylori infection status (positive vs negative).

RESULTS

Literature search identified 824 eligible studies comprising 2 530 706 subjects (cases: 261 386 (10.3%)) and investigating 2841 polymorphisms involving 952 distinct genes. Overall, we performed 456 primary and subgroup meta-analyses on 156 variants involving 101 genes. We identified 11 variants significantly associated with disease risk and assessed to have a high level of summary evidence: MUC1 rs2070803 at 1q22 (diffuse carcinoma subgroup), MTX1 rs2075570 at 1q22 (diffuse), PSCA rs2294008 at 8q24.2 (non-cardia), PRKAA1 rs13361707 5p13 (non-cardia), PLCE1 rs2274223 10q23 (cardia), TGFBR2 rs3087465 3p22 (Asian), PKLR rs3762272 1q22 (diffuse), PSCA rs2976392 (intestinal), GSTP1 rs1695 11q13 (Asian), CASP8 rs3834129 2q33 (mixed) and TNF rs1799724 6p21.3 (mixed), with the first nine variants characterised by a low FPRP. We also identified polymorphisms with lower quality significant associations (n=110).

CONCLUSIONS

We have identified several high-quality biomarkers of gastric cancer susceptibility. These data will form the backbone of an annually updated online resource that will be integral to the study of gastric carcinoma genetics and may inform future screening programmes.

Proteome-wide identification and quantification of S-glutathionylation targets in mouse liver

Protein S-glutathionylation is a reversible post-translational modification regulating sulfhydryl homeostasis. However, little is known about the proteins and pathways regulated by S-glutathionylation in whole organisms and current approaches lack the sensitivity to examine this modification under basal conditions. We now report the quantification and identification of S-glutathionylated proteins from animal tissue, using a highly sensitive methodology combining high-accuracy proteomics with tandem mass tagging to provide precise, extensive coverage of S-glutathionylated targets in mouse liver. Critically, we show significant enrichment of S-glutathionylated mitochondrial and Krebs cycle proteins, identifying that S-glutathionylation is heavily involved in energy metabolism processes in vivo. Furthermore, using mice nulled for GST Pi (GSTP) we address the potential for S-glutathionylation to be mediated enzymatically. The data demonstrate the impact of S-glutathionylation in cellular homeostasis, particularly in relation to energy regulation and is of significant interest for those wishing to examine S-glutathionylation in an animal model.

Nanoparticle-mediated delivery of siRNA for effective lung cancer therapy

Lung cancer is one of the most lethal diseases worldwide, and the survival rate is less than 15% even after the treatment. Unfortunately, chemotherapeutic treatments for lung cancer are accompanied by severe side effects, lack of selectivity and multidrug resistance. In order to overcome the limitations of conventional chemotherapy, nanoparticle-mediated RNA interference drugs represent a potential new approach due to selective silencing effect of oncogenes and multidrug resistance related genes. In this review, we provide recent advancements on nanoparticle-mediated siRNA delivery strategies including lipid system, polymeric system and rigid nanoparticles for lung cancer therapies. Importantly, codelivery of siRNA with conventional anticancer drugs and recent theranostic agents that offer great potential for lung cancer therapy is covered.

Pleiotropic functions of glutathione S-transferase P

Glutathione S-transferase P (GSTP) is one member of the GST superfamily that is prevalently expressed in mammals. Known to possess catalytic activity through deprotonating glutathione allowing formation of thioether bonds with electrophilic substrates, more recent discoveries have broadened our understanding of the biological roles of this protein. In addition to catalytic detoxification, other properties so far ascribed to GSTP include chaperone functions, regulation of nitric oxide pathways, regulation of a variety of kinase signaling pathways, and participation in the forward reaction of protein S-glutathionylation. The expression of GSTP has been linked with cancer and other human pathologies and more recently even with drug addiction. With respect to human health, polymorphic variants of GSTP may determine individual susceptibility to oxidative stress and/or be critical in the design and development of drugs that have used redox pathways as a discovery platform.

Reaction kinetics and targeting to cellular glutathione S-transferase of the glutathione peroxidase mimetic PhSeZnCl and its D,L-polylactide microparticle formulation

Catalytic properties and cellular effects of the glutathione peroxidase (GPx)-mimetic compound PhSeZnCl or its d,l-lactide polymer microencapsulation form (M-PhSeZnCl) were investigated and compared with the prototypical Se-organic compounds ebselen and diselenide (PhSe)2. PhSeZnCl was confirmed to catalyze the ping-pong reaction of GPx with higher Vmax than ebselen and (PhSe)2, but the catalytic efficiency calculated for the cosubstrates glutathione (GSH) and H2O2, and particularly the high reactivity against thiols (lowest KM for GSH in the series of test molecules), suggested poor biological applicability of PhSeZnCl as a GPx mimetic. Cytotoxicity of PhSeZnCl was demonstrated in various cancer cell lines via increased reactive oxygen species (ROS) generation, depletion of intracellular thiols, and induction of apoptosis. Experiments carried out in GSH S-transferase P (GSTP)-overexpressing K562 human erythroleukemia cells and in GSTP1-1-knockout murine embryonic fibroblasts (MEFs) demonstrated that this cytosolic enzyme represents a preferential target of the redox disturbances produced by this Se-compound with a key role in controlling H2O2 generation and the perturbation of stress/survival kinase signaling. Microencapsulation was adopted as a strategy to control the thiol reactivity and oxidative stress effects of PhSeZnCl, then assessing applications alternative to anticancer. The uptake of this "depowered" GPx-mimetic formulation, which occurred through an endocytosis-like mechanism, resulted in a marked reduction of cytotoxicity. In MCF-7 cells transfected with different allelic variants of GSTP, M-PhSeZnCl lowered the burst of cellular ROS induced by the exposure to extracellular H2O2, and the extent of this effect changed between the GSTP variants. Microencapsulation is a straightforward strategy to mitigate the toxicity of thiol-reactive Se-organic drugs that enhanced the antioxidant and cellular protective effects of PhSeZnCl. A mechanistic linkage of these effects with the expression pattern and signaling properties of GSTP . This has overcome the GPx-mimetic paradigm proposed for Se-organic drugs with a more pragmatic concept of GSTP signaling modulators.

A Halloween gene noppera-bo encodes a glutathione S-transferase essential for ecdysteroid biosynthesis via regulating the behaviour of cholesterol in Drosophila

In insects, the precise timing of moulting and metamorphosis is strictly guided by ecdysteroids that are synthesised from dietary cholesterol in the prothoracic gland (PG). In the past decade, several ecdysteroidogenic enzymes, some of which are encoded by the Halloween genes, have been identified and characterised. Here, we report a novel Halloween gene, noppera-bo (nobo), that encodes a member of the glutathione S-transferase family. nobo was identified as a gene that is predominantly expressed in the PG of the fruit fly Drosophila melanogaster. We generated a nobo knock-out mutant, which displayed embryonic lethality and a naked cuticle structure. These phenotypes are typical for Halloween mutants showing embryonic ecdysteroid deficiency. In addition, the PG-specific nobo knock-down larvae displayed an arrested phenotype and reduced 20-hydroxyecdysone (20E) titres. Importantly, both embryonic and larval phenotypes were rescued by the administration of 20E or cholesterol. We also confirm that PG cells in nobo loss-of-function larvae abnormally accumulate cholesterol. Considering that cholesterol is the most upstream material for ecdysteroid biosynthesis in the PG, our results raise the possibility that nobo plays a crucial role in regulating the behaviour of cholesterol in steroid biosynthesis in insects.

Nitric oxide releasing d-α-tocopheryl polyethylene glycol succinate for enhancing antitumor activity of doxorubicin

Nitric oxide (NO) has attracted much attention for its antitumor activity and synergistic effects when codelivered with anticancer agents. However, due to its chemical instability and short half-life, delivering gaseous NO directly to tumors is still challenging. Herein, we synthesized a NO releasing polymer, nitrate functionalized d-α-tocopheryl polyethylene glycol succinate (TNO3). TNO3 was able to self-assemble into stable micelles in physiological conditions, accumulate in tumors, and release ∼90% of NO content in cancer cells for 96 h. It further exhibited significant cancer cell cytotoxicity and apoptosis compared with nitroglycerine (GTN). Notably, TNO3 could also serve as an enhancer for the common chemotherapeutic drug doxorubicin (DOX). Codelivering TNO3 with DOX to hepatocarcinoma HepG2 cancer cells strengthened the cellular uptake of DOX and enabled the synergistic effect between NO and DOX to induce higher cytotoxicity (∼6.25-fold lower IC50). Moreover, for DOX-based chemotherapy in tumor-bearing mice, coadministration with TNO3 significantly extended the blood circulation time of DOX (14.7-fold t1/2, 6.5-fold mean residence time (MRT), and 13.7-fold area under curve (AUC)) and enhanced its tumor accumulation and penetration, thus resulting in better antitumor efficacy. In summary, this new NO donor, TNO3, may provide a simple but effective strategy to enhance the therapeutic efficacy of chemotherapeutic drugs.

Serum peptidome based biomarkers searching for monitoring minimal residual disease in adult acute lymphocytic leukemia

BACKGROUND

The persistence of minimal residual disease (MRD) during therapy is the strongest adverse prognostic factor in acute lymphocytic leukemia (ALL). This study was to identify serum candidate peptides for monitoring MRD in adult ALL.

RESULTS

A total of 33 peptides in the molecular weight range of 1000-10000 Da were detected using ClinProt system and statistically different between adult patients with ALL and healthy controls. Quick classifier (QC) algorithm was used to obtain a diagnostic model consisting of five peptides that could discriminate patients with ALL from controls with a high sensitivity (100%) and specificity (96.67%). The peptides in the QC model were identified as fibrinogen alpha chain (FGA), glutathione S-transferase P1 (GSTP1), isoform 1 of fibrinogen alpha chain precursor, platelet factor 4 (PF4) by high pressure/performance liquid chromatography mass spectrometry/mass spectrometry. Relative intensities of the five peptides were compared among ALL different groups for the potential importance of MRD evaluation in ALL. The peptides with increased relative intensities in newly diagnosed (ND) ALL patients were found to be decreased in their relative intensities after complete remission (CR) of adult ALL. When ALL patients were refractory & relapsed (RR), relative intensities of the peptides were elevated again. Peptides with decreased relative intensities in ND and RR ALL patients were found to be increased in their relative intensities when ALL patients achieved CR. The findings were validated by ELISA and western blot. Further linear regression analyses were performed to eliminate the influence of platelet and white blood cell counts on serum protein contents and indicated that there were no correlations between the contents of all four proteins (PF4, connective tissue active peptide III, FGA and GSTP1) and white blood cell or platelet counts in ALL different groups and healthy control.

CONCLUSIONS

We speculate the five peptides, FGA, isoform 1 of fibrinogen alpha chain precursor, GSTP1, PF4 and connective tissue active peptide III would be potential biomarkers for forecasting relapse, monitoring MRD and evaluating therapeutic response in adult ALL.

S-glutathionylation of buccal cell proteins as biomarkers of exposure to hydrogen peroxide

Background

Exogenous or endogenous hydrogen peroxide (H₂O₂) is a reactive oxygen species (ROS) that can lead to oxidation of cellular nucleophiles, particularly cysteines in proteins. Commercial mouthwashes containing H₂O₂ provide the opportunity to determine clinically whether changes in S-glutathionylation of susceptible proteins in buccal mucosa cells can be used as biomarkers of ROS exposure.

Methods

Using an exploratory clinical protocol, 18 disease-free volunteers rinsed with a mouthwash containing 1.5% H₂O₂ (442 mM) over four consecutive days. Exfoliated buccal cell samples were collected prior and post-treatment and proteomics were used to identify S-glutathionylated proteins.

Results

Four consecutive daily treatments with the H₂O₂-containing mouthwash induced significant dose and time-dependent increases in S-glutathionylation of buccal cell proteins, stable for at least 30 min following treatments. Elevated levels of S-glutathionylation were maintained with subsequent daily exposure. Increased S-glutathionylation preceded and correlated with transcriptional activation of ROS sensitive genes, such as ATF3, and with the presence of 8-hydroxy deoxyguanosine. Data from a human buccal cell line TR146 were consistent with the trial results. We identified twelve proteins that were S-glutathionylated following H₂O₂ exposure.

Conclusions

Buccal cells can predict exposure to ROS through increased levels of S-glutathionylation of proteins. These post-translationally modified proteins serve as biomarkers for the effects of H₂O₂ in the oral cavity and in the future, may be adaptable as extrapolated pharmacodynamic biomarkers for assessing the impact of other systemic drugs that cause ROS and/or impact redox homeostasis.

General significance

S-glutathionylation of buccal cell proteins can be used as a quantitative measure of exposure to ROS.

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Hydrogen peroxide is both a toxin and an endogenous signaling molecule.

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The use of hydrogen peroxide mouthwash causes ROS mediated damage in cheek cells.

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S-glutathionylated proteins are biomarkers for this damage.

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S-glutathionylated proteins may be of future value as pharmacodynamic markers.

Redox proteomics as biomarker for assessing the biological effects of contaminants in crayfish from Doñana National Park

Despite its environmental relevance and sensitivity, Doñana National Park (DNP) is under high ecological pressure. In crayfish (Procambarus clarkii), the utility of redox proteomics as a novel biomarker was evaluated in the aquatic ecosystems of DNP and its surroundings, where agricultural activity is a serious concern. After fluorescence labeling of reversibly oxidized Cys and 2-DE separation, the total density of proteins with reversibly oxidized thiols was found to be much higher in animals from the Matochal (MAT) and Rocina (ROC) streams, while no difference was found in crayfish from Partido (PAR) stream compared to those from the DNP core at Lucio del Palacio (the negative control). The 2-DE analysis revealed 35 spots with significant differences in thiol oxidation, among which 19 proteins were identified via MALDI-TOF/TOF. While 3 spots, identified as ferritin, showed higher oxidation levels in ROC, other identified proteins were more intense at MAT than at ROC (superoxide dismutase, protein disulfide isomerase and actin) or were overoxidized only in MAT (nucleoside diphosphate kinase, fructose-biphosphate aldolase, fatty acid-binding protein, phosphopyruvate hydratase). For most of the identified proteins, spots corresponding to different Cys oxidized forms were detected, and the native forms, without oxidized thiol groups were also found in some of them. Evidence of reversible oxidation was found for specific Cys residues, including Cys13 in ferritin as well as Cys76 and Cys108 in nucleoside diphosphate kinase. The identified thiol-oxidized proteins provide information about the metabolic pathways and/or physiological processes affected by pollutant-elicited oxidative stress.

The glutaredoxin/S-glutathionylation axis regulates interleukin-17A-induced proinflammatory responses in lung epithelial cells in association with S-glutathionylation of nuclear factor κB family proteins

Interleukin-17A (IL-17A) is a newly emerging player in the pathogenesis of chronic lung diseases that amplifies inflammatory responses and promotes tissue remodeling. Stimulation of lung epithelial cells with IL-17A leads to activation of the transcription factor nuclear factor κB (NF-κB), a key player in the orchestration of lung inflammation. We have previously demonstrated the importance of the redox-dependent posttranslational modification S-glutathionylation in limiting activation of NF-κB and downstream gene induction. Under physiological conditions, the enzyme glutaredoxin 1 (Grx1) acts to deglutathionylate NF-κB proteins, which restores functional activity. In this study, we sought to determine the impact of S-glutathionylation on IL-17A-induced NF-κB activation and expression of proinflammatory mediators. C10 mouse lung alveolar epithelial cells or primary mouse tracheal epithelial cells exposed to IL-17A show rapid activation of NF-κB and the induction of proinflammatory genes. Upon IL-17A exposure, sulfenic acid formation and S-glutathionylated proteins increased. Assessment of S-glutathionylation of NF-κB pathway components revealed S-glutathionylation of RelA (RelA-SSG) and inhibitory κB kinase α (IKKα-SSG) after stimulation with IL-17A. SiRNA-mediated ablation of Grx1 increased both RelA-SSG and IKKα-SSG and acutely increased nuclear content of RelA and tended to decrease nuclear RelB. SiRNA-mediated ablation or genetic ablation of Glrx1 decreased the expression of the NF-κB-regulated genes KC and CCL20 in response to IL-17A, but conversely increased the expression of IL-6. Last, siRNA-mediated ablation of IKKα attenuated nuclear RelA and RelB content and decreased expression of KC and CCL20 in response to IL-17A. Together, these data demonstrate a critical role for the S-glutathionylation/Grx1 redox axis in regulating IKKα and RelA S-glutathionylation and the responsiveness of epithelial cells to IL-17A.

Meta-analyses of methylation markers for prostate cancer

Prostate cancer (PCa) is the most frequently diagnosed non-cutaneous cancer that has become the sixth leading cause of mortality in both the developed and developing countries. Accumulating evidence showed a number of genes with aberrant DNA methylation in the pathogenesis of PCa. Here, we conducted a systematic meta-analysis to evaluate the contribution of aberrantly methylated genes to the risk of PCa. Relevant methylation studies were retrieved from PubMed and Wanfang literature databases. In the meta-analysis, Mantel-Haenszel odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated for each methylation event under appropriate models. A total of 594 publications were initially retrieved from PubMed and Wanfang literature database. After a three-step filtration, we harvested 39 case-control articles investigating the role of gene methylation in the prediction of PCa risk. Among the 31 genes involved, 24 genes were shown to be significantly hypermethylated in the PCa patients. Our meta-analyses identified strong associations of four aberrantly methylated genes (GSTP1, RASSF1, p16, and RARB) with PCa. Further research is needed to strengthen our findings in the future.

[Structure and functions of glutathione transferases]

Data about classification, nomenclature, structure, substrate specificity and role of many glutathione transferase's isoenzymes in cell functions have been summarised. The enzyme has been discovered more than 50 years ago. This family of proteins is updated continuously. It has very different composition and will have demand for system analysis for many years.

Substrate profiling of glutathione S-transferase with engineered enzymes and matched glutathione analogues

The identification of specific substrates of glutathione S-transferases (GSTs) is important for understanding drug metabolism. A method termed bioorthogonal identification of GST substrates (BIGS) was developed, in which a reduced glutathione (GSH) analogue was developed for recognition by a rationally engineered GST to label the substrates of the corresponding native GST. A K44G-W40A-R41A mutant (GST-KWR) of the mu-class glutathione S-transferases GSTM1 was shown to be active with a clickable GSH analogue (GSH-R1) as the cosubstrate. The GSH-R1 conjugation products can react with an azido-based biotin probe for ready enrichment and MS identification. Proof-of-principle studies were carried to detect the products of GSH-R1 conjugation to 1-chloro-2,4-dinitrobenzene (CDNB) and dopamine quinone. The BIGS technology was then used to identify GSTM1 substrates in the Chinese herbal medicine Ganmaocongji.

Methylation markers for prostate cancer prognosis: a systematic review

PURPOSE

We conducted a systematic review to summarize current evidence on the prognostic utility of DNA methylation markers in prostate cancer and ascertain knowledge gaps to inform future research.

METHODS

We identified relevant studies using combined key search against PubMed database. Inclusion criteria were studies of human subjects that examined the association between DNA methylation markers and prostate cancer disease outcomes. The methodological quality of each study was systematically evaluated. Findings were qualitatively summarized. Due to heterogeneity and concerns of internal validity, no meta-analysis was performed.

RESULTS

Twenty studies were reviewed; sample size ranged from 35 to 605 men in the prognostic analyses. Sixteen studies examined methylation markers in prostate cancer tissue and four examined circulating DNA methylation markers. Of all genes reviewed, paired-like homeodomain transcription factor 2 (PITX2) methylation was examined in two more rigorously designed studies and was found to be associated with biochemical recurrence. Common limitations in current literature included small sample sizes,lack of adequate adjustment for established prognostic factors, and poor reporting quality.

CONCLUSION

Evidence on the prognostic utility of methylation markers in prostate cancer is inconclusive. Future research should ascertain large samples with adequate follow-up and include patients of racial/ethnic minority and those treated with modalities other than prostatectomy(e.g., using prostate cancer diagnostic biopsy as tissue source).

Biomarkers of mercury exposure in the Amazon

Mercury exposure in the Amazon has been studied since the 1980s decade and the assessment of human mercury exposure in the Amazon is difficult given that the natural occurrence of this metal is high and the concentration of mercury in biological samples of this population exceeds the standardized value of normality established by WHO. Few studies have focused on the discovery of mercury biomarkers in the region's population. In this way, some studies have used genetics as well as immunological and cytogenetic tools in order to find a molecular biomarker for assessing the toxicological effect of mercury in the Amazonian population. Most of those studies focused attention on the relation between mercury exposure and autoimmunity and, because of that, they will be discussed in more detail. Here we introduce the general aspects involved with each biomarker that was studied in the region in order to contextualize the reader and add information about the Amazonian life style and health that may be considered for future studies. We hope that, in the future, the toxicological studies in this field use high technological tools, such as the next generation sequencing and proteomics skills, in order to comprehend basic questions regarding the metabolic route of mercury in populations that are under constant exposure, such as in the Amazon.

Impact of obesity on ovotoxicity induced by 7,12-dimethylbenz[a]anthracene in mice

Insulin, elevated during obesity, regulates xenobiotic biotransformation enzymes, potentially through phosphatidylinositol 3-kinase (PI3K) signaling, in extraovarian tissues. PI3K regulates oocyte viability, follicular activation, and ovarian chemical biotransformation. 7,12-Dimethylbenz[a]anthracene (DMBA), a carcinogen and ovotoxicant, destroys all stages of follicles, leading to premature ovarian failure. Obesity has been reported to promote DMBA-induced tumors, but it remains unknown whether obesity affects ovarian xenobiotic metabolism. Therefore, we investigated ovarian expression of xenobiotic metabolism genes-microsomal epoxide hydrolase (Ephx1), glutathione S-transferase (GST) class Pi (Gstp1) and class mu 1 (Gstm1), and PI3K-signaling members (protein kinase B [AKT] alpha [Akt1], beta [Akt2], and the forkhead transcription factor subfamily 3 [Foxo3])-in lean and obese female mice after DMBA exposure (1 mg/kg; intraperitoneal injection for 14 days). Relative to lean, obese mice had decreased (P < 0.05) healthy primordial and primary follicle numbers but increased (P < 0.05) secondary and preovulatory follicles numbers. Obesity increased (P < 0.05) Akt1, Akt2, Gstm1, and Ephx1 mRNA and pAKT(Ser473/Thr308), GSTM1, GSTP1, and EPHX1 protein levels. DMBA decreased (P < 0.05) ovarian weight in lean and obese mice, however, obese DMBA-treated females had a greater reduction (P < 0.05) in ovarian weight. In both lean and obese mice, DMBA decreased (P < 0.05) all stages of healthy follicle numbers, increased Gstp1 and Ephx1 mRNA as well as GSTM1, GSTP1, and EPHX1 protein levels, and decreased Akt1 and Akt2 mRNA as well as pAKT(Ser473) or pAKT(Thr308), FOXO3, and pFOXO3(Ser253) protein expression. There was an additive effect between obesity and DMBA exposure for increased Gstm1 and Ephx1 mRNA as well as GSTM1 and EPHX1 protein expression.

GSTpi protects against angiotensin II-induced proliferation and migration of vascular smooth muscle cells by preventing signal transducer and activator of transcription 3 activation

Angiotensin II (Ang II)-elicited excessive proliferation, hypertrophy and migration of vascular smooth muscle cells (VSMCs) are vital to the pathogenesis of atheroclerosis. Glutathione S-transferase pi (GSTpi) exists extensively in various kinds of cells and protects cells against different stresses. However, knowledge remains limited about what GSTpi acts in VSMCs. We investigated the effect of GSTpi on Ang II-induced VSMC proliferation, hypertrophy and migration and its latent mechanism. Overexpression and RNAi experiments demonstrated that GSTpi inhibited Ang II-induced proliferation, hypertrophy and migration of VSMCs and arrested progression of cell cycle from G0/G1 to S phase. Immunoprecipitation, mass spectrometry and confocal microscopy analyses showed that GSTpi directly associated with signal transducer and activator of transcription 3 (STAT3) to prevent Ang II-triggered binding of Src to STAT3 and thus suppressed Ang II-stimulated phosphorylation and nuclear translocation of STAT3, as well as cyclin D1 expression. In contrast, GSTpi didn't affect Ang II-activated extracellular signal-regulated kinase (ERK1/2). GSTpi acts as a negative regulator to prevent Ang II-triggered proliferative signaling in VSMCs, suggesting that it may protect vessels against the stresses associated with atherosclerosis formation.

Structural and biochemical studies of a recombinant 25.5 kDa glutathione transferase of Taenia solium metacestode (rTs25GST1-1)

In this work, we studied a recombinant mu-class glutathione transferase of 25.5 kDa from Taenia solium metacestode (rTs25GST1-1) that follows Michaelis–Menten kinetics with 1-chloro-2,4-dinitrobenzene (CDNB). The kinetic parameters obtained for rTs25GST1-1 with CDNB and GSH were V(max) =12.04 μmol/min/mg and K(m)=1.38 mM, and V(max) =10.20 μmol/min/mg and K(m)=0.90, respectively. The optimal activity was found at pH 8 in the 37-40 °C temperature range. Circular dichroism studies for rTs25GST1-1 at different pH showed that it maintains a typical α-helix structure between pH 6.5-7.5, but loses it between pH 8 and 8.5. Thermal CD assays showed rTs25GST1-1 barely changed its secondary structure. Unfolding/refolding assays showed that rTs25GST1-1 retained its structure up to 40 °C without loss of its activity. Additionally, exposure of rTs25GST1-1 to cumene hydroperoxide did not produce significant changes in its structure and only affected 50% of its activity.

Cellular uptake and antiproliferative effects of 11-oxo-eicosatetraenoic acid

Cyclooxygenases (COX) metabolize arachidonic acid (AA) to hydroxyeicosatetraenoic acids (HETE), which can then be oxidized by dehydrogenases, such as 15-hydroxyprostaglandin dehydrogenase (15-PGDH), to oxo-eicosatetraenoic acids (ETE). We have previously established that 11-oxo-eicosatetraenoic acid (oxo-ETE) and 15-oxo-ETE are COX-2/15-PGDH-derived metabolites. Stable isotope dilution (SID) chiral liquid chromatography coupled with electron capture atmospheric pressure chemical ionization (ECAPCI) single reaction monitoring (SRM) MS has been used to quantify uptake of 11-oxo-ETE and 15-oxo-ETE in both LoVo cells and human umbilical vein endothelial cells (HUVEC). Intracellular 11-oxo- and 15-oxo-ETE concentrations reached maximum levels within 1 h and declined rapidly, with significant quantitative differences in uptake between the LoVo cells and the HUVECs. Maximal intracellular concentrations of 11-oxo-ETE were 0.02 ng/4 × 10⁵ cells in the LoVo cells and 0.58 ng/4 × 10⁵ cells in the HUVECs. Conversely, maximal levels of 15-oxo-ETE were 0.21 ng/4 × 10⁵ in the LoVo cells and 0.01 ng/4 × 10⁵ in the HUVECs. The methyl esters of both 11-oxo- and 15-oxo-ETE increased the intracellular concentrations of the corresponding free oxo-ETEs by 3- to 8-fold. 11-oxo-ETE, 15-oxo-ETE, and their methyl esters inhibited proliferation in both HUVECs and LoVo cells at concentrations of 2–10 μM, with 11-oxo-ETE methyl ester being the most potent inhibitor. Cotreatment with probenecid, an inhibitor of multiple drug resistance transporters (MRP)1 and 4, increased the antiproliferative effect of 11-oxo-ETE methyl ester in LoVo cells and increased the intracellular concentration of 11-oxo-ETE from 0.05 ng/4 × 10⁵ cells to 0.18 ng/4 × 10⁵ cells. Therefore, this study has established that the COX-2/15-PGDH-derived eicosanoids 11-oxo- and 15-oxo-ETE enter target cells, that they inhibit cellular proliferation, and that their inhibitory effects are modulated by MRP exporters.

Targeting nitric oxide signaling with nNOS inhibitors as a novel strategy for the therapy and prevention of human melanoma

AIMS

Our previous studies have shown that nitric oxide (NO) plays an important role in increasing the invasion and proliferation of human melanoma cells, suggesting that targeting NO signaling may facilitate therapy and prevention. Neuronal nitric oxide synthase (nNOS) is present in melanocytes, a cell type that originates from the neural crest. The aims of this study were to determine the role of nNOS in melanoma progression and the potential antitumor effects of novel synthesized nNOS inhibitors.

RESULTS

In vitro studies demonstrated abundant expression of nNOS in melanoma compared to melanocytes, which was inducible by ultraviolet radiation and was associated with increased NO generation. nNOS was also detected in melanoma biopsies that increased with disease stage. Knockdown of nNOS in melanoma cells diminished L-arginine-induced NO production; the metastatic capacity was also reduced as well as the levels of MMP-1, Bcl-2, JunD, and APE/Ref-1. Similar inhibition of NO and invasion potential was observed utilizing novel, highly selective nNOS inhibitors. In three-dimensional human skin reconstructs, the nNOS inhibitor cpd8 effectively reversed the melanoma overgrowth stimulated by NO stress.

INNOVATION

Our work lays the foundation for development of clinical "drug-like" nNOS inhibitors as a new and promising strategy for the chemoprevention of early melanoma progression and the inhibition of secondary melanoma in high-risk individuals.

CONCLUSION

Based on our observations, we propose that nNOS in melanoma results in constitutive overproduction of NO, which stimulates proliferation and increases invasion potential, leading to subsequent development of metastases.

Proteomic analysis of non-small cell lung cancer tissue interstitial fluids

BACKGROUND

Non-small cell lung cancer (NSCLC) accounts for more than 80% of all lung cancers, and reliable biomarkers are desirable. The present investigation assesses our ability to identify tumor relevant proteins from NSCLC tissue interstitial fluid (TIF).

METHODS

Paired TIF was collected from three NSCLC patients at the time of surgery, and resolved by two-dimensional gel electrophoresis and in-gel digestion for proteomic analysis. Differentially expressed spots were extracted from the two-dimensional gel and characterized by high-performance liquid chromatography-tandem mass spectrometry. Then, ELISA was used to verify the expression of peroxiredoxin 1 (PRDX1) in TIF of patients with NSCLC and benign lung disease. Finally, the relationship between expression of PRDX1 and clinicopathological features was determined.

RESULTS

Comparative proteomic analysis showed 24 protein spots were differentially expressed with significant changes, including 11 upregulated proteins and 13 downregulated proteins. Of these, PRDX1 was selected for validation in TIF by Western blot and expression of PRDX1 was confirmed to be upregulated in tumor TIF. It was also demonstrated that PRDX1 was significantly elevated in 40 NSCLC patients with a mean level of 36.0 ng/mL compared to 6.26 ng/mL from 20 patients with benign lung disease. A significant correlation was found between the high level of PRDX1 expression and lymph node metastasis and tumor differentiation.

CONCLUSIONS

PRDX1 might be correlated with lymph node metastasis and differentiation, and its elevated expression in TIF may be an adverse biomarker for patients with NSCLC. PRDX1 may be attributed to the malignant transformation of NSCLC, and attention should be paid to a possible target for therapy.