Expression of glyoxalase I and II in normal and breast cancer tissues

Effects of methylglyoxal and glyoxalase I inhibition on breast cancer cells proliferation, invasion, and apoptosis through modulation of MAPKs, MMP9, and Bcl-2

Emerging evidence indicates that methylglyoxal (MG) can inhibit tumorigenesis. Glyoxalase I (GLOI), a MG degradation enzyme, is implicated in the progression of human malignancies. However, little is known about the roles of MG and GLOI in breast cancer. Our purpose was to investigate the anticancer effects of MG and inhibition of GLOI on breast cancer cells and the underlying mechanisms of these effects. Our findings demonstrate that cell viability, migration, invasion, colony formation, and tubule formation were significantly restrained by addition of MG or inhibition of GLOI, while apoptosis was significantly increased. Furthermore, the expression of p-JNK, p-ERK, and p-p38 was markedly upregulated by addition of MG or inhibition of GLOI, whereas MMP-9 and Bcl-2 expression levels were dramatically decreased. These effects were augmented by combined treatment with MG and inhibition of GLOI. Collectively, these data indicate that MG or inhibition of GLOI induces anticancer effects in breast cancer cells and that these effects are potentiated by combination of the 2. These effects were modulated by activation of the MAPK family and downregulation of Bcl-2 and MMP-9. These findings may provide a new approach for the treatment of breast cancer.

Inhibitory Effect of Isoflavones from Erythrina poeppigiana on the Growth of HL-60 Human Leukemia Cells through Inhibition of Glyoxalase I

It has been reported that many malignant human tissues, including breast, colon, and lung cancers, may show an elevated expression of glyoxalase I (GLO I). GLO I catalyzes the reaction to transform hemimercaptal, a compound formed from methylglyoxal (MG) and reduced glutathione, into S-D-lactoylglutathione, which is then converted to D-lactic acid by glyoxalase II. GLO I inhibitors are expected to be useful for inhibiting tumorigenesis through the accumulation of apoptosis-inducible MG in tumor cells. Here, we investigated the anti-proliferative activity of eight kinds of isoflavone isolated from Erythrina poeppigiana against the growth of HL-60 human leukemia cells from the viewpoint of GLO I inhibition. Of the compounds tested, the diprenyl isoflavone, isolupalbigenin, was shown to exhibit the highest anti-proliferative activity against HL-60 cells. Upon the treatment of HL-60 cells with isolupalbigenin, MG was significantly accumulated in the culture medium, and the caspase 3 activity of the cell lysate was elevated in a time-dependent manner. Thus, it is suggested that isolupalbigenin inhibits the enzyme GLO I, resulting in MG accumulation in the medium, and leading to cell apoptosis. Isolupalbigenin, with two prenyl groups in its A- and B-rings, might be expected to become a potent leading compound for the development of anticancer agents.

Triple negative tumors accumulate significantly less methylglyoxal specific adducts than other human breast cancer subtypes

Metabolic syndrome and type 2 diabetes are associated with increased risk of breast cancer development and progression. Methylglyoxal (MG), a glycolysis by-product, is generated through a non-enzymatic reaction from triose-phosphate intermediates. This dicarbonyl compound is highly reactive and contributes to the accumulation of advanced glycation end products. In this study, we analyzed the accumulation of Arg-pyrimidine, a MG-arginine adduct, in human breast adenocarcinoma and we observed a consistent increase of Arg-pyrimidine in cancer cells when compared with the non-tumoral counterpart. Further immunohistochemical comparative analysis of breast cancer subtypes revealed that triple negative lesions exhibited low accumulation of Arg-pyrimidine compared with other subtypes. Interestingly, the activity of glyoxalase 1 (Glo-1), an enzyme that detoxifies MG, was significantly higher in triple negative than in other subtype lesions, suggesting that these aggressive tumors are able to develop an efficient response against dicarbonyl stress. Using breast cancer cell lines, we substantiated these clinical observations by showing that, in contrast to triple positive, triple negative cells induced Glo-1 expression and activity in response to MG treatment. This is the first report that Arg-pyrimidine adduct accumulation is a consistent event in human breast cancer with a differential detection between triple negative and other breast cancer subtypes.

Proteomic analysis indicates that overexpression and nuclear translocation of lactoylglutathione lyase (GLO1) is associated with tumor progression in murine fibrosarcoma

Lactoylglutathione lyase (GLO1), a ubiquitously expressed methylglyoxal (MG) detoxification enzyme, is implicated in the progression of various human malignant diseases. However, the role of GLO1 in the development or progression of murine fibrosarcoma is still unclear. We performed proteomic analysis to identify differences in the intracellular proteins of the regressive tumor cell line QR-32 and the inflammatory cell-promoting progressive tumor cell line QRsP-11 of murine fibrosarcoma by 2DE combined with MS. Seven upregulated proteins were identified in QRsP-11 compared to QR-32 cells, namely, GLO1, annexin A1, adenylate kinase isoenzyme 1, transcription factor BTF3, myosin light polypeptide 6, low molecular weight phosphotyrosine protein phosphatase and nucleoside diphosphate kinase B. Heat shock protein beta-1 (HspB1), a methylglyoxal-adducted protein, is concomitantly over-expressed in QRsP-11 as compared to QR-32 cells. We also found out that GLO1 is translocated into the nucleus to a higher extent in QRsP-11 compared to QR-32 cells, which can be reversed by using a MEK inhibitor (U0126). Moreover, U0126 and GLO1 siRNA can inhibit cell proliferation and migration in QRsP-11 cells. Our data suggest that overexpression and nuclear translocation of GLO1 might be associated with tumor progression in murine fibrosarcoma.

Discovery of selective 2,4-diaminopyrimidine-based photoaffinity probes for glyoxalase I

L1-Bpyne was discovered as a potent inhibitor and cell permeable probe of glyoxalase I.

Glycerophosphoglycerol, Beta-alanine, and pantothenic Acid as metabolic companions of glycolytic activity and cell migration in breast cancer cell lines

In cancer research, cell lines are used to explore the molecular basis of the disease as a substitute to tissue biopsies. Breast cancer in particular is a very heterogeneous type of cancer, and different subgroups of cell lines have been established according to their genomic profiles and tumor characteristics. We applied GCMS metabolite profiling to five selected breast cancer cell lines and found this heterogeneity reflected on the metabolite level as well. Metabolite profiles of MCF-7 cells belonging to the luminal gene cluster proved to be more different from those of the basal A cell line JIMT-1 and the basal B cell lines MDA-MB-231, MDA-MB-435, and MDA-MB-436 with only slight differences in the intracellular metabolite pattern. Lactate release into the cultivation medium as an indicator of glycolytic activity was correlated to the metabolite profiles and physiological characteristics of each cell line. In conclusion, pantothenic acid, beta-alanine and glycerophosphoglycerol appeared to be related to the glycolytic activity designated through high lactate release. Other physiological parameters coinciding with glycolytic activity were high glyoxalase 1 (Glo1) and lactate dehydrogenase (LDH) enzyme activity as well as cell migration as an additional important characteristic contributing to the aggressiveness of tumor cells. Metabolite profiles of the cell lines are comparatively discussed with respect to known biomarkers of cancer progression.

New Arabidopsis thaliana cytochrome c partners: a look into the elusive role of cytochrome c in programmed cell death in plants

Programmed cell death is an event displayed by many different organisms along the evolutionary scale. In plants, programmed cell death is necessary for development and the hypersensitive response to stress or pathogenic infection. A common feature in programmed cell death across organisms is the translocation of cytochrome c from mitochondria to the cytosol. To better understand the role of cytochrome c in the onset of programmed cell death in plants, a proteomic approach was developed based on affinity chromatography and using Arabidopsis thaliana cytochrome c as bait. Using this approach, ten putative new cytochrome c partners were identified. Of these putative partners and as indicated by bimolecular fluorescence complementation, nine of them bind the heme protein in plant protoplasts and human cells as a heterologous system. The in vitro interaction between cytochrome c and such soluble cytochrome c-targets was further corroborated using surface plasmon resonance. Taken together, the results obtained in the study indicate that Arabidopsis thaliana cytochrome c interacts with several distinct proteins involved in protein folding, translational regulation, cell death, oxidative stress, DNA damage, energetic metabolism, and mRNA metabolism. Interestingly, some of these novel Arabidopsis thaliana cytochrome c-targets are closely related to those for Homo sapiens cytochrome c (Martínez-Fábregas et al., unpublished). These results indicate that the evolutionarily well-conserved cytosolic cytochrome c, appearing in organisms from plants to mammals, interacts with a wide range of targets on programmed cell death. The data have been deposited to the ProteomeXchange with identifier PXD000280.

The glyoxalase pathway: the first hundred years... and beyond

The discovery of the enzymatic formation of lactic acid from methylglyoxal dates back to 1913 and was believed to be associated with one enzyme termed ketonaldehydemutase or glyoxalase, the latter designation prevailed. However, in 1951 it was shown that two enzymes were needed and that glutathione was the required catalytic co-factor. The concept of a metabolic pathway defined by two enzymes emerged at this time. Its association to detoxification and anti-glycation defence are its presently accepted roles, since methylglyoxal exerts irreversible effects on protein structure and function, associated with misfolding. This functional defence role has been the rationale behind the possible use of the glyoxalase pathway as a therapeutic target, since its inhibition might lead to an increased methylglyoxal concentration and cellular damage. However, metabolic pathway analysis showed that glyoxalase effects on methylglyoxal concentration are likely to be negligible and several organisms, from mammals to yeast and protozoan parasites, show no phenotype in the absence of one or both glyoxalase enzymes. The aim of the present review is to show the evolution of thought regarding the glyoxalase pathway since its discovery 100 years ago, the current knowledge on the glyoxalase enzymes and their recognized role in the control of glycation processes.

Role of glyoxalase I in the proliferation and apoptosis control of human LNCaP and PC3 prostate cancer cells

BACKGROUND

Glyoxalase I (GLOI) detoxifies reactive dicarbonyls, as methylglyoxal (MG) that, directly or through the formation of MG-derived adducts, is a growth inhibitor and apoptosis inducer. GLOI has been considered a general marker of cell proliferation, but a direct link between the two has yet to be demonstrated. The aim of the present work was to clarify whether GLOI was involved in the proliferation control of LNCaP and PC3 human prostate cancer cells or might play a different role in the growth regulation of these cells.

METHODS

RNA interference was used to study the role of GLOI in cell proliferation or apoptosis. Cell proliferation was evaluated by [3H]thymidine incorporation assay and flow cytometry, that was also used to analyze apoptosis. Real-time TaqMan polymerase chain reaction and spectrophotometric analyses were used to study transcript levels or specific activity, respectively. Proteins levels were analyzed by Western blot. MG was measured by high-performance liquid chromatography.

RESULTS

We found that GLOI is not implicated in the proliferation control of LNCaP and PC3 cells but plays a role in the apoptosis of invasive prostate cancer PC3 cells, through a mechanism involving a specific MG-adduct and NF-kB signaling pathway.

CONCLUSIONS

Our data represent the first systematic demonstration that GLOI cannot be considered a general marker of cell proliferation and that acts as a pro-survival factor in invasive PC3 cells by elusing apoptosis. GLOI may be involved in prostate cancer progression, via the control of key molecules in the mitochondrial apoptotic mechanism, through NF-kB signaling pathway.

Glyoxalase I activity and immunoreactivity in the aging human lens

Glyoxalase I (GLOI) is the first enzyme of the glyoxalase system that catalyzes the metabolism of reactive dicarbonyls, such as methylglyoxal (MGO). During aging and cataract development, human lens proteins are chemically modified by MGO, which is likely due to inadequate metabolism of MGO by the glyoxalase system. In this study, we have determined the effect of aging on GLOI activity and the immunoreactivity and morphological distribution of GLOI in the human lens. A monoclonal antibody was developed against human GLOI. GLOI immunoreactivity was strongest in the anterior epithelial cells and weaker in rest of the lens. Cultured human lens epithelial cells showed immunostaining throughout the cytoplasm. In the human lens, GLOI activity and immunoreactivity both decreased with age. We believe that this would lead to promotion of MGO-modification in aging lens proteins.

Glyoxalase in tumourigenesis and multidrug resistance

Since the discovery by Warburg of high aerobic glycolysis in most tumours in the 1920s, it has remained unclear how to exploit this in chemotherapy. The aim of this review is to assess the evidence for the involvement of the glyoxalase system in tumour growth and multidrug resistance and the importance of the glyoxalase system as a target for anticancer drug development and a source of biomarkers for tumour diagnosis. Increased expression of glyoxalase 1 appears to support the viability of tumour cells with high glycolytic rates. Multidrug resistance conferred by overexpression of glyoxalase 1 suggests mechanisms of toxicity of most current antitumour agents involve, in some part, accumulation of methylglyoxal to cytotoxic levels. The recent finding of glyoxalase 1 gene amplification in tumours and induction of increased glyoxalase 1 expression by malignant transformation and conventional antitumour drug treatment implies a critical role of glyoxalase 1 in innate and acquired multidrug resistance in cancer treatment. Improved understanding of glyoxalase 1 in cancer chemotherapy multidrug resistance is likely vital to achieve improvement of cancer patient survival rates. Advances made to counter glyoxalase 1-linked multidrug resistance with glyoxalase 1 inhibitors and related prodrugs has been translated from in vitro to pre-clinical in vivo studies. Further research is required urgently for next stage clinical translation. Finally, overexpression of glyoxalase 1 may be linked to multidrug resistance in chemotherapy of other disease - such as microbial infections.

Potential molecular targets in chemopreventative action of celecoxib: a proteomics analysis of J774.A1 macrophage-like cell line

The overexpression of cyclooxygenase-2 (COX-2) enzyme has been strongly contributed to tumorigenesis. The efficacy of celecoxib as a selective COX-2 inhibitor has been shown in many studies, but the underlying mechanism as a chemopreventative agent has not yet been well known. For better understanding the chemopreventative molecular mechanisms, we used a comparative proteomics analysis of lipopolysaccharide (LPS) treated and untreated J774.A1 macrophage-like cell lines before and after treatment with celecoxib. Our findings define the contribution of several interesting proteins, including ferritin heavy chain, glyoxalase-1, cofilin, vimentin, and galectin-1, which could extend our understanding of the chemopreventative effects of celecoxib and provide new valuable tools for further anticancer research.

Low red blood cell levels of deglycating enzymes in colorectal cancer patients

AIM: To investigate Glyoxalase I and fructosamine-3-kinase (FN3K) activity in red blood cells from patients with colorectal adenomas and cancer.

METHODS: Thirty three consecutive subjects with one or more histologically confirmed colorectal adenomatous polyps, 16 colorectal cancer patients and a group of 11 control subjects with normal colonoscopy were included in the study. Glyoxalase I and FN3K activities were measured in red blood cells using a spectrophotometric and radiometric assay, respectively.

RESULTS: A significant reduction in both Glyoxalase I and FN3K activity was detected in patients with tumors compared to patients with adenomas and the controls. Erythrocyte Glyoxalase I activity in colorectal cancer was approximately 6 times lower than that detected in patients with adenoma (0.022 ± 0.01 mmol/min per milliliter vs 0.128 ± 0.19 mmol/min per milliliter of red blood cells, P = 0.003, Tukey’s test). FN3K activity in red blood cells from patients with colon cancer was approximately 2 times lower than that detected in adenoma patients (19.55 ± 6.4 pmol/min per milliliter vs 38.6 ± 31.7 pmol/min per milliliter of red blood cells, P = 0.04, Tukey’s test).

CONCLUSION: These findings suggest that deglycating enzymes may be involved in the malignant transformation of colon mucosa.

Identification of curcumin derivatives as human glyoxalase I inhibitors: A combination of biological evaluation, molecular docking, 3D-QSAR and molecular dynamics simulation studies

Several recent developments suggest that the human glyoxalase I (GLO I) is a potential target for anti-tumor drug development. In present study, a series of curcumin derivatives with high inhibitory activity against human GLO I were discovered. Inhibition constant (K(i)) values of compounds 8, 9, 10, 11 and 13 to GLO I are 4.600μM, 2.600μM, 3.200μM, 3.600μM and 3.600μM, respectively. To elucidate the structural features of potent inhibitors, docking-based three-dimensional structure-activity relationship (3D-QSAR) analyses were performed. Satisfactory agreement between experiment and theory suggests that comparative molecular similarity index analysis (CoMSIA) modeling exhibit much better correlation and predictive power. The cross-validated q(2) value is 0.638 while no-validation r(2) value is 0.930. Integrated with docking-based 3D-QSAR CoMSIA modeling, molecular surface property (electrostatic and steric) mapping and molecular dynamics simulation, a set of receptor-ligand binding models and bio-affinity predictive models for rational design of more potent inhibitors of GLO I are established.

GLO1-A novel amplified gene in human cancer

To identify a novel amplified cancer gene a systematic screen of 975 human cancer DNA samples, 750 cell lines and 225 primary tumors, using the Affymetrix 10K SNP microarray was undertaken. The screen identified 193 amplicons. A previously uncharacterized amplicon located on 6p21.2 whose 1 Mb minimal common amplified region contained eight genes (GLO1, DNAH8, GLP1R, C6orf64, KCNK5, KCNK17, KCNK16, and C6orf102) was further investigated to determine which gene(s) are the biological targets of this amplicon. Real time quantitative PCR (qPCR) analysis of all amplicon 6p21.2 genes in 618 human cancer cell lines identified GLO1, encoding glyoxalase 1, to be the most frequently amplified gene [twofold or greater amplification in 8.4% (49/536) of cancers]. Also the association between amplification and overexpression was greatest for GLO1. RNAi knockdown of GLO1 had the greatest and most consistent impact on cell accumulation and apoptosis. Cell lines with GLO1 amplification were more sensitive to inhibition of GLO1 by bromobenzylglutathione cyclopentyl diester (BBGC). Subsequent qPCR of 520 primary tumor samples identified twofold and greater amplification of GLO1 in 8/37 (22%) of breast, 12/71 (17%) of sarcomas, 6/53 (11.3%) of nonsmall cell lung, 2/23 (8.7%) of bladder, 6/93 (6.5%) of renal and 5/83 (6%) of gastric cancers. Amplification of GLO1 was rare in colon cancer (1/35) and glioma (1/94). Collectively the results indicate that GLO1 is at least one of the targets of gene amplification on 6p21.2 and may represent a useful target for therapy in cancers with GLO1 amplification.

GLO1 overexpression in human malignant melanoma

Glyoxalase I [lactoylglutathione lyase (EC 4.4.1.5) encoded by GLO1] is a ubiquitous cellular defense enzyme involved in the detoxification of methylglyoxal, a cytotoxic byproduct of glycolysis. Accumulative evidence suggests an important role of GLO1 expression in protection against methylglyoxal-dependent protein adduction and cellular damage associated with diabetes, cancer, and chronological aging. On the basis of the hypothesis that GLO1 upregulation may play a functional role in glycolytic adaptations of cancer cells, we examined GLO1 expression status in human melanoma tissue. Quantitative reverse transcription polymerase chain reaction analysis of a cDNA tissue array containing 40 human melanoma tissues (stages III and IV) and 13 healthy controls revealed pronounced upregulation of GLO1 expression at the mRNA level. Immunohistochemical analysis of a melanoma tissue microarray confirmed upregulation of glyoxalase I protein levels in malignant melanoma tissue versus healthy human skin. Consistent with an essential role of GLO1 in melanoma cell defense against methylglyoxal cytotoxicity, siRNA interference targeting GLO1-expression (siGLO1) sensitized A375 and G361 human metastatic melanoma cells towards the antiproliferative, apoptogenic, and oxidative stress-inducing activity of exogenous methylglyoxal. Protein adduction by methylglyoxal was increased in siGLO1-transfected cells as revealed by immunodetection using a monoclonal antibody directed against the major methylglyoxal-derived epitope argpyrimidine that detected a single band of methylglyoxal-adducted protein in human LOX, G361, and A375 total cell lysates. Using two-dimensional proteomics followed by mass spectrometry the methylglyoxal-adducted protein was identified as heat shock protein 27 (Hsp27; HSPB1). Taken together, our data suggest a function of GLO1 in the regulation of detoxification and target adduction by the glycolytic byproduct methylglyoxal in malignant melanoma.

Critical evaluation of toxic versus beneficial effects of methylglyoxal

In various organisms, an array of enzymes is involved in the synthesis and breakdown of methylglyoxal. Through these enzymes, it is intimately linked to several other physiologically important metabolites, suggesting that methylglyoxal has some important role to play in the host organism. Several in vitro and in vivo studies showed that methylglyoxal acts specifically against different types of malignant cells. These studies culminated in a recent investigation to evaluate a methylglyoxal-based formulation in treating a small group of cancer patients, and the results were promising. Methylglyoxal acts against a number of pathogenic microorganisms. However, recent literature abounds with the toxic effects of methylglyoxal, which are supposed to be mediated through methylglyoxal-derived advanced glycation end products (AGE). Many diseases such as diabetes, cataract formation, hypertension, and uremia are proposed to be intimately linked with methylglyoxal-derived AGE. However methylglyoxal-derived AGE formation and subsequent pathogenesis might be a very minor event because AGE are nonspecific reaction products that are derived through the reactions of carbonyl groups of reducing sugars with amino groups present in the side chains of lysine and arginine and in terminal amino groups of proteins. Moreover, the results of some in vitro experiments with methylglyoxal under non-physiological conditions were extrapolated to the in vivo situation. Some experiments even showed contradictory results and were differently interpreted. For this reason conclusions about the potential beneficial effects of methylglyoxal have often been neglected, thus hindering the advancement of medical science and causing some confusion in fundamental understanding. Overall, the potential beneficial effects of methylglyoxal far outweigh its possible toxic role in vivo, and it should be utilized for the benefit of suffering humanity.

The effect of electroaucpuncture for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced proteomic changes in the mouse striatum

Using a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) Parkinson's disease mouse model, we investigated protein expression changes associated with the action of electroacupuncture (EA) in the mouse striatum. Twelve-week-old male C57BL/6 mice were injected intraperitoneally with 30 mg/kg of MPTP at 24-h intervals for 5 days, and the 100-Hz EA stimulation was performed at GB34 and GB39 once a day for 12 days consecutively from the first injection. With the EA, the MPTP-induced dopaminergic neuronal destruction was reduced. Of the 13 proteins that were differentially expressed between control and MPTP treated mice, cytosolic malate dehydrogenase, munc18-1, and hydroxyacylglutathione hydrolase, which were increased by MPTP, and cytochrome c oxidase subunit Vb, which was decreased by MPTP, were restored to the level of the saline group after EA treatment. These proteins are likely related to cellular metabolism. Altogether, we propose that the EA may exert neuroprotective effects in mice striatum through reducing MPTP-induced toxicity such as oxidative stress.

Troglitazone reverses the multiple drug resistance phenotype in cancer cells

A major problem in treating cancer is the development of drug resistance. We previously demonstrated doxorubicin (DOX) resistance in K562 human leukemia cells that was associated with upregulation of glyoxalase 1 (GLO-1) and histone H3 expression. The thiazolidinedione troglitazone (TRG) downregulated GLO-1 expression and further upregulated histone H3 expression and post-translational modifications in these cells, leading to a regained sensitivity to DOX. Given the pleiotropic effects of epigenetic changes in cancer development, we hypothesized that TRG may downregulate the multiple drug resistance (MDR) phenotype in a variety of cancer cells. To test this, MCF7 human breast cancer cells and K562 cells were cultured in the presence of low-dose DOX to establish DOX-resistant cell lines (K562/DOX and MCF7/DOX). The MDR phenotype was confirmed by Western blot analysis of the 170 kDa P-glycoprotein (Pgp) drug efflux pump multiple drug resistance protein 1 (MDR-1), and the breast cancer resistance protein (BCRP). TRG markedly decreased expression of both MDR-1 and BCRP in these cells, resulting in sensitivity to DOX. Silencing of MDR-1 expression also sensitized MCF7/DOX cells to DOX. Use of the specific and irreversible peroxisome proliferator-activated receptor gamma (PPARγ) inhibitor GW9662 in the nanomolar range not only demonstrated that the action of TRG on MCF/DOX was PPARγ-independent, but indicated that PPARγ may play a role in the MDR phenotype, which is antagonized by TRG. We conclude that TRG is potentially a useful adjunct therapy in chemoresistant cancers.

Human glyoxalase II contains an Fe(II)Zn(II) center but is active as a mononuclear Zn(II) enzyme

Human glyoxalase II (Glx2) was overexpressed in rich medium and in minimal medium containing zinc, iron, or cobalt, and the resulting Glx2 analogues were characterized using metal analyses, steady-state and pre-steady-state kinetics, and NMR and EPR spectroscopies to determine the nature of the metal center in the enzyme. Recombinant human Glx2 tightly binds nearly 1 equiv each of Zn(II) and Fe. In contrast to previous reports, this study demonstrates that an analogue containing 2 equiv of Zn(II) cannot be prepared. EPR studies suggest that most of the iron in recombinant Glx2 is Fe(II). NMR studies show that Fe(II) binds to the consensus Zn(2) site in Glx2 and that this site can also bind Co(II) and Ni(II), suggesting that Zn(II) binds to the consensus Zn(1) site. The NMR studies also reveal the presence of a dinuclear Co(II) center in Co(II)-substituted Glx2. Steady-state and pre-steady-state kinetic studies show that Glx2 containing only 1 equiv of Zn(II) is catalytically active and that the metal ion in the consensus Zn(2) site has little effect on catalytic activity. Taken together, these studies suggest that Glx2 contains a Fe(II)Zn(II) center in vivo but that the catalytic activity is due to Zn(II) in the Zn(1) site.

Glyoxalase I Glu111Ala polymorphism in patients with breast cancer

Effect of advanced glycation end products (AGEs) in the pathogenesis of cancer could be diminished by interaction with soluble RAGE or by reducing AGE-precursors via glyoxalase I. Glu111Ala polymorphism of glyoxalase I gene, AGEs, and sRAGE serum levels were studied in 113 breast cancer patients and in 58 controls. Higher frequency of the mutated C allele was found in patients with negative estrogen receptors and in patients in clinical stage III compared to controls (P< 0.05). The presence of the C allele could represent a negative prognostic factor; however, further studies are needed to confirm this hypothesis.

Advanced glycation end products of DNA: quantification of N2-(1-Carboxyethyl)-2'-deoxyguanosine in biological samples by liquid chromatography electrospray ionization tandem mass spectrometry

Methylglyoxal (MG) and related alpha-oxoaldehydes react with proteins, lipids, and DNA to give rise to covalent adducts known as advanced glycation end products (AGEs). Elevated levels of AGEs have been implicated in the pathological complications of diabetes, uremia, Alzheimer's disease, and possibly cancer. There is therefore widespread interest in developing sensitive methods for the in vivo measurement of AGEs as prognostic biomarkers and for treatment monitoring. The two diastereomeric MG-DNA adducts of N(2)-(1-carboxyethyl)-2'-deoxyguanosine (CEdG) are the primary glycation products formed in DNA; however, accurate assessment of their distribution in vivo has not been possible since there is no readily available quantitative method for CEdG determination in biological samples. To address these issues, we have developed a sensitive and quantitative liquid chromatography electrospray ionization tandem mass spectrometry assay using the stable isotope dilution method with an (15)N(5)-CEdG standard. Methods for CEdG determination in urine or tissue extracted DNA are described. Changes in urinary CEdG in diabetic rats in response to oral administration of the AGE inhibitor LR-90 are used to demonstrate the potential utility of the method for treatment monitoring. Both stereoisomeric CEdG adducts were detected in a human breast tumor and normal adjacent tissue at levels of 3-12 adducts/10(7) dG, suggesting that this lesion may be widely distributed in vivo. Strategies for dealing with artifactual adduct formation due to oxoaldehyde generation during DNA isolation and enzymatic workup procedures are described.

Phosphorylation on Thr-106 and NO-modification of glyoxalase I suppress the TNF-induced transcriptional activity of NF-kappaB

Glyoxalase I (GLO1), together with glyoxalase II and the co-factor GSH, comprise the glyoxalase system, which is responsible for the detoxification of the cytotoxic glycolytic-derived metabolite methylglyoxal (MG). We, and others, have previously reported that GLO1 is subjected to several post-translational modifications, including a NO-mediated modification and phosphorylation. In this study, we demonstrate that GLO1 is a substrate for calcium, calmodulin-dependent protein kinase II (CaMKII). Site-directed mutagenesis of several serine and threonine residues revealed that CaMKII induced phosphorylation of GLO1 at a single site Thr-106. Mutagenesis of Thr-106 to Ala in GLO1 completely abolished the CaMKII-mediated phosphorylation. A phosphopeptide bracketing phosphothreonine-106 in GLO1 was used as an antigen to generate polyclonal antibodies against phosphothreonine-106. By using this phospho-specific antibody, we demonstrated that TNF induces phosphorylation of GLO1 on Thr-106. Furthermore, we investigated the role of NO-mediated modification and phosphorylation of GLO1 in the TNF-induced transcriptional activity of NF-kappaB. Overexpression of WT GLO1 suppressed TNF-induced NF-kappaB-dependent reporter gene expression. Suppression of the basal and TNF-induced NF-kappaB activity was significantly stronger upon expression of a GLO1 mutant that was either deficient for the NO-mediated modification or phosphorylation on Thr-106. However, upon overexpression of a GLO1 mutant that was deficient for both types of modification, the suppressive effect of GLO1 on TNF-induced NF-kappaB activity was completely abolished. These results suggest that NO-modification and phosphorylation of GLO1 contribute to the suppression of TNF-induced NF-kappaB-dependent reporter gene expression. In line with this, knock-down of GLO1 by siRNA significantly increased TNF-induced NF-kappaB-dependent reporter gene expression. These findings suggest that phosphorylation and NO-modification of glyoxalase I provides another control mechanism for modulating the basal and TNF-induced expression of NF-kappaB-responsive genes.

Arabidopsis thaliana GLX2-1 contains a dinuclear metal binding site, but is not a glyoxalase 2

In an effort to probe the structure and function of a predicted mitochondrial glyoxalase 2, GLX2-1, from Arabidopsis thaliana, GLX2-1 was cloned, overexpressed, purified and characterized using metal analyses, kinetics, and UV-visible, EPR, and (1)H-NMR spectroscopies. The purified enzyme was purple and contained substoichiometric amounts of iron and zinc; however, metal-binding studies reveal that GLX2-1 can bind nearly two equivalents of either iron or zinc and that the most stable analogue of GLX2-1 is the iron-containing form. UV-visible spectra of the purified enzyme suggest the presence of Fe(II) in the protein, but the Fe(II) can be oxidized over time or by the addition of metal ions to the protein. EPR spectra revealed the presence of an anti-ferromagnetically-coupled Fe(III)Fe(II) centre and the presence of a protein-bound high-spin Fe(III) centre, perhaps as part of a FeZn centre. No paramagnetically shifted peaks were observed in (1)H-NMR spectra of the GLX2-1 analogues, suggesting low amounts of the paramagnetic, anti-ferromagnetically coupled centre. Steady-state kinetic studies with several thiolester substrates indicate that GLX2-1 is not a GLX2. In contrast with all of the other GLX2 proteins characterized, GLX2-1 contains an arginine in place of one of the metal-binding histidine residues at position 246. In order to evaluate further whether Arg(246) binds metal, the R246L mutant was prepared. The metal binding results are very similar to those of native GLX2-1, suggesting that a different amino acid is recruited as a metal-binding ligand. These results demonstrate that Arabidopsis GLX2-1 is a novel member of the metallo-beta-lactamase superfamily.

Protein and nucleotide damage by glyoxal and methylglyoxal in physiological systems--role in ageing and disease

Glycation of proteins, nucleotides and basic phospholipids by glyoxal and methylglyoxal--physiological substrates of glyoxalase 1--is potentially damaging to the proteome, genome and lipidome. Glyoxalase 1 suppresses glycation by these alpha-oxoaldehyde metabolites and thereby represents part of the enzymatic defence against glycation. Albert Szent-Györgyi pioneered and struggled to understand the physiological function of methylglyoxal and the glyoxalase system. We now appreciate that glyoxalase 1 protects against dicarbonyl modifications of the proteome, genome and lipome. Latest research suggests there are functional modifications of this process--implying a role in cell signalling, ageing and disease.

Tumour necrosis factor induces phosphorylation primarily of the nitric-oxide-responsive form of glyoxalase I

We have previously shown that TNF (tumour necrosis factor) induces phosphorylation of GLO1 (glyoxalase I), which is required for cell death in L929 cells. In the present paper, we show that the TNF-induced phosphorylation of GLO1 occurs primarily on the NO (nitric oxide)-responsive form of GLO1. In addition, analysis of several cysteine mutants of GLO1 indicated that Cys-138, in combination with either Cys-18 or Cys-19, is a crucial target residue for the NO-mediated modification of GLO1. Furthermore, the NO-donor GSNO (S-nitrosogluthathione) induces NO-mediated modification of GLO1 and enhances the TNF-induced phosphorylation of this NO-responsive form. GSNO also strongly promotes TNF-induced cell death. By the use of pharmacological inhibition of iNOS (inducible NO synthase) and overexpression of mutants of GLO1 that are deficient for the NO-mediated modification, we have shown that the NO-mediated modification of GLO1 is not a requirement for TNF-induced phosphorylation or TNF-induced cell death respectively. In summary, these data suggest that the TNF-induced phosphorylation of GLO1 is the dominant factor for cell death.

Proteomic analysis of protein expression changes in a model of gliomagenesis

Loss of p53 function is a common event in a variety of human cancers including tumors of glial origin. Using an in vitro mouse model of malignant astrocyte transformation, three cleavable isotope coded affinity tag (cICAT) experiments were performed comparing cultured wild-type astrocytes and two p53(-/-) astrocyte cultures before and after malignant transformation. We identified and quantitated an average of 1366 proteins per experiment and demonstrated that the protein quantitation ratios in each individual cICAT experiment correlated well to ratios determined in the other two studies. These data were further supported by microarray analysis which also correlated to changes in protein expression. The results showed significant changes in protein expression in association with malignant transformation. Proteins overexpressed in malignant astrocytes were typically involved in ribosome biogenesis/protein synthesis and DNA replication, while underexpressed proteins were generally associated with the regulation of cell cycle checkpoint control, tumor suppression, and apoptosis. Among the significantly up-regulated proteins and transcripts in malignant mouse astrocytes were members of the minichromosome maintenance (MCM) family. Western blot analysis verified increased expression of MCM proteins in malignant human astrocytoma cell lines, which had not previously been described. These results demonstrate the usefulness of the cICAT approach for comparing differences in protein expression profiles between normal and malignant cells.

Methylglyoxal suppresses TNF-alpha-induced NF-kappaB activation by inhibiting NF-kappaB DNA-binding

Methylglyoxal is a cytotoxic metabolite that is produced in vivo mainly from glycolysis. Increased production of methylglyoxal can be induced by tumor necrosis factor and occurs in a number of pathological conditions, including diabetes and neurodegenerative disorders. Methylglyoxal is highly reactive and can modify proteins, which results in the formation of advanced glycation end products. Yet, we, and others, have recently proposed a role for methylglyoxal as a signaling molecule. In this study, we show that methylglyoxal inhibits TNF-induced NF-kappaB activation and NF-kappaB-dependent reporter gene expression by inhibiting the DNA binding capacity of NF-kappaB p65. Methylglyoxal slightly delayed, but did not inhibit, TNF-induced degradation of IkappaBalpha and strongly inhibited TNF-induced NF-kappaB-dependent re-synthesis of IkappaBalpha. The TNF-induced nuclear translocation of NF-kappaB p65 was also delayed, but not inhibited, in the presence of methylglyoxal. TNF-induced phosphorylation of p65 was not affected by methylglyoxal. We show that the conserved Cys 38 residue, which is located in the DNA binding loop of NF-kappaB p65 and responsible for the redox regulation of the transcription factor, is involved in the methylglyoxal-mediated inhibition of p65 DNA-binding. Furthermore, overexpression of p65 inhibited TNF-induced cell death; however, in the presence of exogenously added methylglyoxal, overexpression of p65 caused far greater TNF-induced cell death. These findings suggest that methylglyoxal provides another control mechanism for modulating the expression of NF-kappaB-responsive genes and that methylglyoxal may be responsible for tipping the balance towards TNF-induced cell death in cells with constitutive NF-kappaB activation.

Polyproline-Rod Approach to Isolating Protein Targets of Bioactive Small Molecules: Isolation of a New Target of Indomethacin

Identification of protein targets of bioactive small molecules has been a technical hurdle of chemical genetics. Here we report a polyproline-rod approach to isolating protein targets of small molecules from cell lysates. The results indicate that insertion of a long, rigid polyproline helix between a small-molecule bait and a biotin tag boosts the capacity of affinity purification and thereby permits isolation of low-abundance or low-affinity proteins. In the course of the proof-of-concept experiments, we isolated glyoxalase 1 (GLO1) as a new target of indomethacin, a widely used antiinflammatory drug. Molecular biological experiments suggest that inhibition of GLO1 enzyme activity is related to the clinically recognized beneficial side effects of the indomethacin family of nonsteroidal antiinflammatory drugs.

A possible regulatory role of 17beta-estradiol and tamoxifen on glyoxalase I and glyoxalase II genes expression in MCF7 and BT20 human breast cancer cells

The glutathione-dependent glyoxalases system, composed of glyoxalase I (GloI) and glyoxalase II (GloII) enzymes, is involved in the detoxification of methylglyoxal, a by-product of cell metabolism. Aberrations in the expression of glyoxalase genes in several human cancers have been reported. Sometimes, these aberrations seem to differ depending on the organs and on the sensitivity of the tumours to estrogens, as we previously detected in the hormone-responsive breast cancer compared to the hormone-independent bladder cancer. To investigate a possible regulatory role of estrogens, as well as antiestrogens, on glyoxalases system, estrogen receptor (ER)-positive MCF7 and ER-negative BT20 human breast cancer cells were cultured in the presence of 17beta-estradiol (E2) and tamoxifen (TAM) performing two independent experiments. After a 24 h or 4 days treatment, we evaluated GloI and GloII mRNA levels, by Ribonuclease Protection Assay (RPA), enzymatic activities spectrophotometrically and cell proliferation by [3H]thymidine incorporation. We found that both steroid molecules affected glyoxalases gene expression and proliferation in a different manner in the cell lines. The modifications in mRNA levels were accompanied by parallel changes in the enzymatic activities. The possibility that modulation of glyoxalase genes by E2 and TAM are due to the presence of estrogen response elements (ERE) or cross-talk mechanisms by proteins of the estrogen signal transduction pathways are discussed. Knowledge regarding the regulation of glyoxalases by E2 and TAM may provide insights into the importance of this enzymes in human breast carcinomas in vivo.

Overexpression of glyoxalase system enzymes in human kidney tumor

PURPOSE

The purpose of this study was to investigate the messenger RNA expression and activity of glyoxalase I and glyoxalase II enzymes in a human renal carcinoma (clear cell adenocarcinoma) and in pair-matched normal tissue.

PATIENTS AND METHODS

Tumor and nontumor pair-matched specimens from the same organ were collected during radical nephrectomy from a group of 12 patients of both sexes. The mean age of the patients was 52.3 years (range, 50-60 years), and none of them had previously undergone neoadjuvant therapy. Gene expression and activity were measured by ribonuclease protection assay and current spectrophotometric methods, respectively. Intracellular levels of methylglyoxal were detected by high performance liquid chromatography.

RESULTS

A significant increase in the transcription levels of both glyoxalase I (about ninefold) and glyoxalase II (about threefold) was observed, compared with the pair-matched noncancerous tissues. Glyoxalase I activity was also higher in the pathological samples (about 2.5-fold) compared with the control samples and correlated with a significant decrease (about twofold) in methylglyoxal concentrations. At variance, glyoxalase II activity was significantly lower in pathological tissues than in the normal ones.

DISCUSSION

Our findings suggest a possible role of the glyoxalase system enzymes in the chemoresistance displayed by the kidney tumor. In fact, such a refractory behavior involves a decrease in the methylglyoxal level, a potent apoptosis activator. In addition, glyoxalase II activity decrease in the adenocarcinoma tissue suggests a likely role of the intermediate S-D-lactoylglutathione by supplying energy in actively proliferating cells. Finally, we point out a possible use of glyoxalase I inhibitors as anticancer drugs.

Glyoxalase II, a Detoxifying Enzyme of Glycolysis Byproduct Methylglyoxal and a Target of p63 and p73, Is a Pro-survival Factor of the p53 Family

The p53 family proteins are transcription factors and have both common and distinct functions. p53 is a classic tumor suppressor, whereas p63 and p73 have fundamental functions in development. To gain an insight into the functional diversities among the p53 family, target genes specifically regulated by p63 and p73 were examined. Here, we found that the GLX2 gene, which encodes glyoxalase II enzyme, is up-regulated by p63 and p73. Accordingly, a specific responsive element was found in intron 1 of the GLX2 gene, which can be activated and bound by p63 and p73. We also found that, upon overexpression, the cytosolic, but not the mitochondrial, GLX2 inhibits the apoptotic response of a cell to methylglyoxal, a by-product of glycolysis. Likewise, we showed that cells deficient in GLX2 are hypersensitive to methylglyoxal-induced apoptosis. Interestingly, a deficiency in GLX2 also enhances the susceptibility of a cell to DNA damage-induced apoptosis in a p53-dependent manner. These observations reveal a novel link between the p53 family and the glyoxalase system. Given that methylglyoxal is frequently generated under both physiological and pathological conditions, we postulate that GLX2 serves as a pro-survival factor of the p53 family and plays a critical role in the normal development and in the pathogenesis of various human diseases, including cancer, diabetes, and neurodegenerative diseases.

Troglitazone overcomes doxorubicin-resistance in resistant K562 leukemia cells

Human myeloid leukemia cells become resistant to doxorubicin (DOX) treatment and this resistance is correlated with an increased glyoxalase 1 (GLO1) expression. Troglitazone (TRG) is an anti-diabetic thiazolidinedione drug previously used to treat insulin-resistance in Type 2 diabetes. We previously showed that TRG down regulates GLO1 gene expression in a number of cell types and reasoned that TRG might be a useful adjunct therapy to overcome DOX resistance. Here we show that TRG treatment overcomes the resistance to DOX in the DOX-resistant K562 human leukemia cells. Higher doses of TRG were found to alter histone H3:H2B ratios with a decreased ratio in DOX-sensitive and increased ratio in DOX-resistant lines. Furthermore, phosphorylated H3 was seen in DOX-resistant but not in DOX-sensitive cells. We conclude that the downstream effect of TRG in DOX-resistant cells may be interference with normal cell cycle events leading to genomic instability. Our data suggest that TRG may be a useful adjunct therapy in circumventing drug resistance in K562 leukemia cells.

Glyoxalase I is critical for human retinal capillary pericyte survival under hyperglycemic conditions

Retinal capillary pericytes undergo premature death, possibly by apoptosis, during the early stages of diabetic retinopathy. The alpha-oxoaldehyde, methylglyoxal (MGO), has been implicated as a cause of cell damage in diabetes. We have investigated the role of MGO and its metabolizing enzyme, glyoxalase I, in high glucose-induced apoptosis (annexin V binding) of human retinal pericyte (HRP). HRP incubated with high glucose (30 mm d-glucose) for 7 days did not undergo apoptosis despite accumulation of MGO. However, treatment with a combination of high glucose and S-p-bromobenzylglutathione cyclopentyl diester, a competitive inhibitor of glyoxalase I, resulted in apoptosis along with a dramatic increase in MGO. Overexpression of glyoxalase I in HRP protected against S-p-bromobenzylglutathione cyclopentyl diester-induced apoptosis under high glucose conditions. Incubation of HRP with high concentrations of MGO resulted in an increase of apoptosis relative to untreated controls. We found an elevation of nitric oxide (NO.) in HRP that was incubated with high glucose when compared with those incubated with either the l-glucose or untreated controls. When HRP were incubated with an NO. donor, DETANONOATE ((Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate), we observed both decreased glyoxalase I expression and activity relative to untreated control cells. Further studies showed that HRP underwent apoptosis when incubated with DETANONOATE and that apoptosis increased further on co-incubation with high glucose. Our findings indicate that glyoxalase I is critical for pericyte survival under hyperglycemic conditions, and its inactivation and/or down-regulation by NO. may contribute to pericyte death by apoptosis during the early stages of diabetic retinopathy.

Structural studies on a mitochondrial glyoxalase II

Glyoxalase 2 is a beta-lactamase fold-containing enzyme that appears to be involved with cellular chemical detoxification. Although the cytoplasmic isozyme has been characterized from several organisms, essentially nothing is known about the mitochondrial proteins. As a first step in understanding the structure and function of mitochondrial glyoxalase 2 enzymes, a mitochondrial isozyme (GLX2-5) from Arabidopsis thaliana was cloned, overexpressed, purified, and characterized using metal analyses, EPR and (1)H NMR spectroscopies, and x-ray crystallography. The recombinant enzyme was shown to bind 1.04 +/- 0.15 eq of iron and 1.31 +/- 0.05 eq of Zn(II) and to exhibit k(cat) and K(m) values of 129 +/- 10 s(-1) and 391 +/- 48 microm, respectively, when using S-d-lactoylglutathione as the substrate. EPR spectra revealed that recombinant GLX2-5 contains multiple metal centers, including a predominant Fe(III)Z-n(II) center and an anti-ferromagnetically coupled Fe(III)Fe(II) center. Unlike cytosolic glyoxalase 2 from A. thaliana, GLX2-5 does not appear to specifically bind manganese. (1)H NMR spectra revealed the presence of at least eight paramagnetically shifted resonances that arise from protons in close proximity to a Fe(III)Fe(II) center. Five of these resonances arose from solvent-exchangeable protons, and four of these have been assigned to NH protons on metal-bound histidines. A 1.74-A resolution crystal structure of the enzyme revealed that although GLX2-5 shares a number of structural features with human GLX2, several important differences exist. These data demonstrate that mitochondrial glyoxalase 2 can accommodate a number of different metal centers and that the predominant metal center is Fe(III)Zn(II).

Argpyrimidine-modified Heat shock protein 27 in human non-small cell lung cancer: a possible mechanism for evasion of apoptosis

Tumors generally display a high glycolytic rate. One consequence of increased glycolysis is the non-enzymatic glycation of proteins leading to the formation of advanced glycation end-products (AGEs). Therefore, we studied the presence of AGEs in non-small cell lung cancer and consequences thereof. We show the presence of two AGEs, i.e. the major AGE N(epsilon)-(carboxymethyl)lysine (CML) and the methylglyoxal-arginine adduct argpyrimidine, in human non-small cell lung cancer tissues by immunohistochemistry. We found in squamous cell carcinoma and adenocarcinoma tissues a strong CML positivity in both tumour cells and tumour-surrounding stroma. In contrast, argpyrimidine positivity was predominantly found in tumor cells and was strong in squamous cell carcinomas, but only weak in adenocarcinomas (2.6+/-0.5 vs. 1.2+/-0.4, respectively; P<0.005). In accordance, argpyrimidine was found in the human lung squamous carcinoma cell line SW1573, while it was almost absent in the adenocarcinoma cell line H460. Heat shock protein 27 (Hsp27) was identified as a major argpyrimidine-modified protein. In agreement with a previously described anti-apoptotic activity of argpyrimidine-modified Hsp27, the percentage of active caspase-3 positive tumor cells in squamous cell carcinomas was significantly lower when compared to adenocarcinomas. In addition, incubation with cisplatin induced almost no caspase-3 activation in SW1573 cells while a strong activation was seen in H460 cells; which was significantly reduced by incubation with an inhibitor of glyoxalase I, the enzyme that catalyzes the conversion of methylglyoxal. These findings suggest that a high level of argpyrimidine-modified Hsp27 is a mechanism of cancer cells for evasion of apoptosis.

Proteomics of breast cancer: Enhanced expression of cytokeratin19 in human epidermal growth factor receptor type 2 positive breast tumors

The human epidermal growth factor receptor, type 2 (HER-2/neu or c-erbB-2) is a 185 kDa transmembrane protein that is phosphorylated upon ligand binding and dimerization with members of the HER/c-erbB family and regulates cell growth and differentiation. Its overexpression is strongly associated with advanced disease, metastasis and poor clinical outcome. To better understand the mechanisms underlying the poor prognosis of breast tumors with HER-2/neu-positive status, parallel proteomic analyses were performed on estrogen receptor-negative and node-positive breast tumors with or without overexpression of the HER-2/neu oncogene, using laser capture microdissection and two-dimensional gel electrophoresis. The differentially expressed proteins were identified by peptide mass fingerprinting using matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Cytokeratin 19 (CK19), one of the identified proteins, was highly expressed in the HER-2/neu-positive breast tumors when compared with HER-2/neu-negative breast tumors. The enhanced overexpression of CK19 in HER-2/neu-positive tumors was further analyzed using semiquantitative reverse-transcription polymerase chain reaction, Western blotting and reverse-phase protein arrays. Immunohistochemical staining of sections from a breast tumor tissue microarray of 97 tumors showed moderate to strong staining against anti-CK19 antibody in 20 (5 with moderate and 15 with strong staining) of the 26 HER-2/neu-positive tumors (76.9%) and in 22 (12 with moderate and 10 with strong staining) of 52 HER-2/neu-negative tumors (48%) (p = 0.002). Our results indicate that CK19, an intermediate fragment of the cytoskeleton, and other proteins showing differential expression, are likely to be intricately involved in intra- and intercellular molecular events driving the more aggressive tumor proliferation, invasion and metastasis associated with HER-2/neu-positive tumors.

The characterisation and functional analysis of the human glyoxalase-1 gene using methods of bioinformatics

Methylglyoxal (MG), which forms MG-derived AGE, is elevated in diabetic subjects with vascular disease. Detoxification of MG occurs through the glyoxalase system incorporating glyoxalase-1 (GLO1) and glyoxalase-2. Perturbations of the glyoxalase-1 gene (GLO1) may result in vulnerability to vascular complications through alterations in AGE interactions. We used bioinformatics to predict the structure, function and genetic variation of GLO1. We identified a previously unreported exon. Seventy single nucleotide polymorphisms (SNPs) were identified bioinformatically. The amino acid substitution Ala 111 Glu was confirmed and predicted to be tolerant. Though no alternative splice variants were identified, novel multiple alternative transcription start sites and alternative 3' UTRs were demonstrated. Ubiquitous expression of GLO1 was confirmed. Conserved regulatory regions were predicted 5' to the transcription start site and in the distal promoter, and several predicted conserved transcription regulatory elements were suggested in the 5' UTR. This study of GLO1 demonstrates multiple sequence variants at DNA and mRNA levels, areas of sequence conservation and SNPs that are predicted to affect function. A differential ability of glyoxalase-1 to reduce the formation and subsequent interaction of AGEs may have a role in the structural and functional manifestations of diabetic vascular disease.

Determination of rat blood S-d-lactoylglutathione by a column-switching high-performance liquid chromatography with precolumn fluorescence derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole

A method for the determination of S-d-lactoylglutathione (SLG), an intermediate metabolite of the glyoxalase system, in rat blood is described. After hemolysis and deproteinization of 30 microl of rat blood, SLG in the blood was determined by a column-switching HPLC system with precolumn fluorescence derivatization with a fluorogenic reagent, 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F). Calibration curves for the determination of SLG showed a good linearity (r2 > 0.999) over the range of 20-100 pmol SLG spiked in rat blood samples. The accuracy was in the range of 97-104% (20-100 pmol SLG spiked in rat blood sample, N = 4). The detection limit was 8.12 fmol, and the quantitation limit was 27.07 fmol, respectively. The intra- and interday coefficients of variance were 4.63% (N = 5) and 9.98% (N = 5), respectively. The concentrations of SLG in whole blood from male Wistar-Kyoto rats (12 weeks old) were 3.48+/-0.78 microM (N = 4, mean+/-SE). In streptozotocin-induced diabetic rats, the concentration of SLG was significantly increased, approx 5-fold, compared with normal rats, suggesting that the metabolic flux of the glyoxalase system increases in red blood cells during hyperglycemia.

Serological cloning of cancer/testis antigens expressed in prostate cancer using cDNA phage surface display

Serological cloning of tumor-associated antigens (TAAs) using patient autoantibodies and tumor cDNA expression libraries (SEREX) has identified a wide array of tumor proteins eliciting B-cell responses in patients. However, alternative cloning strategies with the possibility of high throughput analysis of patient sera and tumor libraries may be of interest. We explored the pJuFo phage surface display system, allowing display of recombinant tumor proteins on the surface of M13 filamentous phage, for cloning of TAAs in prostate cancer (PC). Control experiments established that after a few rounds of selection on immobilized specific IgG, a high degree of enrichment of seroreactive clones was achieved. With an increasing number of selection rounds, a higher yield of positive clones was offset by an apparent loss of diversity in the repertoire of selected clones. Using autologous patient serum IgG in a combined biopanning and immunoscreening approach, we identified 13 different TAAs. Three of these (NY-ESO-1, Lage-1, and Xage-1) were known members of the cancer/testis family of TAAs, and one other protein had previously been isolated by SEREX in cancer types other than PC. Specific IgG responses against NY-ESO-1 were found in sera from 4/20 patients with hormone refractory PC, against Lage-1 in 3/20, and Xage-1 in 1/20. No reactivity against the remaining proteins was detected in other PC patients, and none of the TAAs reacted with serum from healthy subjects. The results demonstrate that phage surface display combined with postselection immunoscreening is suitable for cloning a diverse repertoire of TAAs from tumor tissue cDNA libraries. Furthermore, candidate TAAs for vaccine development of PC were identified.