Analysis of glyoxalase-I from normal and tumor tissue from human colon

The PKM2 inhibitor shikonin enhances piceatannol-induced apoptosis of glyoxalase I-dependent cancer cells

Glyoxalase I (GLO I), a major enzyme involved in the detoxification of the anaerobic glycolytic byproduct methylglyoxal, is highly expressed in various tumors, and is regarded as a promising target for cancer therapy. We recently reported that piceatannol potently inhibits human GLO I and induces the death of GLO I-dependent cancer cells. Pyruvate kinase M2 (PKM2) is also a potential therapeutic target for cancer treatment, so we evaluated the combined anticancer efficacy of piceatannol plus low-dose shikonin, a potent and specific plant-derived PKM2 inhibitor, in two GLO I-dependent cancer cell lines, HL-60 human myeloid leukemia cells and NCI-H522 human non-small-cell lung cancer cells. Combined treatment with piceatannol and low-dose shikonin for 48 h synergistically reduced cell viability, enhanced apoptosis rate, and increased extracellular methylglyoxal accumulation compared to single-agent treatment, but did not alter PKM1, PKM2, or GLO I protein expression. Taken together, these results indicate that concomitant use of low-dose shikonin potentiates piceatannol-induced apoptosis of GLO I-dependent cancer cells by augmenting methylglyoxal accumulation.

[Studies on the Isolation and Molecular Mechanisms of Bioactive Phytochemicals]

Studies on the isolation and molecular mechanisms of phytochemicals with anti-tumor or anti-inflammatory properties are important to developing new drugs for cancer and neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. In the course of a study to screen bioactive isoflavones from Erythrina poeppigiana (Leguminosae), we isolated an isoflavone with potent apoptosis-inducing activity against human leukemia HL-60 cells. It was designated erypoegin K. The studies demonstrated an enantiomer, (S)-erypoegin K, displayed selective cytotoxic activity, was a novel inhibitor of topoisomerase II, and possessed anti-tumor activity both in vitro and in vivo. We identified other apoptosis-inducing isoflavones with the ability to inhibit glyoxalase I. Dimeric acridone alkaloids, carbazole alkaloids, and coumarin and quinoline derivatives-all obtained mainly from plants in the family Rutaceae-induced apoptosis of HL-60 cells via the production of reactive oxygen species and mitochondrial dysfunction. We also identified terpenoid coumarins, carbazole quinones, rotenoid derivatives, and quinolone alkaloids with anti-inflammatory activities. These compounds reduced nitric oxide (NO) production from RAW264.7 macrophage cells stimulated with lipopolysaccharides and interferon-γ. Some of the compounds displayed neuroprotective activity by reducing NO production. This review primarily describes our recent studies on erypoegin K, and other compounds with apoptosis-inducing and anti-inflammatory activities.

Crystal structures of human glyoxalase I and its complex with TLSC702 reveal inhibitor binding mode and substrate preference

Human glyoxalase I (hGLO I) is an enzyme for detoxification of methylglyoxal (MG), and has been considered an attractive target for the development of new anti-cancer drugs. In our previous report, the GLO I inhibitor TLSC702 induced apoptosis in tumor cells. Here, we determined the crystal structures of hGLO I and its complex with TLSC702. In the complex, the carboxy O atom of TLSC702 is coordinated to Zn²⁺ , and TLSC702 mainly shows van der Waals interaction with hydrophobic residues. In the inhibitor-unbound structure, glycerol, which has similar functional groups to MG, was bound to Zn²⁺ , indicating that GLO I can easily bind to MG. This study provides a structural basis to develop better anticancer drugs.

Methylglyoxal Levels in Human Colorectal Precancer and Cancer: Analysis of Tumor and Peritumor Tissue

Colorectal cancer (CRC) is one of the most common cancers worldwide and its incidence is increasing; therefore, an understanding of its oncogenic mechanisms is critical for improving its treatment and management. Methylglyoxal (MGO) has a highly reactive aldehyde group and has been suggested to play a role in oncogenesis. However, no standardized data are currently available on MGO levels in colorectal precancerous and cancerous lesions. We collected 40 matched colorectal tumor and peritumor tissues from patients with low-grade dysplasia (LGD), high-grade dysplasia (HGD), and invasive cancer (IC). MGO levels increased between LGD, HGD, and IC tumor tissues (215.25 ± 39.69, 267.45 ± 100.61, and 587.36 ± 123.19 μg/g protein, respectively; p = 0.014). The MGO levels in peritumor tissue increased and were significantly higher than MGO levels in tumor tissue (197.99 ± 49.40, 738.09 ± 247.87, 933.41 ± 164.83 μg/g protein, respectively; p = 0.002). Tumor tissue MGO levels did not correlate with age, sex, underlying disease, or smoking status. These results suggest that MGO levels fluctuate in progression of CRC and warrants further research into its underlying mechanisms and function in tumor biology.

Glyoxalase 1 and protein kinase Cλ as potential therapeutic targets for late-stage breast cancer

Cancer cells upregulate the expression levels of glycolytic enzymes in order to reach the increased glycolysis required. One such upregulated glycolytic enzyme is glyoxalase 1 (GLO 1), which catalyzes the conversion of toxic methylglyoxal to nontoxic S-D-lactoylglutathione. Protein kinase Cλ (PKCλ) is also upregulated in various types of cancer and is involved in cancer progression. In the present study, the association between enhanced glycolysis and PKCλ in breast cancer was investigated. In human breast cancer, high GLO 1 expression was associated with high PKCλ expression at the protein (P<0.01) and mRNA levels (P<0.01). Furthermore, Wilcoxon and Cox regression model analysis revealed that patients with stage III–IV tumors with high GLO 1 and PKCλ expression had poor overall survival compared with patients expressing lower levels of these genes [P=0.040 (Gehan-Breslow generalized Wilcoxon test) and P=0.031 (hazard ratio, 2.36; 95% confidence interval, 1.08–5.16), respectively]. Treatment of MDA-MB-157 and MDA-MB-468 human basal-like breast cancer cells with TLSC702 (a GLO 1 inhibitor) and/or aurothiomalate (a PKCλ inhibitor) reduced both cell viability and tumor-sphere formation. These results suggested that GLO 1 and PKCλ were cooperatively involved in cancer progression and contributed to a poor prognosis in breast cancer. In conclusion, GLO 1 and PKCλ serve as potentially effective therapeutic targets for treatment of late-stage human breast cancer.

Addition of hydrophobic side chains improve the apoptosis inducibility of the human glyoxalase I inhibitor, TLSC702

Glyoxalase I (GLO I) is a known therapeutic target in cancer. Even though TLSC702, a GLO I inhibitor that we discovered, induces apoptosis in tumor cells, exceptionally higher doses are required compared with those needed to inhibit GLO I activity in vitro. In this work, structure-activity optimization studies were conducted on four sections of the TLSC702 molecule to determine the partial structural features necessary for the inhibition of GLO I. Herein, we found that the carboxy group in TLSC702 was critical for binding with the divalent zinc at the active site of GLO I. In contrast, the side chain substituents in the meta- and para- positions of the benzene ring had little influence on the in vitro inhibition of GLO I. The CLogP values of the TLSC702 derivatives showed a positive correlation with the antiproliferative effects on NCI-H522 cells. Thus, two derivatives of TLSC702, which displayed either high or low lipophilicity due to the types of substituents at the phenyl position, were selected. Even though both derivatives showed comparable inhibitory effects as that of their parent compound, the derivative with the high CLogP value was distinctly more antiproliferative than TLSC702. In contrast, the derivative with the low CLogP value did not decrease cell viability in NCI-H522 and HL-60 cells. These findings suggested that structural improvements, such as the addition of hydrophobic moieties to the phenyl group, enhanced the ability of TLSC702 to induce apoptosis by increasing cell membrane permeability.

Evaluation of Anti-proliferative Effects of Barringtonia racemosa and Gallic Acid on Caco-2 Cells

Barringtonia racemosa leaf water extract (BLE) had been shown to have high gallic acid (GA) content and BLE has been postulated to have anti-proliferative effects towards colorectal cancer. This study aims to further investigate the mechanism underlying the anti-proliferative effect of BLE in Caco-2 cells and to determine if GA is responsible for the observed effects. Both BLE and GA inhibited Caco-2 cells in a dose-dependent manner. Cells exposed to IC₅₀ concentration of BLE and GA showed reduced antioxidant activities. GA-treated Caco-2 cells experienced higher oxidative stress compared to cells treated with BLE. Both BLE and GA significantly up-regulated the expression of SLC2A1. BLE but not GA, significantly down-regulated the expression of ADH4. Meanwhile, GA but not BLE, significantly up-regulated AKRIB10 and GLO1 but significantly down-regulated HAGH. Alterations in gene expression were coupled with changes in extracellular glucose and pyruvate levels. While BLE decreased intracellular pyruvate, GA did the opposite. Both intracellular and extracellular D-lactate were not affected by either BLE or GA. GA showed more pronounced effects on apoptosis while BLE irreversibly reduced cell percentage in the G0/G1 phase. In conclusion, this study demonstrates the multiple-actions of BLE against Caco-2 cells, potentially involving various polyphenolic compounds, including GA.

Effect of piceatannol-rich passion fruit seed extract on human glyoxalase I-mediated cancer cell growth

Passion fruit seed extract (PFSE), a product rich in stilbenes such as piceatannol and scirpusin B, has various physiological effects. It is unclear whether PFSE and its stilbene derivatives inhibit cancer cell proliferation via human glyoxalase I (GLO I), the rate-limiting enzyme for detoxification of methylglyoxal. We examined the anticancer effects of PFSE in two types of human cancer cell lines with different GLO I expression levels, NCI-H522 cells (highly-expressed GLO I) and HCT116 cells (lowly-expressed GLO I). PFSE and its stilbenes inhibited GLO I activity. In addition, PFSE and its stilbenes supressed the cancer cell proliferation of NCI-H522 cells more than HCT116 cells. These observations suggest that PFSE can provide a novel anticancer strategy for prevention and treatment.

Proteomic analysis of the effect of the polyphenol pentagalloyl glucose on proteins involved in neurodegenerative diseases in activated BV‑2 microglial cells

Neuroinflammation and microglial activation are two important hallmarks of neurodegenerative diseases. Continuous microglial activation may cause the release of several cytotoxic molecules, including many cytokines that are involved in the inflammatory process. Therefore, attenuating inflammation caused by activated microglia may be an approach for the therapeutic management of neurodegenerative diseases. In addition, many studies have reported that polyphenol pentagalloyl glucose (1,2,3,4,6-penta-O-galloyl-β-D-glucose; PGG) is a molecule with potent anti-inflammatory effects, such as inhibiting the release of proinflammatory cytokines. Our previous studies revealed that PGG attenuated the expression of two inflammatory cytokines (murine monocyte chemoattractant protein-5 and pro-metalloproteinase-9) in lipopolysaccharide/interferon γ-activated BV-٢ microglial cells. Additionally, PGG modulated the NF-κB and MAPK signaling pathways by altering genes and proteins, which may affect the MAPK cascade and NF-κB activation. The aim of the present study was to investigate the ability of PGG to modulate the expression of proteins released in activated BV-2 microglial cells, which may be involved in the pathological process of inflammation and neurodegeneration. Proteomic analysis of activated BV-2 cells identified 17 proteins whose expression levels were significantly downregulated by PGG, including septin-7, ataxin-2, and adenylosuccinate synthetase isozyme 2 (ADSS). These proteins were previously described as being highly expressed in neurodegenerative diseases and/or involved in the signaling pathways associated with the formation and growth of neuronal connections and the control of Alzheimer's disease pathogenesis. The inhibitory effect of PGG on ataxin-2, septin-7 and ADSS was further confirmed at the protein and transcriptional levels. Therefore, the obtained results suggest that PGG, with its potent inhibitory effects on ataxin-2, septin-7 and ADSS, may have potential use in the therapeutic management of neurodegenerative diseases.

Glyoxalase 1 gene is highly expressed in basal-like human breast cancers and contributes to survival of ALDH1-positive breast cancer stem cells

Glyoxalase 1 (GLO1) is a ubiquitous enzyme involved in the detoxification of methylglyoxal, a cytotoxic byproduct of glycolysis that induces apoptosis. In this study, we found that GLO1 gene expression correlates with neoplasm histologic grade (χ 2 test, p = 0.002) and is elevated in human basal-like breast cancer tissues. Approximately 90% of basal-like cancers were grade 3 tumors highly expressing both GLO1 and the cancer stem cell marker ALDH1A3. ALDH1high cells derived from the MDA-MB 157 and MDA-MB 468 human basal-like breast cancer cell lines showed elevated GLO1 activity. GLO1 inhibition using TLSC702 suppressed ALDH1high cell viability as well as the formation of tumor-spheres by ALDH1high cells. GLO1 knockdown using specific siRNAs also suppressed ALDH1high cell viability, and both TLSC702 and GLO1 siRNA induced apoptosis in ALDH1high cells. These results suggest GLO1 is essential for the survival of ALDH1-positive breast cancer stem cells. We therefore conclude that GLO1 is a potential therapeutic target for treatment of basal-like breast cancers.

New strategies for targeting glucose metabolism-mediated acidosis for colorectal cancer therapy

Colorectal cancer (CRC) is a heterogeneous group of diseases that are the result of abnormal glucose metabolism alterations with high lactate production by pyruvate to lactate conversion, which remodels acidosis and offers an evolutional advantage for tumor cells, even enhancing their aggressive phenotype. This review summarizes recent findings that involve multiple genes, molecules, and downstream signaling in the dysregulated glycolytic pathway, which can allow a tumor to initiate acid byproducts and to progress, thereby resulting in acidosis commonly found in the tumor microenvironment of CRC. Moreover, the relationship between CRC cells and the tumor acidic microenvironment, especially for regulating lactate production and lactate dehydrogenase A levels, is also discussed, as well as comprehensively defining different aspects of glycolytic pathways that affect cancer cell proliferation, invasion, and migration. Furthermore, this review concentrates on glucose metabolism-mediated transduction factors in CRC, which include acid-sensing ion channels, triosephosphate isomerase and key glycolysis-related enzymes that regulate glycolytic metabolites, coupled with the effect on tumor cell glycolysis as well as signaling pathways. In conclusion, glucose metabolism mediated by glycolytic pathways that are integral to tumor acidosis in CRC is demonstrated. Therefore, selective metabolic inhibitors or agents against these targets in glucose metabolism through glycolytic pathways may be clinically useful to regulate the tumor's acidic microenvironment for CRC treatment and to identify specific targets that regulate tumor acidosis through a cancer patient-personalized approach. Furthermore, strategies for modifying the metabolic processes that effectively inhibit cancer cell growth and tumor progression and activate potent anticancer effects may provide more effective antitumor prospects for CRC therapy.

Interdependence of GLO I and PKM2 in the Metabolic shift to escape apoptosis in GLO I-dependent cancer cells

Many cancer cells undergo metabolic reprogramming known as the Warburg effect, which is characterized by a greater dependence on glycolysis for ATP generation, even under normoxic conditions. Glyoxalase I (GLO I) is a rate-limiting enzyme involved in the detoxification of cytotoxic methylglyoxal formed in glycolysis and which is known to be highly expressed in many cancer cells. Thus, specific inhibitors of GLO I are expected to be effective anticancer drugs. We previously discovered a novel GLO I inhibitor named TLSC702. Although the strong inhibitory activity of TLSC702 was observed in the in vitro enzyme assay, higher concentrations were required to induce apoptosis at the cellular level. One of the proposed reasons for this difference is that cancer cells alter the energy metabolism leading them to become more dependent on mitochondrial respiration than glycolysis (Metabolic shift) to avoid apoptosis induction. Thus, we assumed that combination of TLSC702 with shikonin-a specific inhibitor of pyruvate kinase M2 (PKM2) that acts as a driver of TCA cycle by supplying pyruvate and which is known to be specifically expressed in cancer cells-would have anticancer effects. We herein show the anticancer effects of combination treatment with TLSC702 and shikonin, and a possible anticancer mechanism.

The influence of glyoxalase 1 gene polymorphism on its expression at different stages of breast cancer in Egyptian women

Aim

To assess the association of GLO1 C332C gene polymorphism with breast cancer risk at different stages of the disease and to investigate the effect of this gene polymorphism on its mRNA expression and enzyme activity.

Methods

GLO1 C332C gene polymorphism was analyzed by PCR-RFLP in 100 healthy controls and 200 patients with breast cancer (100 patients with stage I & II and 100 patients with stage III & IV). GLO1 mRNA expression was measured by real time PCR. Serum GLO1 enzyme activity was measured colorimetrically.

Results

GLO1 A allele was associated with increased risk of breast cancer [OR (95%CI)= 2.8(1.9-4.1), P < 0.001]. Its frequency was significantly higher among advanced stages of breast cancer compared with localized tumors (OR (95%CI)= 1.9(1.3-2.9), p < 0.001). GLO1 mRNA expression and enzyme activity were significantly higher in breast cancer patients compared to controls and they were much higher in the advanced stages of the disease (P < 0.001). Carriers of AA genotype showed higher GLO1 expression and enzyme activity compared with carriers of CC genotype.

Conclusion

GLO1 C332C SNP was associated with overexpression of GLO1 mRNA and higher enzyme activity in breast cancer patients suggesting its role in the development of breast cancer and its progression from localized to advanced.

Hormetic potential of methylglyoxal, a side-product of glycolysis, in switching tumours from growth to death

Metabolic reprogramming toward aerobic glycolysis unavoidably favours methylglyoxal (MG) and advanced glycation end products (AGEs) formation in cancer cells. MG was initially considered a highly cytotoxic molecule with potential anti-cancer value. However, we have recently demonstrated that MG enhanced tumour growth and metastasis. In an attempt to understand this dual role, we explored MG-mediated dicarbonyl stress status in four breast and glioblastoma cancer cell lines in relation with their glycolytic phenotype and MG detoxifying capacity. In glycolytic cancer cells cultured in high glucose, we observed a significant increase of the conversion of MG to D-lactate through the glyoxalase system. Moreover, upon exogenous MG challenge, glycolytic cells showed elevated amounts of intracellular MG and induced de novo GLO1 detoxifying enzyme and Nrf2 expression. Thus, supporting the adaptive nature of glycolytic cancer cells to MG dicarbonyl stress when compared to non-glycolytic ones. Finally and consistent with the pro-tumoural role of MG, we showed that low doses of MG induced AGEs formation and tumour growth in vivo, both of which can be reversed using a MG scavenger. Our study represents the first demonstration of a hormetic effect of MG defined by a low-dose stimulation and a high-dose inhibition of tumour growth.

Piceatannol, a natural trans-stilbene compound, inhibits human glyoxalase I

Human glyoxalase I (GLO I), a rate-limiting enzyme for detoxification of methylglyoxal (MG), a by-product of glycolysis, is known to be a potential therapeutic target for cancer. Here, we searched new scaffolds from natural compounds for designing novel GLO I inhibitors and found trans-stilbene scaffold. We examined the inhibitory abilities to human GLO I of commercially available trans-stilbene compounds. Among them, piceatannol was found to have the most potent inhibitory activity against human GLO I. Piceatannol could inhibit the proliferation of human lung cancer NCI-H522 cells, which are dependent on GLO I for survival, in a dose- and time-dependent manner. In addition, piceatannol more significantly inhibited the proliferation of NCI-H522 cells than that of NCI-H460 cells, which are less dependent on GLO I. Importantly, overexpression of GLO I in NCI-H522 cells resulted in less sensitive to the antiproliferative activity of piceatannol. Taken together, this is the first report demonstrating that piceatannol inhibits GLO I activity and the GLO I-dependent proliferation of cancer cells. Furthermore, we determined a pharmacophore for novel inhibitors of human GLO I by computational simulation analyses of the binding mode of piceatannol to the enzyme hot spot in the active site. We suggest that piceatannol is a possible lead compound for the development of novel GLO I inhibitory anticancer drugs.

Methylglyoxal-Mediated Stress Correlates with High Metabolic Activity and Promotes Tumor Growth in Colorectal Cancer

Cancer cells generally rely on aerobic glycolysis as a major source of energy. Methylglyoxal (MG), a dicarbonyl compound that is produced as a side product during glycolysis, is highly reactive and induces the formation of advanced glycation end-products that are implicated in several pathologies including cancer. All mammalian cells have an enzymatic defense against MG composed by glyoxalases GLO1 and GLO2 that converts MG to d-lactate. Colorectal cancer (CRC) is one of the most frequently occurring cancers with high morbidity and mortality. In this study, we used immunohistochemistry to examine the level of MG protein adducts, in a series of 102 CRC human tumors divided into four clinical stages. We consistently detected a high level of MG adducts and low GLO1 activity in high stage tumors compared to low stage ones suggesting a pro-tumor role for dicarbonyl stress. Accordingly, GLO1 depletion in CRC cells promoted tumor growth in vivo that was efficiently reversed using carnosine, a potent MG scavenger. Our study represents the first demonstration that MG adducts accumulation is a consistent feature of high stage CRC tumors. Our data point to MG production and detoxification levels as an important molecular link between exacerbated glycolytic activity and CRC progression.

Modulation of GLO1 Expression Affects Malignant Properties of Cells

The energy metabolism of most tumor cells relies on aerobic glycolysis (Warburg effect) characterized by an increased glycolytic flux that is accompanied by the increased formation of the cytotoxic metabolite methylglyoxal (MGO). Consequently, the rate of detoxification of this reactive glycolytic byproduct needs to be increased in order to prevent deleterious effects to the cells. This is brought about by an increased expression of glyoxalase 1 (GLO1) that is the rate-limiting enzyme of the MGO-detoxifying glyoxalase system. Here, we overexpressed GLO1 in HEK 293 cells and silenced it in MCF-7 cells using shRNA. Tumor-related properties of wild type and transformed cells were compared and key glycolytic enzyme activities assessed. Furthermore, the cells were subjected to hypoxic conditions to analyze the impact on cell proliferation and enzyme activities. Our results demonstrate that knockdown of GLO1 in the cancer cells significantly reduced tumor-associated properties such as migration and proliferation, whereas no functional alterations where found by overexpression of GLO1 in HEK 293 cells. In contrast, hypoxia caused inhibition of cell growth of all cells except of those overexpressing GLO1. Altogether, we conclude that GLO1 on one hand is crucial to maintaining tumor characteristics of malignant cells, and, on the other hand, supports malignant transformation of cells in a hypoxic environment when overexpressed.

Clinical significance of AGE-RAGE axis in colorectal cancer: associations with glyoxalase-I, adiponectin receptor expression and prognosis

Background

Advanced glycation end products (AGEs) and their receptor RAGE emerge as important pathogenic contributors in colorectal carcinogenesis. However, their relationship to the detoxification enzyme Glyoxalase (GLO)-I and Adiponectin receptors (AdipoR1, AdipoR2) in colorectal carcinoma (CRC) is currently understudied. In the present study, we investigated the expression levels of the above molecules in CRC compared to adjacent non-tumoral tissue and their potential correlation with clinicopathological characteristics and patients’ survival.

Methods

We analyzed the immunohistochemical expression of AGE, RAGE, GLO-1, AdipoR1 and AdipoR2 in 133 primary CRC cases, focusing on GLO-I. The tumour MSI status was further assessed in mucinous carcinomas. Western immunoblotting was employed for validation of immunohistochemical data in normal and tumoral tissues as well in three CRC cell lines. An independent set of 55 patients was also used to validate the results of univariate survival analysis regarding GLO-I.

Results

CRC tissue showed higher intensity of both AGE and RAGE expression compared with normal colonic mucosa which was negative for GLO-I in most cases (78 %). Western immunoblotting confirmed AGE, RAGE and GLO-I overexpression in tumoral tissue. GLO-I expression was directly related to RAGE and inversely related to AGE immunolabeling. There was a trend towards higher expression of all markers (except for RAGE) in the subgroup of mucinous carcinomas which, although of borderline significance, seemed to be more prominent for AdipoR1 and AGE. Additionally, AGE, AdipoR1 and Adipo R2 expression was related to tumor grade, whereas GLO-1 and AdipoR1 to T-category. In survival analysis, AdipoR2 and GLO-I overexpression predicted shortened survival in the entire cohort and in early stage cases, an effect which for GLO-I was reproduced in the validation cohort. Moreover, GLO-I emerged as an independent prognosticator of adverse significance in the patients’ cohort.

Conclusions

We herein provide novel evidence regarding the possible interactions between the components of AGE-RAGE axis, GLO-I and adiponectin receptors in CRC. AGE and AdipoR1 are possibly involved in colorectal carcinogenesis, whereas AdipoR2 and GLO-I emerged as novel independent prognostic biomarkers of adverse significance for patients with early disease stage. Further studies are warranted to extend our observations and investigate their potential therapeutic significance.

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.

Blockade of the Ras/Raf/ERK and Ras/PI3K/Akt Pathways by Monacolin K Reduces the Expression of GLO1 and Induces Apoptosis in U937 Cells

Monacolin K, a hydrolytic product of icaritin, is the major active component in the traditional fermented Monascus purpureus. Monacolin K inhibits the proliferation of acute myeloid leukemia (AML), but underlying mechanisms remain to be identified. The present study demonstrates that monacolin K inhibits the proliferation of human AML cell line U937 in a dose-dependent manner. Importantly, morphological, DNA fragmentation, and image cytometry analyses indicated that monacolin K induced U937 cell apoptosis. Monacolin K could inactivate Ras translocation from cytosol to cell membrane. Monacolin K could also reduce the Ras-dependent phosphorylation of ERK and Akt, and the subsequent translocation of nuclear factor kappa B (NF-κB) from cytosol to nucleus in U937 cells. The underlying mechanisms of apoptotic activity of monacolin K were associated with inhibition of the Ras/Raf/ERK and Ras/PI3K/Akt signals and down-regulation of HMG-CoA reductase and glyoxalase 1. On the basis of results obtained using specific inhibitors U0126, LY294002, and JSH-23, the Ras/Raf/ERK/NF-κB/GLO1 and Ras/Akt/NF-κB/GLO1 pathways were proposed for the apoptotic effect of monacolin K in U937 cells.

Exploring glyoxalase 1 expression in prostate cancer tissues: targeting the enzyme by ethyl pyruvate defangs some malignancy-associated properties

BACKGROUND

The glyoxalase (GLO)1 is part of a ubiquitous detoxification system in the glycolytic pathway of normal and tumor cells. It protects against cellular damage caused by cytotoxic metabolites.

METHODS

Aiming at exploring the role of GLO1 in prostate cancer, we evaluated and targeted the expression of GLO1 in prostate cancer tissues and cell lines and analyzed its correlation with grading systems and tumor growth indices.

RESULTS

Immunohistochemical studies on 37 prostate cancer specimens revealed a positive correlation between Helpap-grading and the cytoplasmic (P = 0.002)/nuclear (P = 0.006) GLO1 level. A positive correlation between Ki-67 proliferation marker and the cytoplasmic GLO1 (P = 0.006) was evident. Furthermore, the highest GLO1 level was detected in the androgen-sensitive LNCaP compared to the androgen-independent Du-145 and PC-3 prostate cell lines and the breast cancer cell MCF-7, both at protein and mRNA level. Treating cancer cells with ethyl pyruvate was found to defang some malignancy-associated properties of cancer cells including proliferation, invasion and anchorage-independent growth. In vitro results revealed that the potency of ethyl pyruvate is increased when cells are metabolically activated by growth stimulators, for example, by fetal calf serum, dihydrotestosterone, tumor growth factor-β1 and leptin.

CONCLUSIONS

The positive correlation of GLO1 expression level in prostate cancer tissues with the pathological grade and proliferation rate may assign GLO1 as a risk factor for prostate cancer development and progression. Furthermore, our data indicate that inhibitors of GLO1 might be useful to decelerate the cancer cell growth by a novel therapeutic approach that we may call "induced metabolic catastrophe."

Preventive effect of specific antioxidant on oxidative renal cell injury associated with renal crystal formation

OBJECTIVE

To investigate whether calcium oxalate monohydrate (COM), a key element of hyperoxaluria, would induce renal cell injury through oxidative stress and also whether certain antioxidants could prevent chemically induced renal crystal formation in rats.

MATERIALS AND METHODS

COM-exerted oxidative stress on the kidney epithelial Madin-Darby canine kidney cells was assessed using the lipid peroxidation assay. Glyoxalase I (Gly-I) activity was also determined. Two antioxidants, vitamin C and N-acetylcysteine (NAC), were then tested to determine whether they could abolish such oxidative stress in Madin-Darby canine kidney cells. Both antioxidants were also tested to determine whether they might prevent or reduce renal crystal formation induced with ethylene glycol (EG) and vitamin D3 (VD3) in Wistar rats.

RESULTS

COM (200 μg/mL) demonstrated ∼1.3-fold greater oxidative stress with a significant reduction in cell viability and Gly-I activity compared with controls. However, such adverse events were almost completely prevented with NAC but not with vitamin C. In the animal study, no renal crystals were seen in the sham group. However, numerous crystals, with reduced Gly-I activity and elevated oxidative stress, were found in the EG-VD3 group. However, markedly (>70%) fewer crystals, with full Gly-I activity and diminished oxidative stress, were detected in the EG-VD3+NAC group.

CONCLUSION

COM exerted oxidative stress on Madin-Darby canine kidney cells, leading to cell viability reduction and Gly-I inactivation, with NAC fully preventing such adverse consequences. Similarly, numerous crystals with Gly-I inactivation and elevated oxidative stress seen in the rats (EG-VD3) were also significantly prevented with NAC supplement. Thus, NAC might have clinical implications in preventing oxidative renal cell injury and, ultimately, kidney stone formation.

Nephrotoxin-induced renal cell injury involving biochemical alterations and its prevention with antioxidant

Background

Although nephrotoxic agents or nephrotoxins are known to induce acute renal cell injury, their cytotoxic action is not fully elucidated. It is thus crucial to explore such a cytotoxic mechanism and the increasing volume of reports indicated a significant involvement of oxidative stress. To test this possibility, we investigated if a nephrotoxin would exert oxidative stress, leading to renal cell injury accompanied by certain biochemical alterations. We also examined if specific antioxidant might help prevent such oxidative cell injury. These studies may then help establish a prophylactic or preventive modality for renal cell injury induced by nephrotoxins.

Methods

As glycerol has been commonly used for studying acute renal failure in animals, whether it would induce cellular injury was tested in renal proximal tubular OK cells in vitro. Cells were exposed to the varying concentrations of glycerol and cell number/viability was determined in 24 hours. Severity of oxidative stress was assessed by lipid peroxidation assay. Possible effects of glycerol on biochemical parameters were also examined on glyoxalase I activity and heat shock protein 90 using spectrophotometric (enzymatic) assay and Western blot analysis.

Results

Glycerol (2.5%) was highly cytotoxic to OK cells, inducing 95% cell death in 24 hours. Lipid peroxidation assay indicated that nearly 3-fold greater oxidative stress was exerted by this glycerol. Concurrently, glyoxalase I activity was drastically lost by 75% and heat shock protein 90 was partially degraded following glycerol exposure. However, N-acetylcysteine, a potent glutathione-based antioxidant, was capable of almost completely preventing the glycerol-mediated adverse outcomes, such as cell death, glyoxalase I inactivation, and heat shock protein 90 degradation.

Conclusions

Glycerol is cytotoxic, capable of inducing specific biochemical alterations such as inactivation of glyoxalase I and degradation of heat shock protein 90, which may reflect a breakdown of the cellular detoxification and defense systems, leading ultimately to OK cell death. Nevertheless, as N-acetylcysteine can provide full cytoprotection against such glycerol toxicity, it could be considered a prophylactic modality for nephrotoxin-induced oxidative renal cell injury and death.

Keywords

Glycerol; Glyoxalase I; Heat shock protein; N-acetylcysteine; Renal cell injury

Delphinidin, a dietary anthocyanidin in berry fruits, inhibits human glyoxalase I

Glyoxalase I (GLO I) is the rate-limiting enzyme for detoxification of methylglyoxal (MG), a side-product of glycolysis, which is able to induce apoptosis. Since GLO I is known to be highly expressed in the most tumor cells and little in normal cells, inhibitors of this enzyme has been expected to be new anticancer drugs. Here, we examined the inhibitory abilities to the human GLO I of anthocyanidins, such as delphinidin, cyanidin and pelargonidin. Among them, delphinidin was found to have the most potent inhibitory effect on human GLO I. Also, only delphinidin-induced apoptosis in HL-60 cells in a dose- and time-dependent manner. Furthermore, we determined a pharmacophore for delphinidin binding to the human GLO I by computational simulation analyses of the binding modes of delphinidin, cyanidin and pelargonidin to the enzyme hot spot. These results suggest that delphinidin could be a useful lead compound for the development of novel GLO I inhibitory anticancer drugs.

Oxidative renal cell injury induced by calcium oxalate crystal and renoprotection with antioxidants: a possible role of oxidative stress in nephrolithiasis

PURPOSE

Calcium oxalate (CaOx) is one of the key elements for kidney stone formation, but the exact mechanism needs to be defined. CaOx has been shown to cause renal cell injury through oxidative stress, leading to potential crystal deposition in the kidneys. We thus investigated if CaOx crystal would induce such renal cell injury in vitro and also explored how it would be carried out.

MATERIALS AND METHODS

Renal tubular epithelial LLC-PK(1) cells were employed, and CaOx monohydrate (COM) was used as CaOx crystal in this study. Cytotoxic effects of COM were assessed on cell viability and biochemical parameters, while protective effect of antioxidants against COM was also examined.

RESULTS

COM demonstrated its cytotoxicity on LLC-PK(1) cells, exhibiting a approximately 35% cell viability reduction with 500 microg/mL COM in 6 hours. This was presumably attributed to oxidative stress, indicated by lipid peroxidation assay, and N-acetylcysteine (NAC), a potent antioxidant, indeed neutralized such COM cytotoxicity. Although COM also induced inactivation of glutathione-dependent enzymes and partial degradation of heat shock protein 90, these adverse effects were completely prevented with NAC. Moreover, such reduced cell viability with COM was rather associated with apoptosis, evidenced by DNA analysis.

CONCLUSION

COM is cytotoxic to LLC-PK(1) cells through oxidative stress, leading to the cell viability reduction, adverse effects on biochemical parameters, and, consequently, apoptosis. However, NAC effectively averted such severe cytotoxic effects, sustaining the renal cell integrity. Thus, NAC may provide full renoprotection against COM assault, preventing renal cell injury and ultimate stone formation.

Immunoscreening of the extracellular proteome of colorectal cancer cells

Background

The release of proteins from tumors can trigger an immune response in cancer patients involving T lymphocytes and B lymphocytes, which results in the generation of antibodies to tumor-derived proteins. Many studies aim to use humoral immune responses, namely autoantibody profiles, directly, as clinical biomarkers. Alternatively, the antibody immune response as an amplification system for tumor associated alterations may be used to indicate putative protein biomarkers with high sensitivity. Aiming at the latter approach we here have implemented an autoantibody profiling strategy which particularly focuses on proteins released by tumor cells in vitro: the so-called secretome.

Methods

For immunoscreening, the extracellular proteome of five colorectal cancer cell lines was resolved on 2D gels, immobilized on PVDF membranes and used for serological screening with individual sera from 21 colorectal cancer patients and 24 healthy controls. All of the signals from each blot were assigned to a master map, and autoantigen candidates were defined based of the pattern of immunoreactivities. The corresponding proteins were isolated from preparative gels, identified by MALDI-MS and/or by nano-HPLC/ESI-MS/MS and exemplarily confirmed by duplex Western blotting combining the human serum samples with antibodies directed against the protein(s) of interest.

Results

From 281 secretome proteins stained with autoantibodies in total we first defined the "background patterns" of frequently immunoreactive extracellular proteins in healthy and diseased people. An assignment of these proteins, among them many nominally intracellular proteins, to the subset of exosomal proteins within the secretomes revealed a large overlap. On this basis we defined and consequently confirmed novel biomarker candidates such as the extreme C-terminus of the extracellular matrix protein agrin within the set of cancer-enriched immunorectivities.

Conclusions

Our findings suggest, first, that autoantibody responses may be due, in large part, to cross-presentation of antigens to the immune system via exosomes, membrane vesicles released by tumor cells and constituting a significant fraction of the secretome. In addition, this immunosecretomics approach has revealed novel biomarker candidates, some of them secretome-specific, and thus serves as a promising complementary tool to the frequently reported immunoproteomic studies for biomarker discovery.

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.

Mode of cytotoxic action of nephrotoxic agents: oxidative stress and glutathione-dependent enzyme

OBJECTIVE

To investigate the cytotoxic action of nephrotoxic agents using an in vitro renal cell model, focusing on the cellular oxidative status and a specific glutathione (GSH)-dependent enzyme, glyoxalase I (Gly-I).

MATERIALS AND METHODS

Renal proximal tubular LLC-PK(1) cells were exposed to mercuric chloride, glycerol, cisplatin, gentamicin and cyclosporin A, and cell number/viability were determined. Oxidative stress was assessed by lipid peroxidation (LPO) assay, and Gly-I activity was measured by enzymatic method on a spectrophotometer.

RESULTS

Both mercuric chloride (30 microm) and glycerol (2.5%) were highly toxic to LLC-PK(1) cells, inducing >90% cell death within 24 h. The remaining agents led to slightly >50% growth inhibition at 72 h. The LPO levels at 3 h in cells exposed to mercuric chloride or glycerol were approximately 2.5 times higher than that in controls. N-acetylcysteine (NAC), a potent antioxidant and precursor for GSH, almost completely (>95%) prevented renal cell death from mercuric chloride or glycerol. Gly-I activity was dependent on NAC and closely associated with cell viability. A approximately 65% loss in Gly-I activity by mercuric chloride/glycerol led to >90% cell death, while restoring a basal activity of Gly-I with NAC was accompanied by complete cell viability.

CONCLUSIONS

The cytotoxic action of nephrotoxic agents appears to be triggered by oxidative stress, leading to Gly-I inactivation. As Gly-I plays a key role in cellular detoxification, its inactivation under oxidative stress probably becomes fatal to cells. However, cytoprotection provided with NAC is significant and might have implications in preventing renal cell injury mediated through nephrotoxic agents.

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.

Structure-activity relationship of human GLO I inhibitory natural flavonoids and their growth inhibitory effects

Glyoxalase I (GLO I) is the rate-limiting enzyme for detoxification of methylglyoxal (MG), a side product of glycolysis, which is able to induce apoptosis. Since GLO I is known to be highly expressed in the most tumor cells and little in normal cells, specific inhibitors of this enzyme have been expected as effective anticancer drugs. The purpose of this study is a good construction of the human GLO I/inhibitor pharmacophore to obtain unique human GLO I inhibitory seed compounds for the development of useful anticancer drugs. Here, we selected natural flavonoid compounds that possess a plane configuration of cis C-4 ketone and C-5 hydroxy groups as the substrate (MG) transition-state mimetic structure. These compounds were examined the inhibitory abilities to human GLO I activity and analyzed their structure-activity relationships to determine an important pharmacophore of flavonoids for the human GLO I binding. Our results point to the contribution of hydroxy groups at the B ring of flavonoids to the effective inhibition of the human GLO I. Based on the binding mode of flavonoids, we constructed the human GLO I/inhibitor pharmacophore. This work delivers the first three-dimensional (3D) structural data and explains certain flavonoids interact specifically with the human GLO I.

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.

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.

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.

Methotrexate inhibits the glyoxalase system in vivo in children with acute lymphoid leukaemia

The inhibition of glyoxalase I leads to antitumour activity through the accumulation of methylglyoxal. Our earlier observations suggested that methotrexate (MTX) may affect the glyoxalase system. This prompted a serial study of the drug on this metabolic pathway. Ten children with acute lymphoid leukaemia (ALL), admitted to our department between January 2002 and July 2003, were enrolled. Plasma D-lactate was assayed before, 24 and 72 h after the start of four consecutive MTX infusions (5 g/m(2)/24 h) in each patient. Inhibition of glyoxalase I was tested in vitro, using human erythrocyte lysates and yeast enzyme. The elevated initial plasma D-lactate levels (P<0.02) fell significantly (P<0.001) in response to 24 h MTX infusions. In vitro, MTX, folic and folinic acids inhibited the activity of glyoxalase I. Thus, MTX seems to affect the alpha-oxoaldehyde metabolism in vivo, as a likely consequence of glyoxalase I inhibition. This action probably contributes to the anticancer activity and toxicity of the drug.

Chemosensitization of carmustine with maitake beta-glucan on androgen-independent prostatic cancer cells: involvement of glyoxalase I

OBJECTIVE

To improve the poor efficacy (< 10%) of chemotherapy for patients with hormone-refractory prostate cancer, we investigated a possible cytotoxic effect of carmustine/beta-glucan combination on prostatic cancer PC-3 cells, focusing on a glutathione-dependent detoxifying enzyme, glyoxalase I (Gly-I).

METHODS

Carmustine (BCNU) is an anticancer agent and a putative inhibitor of Gly-I, while beta-glucan is a unique, nontoxic polysaccharide extracted from maitake mushrooms. The cytotoxic effects of BCNU or other anticancer agents with beta-glucan on PC-3 cells were assessed by cell-viability testing and Gly-I activity was measured using the spectrophotometric method.

RESULTS

BCNU, 5-fluorouracil (5-FU), and methotrexate (MTX) were capable of inducing approximately a 50% reduction in cell viability at 72 hours, while etoposide, cisplatin, and mitomycin C were all ineffective. Only the combination of BCNU (50 micro ;mol) and beta-glucan (60 micro g/mL) exhibited an enhanced cytotoxicity with an approximate 90% cell viability reduction, but little improvement was seen with any combinations of 5-FU, MTX, or beta-glucon. Gly-I assays revealed that such a profound (approximately 90%) cell death was accompanied by an approximate 80% reduction in Gly-I activity by 6 hours.

CONCLUSION

This study demonstrates a sensitized cytotoxic effect of BCNU with beta-glucan in PC-3 cells, which was associated with a drastic (approximately 80%) inactivation of Gly-I. Therefore, the BCNU/beta-glucan combination may help to improve current treatment efficacy by targeting Gly-I, which appears to be critically involved in prostate cancer viability.

Cloning and characterization of a novel gene (C17orf25) from the deletion region on chromosome 17p13.3 in hepatocelular carcinoma

Using a combination of hybridization of PAC to a cDNA library and RACE technique, we isolated a novel cDNA, designated as C17orf25 (Chromosome 17 open reading frame 25, previously named it HC71A), from the deletion region on chromosome 17p13.3. The cDNA encodes a protein of 313 amino acids with a calculated molecular mass of 34.8 kDa. C17orf25 is divided into 10 exons and 9 introns, spanning 23 kb of genomic DNA. Northern blot analysis showed that the mRNA expression of C17orf25 was decreased in hepatocellular carcinoma samples as compared to adjacent noncancerous liver tissues from the same patients. The transfection of C17orf25 into the hepatocellular carcinoma cell SMMC7721 and overexpression could inhibit the cell growth. The above results indicate that C17orf25 is a novel human gene, and the cloning and preliminary characterization of C17orf25 is a prerequisite for further functional analysis of this novel gene in human hepatocellular carcinoma.

Inhibitory effects of S-nitrosoglutathione on cell proliferation and DNA synthesis: possible role of glyoxalase I inactivation

We investigated the inhibitory effects of S-nitrosoglutathione (GSNO) on cell proliferation, DNA synthesis and several enzymatic activities using spontaneously immortalized human endothelial cells (ECV304). Proliferation of ECV304 was inhibited by GSNO in a dose-dependent manner (125-1000 microM). DNA synthesis was decreased 2 h after addition of GSNO to cells and was markedly repressed from 20 h after the addition. The activity of ribonucleotide reductase, a rate-limiting enzyme for DNA synthesis, was unchanged in GSNO-treated cells. GSNO inhibited less than 40% of mitochondrial respiration activity, and the membrane potential and cellular levels of ATP were not significantly decreased by GSNO. GSNO had no inhibitory effect on activities of glutathione peroxidase, glutathione S-transferase and glutathione reductase. However, glyoxalase I (Glo I) activity was decreased to 20% of the control level within 60 min, and was consistently repressed during exposure to GSNO for 20 h. A membrane-permeable Glo I inhibitor, S-bromobenzylglutathione diethylester, inhibited proliferation of ECV304 cells, while methylglyoxal (MG), a toxic metabolite generated during glycolysis and a substrate for Glo I, failed to inhibit the cell growth even at 100 microM. Glo I in several mammalian cell lines was inactivated by GSNO with a pI shift. Although we failed to detect accumulation of MG under conditions of Glo I inactivation, these results suggest that the inhibitory effects of GSNO on cell proliferation and DNA synthesis might be at least partly due to inactivation of Glo I.

Glyoxalase I phenotype as a potential risk factor for prostate carcinoma

OBJECTIVES

To elicit a possible link between glyoxalase I (Gly-I), a detoxifying enzyme, and the incidence of prostate cancer (PCa), we investigated Gly-I phenotypic expression in the prostatic tissue and red blood cells (RBCs) from patients with PCa.

METHODS

Eighty-seven clinical specimens, including 42 PCa tissue samples, 20 RBC samples, and 25 matched pair (prostate and RBC) samples from patients at prostatectomy were examined. The Gly-I phenotypes in these specimens were assessed by nondenaturing starch-polyacrylamide gel electrophoresis.

RESULTS

Of the 87 patients, 63 (72.4%) were white, 15 (17.2%) were black, and 9 (10.4%) were another ethnicity (eg, Hispanic, Asian, Indian). Three Gly-I phenotypes were detected in these specimens as fast, intermediate, and slow-moving bands on the gel. The fast phenotype was the most common form found in the white (34 [54%] of 63) and black (8 [53.3%] of 15) patients, but the third ethnic group was too small for proper analysis. To validate this finding, the data from the white patients were compared with the Gly-I phenotypic frequencies in U.S. populations. The data analysis confirmed that a higher incidence (54%) of the fast type in our white patients was statistically significant (P <0.0001) compared with its phenotypic frequency of 30.6% in the general U.S. white population.

CONCLUSIONS

The significantly high frequency (P <0.0001) of the fast Gly-I phenotype was detected among patients with PCa, suggesting it is a potential risk factor for PCa. Whether its increased incidence in whites reflects the lack of sample numbers for other ethnic groups needs additional investigation.

Glyoxalase I is involved in resistance of human leukemia cells to antitumor agent-induced apoptosis

Abnormality in the machinery of apoptosis is associated with a resistant phenotype of the tumor cell to chemotherapy. To determine the molecular basis of resistance to antitumor agent-induced apoptosis, we performed a complementary DNA (cDNA) subtractive hybridization with messenger RNA (mRNA) from human monocytic leukemia U937 and its variant UK711, which is resistant to apoptosis induced by antitumor agents. We found that glyoxalase I (GLO1), an enzyme that detoxifies methylglyoxal, is selectively overexpressed in the apoptosis-resistant UK711 cells. The GLO1 enzyme activity was significantly elevated in UK711 and UK110 cells, another drug-resistant mutant, as well as in K562/ADM, adriamycin-resistant leukemia cells, compared with their parental cells. When overexpressed in human Jurkat cells, GLO1 inhibited etoposide- and adriamycin-induced caspase activation and apoptosis, indicating the involvement of GLO1 in apoptosis suppression caused by these drugs. Moreover, cotreatment withS-p-bromobenzylglutathione cyclopentyl diester (BBGC), a cell-permeable inhibitor of GLO1, enhanced etoposide-induced apoptosis in resistant UK711 cells but not in parental U937 cells. Taken together, these results indicate that GLO1 is a resistant factor to antitumor agent-induced apoptosis in human leukemia cells and that the GLO1 inhibitor could be a drug resistance-reversing agent.

Glyoxalase I is involved in resistance of human leukemia cells to antitumor agent-induced apoptosis

Abnormality in the machinery of apoptosis is associated with a resistant phenotype of the tumor cell to chemotherapy. To determine the molecular basis of resistance to antitumor agent-induced apoptosis, we performed a complementary DNA (cDNA) subtractive hybridization with messenger RNA (mRNA) from human monocytic leukemia U937 and its variant UK711, which is resistant to apoptosis induced by antitumor agents. We found that glyoxalase I (GLO1), an enzyme that detoxifies methylglyoxal, is selectively overexpressed in the apoptosis-resistant UK711 cells. The GLO1 enzyme activity was significantly elevated in UK711 and UK110 cells, another drug-resistant mutant, as well as in K562/ADM, adriamycin-resistant leukemia cells, compared with their parental cells. When overexpressed in human Jurkat cells, GLO1 inhibited etoposide- and adriamycin-induced caspase activation and apoptosis, indicating the involvement of GLO1 in apoptosis suppression caused by these drugs. Moreover, cotreatment withS-p-bromobenzylglutathione cyclopentyl diester (BBGC), a cell-permeable inhibitor of GLO1, enhanced etoposide-induced apoptosis in resistant UK711 cells but not in parental U937 cells. Taken together, these results indicate that GLO1 is a resistant factor to antitumor agent-induced apoptosis in human leukemia cells and that the GLO1 inhibitor could be a drug resistance-reversing agent.