Glutathione S transferase Pi is a powerful indicator in chemotherapy of human lung squamous-cell carcinoma

Anti-influenza A virus activity and structure-activity relationship of a series of nitrobenzoxadiazole derivatives

Influenza viruses represent a major threat to human health and are responsible for seasonal epidemics, along with pandemics. Currently, few therapeutic options are available, with most drugs being at risk of the insurgence of resistant strains. Hence, novel approaches targeting less explored pathways are urgently needed. In this work, we assayed a library of nitrobenzoxadiazole derivatives against the influenza virus A/Puerto Rico/8/34 H1N1 (PR8) strain. We identified three promising 4-thioether substituted nitrobenzoxadiazoles (12, 17, and 25) that were able to inhibit viral replication at low micromolar concentrations in two different infected cell lines using a haemagglutination assay. We further assessed these molecules using an In-Cell Western assay, which confirmed their potency in the low micromolar range. Among the three molecules, 12 and 25 displayed the most favourable profile of activity and selectivity and were selected as hit compounds for future optimisation studies.

Metabolites as Prognostic Markers for Metastatic Non-Small Cell Lung Cancer (NSCLC) Patients Treated with First-Line Platinum-Doublet Chemotherapy

The metabolic requirements of metastatic non-small cell lung (mNSCLC) tumors from patients receiving first-line platinum-doublet chemotherapy are hypothesized to imprint a blood signature suitable for survival prediction. Pre-treatment samples prospectively collected at baseline from a randomized phase III trial were assayed using nuclear magnetic resonance (NMR) spectroscopy (n = 341) and ultra-high performance liquid chromatography – mass spectrometry (UPLC-MS) (n = 297). Distributions of time to event outcomes were estimated by Kaplan-Meier analysis, and baseline characteristics adjusted Cox regression modeling was used to correlate markers’ levels to time to event outcomes. Sixteen polar metabolites were significantly correlated with overall survival (OS) by univariate analysis (p < 0.025). Formate, 2-hydroxybutyrate, glycine and myo-inositol were selected for a multivariate model. The median OS was 6.6 months in the high-risk group compared to 11.4 months in the low risk group HR (Hazard Ratio) = 1.99, 95% C.I. (Confidence Interval) 1.45–2.68; p < 0.0001). Modeling of lipids by class (sphingolipids, acylcarnitines and lysophosphatidylcholines) revealed a median OS = 5.7 months vs. 11. 9 months for the high vs. low risk group. (HR: 2.23, 95% C.I. 1.55–3.20; p < 0.0001). These results demonstrate that metabolic profiles from pre-treatment samples may be useful to stratify clinical outcomes for mNSCLC patients receiving chemotherapy. Genomic and longitudinal measurements pre- and post-treatment may yield addition information to personalize treatment decisions further.

On the Inhibition Mechanism of Glutathione Transferase P1 by Piperlongumine. Insight From Theory

Piperlongumine (PL) is an anticancer compound whose activity is related to the inhibition of human glutathione transferase of pi class (GSTP1) overexpressed in cancerous tumors and implicated in the metabolism of electrophilic compounds. In the present work, the inhibition mechanism of hydrolyzed piperlongumine (hPL) has been investigated employing QM and QM/MM levels of theory. The potential energy surfaces (PESs) underline the contributions of Tyr residue close to G site in the catalytic pocket of the enzyme. The proposed mechanism occurs through a one-step process represented by the nucleophilic addition of the glutathione thiol to electrophilic species giving rise to the simultaneous C-S and H-C bonds formation. Both the used methods give barrier heights (19.8 and 21.5 kcal mol⁻¹ at QM/MM and QM, respectively) close to that experimentally measured for the C-S bond formations (23.8 kcal mol⁻¹).

6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio) hexanol: a promising new anticancer compound

The 7-nitro-2,1,3-nitrobenzoxadiazole (NBD) derivatives are a series of compounds containing the NBD scaffold that are not glutathione (GSH) peptidomimetics, and result in a strong inhibition of glutathione S-transferases (GSTs). Growing evidences highlight their pivotal roles and outstanding anticancer activity in different tumor models. In particular, 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio) hexanol (NBDHEX) is extensively studied, which is a very efficient inhibitor of GSTP1-1. It triggers apoptosis in several tumor cell lines and this cytotoxic activity is observed at micro and submicromolar concentrations. Importantly, studies have shown that NBDHEX acts as an anticancer drug by inhibiting GSTs catalytic activity, avoiding inconvenience of the inhibitor extrusion from the cell by specific pumps and disrupting the interaction between the GSTP1-1 and key signaling effectors. Additionally, some researchers also have discovered that NBDHEX can act as late-phase autophagy inhibitor, which opens new opportunities to fully exploit its therapeutic potential. In this review, we summarize the advantages, anticancer mechanisms, and analogs of this compound, which will establish the basis on the usage of NBDHEX in clinical applications in future.

Recent Progress in Triple Negative Breast Cancer Research

Triple-negative breast cancer (TNBC) is defined as a type of breast carcinoma that is negative for expression of oestrogene and progesterone hormone receptors (ER, PR) and HER2. This form of breast cancer is marked by its aggressiveness, low survival rate and lack of specific therapies. Recently, important molecular characteristics of TNBC have been highlighted and led to the identification of some biomarkers that could be used in diagnosis, as therapeutic targets or to assess the prognosis. In this review, we summarize recent progress in TNBC research focusing on the genetic and epigenetic alterations of TNBC and the potential use of these biomarkers in the targeted therapy for better management of TNBC.

MRP1 and GSTp1 expression in non-small cell lung cancer does not correlate with clinicopathological parameters: A Slovakian population study

We detected MRP1 (multidrug resistance-associated protein 1) and GSTp1 (glutathione-S-transferase p1) protein expression in samples of non-small cell lung cancer (NSCLC) and our results were compared to basic clinicopathological parameters. The indirect immunohistochemical method was used for localization of monitored proteins. A total of 135 tissue samples of NSCLC were characterized according to histopathological type of tumor. Next, we compared our results with basic clinicopathological parameters (histopathological type of tumor, tumor grade and TNM stage of disease). In MRP1 and GSTp1 positive tumor cells, strong brown cytoplasmic immunostaining was visible. In our set of samples 71% showed MRP1 positivity, while according to histopathological type the squamous cell carcinoma reached the highest level of positivity (76%). Our GSTp1 results showed that similarly to MRP1, 70% of samples were GSTp1 positive. According to histopathological type the adenocarcinoma samples showed the highest GSTp1 expression (77%). For precise statistical evaluation the Kruskal-Wallis, Chi-square and Mann-Whitney tests were used. We did not find any statistically significant correlations between MRP1 and clinicopathological parameters. In the group of GSTp1, by Mann-Whitney test we found a statistically significant correlation between GSTp1 and histological grade (p=0.025) in adenocarcinoma samples. As this was only one group of statistically significant correlation we wanted to confirm this finding. For this we applied also Chi-square test which revealed no statistically significant dependence (p=0.077). No statistically significant relation was seen in the coexpression of both proteins (p=0.753). Despite this, the majority of samples simultaneously expressed MRP1 and GSTp1 proteins. In conclusion, our results show that MRP1 and GSTp1 proteins represent independent prognostic features in NSCLC. Nevertheless, the clinical outcome in individual patients is often difficult to predict. Identification of the factors that characterize the resistant cases would permit immediate treatment of the patients with alternative therapeutic approaches.

GSTP1 negatively regulates Stat3 activation in epidermal growth factor signaling

Glutathione S-transferases (GSTs) are the enzymes that defend cells against the damage mediated by oxidant and electrophilic carcinogens. GSTπ (GSTP1) is a member of the GST family and the hypermethylation GSTP1 CpG island DNA is detected in human hepatocellular carcinoma (HCC) tissues, which contributes to the negative expression of GSTP1 mRNA and protein. GSTP1 expression is considered to be an early event in HCC. Stat3, a member of the signal transduction and activator of transcription (Stat) family, is important for promoting the proliferation, survival and other biological processes of cells triggered by cytokines and growth factors. Activated Stat3 may participate in oncogenesis. Previous studies have demonstrated that overexpression of phosphorylated Stat3 is important in the proliferation of HCC cells, suggesting that disturbance of the Stat3 pathway may be an early event. We hypothesize that the suppression of GSTP1 expression in HCC cells increases Stat3 activation. In order to test this hypothesis, HepG2 cells were genetically modified to transiently express high levels of GSTP1. The transient expression of GSTP1 specifically downregulated epidermal growth factor (EGF)-mediated tyrosine phosphorylation of Stat3, and subsequently suppressed the transcriptional activity of Stat3. By contrast, GSTP1 RNAi was able to lead to an increase in the phosphorylation of Stat3. In addition, overexpression of GSTP1 was capable of reducing the survival of HepG2 cells and inducing cell cycle arrest. This inhibition was mediated by a direct interaction between GSTP1 and Stat3. Overall, our results suggest that GSTP1 is important in the regulation of the transcriptional activity of Stat3, and that it is also a regulator of the cell cycle via EGF signaling.

Tumor and host factors that may limit efficacy of chemotherapy in non-small cell and small cell lung cancer

While chemotherapy provides useful palliation, advanced lung cancer remains incurable since those tumors that are initially sensitive to therapy rapidly develop acquired resistance. Resistance may arise from impaired drug delivery, extracellular factors, decreased drug uptake into tumor cells, increased drug efflux, drug inactivation by detoxifying factors, decreased drug activation or binding to target, altered target, increased damage repair, tolerance of damage, decreased proapoptotic factors, increased antiapoptotic factors, or altered cell cycling or transcription factors. Factors for which there is now substantial clinical evidence of a link to small cell lung cancer (SCLC) resistance to chemotherapy include MRP (for platinum-based combination chemotherapy) and MDR1/P-gp (for non-platinum agents). SPECT MIBI and Tc-TF scanning appears to predict chemotherapy benefit in SCLC. In non-small cell lung cancer (NSCLC), the strongest clinical evidence is for taxane resistance with elevated expression or mutation of class III beta-tubulin (and possibly alpha tubulin), platinum resistance and expression of ERCC1 or BCRP, gemcitabine resistance and RRM1 expression, and resistance to several agents and COX-2 expression (although COX-2 inhibitors have had minimal impact on drug efficacy clinically). Tumors expressing high BRCA1 may have increased resistance to platinums but increased sensitivity to taxanes. Limited early clinical data suggest that chemotherapy resistance in NSCLC may also be increased with decreased expression of cyclin B1 or of Eg5, or with increased expression of ICAM, matrilysin, osteopontin, DDH, survivin, PCDGF, caveolin-1, p21WAF1/CIP1, or 14-3-3sigma, and that IGF-1R inhibitors may increase efficacy of chemotherapy, particularly in squamous cell carcinomas. Equivocal data (with some positive studies but other negative studies) suggest that NSCLC tumors with some EGFR mutations may have increased sensitivity to chemotherapy, while K-ras mutations and expression of GST-pi, RB or p27kip1 may possibly confer resistance. While limited clinical data suggest that p53 mutations are associated with resistance to platinum-based therapies in NSCLC, data on p53 IHC positivity are equivocal. To date, resistance-modulating strategies have generally not proven clinically useful in lung cancer, although small randomized trials suggest a modest benefit of verapamil and related agents in NSCLC.

Phase 1-2a multicenter dose-ranging study of canfosfamide in combination with carboplatin and paclitaxel as first-line therapy for patients with advanced non-small cell lung cancer

INTRODUCTION

We aimed to evaluate the safety and efficacy of canfosfamide in combination with carboplatin and paclitaxel as first-line therapy in patients with locally advanced or metastatic non-small cell lung cancer.

METHODS

This was a phase 1-2a, multicenter, dose-ranging trial that enrolled patients with stage IIIB or IV non-small cell lung cancer with measurable disease. Patients received canfosfamide in doses ranging from 400 to 1000 mg/m2 intravenously (IV) with carboplatin at area under the curve 6 IV and paclitaxel at 200 mg/m2 IV day 1 every 3 weeks. The primary end point was objective response rate, and the secondary endpoints were safety and progression-free survival.

RESULTS

One hundred twenty-nine patients were treated with canfosfamide at dose levels of 400 (n = 3), 500 (n = 51), 750 (n = 54), and 1000 mg/m2 (n = 21). Objective tumor responses by RECIST were observed in 40 patients [34% (95% confidence interval [CI], 26-44)], the median progression-free survival was 4.3 months (95% CI, 3.7-5.2) and the median survival 9.9 months (95% CI, 7.7-11.9). The percent of patients alive at 1 year was 43.1%. The overall safety profile of the combination was acceptable and consistent with the profiles of the individual agents. In an exploratory analysis, patients receiving the optional maintenance canfosfamide therapy had a prolonged median survival of 16.8 months compared with those eligible for but not receiving maintenance therapy at 8.8 months (hazard ratio = 0.38, p < 0.001).

CONCLUSIONS

The combination of canfosfamide with carboplatin and paclitaxel chemotherapy is well tolerated and active. Maintenance canfosfamide may further improve outcomes. This regimen is worthy of additional study.

Structural basis for the binding of the anticancer compound 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol to human glutathione s-transferases

Glutathione S-transferases (GST) constitute a superfamily of enzymes with diversified functions including detoxification from xenobiotics. In many human cancers, Pi class GST (GSTP1-1) is overexpressed and contributes to multidrug resistance by conjugating chemotherapeutics. In addition, GSTP1-1 displays antiapoptotic activity by interacting with c-Jun NH(2)-terminal kinase, a key regulator of apoptosis. Therefore, GSTP1-1 is considered a promising target for pharmaceutical treatment. Recently, a potent inhibitor of GSTs, 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol (NBDHEX), was identified and tested on several tumor cell lines demonstrating high antiproliferative activity. To establish the structural basis of NBDHEX activity, we determined the crystal structure of NBDHEX bound to either GSTP1-1 or GSTM2-2 (mu class). NBDHEX in both cases binds to the H-site but occupies different positions. Furthermore, the compound is covalently attached to the GSH sulfur in the GSTM2-2 crystal, forming a sigma-complex, although it is bound but not conjugated in the GSTP1-1 crystal. Several differences in the H-sites of the two isozymes determine the higher affinity of NBDHEX for GSTM2-2 with respect to GSTP1-1. One such difference is the presence of Ile(104) in GSTP1-1 close to the bound NBDHEX, whereas the corresponding position is occupied by an alanine in GSTM2-2. Mutation of Ile(104) into valine is a frequent GSTP1-1 polymorphism and we show here that the Ile(104)Val and Ile(104)Ala variants display a 4-fold higher affinity for the compound. Remarkably, the GSTP1-1/Ile(104)Ala structure in complex with NBDHEX shows a considerable shift of the compound inside the H-site. These data might be useful for the development of new anticancer compounds.

Meta- and pooled analysis of GSTP1 polymorphism and lung cancer: a HuGE-GSEC review

Lung cancer is the most common cancer worldwide. Polymorphisms in genes associated with carcinogen metabolism may modulate risk of disease. Glutathione S-transferase pi (GSTP1) detoxifies polycyclic aromatic hydrocarbons found in cigarette smoke and is the most highly expressed glutathione S-transferase in lung tissue. A polymorphism in the GSTP1 gene, an A-to-G transition in exon 5 (Ile105Val, 313A --> 313G), results in lower activity among individuals who carry the valine allele. The authors present a meta- and a pooled analysis of case-control studies that examined the association between this polymorphism in GSTP1 and lung cancer risk (27 studies, 8,322 cases and 8,844 controls and 15 studies, 4,282 cases and 5,032 controls, respectively). Overall, the meta-analysis found no significant association between lung cancer risk and the GSTP1 exon 5 polymorphism. In the pooled analysis, there was an overall association (odds ratio = 1.11, 95% confidence interval: 1.03, 1.21) between lung cancer and carriage of the GSTP1 Val/Val or Ile/Val genotype compared with those carrying the Ile/Ile genotype. Increased risk varied by histologic type in Asians. There appears to be evidence for interaction between amount of smoking, the GSTP1 exon 5 polymorphism, and risk of lung cancer in whites.

Hepatoprotective effects of Solanum nigrum Linn extract against CCl(4)-induced oxidative damage in rats

Solanum nigrum L. (SN) is an herbal plant that has been used as hepatoprotective and anti-inflammation agent in Chinese medicine. In this study, the protective effects of water extract of SN (SNE) against liver damage were evaluated in carbon tetrachloride (CCl4)-induced chronic hepatotoxicity in rats. Sprague-Dawley (SD) rats were orally fed with SNE (0.2, 0.5, and 1.0 g kg(-1) bw) along with administration of CCl4 (20% CCl4/corn oil; 0.5 mL kg(-1) bw) for 6 weeks. The results showed that the treatment of SNE significantly lowered the CCl4-induced serum levels of hepatic enzyme markers (GOT, GPT, ALP, and total bilirubin), superoxide and hydroxyl radical. The hepatic content of GSH, and activities and expressions of SOD, GST Al, and GST Mu that were reduced by CCl4 were brought back to control levels by the supplement of SNE. Liver histopathology showed that SNE reduced the incidence of liver lesions including hepatic cells cloudy swelling, lymphocytes infiltration, hepatic necrosis, and fibrous connective tissue proliferation induced by CCl4 in rats. Therefore, the results of this study suggest that SNE could protect liver against the CCl4-induced oxidative damage in rats, and this hepatoprotective effect might be contributed to its modulation on detoxification enzymes and its antioxidant and free radical scavenger effects.

Local photodynamic therapy for equine squamous cell carcinoma: evaluation of a novel treatment method in a murine model

The objective of this study was to evaluate the effect of local photodynamic therapy (PDT) with verteporfin on tumor growth inhibition of squamous cell carcinoma (SCC) in a murine model. SCC was implanted in 85 nude mice by subcutaneous injection of A-431 SCC cells. Treatment groups (10 mice/group) received an intra-tumoral injection of verteporfin dissolved in dimethyl sulfoxide (DMSO) or 5% dextrose solution at a dose of 0.01 or 0.1mg/cm3. Controls received only solvent, or no injectate. All groups received identical light illumination (100J/cm2). Relative change in tumor volume (RCTV) at day 30 was compared between groups using the Wilcoxon rank sum test (P< 0.05). Local PDT with verteporfin at a dose of 0.1mg/cm3 resulted in significantly lower RCTV at day 30 compared to controls. Choice of solvent (DMSO versus D5W) did not affect the results. Local PDT may be an effective adjunctive therapy for the treatment of periocular equine SCC.

Glutathione S-transferase: differential expression of alpha, mu, and pi isoenzymes in benign prostate, prostatic intraepithelial neoplasia, and prostatic adenocarcinoma

Glutathione S-transferases (GST) comprise a family of enzymes which are critical for inactivation of toxins and carcinogens. We examined the cellular expression of multiple subclasses of GST immunohistochemically in 25 radical prostatectomy specimens with clinically localized prostate cancer. Gleason scores ranged from 5 to 9, and pathologic stages varied from pT2a to pT3b (all N0M0). Antibodies were directed against GST Ya, Yc, and Yk (alpha subclass), Yb1 (micro subclass), and YPr (pi subclass). The percentage of positive cells and intensity of staining was assessed for benign epithelium, high-grade prostatic intraepithelial neoplasia (PIN), and adenocarcinoma. GSTalpha (Ya) was detected in 30% of cells (mean) in benign acini, 4.9% of cells in high-grade PIN, and 4.5% of cells in adenocarcinoma. The corresponding results for alpha (Yk), micro (Yb1), and pi (Yp) were 12.7%, 10.9%, and 3.5%; 8.7%, 5.2%, and 0.6%; and 66.7,% 0%, and 0%, respectively. GST Yc (alpha subclass) displayed the lowest level of expression, with diffuse weak staining in scattered benign secretory cells and only single cells (<1%) in high-grade PIN and carcinoma. These results demonstrate consistent reduction or loss of expression of all subclasses of GST with progression of prostatic neoplasia from benign epithelium to high-grade PIN and carcinoma. We hypothesize that carcinogenesis in the prostate results from impaired cellular handling of mutagenic agents owing to reduction or loss of expression of multiple GST and other detoxifying and antimutagenesis agents.

Glutathione S-transferase pi (GSTP1) hypermethylation in prostate cancer: review 2007

Prostatic carcinoma is characterised by the silencing of the pi-class glutathione S-transferase gene (GSTP1), which encodes a detoxifying enzyme. The silencing of GSTP1 results from aberrant methylation at the CpG island in the promoter-5' and occurs in the vast majority of cases of high-grade prostatic intraepithelial neoplasia (PIN) and prostate cancers. We review the potential novel role of GSTP1 and its related expression in prostate cancer. The loss of expression (silencing) of the GSTP1 gene is the most common (>90%) genetic alteration reported to date in prostate cancer. Quantitative methylation-specific PCR assays allow detection of GSTP1 methylation in prostate biopsies and may improve the sensitivity of cancer detection. Advances in the epigenetic characterisation of prostate cancer have enabled the development of DNA methylation assays that may soon be used in diagnostic testing of serum and tissue for prostate cancer. Inhibition of aberrant promoter methylation could theoretically prevent carcinogenesis.

Expression of glutathione S-transferase pi and glutathione synthase correlates with survival in early stage non-small cell carcinomas of the lung

The glutathione S-transferase (GST) family of genes encode for detoxification enzymes that protect against reactive oxygen species and influence host susceptibility to carcinogens, including tobacco smoke. It has not been determined whether isoenzyme GST-pi or glutathione synthase (GSH2) expression by tumor cells bears a relationship to survival. A total of 201 non-small cell lung cancers (NSCLC) with long-term follow-up were immunostained with antibodies to GST-pi and GSH2 using standard immunostaining techniques. Results were graded semiquantitatively using a scale of 0 to 3 (0 < or = 10%; 1 = 10%-50%; 2 = 51%-80%; 3 > or = 80%) for both nuclear and cytoplasmic staining. Results were correlated with patient survival using Kaplan-Meier analysis. Nuclear staining with GST-pi in greater than 10% of the cells was closely associated with decreased survival (P = .02) in stage I and II squamous cell carcinomas (n = 40). Cytoplasmic staining showed a similar trend that did not reach statistical significance. No significant correlation between GST-pi staining and survival was determined for other histologic types of NSCLC. Cytoplasmic GSH2 staining in greater than 80% of tumor cells was associated with a trend toward improved survival for stage I adenocarcinoma (P = .08) but did not show a relationship to survival for other histologic types of NSCLC. GST-pi expression predicts prognosis in stage I and II squamous cell lung carcinoma, and GSH2 expression may indicate better survival in early stage adenocarcinoma of the lung. Manipulation of GST-pi and GSH2 may be a potential basis for treatment of some NSCLC.

Therapeutic resistance in lung cancer

Despite considerable progress over the last 25 years in the systemic therapy of lung cancer, intrinsic and acquired resistance to chemotherapeutic agents and radiation remains a vexing problem. The number of mechanisms of therapeutic resistance in lung cancer has expanded considerably over the past three decades, and the crucial role of stress resistance pathways is increasingly recognised as a cause of intrinsic and acquired chemo- and radiotherapy resistance. This paper reviews recent evidence for stress defence proteins, particularly RALBP1/RLIP76, in mediating intrinsic and acquired chemotherapy and radiation resistance in human lung cancer.

Role of the Glutathione Metabolic Pathway in Lung Cancer Treatment and Prognosis: A Review

Inherent and acquired drug resistance is a cause of chemotherapy failure, and pharmacogenomic studies have begun to define gene variations responsible for varied drug metabolism, which influences drug efficacy. Platinum-based compounds are the most commonly used chemotherapeutic agents in the treatment of advanced stage lung cancer patients, and the glutathione metabolic pathway is directly involved in the detoxification or inactivation of platinum drugs. Consequently, genotypes corresponding to higher drug inactivation enzyme activity may predict poor treatment outcome. Available evidence is consistent with this hypothesis, although a definitive role for glutathione system genes in lung cancer prognosis needs to be elucidated. We present evidence supporting a role of the glutathione system in acquired and inherited drug resistance and/or adverse effects through the impact of either drug detoxification or drug inactivation, thus adversely effecting lung cancer treatment outcome. The potential application of glutathione system polymorphic genetic markers in identifying patients who may respond favorably, selecting effective antitumor drugs, and balancing drug efficacy and toxicity are discussed.

Association between glutathione S-transferase pi polymorphisms and survival in patients with advanced nonsmall cell lung carcinoma

BACKGROUND

Glutathione S-transferase (GST) pi (GSTP1) is a detoxification enzyme with substrate specificity for both exogenous carcinogens and chemotherapy agents. Genetic polymorphisms of GSTP1 exon 5 (Ile105Val) and exon 6 (Ala114Val) appear to reduce this enzyme's activity. Previously, the authors reported that the exon 6 variant was associated with an increased risk of lung carcinoma, particularly among men, younger patients, and ever smokers. In this study, the authors hypothesized that variant GSTP1 genotype would result in reduced inactivation of chemotherapy agents and improved survival in patients with advanced-stage nonsmall cell lung carcinoma (NSCLC), a population that is likely to receive platinum-based chemotherapy.

METHODS

Patients with Stage III and IV NSCLC who were enrolled in a molecular epidemiology study were identified, and a polymerase chain reaction-restriction fragment length polymorphism assay was used to genotype GSTP1 exons 5 and 6 in 424 patients and 425 patients, respectively.

RESULTS

Patients who had the exon 6 variant genotype (Ala/Val or Val/Val) had significantly better survival compared with patients who had the wild type genotype (Ala/Ala; P = 0.037), with median survival of 16.1 months and 11.4 months, respectively. Multivariate analysis revealed a reduced adjusted hazard ratio (HR) of death associated with the exon 6 variant genotype of 0.75 (95% confidence interval [95% CI], 0.54-1.05). This protective association was observed in younger patients (younger than age 62 yrs; HR, 0.59; 95% CI, 0.57-0.97) and in males (HR, 0.64; 95% CI, 0.41-0.99). GSTP1 exon 5 genotype was not associated with survival.

CONCLUSIONS

GSTP1 exon 6 variant genotypes may be associated with improved survival among patients with Stage III and IV NSCLC.

Increased sensitivity of Hep G2 cells toward the cytotoxicity of cisplatin by the treatment of piper betel leaf extract

Piper betel leaves (PBL) are used in Chinese folk medicine for the treatment of various disorders. PBL has the biological capabilities of de-toxication, anti-oxidation and anti-mutation. In this study we first examined the effect of PBL extract on the activity of Glutathione S-transferase (GST) isoforms, and found that it inhibited total GST and the alpha class of GST (GSTA), but not the pi class of GST (GSTP), and the mu class of GST (GSTM), activity in Hep G2 cells. RT-PCR results verified a reduction in the expression of GSTA1. Next, we examined whether PBL extract could increase the sensitivity of Hep G2 cells to anti-cancer drugs. The data showed that the cytotoxicity of cisplatin was significantly enhanced by the presence of PBL extract, accompanied by a reduction in the expression of multidrug resistance protein 2 (MRP2). These effects of PBL extract were compared to its major constitute, eugenol. Although eugenol decreased MRP2 level more effectively than PBL extract, it exhibited less sensitizing effect. In conclusion, we demonstrated that PBL extract was able to increase the sensitivity of Hep G2 cells to cisplatin via at least two mechanisms, reducing the expression of MRP2 and inhibiting the activity of total GST and the expression of GSTA. The data of this study support an application of PBL as an additive to reduce drug resistance.

Geniposide activates GSH S-transferase by the induction of GST M1 and GST M2 subunits involving the transcription and phosphorylation of MEK-1 signaling in rat hepatocytes

Geniposide, an iridoid glycoside isolated from the fruit of Gardenia jasminoides Ellis, has biological capabilities of detoxication, antioxidation, and anticarcinogenesis. We have recently found that geniposide possesses a potential for detoxication by inducing GST activity and the expression of GST M1 and GST M2 subunits. In this study, the signaling pathway of geniposide leading to the activation of GSH S-transferase (GST) was investigated. Primary cultured rat hepatocytes were treated with geniposide in the presence or absence of mitogen-activated protein kinase (MAPK) inhibitors and examined for GST activity, expression of GST M1 and M2 subunits, and protein levels of MAPK signaling proteins. Western blotting data demonstrated that geniposide induced increased protein levels of GST M1 and GST M2 (approximately 1.76- and 1.50-fold of control, respectively). The effect of geniposide on the increased protein levels of GST M1 and GST M2 was inhibited by the MEK-1 inhibitor PD98059, but not by other MAPK inhibitors. The GST M1 and GST M2 transcripts as determined by RT-PCR and GST activity were also inhibited concurrently by the MEK-1 inhibitor PD98059. The protein levels of up- and down-stream effectors of the MEK-1, including Ras, Raf, and Erk1/2, and the phosphorylation state of Erk1/2 were found to be induced by geniposide, indicating a two-phase influence of geniposide. The results suggest that geniposide induced GST activity and the expression of GST M1 and GST M2 acting through MEK-1 pathway by activating and increasing expression of Ras/Raf/MEK-1 signaling mediators.

Characterization of the molecular forms of glutathione S-transferase P1 in human gastric cancer cells (Kato III) and in normal human erythrocytes

GSTP1 (glutathione S-transferase pi) is involved in stress responses and in cellular proliferation pathways as an inhibitor of JNK (c-Jun N-terminal kinase). It has been proposed that monomeric GSTP1 functions as a JNK inhibitor. All of the studies to date have been performed using rodent cells, and it is unclear if monomeric GSTP1 exists in human cells. Monomeric GSTP1 was sought in human gastric cancer cells (Kato III) and in normal human erythrocytes using gel filtration, ELISA and Western blots. Monomeric GSTP1 was found in conditioned medium, in cytosol of Kato III cells and in cytosol of erythrocytes. GSTP1 subunits from Kato III cells and erythrocytes were heterogeneous when analysed by MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight) MS, suggesting that there were post-translational modifications to GSTP1. One post-translational modification, phosphorylation of a serine residue in the C-terminal portion of GSTP1 where JNK binds, was identified in GSTP1 purified from Kato III cells, but not in GSTP1 purified from human erythrocytes. Therefore normal and malignant human cells contain GSTP1 monomers with post-translational modifications, and it is likely that GSTP1 monomers regulate JNK activity in human cells in the same manner as in rodent cells.

Integrative epidemiology: from risk assessment to outcome prediction

In this paper, we advance the concept of integrative epidemiology. Our unifying premise is that the same genes that are implicated in cancer risk may also be involved in a person's propensity to carcinogenic exposure and/or to modulation of therapeutic outcome. In the coming years, molecular epidemiology will play an increasingly prominent role in early detection of cancer and in identifying genetically high-risk subgroups that might benefit disproportionately from more intensive screening or chemoprevention interventions. Molecular epidemiology is also integral to pharmacogenetic research, by constructing genetic profiles that could be used to individualize therapy and to understand the functional consequences of chemoprevention, chemotherapy, or radiotherapy response. At the level of risk assessment, the focus might be on germline polymorphisms in candidate genes; for early detection, epigenetic events in these same or other genes may be relevant; and tumor tissue expression levels, loss of heterozygosity, genomic amplification, rearrangements, or somatic mutations in the same classes of genes may determine outcome. We will provide examples of how changes in the function of a single gene can contribute to susceptibility to carcinogenic exposure, predisposition to cancer development, patient prognosis, and prediction of outcome.

Expression of glutathione S-transferase P1-1 in leukemic cells is regulated by inducible AP-1 binding

Glutathione S-transferases (GST) are involved in cellular protection against xenobiotics, oxidative stress as well as in resistance against chemotherapeutic compounds such as doxorubicin. Levels of human placental type GSTP1-1 are known to be increased in many tumors and hematopoietic diseases. In this work, we compare transcriptional mechanisms in cells that express or not GSTP1-1. Transient transfection assays are used to show that different GST-promoter reporter constructs generate cell-type specific levels of luciferase activity. In expressing cells, transcriptional activity is strongly dependent on AP-1 binding elements within the -65 to -75 bp region of the GSTP1 gene as shown by site-directed mutagenesis. Electrophoretic mobility shift assays show that DNA binding activity is exclusively observed in GSTP1-1-expressing cells and is increased after stimulation with hydrogen peroxide, TPA, tert-butylhydroquinone and doxorubicin. Non-expressing cells present neither constitutive nor inducible AP-1 binding. Taken together, our results provide evidence for the induction of the GSTP1 gene via AP-1 binding activity in leukemia cells and contribute to a better understanding of the molecular events regulating genes involved in drug resistance mechanisms.

Induction of apoptosis by curcumin: mediation by glutathione S-transferase P1-1 inhibition

Expression of glutathione S-transferase P1-1 (GSTP1-1) is correlated to carcinogenesis and resistance of cancer cells against chemotherapeutic agents. Curcumin, a natural compound extracted from Curcuma longa, has shown strong antioxidant and anticancer properties and also the ability to regulate a wide variety of genes that require activating protein 1 and nuclear factor kappaB (NF-kappaB) activation. In the present study, we examined the inhibitory effect of curcumin on the expression of GSTP1-1 mRNA as well as protein, and we correlated this inhibition with the apoptotic effect of curcumin on K562 leukemia cells. Curcumin efficiently inhibited the tumour necrosis factor alpha- and phorbol ester-induced binding of AP-1 and NF-kappaB transcription factors to sites located on the GSTP1-1 gene promoter. TNFalpha-induced GSTP1-1 promoter activity was also inhibited by curcumin as shown by reporter gene assay. In parallel, curcumin induced pro-caspases 8 and 9 as well as poly ADP ribose polymerase cleavage and thus leading to apoptosis in K562 cells. Our results overall add a novel role for curcumin as this chemoprotective compound could contribute to induce apoptosis by its ability to inhibit the GSTP1-1 expression at the level of transcription.

Glutathion S transferase pi indicates chemotherapy resistance in breast cancer

BACKGROUND

Breast cancer is the most common malignant disease of women. Pathologic response of breast cancer to chemotherapy has a great prognostic importance. Glutathion S Transferases (GSTs) might detoxify chemotherapeutic drugs within the cancer cells, thus contributing to chemotherapy resistance. The pi isoenzyme of GSTs seems to be of great relevance. Thus, we hypothesized that GSTpi expression in cancer biopsy can be a prognostic indicator for resistance to chemotherapy. To test this hypothesis, we evaluated before and after chemotherapy, tumor size, apoptosis of tumor cells with TUNEL assay, and proliferation of tumor cells by determining PCNA expression in biopsy samples, or in the surgically removed tumor tissue of GSTpi (-), and GSTpi (+) cases.

MATERIALS AND METHODS

GSTpi immunoreactivity was determined in 42 female patients with breast cancer. Patients were divided into two groups according to the expression of GSTpi in the pre-treatment biopsy specimen: (+) (n = 22) and (n = 20) samples were analyzed. Surgery was performed 2 weeks after a single intravenous injection of the chemotherapeutic drugs [5-fluorouracil, adriamycin, mitomycin (FAM protocol)].

RESULTS

Pre-chemotherapy values of tumor size, apoptosis, or proliferation did not differ between GSTpi (-) and (+) samples. Chemotherapy significantly inhibited tumor growth, and cell proliferation, and induced apoptosis in GSTpi (-) cases. However, these effects were significantly reduced in GSTpi (+) patients.

CONCLUSION

These results suggest, that the presence of GSTpi in breast cancer tissue is a bad prognostic indicator, and these tumors are largely resistant to chemotherapy. Thus, GSTpi might be important in inactivating one or more of the chemotherapeutic agents used in this treatment.

Blood glutathione as a surrogate marker of cancer tissue glutathione S-transferase activity in non-small cell lung cancer and squamous cell carcinoma of the head and neck

The identification of markers predicting the response to therapy is of the utmost importance in oncology. Several authors have suggested that increased levels of glutathione (GSH) and glutathione S-transferase (GST) activity might be meaningful predictors of poor responsiveness to chemotherapy in several human cancers, but the biological assays have not been standardised and published studies show conflicting evidence. The aim of the present study was to select a validated panel of tests to assess the GST/GSH system in a clinical setting. Matched blood and tissue samples (normal and malignant) from 52 cancer patients with either non-small cell lung cancer (NSCLC) or head and neck squamous cell carcinoma (SCCHN) were investigated. GSH levels and GST activity were higher in cancer tissues than in matched normal tissues in both malignancies. The difference was statistically significant in NSCLC (P=0.0004 and P=0.0002, for GSH and GST, respectively) and borderline in SCCHN (P=0.03 and P=0.02, for GSH and GST, respectively). Moreover a strong correlation was found between the GSH level in whole blood and GST activity in cancer tissue in both malignancies (P=0.003, r=0.53 in NSCLC, P<0.0001, r=0.89 in SCCHN). In conclusion, reliable and robust methods for routine use in tissue extracts and in whole blood have been validated. Our finding regarding the GSH level in blood indicates that circulating GSH could have a clinical relevance as a surrogate marker of GST activity in tumour tissue.

Allelic variants of the human glutathione S-transferase P1 gene confer differential cytoprotection against anticancer agents in Escherichia coli

The polymorphic human GSTP1 gene locus encodes proteins that differentially metabolize electrophilic substrates, including, many chemotherapeutic agents used in clinical cancer therapy. In this study, we used XL1-Blue MRF strain, transformed with phagemid expression vectors carrying cDNAs of three GSTP1 alleles, to investigate the cytoprotective abilities of the different GSTP1 alleles against four clinically active anticancer agents, namely, carboplatin, cisplatin, thiotepa, and 4-hydroperoxyifosfamide. Following induction of protein expression with isopropyl-beta-d-thiogalactoside, the cells were treated with each drug for 3 h (1 h for 4-hydroperoxyifosfamide). Surviving fractions were determined and used to compute a cytoprotective factor for each allele against each drug. The results showed all the GSTP1 alleles to be cytoprotective, albeit, to different degrees. For cisplatin and carboplatin, the allele was most protective, with CPs of 5.58 and 3.76, respectively, compared with 1.21 and 1.61 for and 2.50 and 2.79 for. In contrast, protection against thiotepa was highest for the allele, with a cytoprotective factor of 1.56, compared to 1.32 for and 1.1 for. For 4-hydroperoxyifosfamide, the CP for and was the same, 1.45, compared with 1.18 for. These data demonstrate significant differences in the ability of the different GSTP1 alleles to protect against the cytotoxicity of electrophilic anticancer agents. The level of protection differs significantly between different GSTP1 alleles, and between different anticancer agents. The optimized prokaryotic system described provides a useful and rapid tool for pharmacogenetic analysis of the effects of genes on drug sensitivity.

Particular aspects of platinum compounds used at present in cancer treatment

The history of platinum in cancer treatment began 150 years ago with the first synthesis of cisplatin; but it was not used in the clinic before 30 years ago. Then 3000 derivatives were synthesised and tested, with poor successes: three other derivatives only are available today. Clearly they are not more active, but they are less toxic than cisplatin, although two, carboplatin and nedaplatin, yield a cross-resistance, while one, oxaliplatin, does not. Their mechanisms of action are similar: these four pro-drugs form adducts with DNA, impairing DNA synthesis and repair then. Their pharmacokinetics are complicated since we always measure two overlapping pharmacokinetics: those of the parent compound and of the bound platinum. Cisplatin is now recommended for few cancers, it is replaced by less-toxic carboplatin, and therefore more easily used in combination. Oxaliplatin give interesting results in a number of cancers. The official recommendation in Japan for nedaplatin is head and neck, testicular, lung, oesophageal, ovarian, and cervical cancer.

Genetic determinants of lung cancer short-term survival: the role of glutathione-related genes

PURPOSE

Survival of lung cancer patients has been dismal. Glutathione enzymes are directly involved in the metabolism of platinum compounds, a group of important chemotherapeutic drugs in cancer treatment. We tested the hypothesis that genes encoding glutathione enzymes may predict lung cancer short-term survival.

METHODS

We studied DNA polymorphisms of 250 primary lung cancer patients at four glutathione-related loci: GSTP1, GSTM1, GSTT1 and gamma-GCS that encode glutathione-S-transferase-pi, glutathione-S-transferase-mu, glutathione-S-transferase-theta, and gamma-glutamylcysteine synthetase, respectively. Pearson's chi(2)-square tests, Kaplan-Meier survival curves, log rank tests, and Cox regression models were applied in the analysis.

RESULTS

There were 150 (60%) men and 100 (40%) women in this study. Seventeen percent of the patients had never smoked cigarettes, and 61% had stopped smoking at least 6 months prior to their lung cancer diagnosis. Among never smokers, those with null (N) or low (L) genotype experienced a better 1-year-survival rate than those with a positive (P) or high (H) genotype. Patients with P or H at two loci (PP or PH) were compared with patients with N or L at one or both loci (other). Among never smokers, 1-year-survival rates were 60-78% for patients with PP or PH genotypes compared with 89-100% for other types. The survival advantage was greater among advanced-stage patients who were NL or NN than low-stage patients. Similar results were not observed among smokers.

CONCLUSIONS

Glutathione-related genes may determine lung cancer survival. Our results, if confirmed, would suggest new directions to enhance cancer treatment, and provide easily measurable markers for clinicians to plan patient-specific therapy.

Inhibition of glutathione S-transferases by antimalarial drugs possible implications for circumventing anticancer drug resistance

A strategy to overcome multidrug resistance in cancer cells involves treatment with a combination of the antineoplastic agent and a chemomodulator that inhibits the activity of the resistance-causing protein. The aim of our study was to investigate the effects of antimalarial drugs on human recombinant glutathione S-transferase (GSTs) activity in the context of searching for effective and clinically acceptable inhibitors of these enzymes. Human recombinant GSTs heterologously expressed in Escherichia coli were used for inhibition studies. GST A1-1 activity was inhibited by artemisinin with an IC(50) of 6 microM, whilst GST M1-1 was inhibited by quinidine and its diastereoisomer quinine with IC(50)s of 12 microM and 17 microM, respectively. GST M3-3 was inhibited by tetracycline only with an IC(50) of 47 microM. GST P1-1 was the most susceptible enzyme to inhibition by antimalarials with IC(50) values of 1, 2, 1, 4, and 13 microM for pyrimethamine, artemisinin, quinidine, quinine and tetracycline, respectively. The IC(50) values obtained for artemisinin, quinine, quinidine and tetracycline are below peak plasma concentrations obtained during therapy of malaria with these drugs. It seems likely, therefore, that GSTs may be inhibited in vivo at doses normally used in clinical practice. Using the substrate ethacrynic acid, a diuretic drug also used as a modulator to overcome drug resistance in tumour cells, GST P1-1 activity was inhibited by tetracycline, quinine, pyrimethamine and quinidine with IC(50) values of 18, 27, 45 and 70 microM, respectively. The ubiquitous expression of GSTs in different malignancies suggests that the addition of nontoxic reversing agents such as antimalarials could enhance the efficacy of a variety of alkylating agents.

Specific induction of glutathione S-transferase GSTM2 subunit expression by epigallocatechin gallate in rat liver

The antitumor effect of green tea polyphenols has been well characterized in numerous papers. However, the mechanism of their action is still poorly defined. In this study, epigallocatechin gallate (EGCG), the main ingredient of green tea extract, was studied for its effect on the expression of glutathione S-transferases (GSTs) in rat liver to examine the mechanism of action. Liver samples were collected from Sprague-Dawley rats treated with EGCG in H(2)O by portal vein perfusion and examined for total GST activity and GST expression. The results showed that the induction of GST activity by EGCG was dose- and time-dependent. GST activity was increased about 28-fold at 12 hr after treatment. Three GST subunits (GSTA1/2, GSTM1, and GSTM2) were examined by Western blot for changes in protein level affected by EGCG (1 mg/kg weight). Only GSTM2 revealed a significant time-dependent increase, with a maximal induction of approximately 2.0-fold. The differential effect of EGCG on GST subunit expression was also verified by immunocytochemical examination and showed strong induction of the GSTM2 (but not the GSTA1/2 and GSTM1) level in liver section. This induction occurred as early as 3 hr after treatment and extended gradually outward from the hepatic veins as treatment time increased. The change in the GSTM2 protein level was accompanied by a corresponding alteration in mRNA quantity ( approximately 2.0-fold of control). Our report is the first to demonstrate a specific induction of the GSTM2 subunit by a chemopreventor and suggests a primary influence of EGCG on GSTM2 gene expression.

Increased skin tumorigenesis in mice lacking pi class glutathione S-transferases

The activity of chemical carcinogens is a complex balance between metabolic activation by cytochrome P450 monooxygenases and detoxification by enzymes such as glutathione S-transferase (GST). Regulation of these proteins may have profound effects on carcinogenic activity, although it has proved impossible to ascribe the observed effects to the activity of a single protein. GstP appears to play a very important role in carcinogenesis, although the precise nature of its involvement is unclear. We have deleted the murine GstP gene cluster and established the effects on skin tumorigenesis induced by the polycyclic aromatic hydrocarbon 7, 12-dimethylbenz anthracene and the tumor promoting agent 12-O-tetradecanoylphorbol-13-acetate. After 20 weeks, a highly significant increase in the number of papillomas was found in the GstP1/P2 null mice [GstP1/P2(-/-) mice, 179 papillomas, mean 9.94 per animal vs. GstP1/P2(+/+) mice, 55 papillomas, mean 2.89 per animal, (P < 0.001)]. This difference in tumor incidence provides direct evidence that a single gene involved in drug metabolism can have a profound effect on tumorigenicity, and demonstrates that GstP may be an important determinant in cancer susceptibility, particularly in diseases where exposure to polycyclic aromatic hydrocarbons is involved, for instance in cigarette smoke-induced lung cancer.

The relationship between tumour glutathione concentration, glutathione S-transferase isoenzyme expression and response to single agent carboplatin in epithelial ovarian cancer patients

There is evidence to suggest that glutathione (GSH) and glutathione-S-transferases (GST) are important factors in determining sensitivity to cytotoxic drugs in vitro and in preclinical in vivo model systems. To define the relationship between tumour GSH concentration, GST isoenzyme expression and response to carboplatin in epithelial ovarian cancer (EOC), tumour samples from 39 patients with assessable disease after primary surgery were analyzed for GSH content and GST expression. Response was assessed after completing six courses of single agent carboplatin therapy. GSH was measured by high performance liquid chromatography (HPLC) in fresh tumour samples taken at primary laparatomy. GST isoenzyme expression was assessed by immunohistochemistry of fixed tumour material using antibodies specific for pi, alpha and mu classes. GST isoenzyme expression was defined as positive if the staining intensity was strong and more than 10% of tumour cells were involved. The mean GSH concentrations were: 8351 +/- 4496, 7211 +/- 5026, 6559 +/- 4573 and 3758 +/- 1885 (nmol g-1 tissue dry weight mean +/- s.d.) for tumours from patients who subsequently achieved a complete response (CR, n = 18), partial response (PR, n = 10) or who had static disease (SD, n = 7) or progressive disease (PD, n = 4) respectively. There was no relationship between GSH concentration and response (ANOVA, P = 0.32). There were also no relationship between GST isoenzyme expression and response (P Fisher's exact test 0.51-0.55 and chi-squared test 0.98-0.99). In conclusion, there was no association between the concentration of GSH or expression of GST isoenzymes and response to single agent carboplatin in primary previously untreated EOC.