Differential catalytic efficiency of allelic variants of human glutathione S-transferase Pi in catalyzing the glutathione conjugation of thiotepa

Role of Genetic Polymorphisms in Drug-Metabolizing Enzyme-Mediated Toxicity and Pharmacokinetic Resistance to Anti-Cancer Agents: A Review on the Pharmacogenomics Aspect

The inter-individual differences in cancer susceptibility are somehow correlated with the genetic differences that are caused by the polymorphisms. These genetic variations in drug-metabolizing enzymes/drug-inactivating enzymes may negatively or positively affect the pharmacokinetic profile of chemotherapeutic agents that eventually lead to pharmacokinetic resistance and toxicity against anti-cancer drugs. For instance, the CYP1B1*3 allele is associated with CYP1B1 overexpression and consequent resistance to a variety of taxanes and platins, while 496T>G is associated with lower levels of dihydropyrimidine dehydrogenase, which results in severe toxicities related to 5-fluorouracil. In this context, a pharmacogenomics approach can be applied to ascertain the role of the genetic make-up in a person's response to any drug. This approach collectively utilizes pharmacology and genomics to develop effective and safe medications that are devoid of resistance problems. In addition, recently reported genomics studies revealed the impact of many single nucleotide polymorphisms in tumors. These studies emphasized the importance of single nucleotide polymorphisms in drug-metabolizing enzymes on the effect of anti-tumor drugs. In this review, we discuss the pharmacogenomics aspect of polymorphisms in detail to provide an insight into the genetic manipulations in drug-metabolizing enzymes that are responsible for pharmacokinetic resistance or toxicity against well-known anti-cancer drugs. Special emphasis is placed on different deleterious single nucleotide polymorphisms and their effect on pharmacokinetic resistance. The information provided in this report may be beneficial to researchers, especially those who are working in the field of biotechnology and human genetics, in rationally manipulating the genetic information of patients with cancer who are undergoing chemotherapy to avoid the problem of pharmacokinetic resistance/toxicity associated with drug-metabolizing enzymes.

Potential role of glutathione S-transferase P1 gene polymorphism and metabolic syndrome in lower urinary tract symptoms attributed to benign prostatic hyperplasia

OBJECTIVE

The aim of the study is to investigate the effects of glutathione S-transferase P1 (GSTP1) gene polymorphism and metabolic syndrome (MS) on lower urinary tract symptoms (LUTS) attributed to benign prostatic hyperplasia (BPH).

METHODS

This study included 195 patients diagnosed with LUTS secondary to BPH as case group, divided into simple BPH group (S-BPH group) and combined with MS group (MS-BPH group). Control group included 200 healthy elderly men without LUTS. Use peripheral blood samples detected the GSTP1 gene polymorphism (Ile 105 Val A → G polymorphism) by polymerase chain reaction-restriction fragment length polymorphism. Recorded age, GSTP1 gene polymorphism, international prostate symptom score (IPSS), prostate volume (PV), residual urine volume (RV), maximal urinary flowrate (Qmax), and prostate-specific antigen (PSA) to statistical analysis.

RESULTS

Pairwise compared between control group, S-BPH group and MS-BPH, the PV (P < 0.001), PSA (P < 0.001), RV (P < 0.001), Qmax (P < 0.001), IPSS (P < 0.001), frequencies of GSTP1 gene (P < 0.05) were shown significant different, and MS-BPH group had larger PV, and more severe LUTS. In case group, variation genotypes (GSTP1 A/G + G/G) always had larger PV, higher PSA and IPSS, more RV and lower Qmax than homozygote (GSTP1 A/A) and the comparison were significant different (P < 0.05). Variation genotypes were positively correlated with PV (β = 0.092, P < 0.001), RV (β = 0.228, P = 0.004), IPSS (β = 0.274, P = 0.038), PSA (β = 1.243, P < 0.001) and negatively correlated with Qmax (β = -0.362, P = 0.025).

CONCLUSION

In patients with BPH, GSTP1 variation genotypes and MS might be potential risk factors for faster progression of benign prostatic enlargement and LUTS, which might increase the surgical rate.

TRIAL REGISTRATION

ChiCTR-IPR-14005580.

Activity of glutathione S-transferase and its π isoenzyme in the context of single nucleotide polymorphism in the GSTP1 gene (rs1695) and tobacco smoke exposure in the patients with acute pancreatitis and healthy subjects

Oxidative stress associated with the course of acute pancreatitis (AP) can cause changes in the involvement of antioxidants, which can result in the increased production of free radicals with pro-inflammatory potential. Through its noncatalytic activity, the glutathione S-transferase and its π isoenzyme (GST-π), apart from cellular xenobiotics detoxification, are involved in the regulation of cellular signalling, metabolism and apoptosis. This study aimed to evaluate the impact of SNP rs1695 in the GSTP1 gene on GST and GST-π activity in healthy subjects and patients with acute pancreatitis (AP). The concentration of glutathione (GSH) as an important component of the antioxidant system, necessary for environmental xenobiotics detoxification by GST, and malonyldialdehyde (MDA) as a marker of oxidative stress induced by inflammation were also assessed. SNP was examined in 39 AP patients and 51 healthy subjects using PCR-RFLP methods. GST activity (in plasma and erythrocyte lysate) and GST-π activity (in erythrocyte lysate) were measured using the spectrophotometric method with 1-chloro-2,4-dinitrobenzene and ethacrynic acid as substrate, respectively. Blood GSH concentration was measured using the Patterson method. Concentrations of high-sensitive C-reactive protein (hs-CRP) and MDA were measured using commercial tests. In the blood of non-smoking AP patients with GG genotypes for SNP rs1695 in the GSTP1 gene, the lowest GST-π activity was shown. It was accompanied by the lowest hsCRP concentration in this group. In the blood of smoking healthy subjects with AG genotype, a decrease in GST-π activity was noted compared to non-smokers from this group. However, in the blood of smokers with AP, a gradually decreasing GST-π activity was noted in individuals with AA genotype, which was associated with the increasing MDA concentration. It confirms the role of GST-π in the neutralization of oxidative stress induced by the exposure to smoke xenobiotics.

Variability of the Genes Involved in the Cellular Redox Status and Their Implication in Drug Hypersensitivity Reactions

Adverse drug reactions are a major cause of morbidity and mortality. Of the great diversity of drugs involved in hypersensitivity drug reactions, the most frequent are non-steroidal anti-inflammatory drugs followed by β-lactam antibiotics. The redox status regulates the level of reactive oxygen and nitrogen species (RONS). RONS interplay and modulate the action of diverse biomolecules, such as inflammatory mediators and drugs. In this review, we address the role of the redox status in the initiation, as well as in the resolution of inflammatory processes involved in drug hypersensitivity reactions. We summarize the association findings between drug hypersensitivity reactions and variants in the genes that encode the enzymes related to the redox system such as enzymes related to glutathione: Glutathione S-transferase (GSTM1, GSTP, GSTT1) and glutathione peroxidase (GPX1), thioredoxin reductase (TXNRD1 and TXNRD2), superoxide dismutase (SOD1, SOD2, and SOD3), catalase (CAT), aldo-keto reductase (AKR), and the peroxiredoxin system (PRDX1, PRDX2, PRDX3, PRDX4, PRDX5, PRDX6). Based on current evidence, the most relevant candidate redox genes related to hypersensitivity drug reactions are GSTM1, TXNRD1, SOD1, and SOD2. Increasing the understanding of pharmacogenetics in drug hypersensitivity reactions will contribute to the development of early diagnostic or prognosis tools, and will help to diminish the occurrence and/or the severity of these reactions.

Responses of cytochrome P450, GST and MXR in the mussel Perna viridis to the exposure of Aureococcus anophagefferens

The brown tide formed by a microscopic alga called Aureococcus anophagefferens has a devastating effect on filter-feeding bivalves, however, the related toxic principle remains an open question. In this study, we found that A. anophagefferens cells could motivate detoxification associated genes including CYP450, GST, P-gp and MVP, and induce SOD activity in the mussel Perna viridis. D1-like and D2-like receptors were expressed at high level in the gills of P. viridis, however, D2-like receptor transcript was too low to detect in digestive gland. The exposure of A. anophagefferens did not lead to any significant alterations in the expression of D1-like and D2-like receptors in both gills and digestive gland. These findings suggested that A. anophagefferens exhibited cytotoxicity toward bivalves, but did not obviously disrupt the dopamine system at transcriptional level in the acute exposure. Further studies are warranted to explore the nature of toxic compounds in A. anophagefferens affected bivalves.

The mercapturic acid pathway

The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.

Racial disparities, cancer and response to oxidative stress

At the intersection of genetics, biochemistry and behavioral sciences, there is a largely untapped opportunity to consider how ethnic and racial disparities contribute to individual sensitivity to reactive oxygen species and how these might influence susceptibility to various cancers and/or response to classical cancer treatment regimens that pervasively result in the formation of such chemical species. This chapter begins to explore these connections and builds a platform from which to consider how the disciplines can be strengthened further.

Single nucleotide polymorphism of <italic>GSTP1</italic> and pathological complete response in locally advanced rectal cancer patients treated with neoadjuvant concomitant radiochemotherapy

Purpose

Standard treatment for locally advanced rectal cancer consists of neoadjuvant radiochemotherapy with concomitant fluoropyrimidine or oxaliplatin and surgery with curative intent. Pathological complete response has shown to be predictive for better outcome and survival; nevertheless there are no biological or genetic factors predictive for response to treatment. We explored the correlation between the single nucleotide polymorphisms (SNPs) GSTP1 (A313G) and XRCC1 (G28152A), and the pathological complete response and survival after neoadjuvant radiochemotherapy in locally advanced rectal cancer patients.

Materials and Methods

Genotypes GSTP1 (A313G) and XRCC1 (G28152A) were determined by pyrosequencing technology in 80 patients affected by locally advanced rectal cancer.

Results

The overall rate of pathological complete response in our study population was 18.75%. Patients homozygous AA for GSTP1 (A313G) presented a rate of pathological complete response of 26.6% as compared to 8.5% of the AG+GG population (p = 0.04). The heterozygous comparison (AA vs. AG) showed a significant difference in the rate of pathological complete response (26.6% vs. 6.8%; p = 0.034). GSTP1 AA+AG patients presented a 5- and 8-year cancer-specific survival longer than GSTP1 GG patients (87.7% and 83.3% vs. 44.4% and 44.4%, respectively) (p = 0.014). Overall survival showed only a trend toward significance in favor of the haplotypes GSTP1 AA+AG. No significant correlations were found for XRCC1 (G28152A).

Conclusion

Our results suggest that GSTP1 (A313G) may predict a higher rate of pathological complete response after neoadjuvant radiochemotherapy and a better outcome, and should be considered in a more extensive analysis with the aim of personalization of radiation treatment.

Host genetic profiling to increase drug safety in colorectal cancer from discovery to implementation

Adverse events affect the pharmacological treatment of approximately 90% of colorectal cancer (CRC) patients at any stage of the disease. Chemotherapy including fluoropyrimidines, irinotecan, and oxaliplatin is the cornerstone of the pharmacological treatment of CRC. The introduction of novel targeted agents, as anti-EGFR (i.e. cetuximab, panitumumab) and antiangiogenic (i.e. bevacizumab, ziv-aflibercept, regorafenib, and ramucirumab) molecules, into the oncologist's toolbox has led to significant improvements in the life expectancy of advanced CRC patients, but with a substantial increase in toxicity burden. In this respect, pharmacogenomics has largely been applied to the personalization of CRC chemotherapy, focusing mainly on the study of inhered polymorphisms in genes encoding phase I and II enzymes, ATP-binding cassette (ABC)/solute carrier (SLC) membrane transporters, proteins involved in DNA repair, folate pathway and immune response. These research efforts have led to the identification of some validated genetic markers of chemotherapy toxicity, for fluoropyrimidines and irinotecan. No validated genetic determinants of oxaliplatin-specific toxicity, as peripheral neuropathy, has thus far been established. The contribution of host genetic markers in predicting the toxicity associated with novel targeted agents' administration is still controversial due to the heterogeneity of published data. Pharmacogenomics guidelines have been published by some international scientific consortia such as the Clinical Pharmacogenomics Implementation Consortium (CPIC) and the Dutch Pharmacogenetics Working Group (DPWG) strongly suggesting a pre-treatment dose adjustment of irinotecan based on UGT1A1*28 genotype and of fluoropyrimidines based on some DPYD genetic variants, to increase treatment safety. However, these recommendations are still poorly applied at the patient's bedside. Several ongoing projects in the U.S. and Europe are currently evaluating how pharmacogenomics can be implemented successfully in daily clinical practice. The majority of drug-related adverse events are still unexplained, and a great deal of ongoing research is aimed at improving knowledge of the role of pharmacogenomics in increasing treatment safety. In this review, the issue of pre-treatment identification of CRC patients at risk of toxicity via the analysis of patients' genetic profiles is addressed. Available pharmacogenomics guidelines with ongoing efforts to implement them in clinical practice and new exploratory markers for clinical validation are described.

Potential Role of Single Nucleotide Polymorphisms of XRCC1, XRCC3, and RAD51 in Predicting Acute Toxicity in Rectal Cancer Patients Treated With Preoperative Radiochemotherapy

OBJECTIVES

To investigate the association between polymorphisms of DNA repair genes and xenobiotic with acute adverse effects in locally advanced rectal cancer patients treated with neoadjuvant radiochemotherapy.

METHODS

Sixty-seven patients were analyzed for the current study. Genotypes in DNA repair genes XRCC1 (G28152A), XRCC3 (A4541G), XRCC3 (C18067T), RAD51 (G315C), and GSTP1 (A313G) were determined by pyrosequencing technology.

RESULTS

The observed grade ≥3 acute toxicity rates were 23.8%. Chemotherapy and radiotherapy were interrupted for 46 and 14 days, respectively, due to critical complications. Four patients were hospitalized, 6 patients had been admitted to the ER, and 5 patients received invasive procedures (2 bladder catheters, 2 blood transfusions, and 1 growth factor therapy).RAD51 correlated with acute severe gastrointestinal toxicity in heterozygosity (Aa) and homozygosity (AA) (P=0.036). Grade ≥3 abdominal/pelvis pain toxicity was higher in the Aa group (P=0.017) and in the Aa+AA group (P=0.027) compared with homozygous (aa) patients. Acute skin toxicity of any grade occurred in 55.6% of the mutated patients versus 22.8% in the wild-type group (P=0.04) for RAD51. XRCC1 correlated with skin toxicity of any grade in the Aa+AA group (P=0.03) and in the Aa group alone (P=0.044). Grade ≥3 urinary frequency/urgency was significantly higher in patients with AA (P=0.01), Aa (P=0.022), and Aa+AA (P=0.031) for XRCC3 compared with aa group.

CONCLUSIONS

Our study suggested that RAD51, XRCC1, and XRCC3 polymorphisms may be predictive factors for radiation-induced acute toxicity in rectal cancer patients treated with preoperative combined therapy.

Epistatic interactions among CYP2C19*2, CYP3A4 and GSTP1 on the cyclophosphamide therapy in lupus nephritis patients

AIM

To investigate the impact of genetic variants in CYP2C9, CYP2C19, CYP3A4, GSTT1, GSTM1 and GSTP1 on the efficacy of cyclophosphamide (CYC) therapy in patients with lupus nephritis.

MATERIALS & METHODS

Lupus nephritis patients (n = 220) treated with CYC were included in the study.

RESULTS

Logistic regression analysis identified CYP2C19*2 as an independent predictor of CYC therapeutic failure (odds ratio [OR]: 2.69; p = 0.0043). Bivariate and trivariate analysis showed the subjects harboring CYP2C19*2 and GSTP1 (OR: 3.25; p = 0.03), and CYP2C19*2, GSTP1 and CYP3A5*3 have synergistic influence on CYC failure (OR: 8.2; p < 0.0001). Significant decrease in AUC_0-t, C_max and t_½ of 4-OH-CYC in patients carrying CYP3A5*3 (p < 0.02).

CONCLUSION

Patients with CYP2C19*2 were at increased risk and CYP2C19*2, CYP3A5*3 and GSTP1 have synergistic influence on CYC failure.

Polymorphisms and mutations in GSTP1, RAD51, XRCC1 and XRCC3 genes in breast cancer patients

BACKGROUND

Genotoxic factors, including ionizing radiation and oxidative stress, are associated with genomic instability and development of breast cancer (BC). The homologous recombination DNA repair (HRR) pathway, base excision repair (BER) mechanism, and antioxidative enzymes are required as defense mechanisms against these DNA damaging agents. GSTP1, XRCC1, XRCC3 and RAD51 proteins are essential components of antioxidation, BER and HRR of DNA, respectively. Deficiencies in BER, HRR and antioxidation pathways are involved in the progression of cancer.

METHODS

Genomic DNA was extracted from formalin-fixed, paraffin-embedded tissue and blood samples of BC patients of an Italian population. Genomic DNA was also extracted from blood specimens of a control group. DNA sequencing was performed for six single-nucleotide polymorphisms (SNPs) in the GSTP1, RAD51, XRCC1 and XRCC3 genes in BC patients and the control group.

RESULTS

Two variants in the 5'-UTR of the XRCC3 (rs1799794 A/G) and RAD51 (rs1801321) genes showed a significant association with susceptibility to BC (OR = 4.125; 95% CI 1.057-16.102; p = 0.03 and OR = 2.04; 95% CI 0.4925-8.449; p = 0.007, respectively). Additionally, we reported 2 mutations in intron 7 of the XRCC3 gene, CTdel (rs543072564) and A/G (rs369703243).

CONCLUSIONS

Our results underscored the existence of an association between XRCC3-5'-UTR-A/G (rs1799794) and RAD51-5'-UTR G172T (rs1801321) genotypes and BC risk in an Italian population. The presence of mutations in the intronic region of the XRCC3 gene highlights the importance of more sequence screening of DNA repair genes for possible genetic penetrance in BC.

GSTP1 c.313A>G polymorphism in Russian and Polish athletes

The GSTP1 gene encodes glutathione S-transferase P1, which is a member of the glutathione S-transferases (GSTs), a family of enzymes playing an important role in detoxification and in the antioxidant defense system. There is some evidence indicating that GSTP1 c.313A>G polymorphism may be beneficial for exercise performance. Therefore, we decided to verify the association between the frequency of GSTP1 c.313A>G variants, physical performance, and athletes' status in two cohorts: in a group of Russian athletes (n = 507) and in an independent population of Polish athletes (n = 510) in a replication study. The initial association study conducted with the Russian athletes revealed that the frequency of the minor G allele was significantly higher in all athletes than in controls; that was confirmed in the replication study of Polish athletes. In the combined cohort, the differences between athletes (n = 1017) and controls (n = 1246) were even more pronounced (32.7 vs 25.0%, P < 0.0001). Our findings emphasize that the G allele of the GSTP1 gene c.313A>G single nucleotide polymorphism is associated with improved endurance performance. These observations could support the hypothesis that the GSTP1 G allele may improve exercise performance by better elimination of exercise-induced ROS.

Improving risk stratification of patients with childhood acute lymphoblastic leukemia: Glutathione-S-Transferases polymorphisms are associated with increased risk of relapse

The inclusion of genotype at Acute Lymphoblastic Leukemia (ALL) diagnosis as a genetic predictor of disease outcome is under constant study. However, results are inconclusive and seem to be population specific. We analyzed the predictive value of germline polymorphisms for childhood ALL relapse and survival. We retrospectively recruited 140 Argentine patients with de novo ALL. Genotypes were analyzed using PCR-RFLP (GSTP1 c.313A > G, MDR1 c.3435T > C, and MTHFR c.665C > T) and multiplex PCR (GSTT1 null, GSTM1 null). Patients with the GSTP1 c.313GG genotype had an increased risk for relapse in univariate (OR = 2.65, 95% CI = 1.03-6.82, p = 0.04) and multivariate (OR = 3.22, 95% CI = 1.17-8.83, p = 0.02) models. The combined genotype slightly increased risk for relapse in the univariate (OR = 2.82, 95% CI = 1.09-7.32, p = 0.03) and multivariate (OR = 2.98, 95% CI = 1.14-7.79, p = 0.03) models for patients with 2/3-risk-genotypes (GSTT1 null, GSTM1 null, GSTP1 c.313GG). The Recurrence-Free Survival (RFS) was shorter for GSTP1 c.313GG (p = 0.025) and 2/3-risk-genotypes (p = 0.021). GST polymorphisms increased the risk of relapse and RFS of patients with childhood ALL. The inclusion of these genetic markers in ALL treatment protocols might improve risk stratification and reduce the number of relapses and deaths.

GSTP1, GSTM1, and GSTT1 polymorphisms as predictors of response to chemotherapy in patients with breast cancer: a meta-analysis

Several studies have investigated the effects of polymorphisms in the GSTP1, GSTT1, and GSTM1 genes on responsiveness to chemotherapy in breast cancer, but the results have been inconsistent. The aim of this study was to determine the association between polymorphisms of GSTP1, GSTT1, and GSTM1 genes and response to chemotherapy in patients with breast cancer. The relevant studies were retrieved from PubMed, Embase, ISI Web of Knowledge, China National Knowledge Infrastructure, and Wanfang databases. The articles evaluating the correlations between response to chemotherapy and GSTP1, GSTT1, and GSTM1 polymorphisms in breast cancer patients were comprehensively reviewed. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to measure the strength of the associations. These associations were assessed with the χ ² test in this meta-analysis. Subgroup analysis by chemotherapy protocol and ethnicity were conducted to explore the source of heterogeneity among studies. A total of 14 articles with 31 studies involving GSTP1, GSTT1, and GSTM1 polymorphisms with response to chemotherapy were identified in the final meta-analysis. In the overall analysis, a significant association of GSTM1-present/GSTM1-null polymorphism with responsiveness to chemotherapy was observed in breast cancer patients (OR 0.74, CI 0.60-0.92, P = 0.006), whereas the GSTT1-present/GSTT1-null and GSTP1rs1695 polymorphisms were not significantly associated with clinical response to chemotherapy. The subgroup analysis by chemotherapy protocol indicated that the patients who harboring GSTP1rs1695 AA or AG variant had a higher response rate to anthracycline-based chemotherapy than those carrying GSTP1rs1695 GG variant [AA vs. GG: OR 0.48, CI 0.29-0.80, P < 0.05; AA vs. AG: OR 0.60, CI 0.43-0.83, P < 0.05; A vs. G: OR 0.60, CI 0.47-0.77, P < 0.05; AA vs. (AG + GG): OR 0.56, CI 0.42-0.76, P < 0.05; (AA + AG) vs. GG: OR 0.57, CI 0.34-0.94, P < 0.05]. In addition, the heterogeneity existed among studies for GSTP1 polymorphism, while no obvious heterogeneity was detected for GSTT1 and GSTM1 polymorphisms. And the heterogeneity present in different studies, evaluating the association of GSTP1 polymorphism with response to anthracycline-based chemotherapy, disappeared in breast cancer patients after subgroup analysis by chemotherapy regimen was performed. In conclusion, this meta-analysis suggested that GSTP1rs1695 and GSTM1-present/GSTM1-null polymorphisms could be considered as reliable predictors of response to anthracycline-based chemotherapy in patients with breast cancer.

Pharmacogenomics of platinum-based chemotherapy sensitivity in NSCLC: toward precision medicine

Lung cancer is one of the leading causes of cancer-related death in the world. Platinum-based chemotherapy is the first-line treatment for non-small-cell lung cancer (NSCLC), however, the therapeutic efficiency varies remarkably among individuals. A large number of pharmacogenomics studies aimed to identify genetic variations which can be used to predict platinum response. Those studies are leading NSCLC treatment to the new era of precision medicine. In the current review, we provided a comprehensive update on the main recent findings of genetic variations which can be used to predict platinum sensitivity in the NSCLC patients.

Expression profile of eight glutathione S-transferase genes in Crassostrea ariakensis after exposure to DSP toxins producing dinoflagellate Prorocentrum lima

In this study, changes in eight GSTs mRNA level including GST-α, GST-σ, GST-ω, GST-π, GST-μ, GST-ρ, GST-θ and microsomal GST (mGST) in the oyster Crassostrea ariakensis after exposure to Prorocentrum lima have been evaluated by quantitative real-time PCR. Additionally, the contents of five GST isoforms were detected by ELISA. After exposure to P. lima at density of 2 × 10(5) cells/L, mGST mRNA significantly increased in gill, while GST-σ was induced in digestive gland. After exposure to P. lima at density of 2 × 10(6) cells/L, GST-ω and mGST expressions increased in gill, whereas GST-α and GST-σ were induced in digestive gland. The GST content and activity in oysters exposed to P. lima also showed a different pattern when the different isoforms and organs were compared. After exposure to P. lima (2 × 10(6) cell/L), GST-π increased in gill but decreased in digestive gland. The total GST enzyme activity increased in gill, while remained unchanged in digestive gland. These various regulation of GST gene expressions indicated that the GSTs isoenzymes might play divergent physiological roles in the detoxification of DSP toxins in C. ariakensis.

Association of glutathione S-transferase pi (GSTP1) Ile105Val polymorphism with the risk of skin cancer: a meta-analysis

Numerous epidemiological studies have evaluated the association of Glutathione S-transferase P1 (GSTP1) Ile105Val polymorphism with the risk of skin cancer. However, the results remain inconclusive. To derive a more precise estimation of the association between the GSTP1 Ile105Val polymorphism and skin cancer risk, a meta-analysis was performed. A comprehensive search was conducted to identify the eligible studies. We used odds ratios (ORs) with 95 % confidence intervals (CIs) to assess the association of GSTP1 Ile105Val polymorphism with skin cancer risk. Thirteen case-control studies in nine articles, which included a total of 1504 cases and 2243 controls. Overall, we found that GSTP1 Ile105Val polymorphism was not associated with skin cancer risk. Furthermore, subgroup analysis by histological types showed that GSTP1 Ile105Val polymorphism was associated with risks of malignant melanoma under the dominant model (Val/Val + Val/Ile vs. Ile/Ile: OR 1.230, 95 % CI 1.017-1.488, P = 0.033). However, lack of association between GSTP1 Ile105Val polymorphism and BCC and SCC risk in all genetic models. Our meta-analysis suggested that the GSTP1 Ile105Val polymorphism might be associated with increased risk of malignant melanoma in Caucasian population.

THE GSTP1 c.313A>G POLYMORPHISM MODULATES THE CARDIORESPIRATORY RESPONSE TO AEROBIC TRAINING

The GSTP1 c.313A>G polymorphism is a candidate to explain some of the individual differences in cardiorespiratory fitness phenotypes’ responses to aerobic exercise training. We aim to explore the association between the GSTP1 c.313A>G polymorphism and the response to low-high impact aerobic exercise training. Sixty-six Polish Caucasian women were genotyped for the GSTP1 c.313A>G polymorphism; 62 of them completed 12-week aerobic (50-75% HR_max) exercise training and were measured for selected somatic features (body mass and BMI) and cardiorespiratory fitness indices – maximal oxygen uptake (VO_2max, maximum heart rate (HR_max), maximum ventilation (V_Emax) and anaerobic threshold (AT) – before and after the training period. Two-factor analysis of variance revealed a main training effect for body mass reduction (p=0.007) and BMI reduction (p=0.013), improvements of absolute and relative VO_2max (both p<0.001), and increased V_Emax (p=0.005), but not for changes in fat-free mass (FFM) (p=0.162). However, a significant training x GSTP1 c.313A>G interaction was found only for FFM (p=0.042), absolute and relative VO_2max (p=0.029 and p=0.026), and V_Emax (p=0.005). As the result of training, significantly greater improvements in VO_2max, V_Emax and FFM were gained by the GG+GA group compared to the AA genotype group. The results support the hypothesis that heterogeneity in individual response to training stimuli is at least in part determined by genetics, and GSTP1 c.313A>G may be considered as one (of what appear to be many) target polymorphisms to influence these changes.

Associations between null mutations in GSTT1 and GSTM1, the GSTP1 Ile(105)Val polymorphism, and mortality in breast cancer survivors

Purpose

Here we assessed associations between null mutations in glutathione-S-transferase (GST)T1 and GSTM1 genes, and the rs1695 polymorphism in GSTP1 (Ile¹⁰⁵Val), and risk of breast cancer-specific (n=45) and all-cause (n=99) mortality in a multiethnic, prospective cohort of 533 women diagnosed with stage I-IIIA breast cancer in 1995–1999, enrolled in the Health, Eating, Activity, and Lifestyle (HEAL) Study.

Methods

We measured the presence of the null mutation in GSTT1 and GSTM1, and the rs1695 polymorphism in GSTP1 by polymerase chain reaction. We assessed associations between breast-cancer specific and all-cause mortality using Cox proportional hazards models.

Results

Participants with ER-negative tumors were more likely to be GSTT1 null (χ²=4.52; P=0.03), and African American women were more likely to be GSTM1 null (χ²=34.36; P<0.0001). Neither GSTM1 nor GSTT1 null mutations were associated with breast cancer-specific or all-cause mortality. In a model adjusted for body mass index, race/ethnicity, tumor stage and treatment received at diagnosis, the variant Val allele of rs1695 was associated with increased risk of all-cause (HR=1.81, 95% CI 1.16-2.82, P=0.008), but not breast cancer-specific mortality. The GSTT1 null mutation was associated with significantly higher levels of C-reactive protein.

Conclusions

GSTM1 and GSTT1 null genotypes had no effect on outcome; however the variant allele of rs1695 appears to confer increased risk for all-cause mortality in breast-cancer survivors.

Given the limited sample size of most studies examining associations between GST polymorphisms with breast cancer survival, and the lack of women undergoing more contemporary treatment protocols (treated prior to 1999), it may be helpful to re-examine this issue among larger samples of women diagnosed after the late 1990s, who all received some form of chemotherapy or radiotherapy.

Predictive role of glutathione-S-transferase gene polymorphisms in risk and prognosis of hepatocellular carcinoma

AIM

We conducted a prospective study in an Chinese population to detect associations of GSTM, GSTT and GSTP polymorphisms with hepatocellular carcinoma (HCC), and analyze roles in determining survival outcome.

METHODS

A prospective follow-up study was conducted with 476 HCC patients and 481 controls collected from May 2005 to May 2007. All patients were followed up until the end of Dec. 2011. GSTM1, GSTT1 and GSTP1 genotyping were performed by PCR-CTPP methods.

RESULTS

Null GSTM1 carriers had a 1.64 fold risk of HCC compared with non-null genotype, while GSTP1 Val/Val carriers had a 93% increased risk over the GSTP1 IIe/IIe genotype. The median follow-up time for the 476 patients was 34.2 months (range: 1 to 78 months). Individuals with null GSTM1 genotype had better survival of HCC than non-null genotype carriers (HR=0.71, 95%CI=0.45-0.95). Similarly, GSTP1 Val/Val genotypes had significant better survival than the GSTP1 IIe/IIe genotype (HR=0.34, 95%CI=0.18-0.65). Individuals carrying null GSTM1 and GSTP1 Val/Val who received chemotherapy had lower risk of death from HCC than those without chemotherapy.

CONCLUSION

This study indicated carriage of null GSTM1 and GSTP1 Val/Val genotypes to have roles in susceptibility to and survival from HCC.

Association between GSTM1 and CYP1A1 polymorphisms and survival in oral cancer patients

AIMS

Cancer patient's inherited genotype may influence his or her survival, but evidence for the role of these genetic differences in oral cancer survival has not yet been explored.

METHODS

The authors evaluated polymorphisms in the GSTM1 and CYP1A1 genes for associations with overall survival in 100 oral squamous cell carcinoma (OSCC) treated patients and 100 controls who were followed up for survival within 2 years of the date of completion of their treatment. Overall survival was evaluated in Kaplan-Meier survival functions and Cox proportional hazards models.

RESULTS

After adjustment for stage and histology, GSTM1null genotype was associated with shorter survival among OSCC patients, compared with GSTM1 present genotype. There was no association between CYP1A1 C genotype and survival in the overall study population.

CONCLUSION

The study indicated a potential role for GSTM1 polymorphism in predicting the clinical outcomes of treated oral carcinoma patients.

Predictive role of glutathione-S-transferase gene polymorphisms in the survival of gastric cancer cases

AIM

We conducted a prospective study in an Chinese population to detect the association between GSTM, GSTT and GSTP gene polymorphisms and survival of gastric cancer.

METHODS

A prospective follow-up study with 317 gastric cancer patients was conducted between January 2003 and January 2005. GSTM1, GSTT1 and GSTP1 genotyping was performed using ABI TaqMan Gene Expression assays.

RESULTS

Of 317 patients, 5 were lost to follow-up due to migration, while the remaining 302 patients completed the study. The median follow-up time was 34.2 months (range: 2 to 60 months), during which a total of 120 (39.1%) died of gastric cancer. The GSTT1-null genotype showed a significant increased risk of death from gastric cancer, with an HR (95% CI) of 1.59 (1.04-3.58). Moreover, we found individuals carrying null-GSTM1 and null-GSTT1 had a moderate higher risk of death from gastric cancer, with an HR of 1.92 (1.05-3.65).

CONCLUSION

This study reported the carriage of null GSTT1 and null GSTM1 might be linked to the higher death risk from gastric cancer in Chinese population.

Glutathione transferases, regulators of cellular metabolism and physiology

BACKGROUND

The cytosolic glutathione transferases (GSTs) comprise a super family of proteins that can be categorized into multiple classes with a mixture of highly specific and overlapping functions.

SCOPE OF REVIEW

The review covers the genetics, structure and function of the human cytosolic GSTs with particular attention to their emerging roles in cellular metabolism.

MAJOR CONCLUSIONS

All the catalytically active GSTs contribute to the glutathione conjugation or glutathione dependant-biotransformation of xenobiotics and many catalyze glutathione peroxidase or thiol transferase reactions. GSTs also catalyze glutathione dependent isomerization reactions required for the synthesis of several prostaglandins and steroid hormones and the catabolism of tyrosine. An increasing body of work has implicated several GSTs in the regulation of cell signaling pathways mediated by stress-activated kinases like Jun N-terminal kinase. In addition, some members of the cytosolic GST family have been shown to form ion channels in intracellular membranes and to modulate ryanodine receptor Ca(2+) channels in skeletal and cardiac muscle.

GENERAL SIGNIFICANCE

In addition to their well established roles in the conjugation and biotransformation of xenobiotics, GSTs have emerged as significant regulators of pathways determining cell proliferation and survival and as regulators of ryanodine receptors that are essential for muscle function. This article is part of a Special Issue entitled Cellular functions of glutathione.

Glutathione-S-transferase (GST) polymorphisms are associated with relapse after radical prostatectomy

BACKGROUND

Organ confined prostate cancer (PCa) can be cured by radical retropubic prostatectomy (RRP); however, some tumors will still recur. Current tools fail to identify patients at risk of recurrence. Glutathione-S-transferases (GSTs) are involved in the metabolism of carcinogens, hormones and drugs. Thus, genetic polymorphisms that modify the GST activities may modify the risk of PCa recurrence.

METHODS

We retrospectively recruited Argentine PCa patients treated with RRP to study the association between GST polymorphisms and PCa biochemical relapse after RRP. We genotyped germline DNA in 105 patients for: GSTP1 c.313A>G (p.105 Ile>Val, rs1695) by PCR-RFLP; and GSTT1 null and GSTM1 null polymorphisms by multiplex PCR. Kaplan-Meier curves and Cox proportional hazard models were used to evaluate these associations.

RESULTS

Patients with GSTP1 c.313GG genotype showed shorter biochemical relapse-free survival (BRFS) (P = 0.003) and higher risk for recurrence in unadjusted (Hazard ratio (HR) = 3.16, 95% confidence interval (95% CI) = 1.41-7.06, P = 0.005) and multivariate models (HR = 3.01, 95% CI = 1.13-8.02, P = 0.028). We did not find significant associations for GSTT1 and GSTM1 genotypes. In addition, we found shorter BRFS (P = 0.010) and increased risk for recurrence for patients having two or more risk alleles when we combined the genotypes of the three GSTs in multivariate models (HR = 3.06, 95% CI = 1.20-7.80, P = 0.019).

CONCLUSIONS

Our results give support to the implementation of GSTs genotyping for personalized therapies as a novel alternative for PCa management for patients who undergo RRP. To the best of our knowledge, this is the first study that examined GST polymorphisms in PCa progression in Argentine men. Replication of our findings in larger cohort is warranted.

Evaluation of glutathione s-transferase as toxicity indicator for roxarsone and arsanilic acid in Eisenia fetida

Different compounds can induce stress response by targeting specific genes. Studies related to elucidating the detoxification and adaptive responses of proteins like glutathione-s-transferase (GST) can be helpful in better understanding toxicity. Roxarsone and arsanilic acid, which have been exhaustively used as animal and poultry feed additives, pose a threat to the environment and human health. GST enzyme bioassay revealed fluctuations in response to different concentrations of roxarsone and arsanilic acid at different time intervals. The highest GST enzyme activity (40.51%) was observed on day 15 of treatment with roxarsone. On the other hand, arsanilic acid caused the maximum enzyme activity (52.11%) on day 10 of treatment. During this study, the full-length gene sequence of GST, having the size 984 bp (Genbankno. HQ693699), was achieved from Eisenia fetida and established as a biomarker to assess the toxicity of roxarsone and arsanilic acid. The deduced protein has a computed molecular mass of 23.56 kDa and a predicted isoelectric point of 9.92. Quantitative real-time PCR revealed significant differential gene expression in response to roxarsone and arsanilic acid treatment as compared with control treatment. Roxarsone caused the highest gene expression of 7.0-fold increase over control on day 15 of treatment, whereas arsanilic acid resulted in the highest gene expression reaching to 14.56-fold as compared with control. This study is helpful in understanding the role of GST as a potential biomarker for chemicals like roxarsone and arsanilic acid, which can pollute the food chain.

Effects of atrazine and chlorpyrifos on activity and transcription of glutathione S-transferase in common carp (Cyprinus carpio L.)

Glutathione S-transferase isoenzymes (GSTs) play a critical role in detoxification pathways. Here we report the tissue distribution of four antioxidant GSTs gene in common carp, and their expression profiles. We also investigated the GSTs activity in different tissues after exposure to the agricultural chemicals atrazine (ATR), chlorpyrifos (CPF), and their mixture. Relative changes in the mRNA abundance of the GST isoforms were examined by real time PCR in liver, brain, kidney and gill of common carp. After exposure and recovery, we observed a statistically significant decrease in the GSTs activity in animals exposed to high concentrations of ATR (428 μg/L), CPF (116 μg/L), and their mixture (113 μg/L). At basal levels of tissue expression, four GSTs transcript were detected in liver, brain, kidney, and gill. High expression levels were found in all examined tissues. Transcription of some GST isoforms, GST kappa (GSTK), GST theta (GSTT) and GST rho (GSTR), decreased after exposure to CPF and ATR for the entire experimental period in both the kidney and gill. However, increased transcription of GST mu (GSTM) was observed in the kidney or gill 20 d after exposure to ATR or CPF, respectively. Transcription of both GSTT and GSTR was inhibited for the entire experimental period in the brain, kidney and gill of animals exposed to the ATR/CPF mixture, but transcription of GSTM was induced in the liver after 40 d of exposure. In summary, changes in the GSTs activity and their transcription varied within each organ and among organs of common carp after exposure to ATR, CPF, and their mixture.

Pharmacogenomics and metastatic colorectal cancer: current knowledge and perspectives

The pharmacogenomics field is crucial for optimizing the selection of which chemotherapy regimen to use according to the patient's genomic profile. Indeed, the individual's inherited genome accounts for a large proportion of the variation in his or her response to chemotherapeutic agents both in terms of efficiency and toxicity. Patients with metastatic disease are more likely to receive different lines of chemotherapy with variable efficacy and experience some related complications. It is therefore critical to tailor the best therapeutic arsenal to improve the efficacy and avoid as much as possible related complications that are susceptible to interrupt the treatment. The pharmacogenomics approach investigates for each drug the implicated metabolic pathway and the potential personal variations in gene function. The aim of this review is to present a clear overview of the most accurate polymorphisms that have been identified as related to drug response in patients with mCRC.

Variants of glutathione s-transferase pi 1 exhibit differential enzymatic activity and inhibition by heavy metals

Nonsynonymous single nucleotide polymorphisms in glutathione s-transferase pi 1 (GSTP1; Ile/Val 105, Ala/Val 114) have been associated with altered toxicant metabolism in epidemiological cohorts. We explored the impact of GSTP1 genotype on enzyme kinetics and heavy metal inhibition in vitro. Four GSTP1 allozymes (105/114: Ile/Ala, Val/Ala, Ile/Val, Val/Val) were expressed in and purified from Escherichia coli. Enzyme activity assays quantifying the rate of glutathione conjugation with 1-chloro-2,4-dinitrobenzene (CDNB) revealed significant differences in kinetic parameters depending on genotype (p<0.01). Allozymes with Ile105 had better catalytic efficiency and greater affinity for CDNB (mean ± SEM: Ile105 Ala114 K(m)=0.33 ± 0.07 mM vs. Val105 Ala114 K(m)=1.15 ± 0.07 mM). Inhibition of GSTP1 activity by heavy metals was assessed following treatment with mercury (inorganic-HgCl(2), methylmercury-MeHg), selenium, cadmium, lead, arsenic, and manganese. All allozymes were inhibited by HgCl(2) (IC(50) range: 24.1-172 μM), MeHg (93.9-480 μM), and selenium (43.7-62.8 μM). Genotype significantly influenced the potency of mercury with GSTP1 Ile105 Val114 the least sensitive and Val105 Ala114 the most sensitive to inhibition by HgCl(2) and MeHg. Overall, genotype of two nonsynonymous polymorphisms in GSTP1 influenced enzyme kinetics pertaining to an electrophilic substrate and inhibition by two mercury species.

Glutathione S-transferase P1 c.313A > G polymorphism could be useful in the prediction of doxorubicin response in breast cancer patients

BACKGROUND

Identification of predicting factors for anthracyclines-based chemotherapy remains a clinical challenge. Glutathione S-transferase (GSTs) enzymes detoxify chemotherapy drugs and their metabolites. Several polymorphisms in GST genes result in reduced or no activity of the enzymes. Specifically, GSTM1 and GSTT1 genes are polymorphically deleted, the polymorphism GSTP1 c.313A>G (rs1695) determines the amino acid substitution Ile105Val, where the Val-containing enzyme has reduced activity. Also, GSTA1*B allele has reduced levels of GSTA1 enzyme. Several polymorphisms in GSTs have been associated with differences in survival for cancer patients treated with chemotherapy.

PATIENTS AND METHODS

We genotyped a total of five polymorphisms in GSTM1, GSTT1, GSTP1 and GSTA1 genes in 159 patients with locally advanced breast cancer, treated with single-agent doxorubicin or docetaxel (Taxotere). Gene expression microarrays were performed in 67 breast tumor samples. We correlate this data with treatment outcome.

RESULTS

In multivariate analysis, patients homozygous GG for GSTP1 c.313A>G SNP had a lower risk of chemoresistance when treated with doxorubicin (odds ratio 0.106; confidence interval 0.012-0.898; P=0.040). No association was found in the docetaxel arm. Also, we found that GSTP1 expression varied significantly among breast cancer molecular subtypes.

CONCLUSIONS

GSTP1 may constitute another tool contributing to individualized anthracycline-based therapy.

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

Glutathione S-transferase P is abundantly expressed in some mammalian tissues, particularly those associated with malignancies. While the enzyme can catalyze thioether bond formation between some electrophilic chemicals and GSH, novel nondetoxification functions are now ascribed to it. This review summarizes recent material that implicates GSTP in mediating S-glutathionylation of specific clusters of target proteins and in reactions that define a negative regulatory role in some kinase pathways through ligand or protein:protein interactions. It is becoming apparent that GSTP participates in the maintenance of cellular redox homeostasis through a number of convergent and divergent mechanisms. Moreover, drug platforms that have GSTP as a target have produced some interesting preclinical and clinical candidates.

Overcoming drug resistance in mantle cell lymphoma using a combination of dose-dense and intense therapy

We present a study of the prevalence of genetic polymorphisms and expression of genes encoding the drug-resistance proteins glutathione S-transferases (GSTs) in order to gain insights into the pattern of failure evident in mantle cell lymphoma. We note a high preponderance of genetic alterations conferring resistance to standard chemotherapy in this illness. Concurrent with this investigation, we present a series of patients who were provided dose-dense and intense chemotherapy to circumvent these drug-resistance mechanisms. High responses were noted, though durable remissions were few, indicating non-traditional chemotherapy options are important to investigate in this illness.

Genetic polymorphism of GSTP1: prediction of clinical outcome to oxaliplatin/5-FU-based chemotherapy in advanced gastric cancer

The aim of this study was to evaluate the predictive value of the polymorphism Glutathione S-transferase P1 (GSTP1) Ile(105)Val on oxaliplatin/5-FU-based chemotherapy in advanced gastric cancer. Patients with advanced gastric cancer accepted oxaliplatin/5-FU-based chemotherapy as first-line chemotherapy were investigated. GSTP1 Ile(105)Val polymorphism was detected by TaqMan-MGB probe allelic discrimination method. Response to treatment was assessed by disease controlled rate. Time to progression, overall survival and toxicities were recorded. Final patient outcomes were as follows: the allele frequencies of GSTP1 were (105)Ile/(105)Ile 52%, (105)Ile/(105)Val 41% and (105)Val/(105)Val 7%. For patients with (105)Ile/(105)Ile and those with at least one (105)Val allele, disease control rate was 39% and 71% (P=0.026), respectively; median time to progression was 4.0 and 7.0 months (P=0.002); median overall survival time was 7.0 and 9.5 months (P=0.002). Neurological toxicity was more frequently occurred in patients with two (105)Ile alleles (P=0.005). In conclusion, patients with at least one (105)Val allele have better prognosis and response to oxaliplatin/5-FU-based regimen as first-line treatment for patients with advanced gastric cancer.

Glutathione S-transferase polymorphisms are associated with survival in anaplastic glioma patients

BACKGROUND

Glutathione S-transferases (GSTs) are polymorphic enzymes that are responsible for glutathione conjugation of alkylators and scavenging of free radicals created by radiation. GST polymorphisms may result in altered or absent enzyme activity and have been associated with survival in patients with cancer. The authors of this report hypothesized that patients with anaplastic glioma (AG) who have GST genotypes that encode for lower activity enzymes will have longer survival than similar patients who have higher activity genotypes. The current study was performed to investigate the role of GST enzyme polymorphisms in predicting the survival of patients with AG.

METHODS

The medical records of 207 patients with AG from a single cancer center were reviewed retrospectively. Polymorphisms for the GST micro1 (GSTM1), GST theta1 (GSTT1), and GST pi1 (GSTP1) enzymes were identified. Overall survival was compared using the Kaplan-Meier method and Cox proportional hazards analyses adjusting for age, sex, histology, and therapy.

RESULTS

Among the patients with oligodendroglial tumors (n = 94), patients who had the GSTT1 null genotype had a 2.9 times increased risk of death (95% confidence interval [CI], 1.3-6.3) compared with patients who had the GSTT1 non-null genotype. Adjustment for 1p/19q status did not change the finding. In the patients who had anaplastic astrocytoma (n = 113), the patients with all GSTP1 genotypes except GSTP1 *B/*B had a 3.8 times increased risk of death (95% CI, 0.5-29.6) compared with patients who had the GSTP1 *B/*B genotype.

CONCLUSIONS

In patients with anaplastic oligodendroglial tumors, the GSTT1 null genotype may be associated with poor survival, possibly because of modifications in therapy secondary to increased toxicity. This hypothesis is under investigation. In patients with anaplastic astrocytoma, the GSTP1 *B/*B genotype may confer a survival advantage.

Drug focus: Pharmacogenetic studies related to cyclophosphamide-based therapy

Cyclophosphamide is a cornerstone in the treatment of many pediatric and adult malignancies, as well as in the treatment of refractory autoimmune conditions. Genetic factors are thought to play a role in the interindividual variation in both response and toxicities associated with cyclophosphamide-based therapies. This drug focus reviews the most compelling studies conducted on the pharmacogenetics of cyclophosphamide-based therapies. Broader pharmacogenomic studies are needed and may reveal additional factors important in susceptibility to toxicity and/or response to therapy.

Association study between sick building syndrome and polymorphisms of seven human detoxification genes in the Japanese

Sick building syndrome (SBS) is a chronic disorder caused by exposure to diverse indoor environmental or chemical pollutants. This study examined the association between seven detoxification genes (CYP1A1, CYP2E1, EPHX1, GSTM1, GSTT1, GSTP1, and NAT2) and SBS in the Japanese population. One hundred eighty patients with SBS and 401 healthy controls were enrolled in this study. We examined the prevalence for total of eleven genetic polymorphisms of detoxification genes. However, no statistically significant differences in allele and genotype frequency distributions of eleven genetic polymorphisms of these detoxification genes were found between patients and controls. On this basis, we conclude that the polymorphisms that we assessed for the detoxification genes do not contribute to the etiology of SBS.

Expression profiles of seven glutathione S-transferase (GST) genes in cadmium-exposed river pufferfish (Takifugu obscurus)

Glutathione S-transferase (GST; EC 2.5.1.18) plays a critical role in detoxification pathways. In this study, we report cloning and expression of seven genes of the GST family of the pufferfish Takifugu obscurus together with mRNA tissue distribution pattern and time-course of expression in response to exposure to cadmium. At basal levels of tissue expression, GST-Mu is highly expressed in liver compared with other tissues. When fish were exposed to cadmium (5 mg/L for 96 h), expression of GST-MAPEG, GST-Mu, GST-Omega, and GST-Zeta was greatly increased, whereas GST-Alpha and GST-Kappa genes showed no significant response. These findings suggest that gene expression of a number of GST isoforms in T. obscurus is modulated in response to exposure to cadmium. We propose GST-Mu, GST-Theta, and GST-Zeta as candidate biomarkers for heavy metal exposure in this fish.

Glutathione S-transferase polymorphisms and survival in African-American and white colorectal cancer patients

BACKGROUND

Glutathione S-transferase (GST) enzymes are involved in electrophile detoxification. The authors investigated the association between GST genotype and survival in a racially diverse, population-based cohort of colorectal cancer (CRC) patients followed for a median of 9.6 years.

METHODS

Interviews were conducted with 315 African-American and White CRC patients in Connecticut, 1987-1991. Tumor tissue (n=197) was later retrieved from hospital of diagnosis and assayed using multiplex PCR (GSTM1 and GSTT1) and PCR and RFLP analysis (GSTP1). Cox proportional hazards models provided adjusted hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Individuals with Ile/Val or Val/Val GSTP1 genotypes had a decreased risk of death (multivariate adjusted HR=0.72, 95% CI: 0.48, 1.09) relative to those with wild type (Ile/Ile). Among those who received chemotherapy, this benefit was more pronounced (HR=0.35, 95% CI: 0.16, 0.79); the interaction of reduced function GSTP1 genotype and chemotherapy was significant (P=0.05). GSTM1 and GSTT1 genotype were not associated with survival. GSTM1, GSTT1, and GSTP1 genotype did not vary by race and did not contribute significantly to the survival disadvantage observed in African-Americans.

CONCLUSIONS

In summary, GSTP1 genotype may play a role in CRC survival in African-Americans and Whites, particularly among those who receive chemotherapy.

Pharmacogenetics of fluoropyrimidine and cisplatin. A future application to gastric cancer treatment

Chemotherapy plays an important role in the treatment of gastric cancer both in adjuvant or advanced settings. Recent randomized trials in Japan have proved that S-1, a novel fluoropyrimidine derivative, and cisplatin are the most promising agents. However, both the efficacy and toxicity of a given regimen vary widely among patients due to the inherited variability of genes that involve drug anabolism and catabolism. A narrow therapeutic index of antitumor agents, i.e. a given regimen being too toxic and/or less effective to some segment of patients, prevents the overall improvement of treatment outcomes. Pharmacogenetics, a research field elucidating genetic polymorphism in drug metabolizing enzymes, may contribute to identifying patients who benefit from chemotherapy or who will experience life-threatening toxicity. There are several crucial enzymes identified involving anabolism and the catabolism of fluoropyrimidine and cisplatin, including dihydropyrimidine dehydrogenase, thymidylate synthase, orotate phosphoribosyl transferase, glutathione S transferase, and excision repair cross complementary group. Various polymorphisms and ethnic variabilities of these genes have been elucidated. This review highlights variations within biological functions, detection systems, and possible clinical applications of these enzymatic polymorphisms. This knowledge provides a tool to determine an optimum regimen according to the patient's drug metabolizing characteristics. This stance will contribute to establishing individualized therapies for gastric cancer, which offers superior efficacy with a minimal chance of severe toxicity.

Genetic Polymorphism in Glutathione Transferases (GST): Population distribution of GSTM1, T1, and P1 conjugating activity

Glutathione transferases (GST) catalyze the conjugation of glutathione (GSH) with electrophiles, many of which may otherwise interact with protein or DNA. In select cases such as halogenated solvents, GST-mediated conjugation may lead to a more toxic or mutagenic metabolite. Polymorphisms that exert substantial effects on GST function were noted in human populations for several isozymes. This analysis focuses on three well-characterized isozymes, GSTM1, T1, and P1, in which polymorphisms were extensively studied with respect to DNA adducts and cancer in molecular epidemiologic studies. The current review and analysis focused upon how polymorphisms in these GST contributed to population variability in GST function. The first step in developing this review was to characterize the influence of genotype on phenotype (enzyme function) and the frequency of the polymorphisms across major population groups for all three GST. This information was then incorporated into Monte Carlo simulations to develop population distributions of enzyme function. These simulations were run separately for GSTM1, T1, and P1, and also for the combination of these isozymes, to assess the possibility of overlapping substrate specificity. Monte Carlo simulations indicated large interindividual variability for GSTM1 and T1 due to the presence of the null (zero activity) genotype, which is common in all populations studied. Even for GSTM1 or T1 non-null individuals, there was considerable interindividual variability with a bimodal distribution of enzyme activity evident. GSTP1 polymorphisms are associated with somewhat less variability due to the absence of null genotypes. However, in all cases simulated, the estimated variability is sufficiently large to warrant consideration of GST function distributions in assessments involving GST-mediated activation or detoxification of xenobiotics. Ideally, such assessments would involve physiologically based toxicokinetic (PBTK) modeling to assess population variability in internal dose.

The influence of genetic polymorphisms on population variability in six xenobiotic-metabolizing enzymes

This review provides variability statistics for polymorphic enzymes that are involved in the metabolism of xenobiotics. Six enzymes were evaluated: cytochrome P-450 (CYP) 2D6, CYP2E1, aldehyde dehydrogenase-2 (ALDH2), paraoxonase (PON1), glutathione transferases (GSTM1, GSTT1, and GSTP1), and N-acetyltransferases (NAT1 and NAT2). The polymorphisms were characterized with respect to (1) number and type of variants, (2) effects of polymorphisms on enzyme function, and (3) frequency of genotypes within specified human populations. This information was incorporated into Monte Carlo simulations to predict the population distribution and describe interindividual variability in enzyme activity. The results were assessed in terms of (1) role of these enzymes in toxicant activation and clearance, (2) molecular epidemiology evidence of health risk, and (3) comparing enzyme variability to that commonly assumed for pharmacokinetics. Overall, the Monte Carlo simulations indicated a large degree of interindividual variability in enzyme function, in some cases characterized by multimodal distributions. This study illustrates that polymorphic metabolizing systems are potentially important sources of pharmacokinetic variability, but there are a number of other factors including blood flow to liver and compensating pathways for clearance that affect how a specific polymorphism will alter internal dose and toxicity. This is best evaluated with the aid of physiologically based pharmacokinetic (PBPK) modeling. The population distribution of enzyme activity presented in this series of articles serves as inputs to such PBPK modeling analyses.

Polymorphisms of drug-metabolizing enzymes (GST, CYP2B6 and CYP3A) affect the pharmacokinetics of thiotepa and tepa

AIMS

Thiotepa is widely used in high-dose chemotherapy. Previous studies have shown relations between exposure and severe organ toxicity. Thiotepa is metabolized by cytochrome P450 and glutathione S-transferase enzymes. Polymorphisms of these enzymes may affect elimination of thiotepa and tepa, its main metabolite. The purpose of this study was to evaluate effects of known allelic variants in CYP2B6, CYP3A4, CYP3A5, GSTA1 and GSTP1 genes on pharmacokinetics of thiotepa and tepa.

METHODS

White patients (n = 124) received a high-dose regimen consisting of cyclophosphamide, thiotepa and carboplatin as intravenous infusions. Genomic DNA was analysed using polymerase chain reaction and sequencing. Plasma concentrations of thiotepa and tepa were determined using validated GC and LC-MS/MS methods. Relations between allelic variants and elimination pharmacokinetic parameters were evaluated using nonlinear mixed effects modelling (nonmem).

RESULTS

The polymorphisms CYP2B6 C1459T, CYP3A4*1B, CYP3A5*3, GSTA1 (C-69T, G-52A) and GSTP1 C341T had a significant effect on clearance of thiotepa or tepa. Although significant, most effects were generally not large. Clearance of thiotepa and tepa was predominantly affected by GSTP1 C341T polymorphism, which had a frequency of 9.3%. This polymorphism increased non-inducible thiotepa clearance by 52% [95% confidence interval (CI) 41, 64, P < 0.001] and decreased tepa clearance by 32% (95% CI 29, 35, P < 0.001) in heterozygous patients, which resulted in an increase in combined exposure to thiotepa and tepa of 45% in homozygous patients.

CONCLUSIONS

This study indicates that the presently evaluated variant alleles explain only a small part of the substantial interindividual variability in thiotepa and tepa pharmacokinetics. Patients homozygous for the GSTP1 C341T allele may have enhanced exposure to thiotepa and tepa.

Influence of glutathione S-transferase polymorphisms on cognitive functioning effects induced by p,p'-DDT among preschoolers

BACKGROUND

Early-life exposure to p,p'-DDT [2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane] is associated with a decrease in cognitive skills among preschoolers at 4 years of age. We hypothesized that genetic variability in glutathione S-transferase (GST) genes (GSTP1, GSTM1, and GSTT1) could influence the effects of prenatal exposure to p,p'-DDT.

METHODS

We used data from 326 children assessed in a prospective population-based birth cohort at the age of 4 years. In that study, the McCarthy Scales of Children's Abilities were administrated by psychologists, organochlorine compounds were measured in cord serum, and genotyping was conducted for the coding variant Ile105Val from GSTP1 and for null alleles from GSTM1 and GSTT1. We used linear regression models to measure the association between organochlorines and neurodevelopmental scores by GST polymorphisms.

RESULTS

p,p'-DDT cord serum concentration was inversely associated with general cognitive, memory, quantitative, and verbal skills, as well as executive function and working memory, in children who had any GSTP1 Val-105 allele. GSTP1 polymorphisms and prenatal p,p'-DDT exposure showed a statistically significant interaction for general cognitive skills (p = 0.05), quantitative skills (p = 0.02), executive function (p = 0.01), and working memory (p = 0.02). There were no significant associations between p,p'-DDT and cognitive functioning at 4 years of age according to GSTM1 and GSTT1 polymorphisms.

CONCLUSIONS

Results indicate that children with GSTP1 Val-105 allele were at higher risk of the adverse cognitive functioning effects of prenatal p,p'-DDT exposure.