Cancer drugs, genetic variation and the glutathione-S-transferase gene family

Comprehensive analysis of the prognostic value of glutathione S-transferases Mu family members in breast cancer

Breast cancer (BC) remains a significant public health concern globally, with a high number of reported cases and a substantial number of deaths every year. Accumulating reactive oxygen species (ROS) and oxidative stress are related to BC and the Glutathione S-transferases Mu (GSTM) family is one of the most important enzymatic detoxifiers associated with many cancers. In this study, UALCAN, Kaplan-Meier plotter, bc-GenExMiner, cBioPortal, STRING, Enrichr, and TIMER databases were employed to carry out a comprehensive bioinformatic analysis and provide new insight into the prognostic value of GSTMs in BC. GSTM2-5 genes in mRNA and protein levels were found to be expressed at lower levels in breast tumors compared to normal tissues, and reduction in mRNA levels is linked to shorter overall survival (OS) and relapse-free survival (RFS). The lower mRNA levels of GSTMs were strongly associated with the worse Scarff-Bloom-Richardson (SBR) grades (p < 0.0001). The mRNA levels of all five GSTMs were substantially higher in estrogen receptor (ER)-positive and progesterone receptor (PR)-positive compared to ER-negative and PR-negative BC patients. As well, when nodal status was compared, GSTM1, GSTM3, and GSTM5 were significantly higher in nodal-positive BC patients (p < .01). Furthermore, GSTM4 had the most gene alteration (4%) among other family members, and GSTM5 showed the strongest correlation with CD4+ T cells (Cor= .234, p = 2.22e-13). In conclusion, our results suggest that GSTM family members may be helpful as biomarkers for prognosis and as therapeutic targets in BC.

Unravelling the complexities of non-alcoholic steatohepatitis: The role of metabolism, transporters, and herb-drug interactions

Nonalcoholic fatty liver disease (NAFLD) is a mainstream halting liver disease with high prevalence in North America, Europe, and other world regions. It is an advanced form of NAFLD caused by the amassing of fat in the liver and can progress to the more severe form known as non-alcoholic steatohepatitis (NASH). Until recently, there was no authorized pharmacotherapy reported for NASH, and to improve the patient's metabolic syndrome, the focus is mainly on lifestyle modification, weight loss, ensuring a healthy diet, and increased physical activity; however, the recent approval of Rezdiffra (Resmetirom) by the US FDA may change this narrative. As per the reported studies, there is an increased articulation of uptake and efflux transporters of the liver, including OATP and MRP, in NASH, leading to changes in the drug's pharmacokinetic properties. This increase leads to alterations in the pharmacokinetic properties of drugs. Furthermore, modifications in Cytochrome P450 (CYP) enzymes can have a significant impact on these properties. Xenobiotics are metabolized primarily in the liver and constitute liver enzymes and transporters. This review aims to delve into the role of metabolism, transport, and potential herb-drug interactions in the context of NASH.

The glutathione S-transferase Gstt1 drives survival and dissemination in metastases

Identifying the adaptive mechanisms of metastatic cancer cells remains an elusive question in the treatment of metastatic disease, particularly in pancreatic cancer (pancreatic adenocarcinoma, PDA). A loss-of-function shRNA targeted screen in metastatic-derived cells identified Gstt1, a member of the glutathione S-transferase superfamily, as uniquely required for dissemination and metastasis, but dispensable for primary tumour growth. Gstt1 is expressed in latent disseminated tumour cells (DTCs), is retained within a subpopulation of slow-cycling cells within existing metastases, and its inhibition leads to complete regression of macrometastatic tumours. This distinct Gstt1high population is highly metastatic and retains slow-cycling phenotypes, epithelial-mesenchymal transition features and DTC characteristics compared to the Gstt1low population. Mechanistic studies indicate that in this subset of cancer cells, Gstt1 maintains metastases by binding and glutathione-modifying intracellular fibronectin, in turn promoting its secretion and deposition into the metastatic microenvironment. We identified Gstt1 as a mediator of metastasis, highlighting the importance of heterogeneity and its influence on the metastatic tumour microenvironment.

Potential antitumour effect of all-trans retinoic acid on regorafenib-treated human colon cancer cell lines

Introduction

Colorectal cancer (CRC) is a significant contributor to cancer-related mortality worldwide, ranking as the second leading cause of such deaths. Central to the progression of this malignancy is angiogenesis - a complex process orchestrated by vascular endothelial growth factor (VEGF). Regorafenib, a potent multikinase inhibitor, acts as a critical antagonist of multiple kinases involved in angiogenesis, proliferation, and metastasis. Conversely, all-trans retinoic acid (ATRA) has demonstrated compelling antitumour effects across various cancer types. This study aims to comprehensively evaluate the combined antitumour potential of ATRA and regorafenib in human colon cancer cell lines while elucidating the intricate molecular mechanisms that underlie their action.

Material and methods

Our investigative approach involved an enzyme-linked immunosorbent assay to meticulously analyse the levels of key players in the VEGF signalling pathway, including VEGF itself, activated protein kinase (AMPK), extracellular signal-regulated protein kinase 1 (ERK1), and nuclear factor kappa B (NF-κB). Additionally, we assessed caspase-3 activity as a fundamental marker of apoptosis.

Results

The combined use of ATRA and regorafenib exhibited a remarkable augmentation in both AMPK and caspase-3 activities. This was accompanied by a significant reduction in VEGF, ERK1, and NF-κB levels within human colon cancer cell lines subjected to regorafenib treatment.

Conclusions

Our findings underscore the remarkable antiproliferative, antiangiogenic, and proapoptotic effects resulting from the combined use of ATRA and regorafenib in the context of CRC. This modulation of tumourigenic processes is predominantly mediated through the VEGF signalling axis.

Genotoxicity of cytokines at chemotherapy-induced 'storm' concentrations in a model of the human bone marrow

Donor cell leukaemia (DCL) is a complication of haematopoietic stem cell transplantation where donated cells become malignant within the patient's bone marrow. As DCL predominates as acute myeloid leukaemia, we hypothesized that the cytokine storm following chemotherapy played a role in promoting and supporting leukaemogenesis. Cytokines have also been implicated in genotoxicity; thus, we explored a cell line model of the human bone marrow (BM) to secrete myeloid cytokines following drug treatment and their potential to induce micronuclei. HS-5 human stromal cells were exposed to mitoxantrone (MTX) and chlorambucil (CHL) and, for the first time, were profiled for 80 cytokines using an array. Fifty-four cytokines were detected in untreated cells, of which 24 were upregulated and 10 were downregulated by both drugs. FGF-7 was the lowest cytokine to be detected in both untreated and treated cells. Eleven cytokines not detected at baseline were detected following drug exposure. TNFα, IL6, GM-CSF, G-CSF, and TGFβ1 were selected for micronuclei induction. TK6 cells were exposed to these cytokines in isolation and in paired combinations. Only TNFα and TGFβ1 induced micronuclei at healthy concentrations, but all five cytokines induced micronuclei at storm levels, which was further increased when combined in pairs. Of particular concern was that some combinations induced micronuclei at levels above the mitomycin C positive control; however, most combinations were less than the sum of micronuclei induced following exposure to each cytokine in isolation. These data infer a possible role for cytokines through chemotherapy-induced cytokine storm, in the instigation and support of leukaemogenesis in the BM, and implicate the need to evaluate individuals for variability in cytokine secretion as a potential risk factor for complications such as DCL.

The Multifaceted Role of Glutathione S-Transferases in Health and Disease

In humans, the cytosolic glutathione S-transferase (GST) family of proteins is encoded by 16 genes presented in seven different classes. GSTs exhibit remarkable structural similarity with some overlapping functionalities. As a primary function, GSTs play a putative role in Phase II metabolism by protecting living cells against a wide variety of toxic molecules by conjugating them with the tripeptide glutathione. This conjugation reaction is extended to forming redox sensitive post-translational modifications on proteins: S-glutathionylation. Apart from these catalytic functions, specific GSTs are involved in the regulation of stress-induced signaling pathways that govern cell proliferation and apoptosis. Recently, studies on the effects of GST genetic polymorphisms on COVID-19 disease development revealed that the individuals with higher numbers of risk-associated genotypes showed higher risk of COVID-19 prevalence and severity. Furthermore, overexpression of GSTs in many tumors is frequently associated with drug resistance phenotypes. These functional properties make these proteins promising targets for therapeutics, and a number of GST inhibitors have progressed in clinical trials for the treatment of cancer and other diseases.

GSTP1 as a novel target in radiation induced lung injury

The glutathione S-transferase P1(GSTP1) is an isoenzyme in the glutathione-S transferases (GSTs) enzyme system, which is the most abundant GSTs expressed in adult lungs. Recent research shows that GSTP1 is closely related to the regulation of cell oxidative stress, inhibition of cell apoptosis and promotion of cytotoxic metabolism. Interestingly, there is evidence that GSTP1 single nucleotide polymorphisms (SNP) 105Ile/Val related to the risk of radiation induced lung injury (RILI) development, which strongly suggests that GSTP1 is closely associated with the occurrence and development of RILI. In this review, we discuss our understanding of the role of GSTP1 in RILI and its possible mechanism.

Genetic polymorphisms on the effectiveness or safety of breast cancer treatment: Clinical relevance and future perspectives

Breast cancer (BC) is the most frequent neoplasm and one of the main causes of death in women. The pharmacological treatment of BC consists of hormonal therapy, chemotherapeutic agents and targeted therapy. The response to BC therapy is highly variable in clinical practice. This variability can be explained by the presence of genetic polymorphisms in genes involved in the pharmacokinetics, pharmacodynamics or immune response of patients. The abundant evidence of associations between low-activity alleles CYP2D6*3, *4, *5, *6, *10 and *41 and poor results with tamoxifen therapy, and between DPYD gene polymorphisms rs3918290, rs55886062, rs67376798 and rs75017182 and increased risk of toxicity to fluoropyrimidine therapy, justify the existence of clinical pharmacogenetic guidelines. The NQO1 rs1800566 polymorphism is related to poorer results in BC therapy with chemotherapy agents. The polymorphism rs1695 of the GSTP1 gene has been associated with the effectiveness and toxicity of fluorouracil, cyclophosphamide and epirubicin therapy. Finally, the HLA-DQA1*02:01 allele is significantly associated with the occurrence of liver toxicity events in patients receiving lapatinib. There is moderate evidence to support the aforementioned associations and, therefore, a high probability of these being considered as future predictive genetic biomarkers of response. However, further studies are required to reinforce or clarify their clinical relevance.

Glutathione-S-transferases genes-promising predictors of hepatic dysfunction

One of the most commonly known genes involved in chronic diffuse liver diseases pathogenesis are genes that encodes the synthesis of glutathione-S-transferase (GST), known as the second phase enzyme detoxification system that protects against endogenous oxidative stress and exogenous toxins, through catalisation of glutathione sulfuric groups conjugation and decontamination of lipid and deoxyribonucleic acid oxidation products. The group of GST enzymes consists of cytosolic, mitochondrial and microsomal fractions. Recently, eight classes of soluble cytoplasmic isoforms of GST enzymes are widely known: α-, ζ-, θ-, κ-, μ-, π-, σ-, and ω-. The GSTs gene family in the Human Gene Nomenclature Committee, online database recorded over 20 functional genes. The level of GSTs expression is considered to be a crucial factor in determining the sensitivity of cells to a broad spectrum of toxins. Nevertheless, human GSTs genes have multiple and frequent polymorphisms that include the complete absence of the GSTM1 or the GSTT1 gene. Current review supports the position that genetic polymorphism of GST genes is involved in the pathogenesis of various liver diseases, particularly non-alcoholic fatty liver disease, hepatitis and liver cirrhosis of different etiology and hepatocellular carcinoma. Certain GST allelic variants were proven to be associated with susceptibility to hepatological pathology, and correlations with the natural course of the diseases were subsequently postulated.

Elevated exposure to polycyclic aromatic hydrocarbons (PAHs) may trigger cancers in Pakistan: an environmental, occupational, and genetic perspective

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic compounds which are emitted through incomplete combustion of organic materials, fossil fuels, consumption of processed meat, smoked food, and from various industrial activities. High molecular mass and mobility make PAHs widespread and lethal for human health. A cellular system in human detoxifies these toxicants through specialized enzymatic machinery called xenobiotic-metabolizing (CYP450) and phase-II (GSTs) enzymes (XMEs). These metabolizing enzymes include cytochromes P450 family (CYP1, CYP2), glutathione s-transferases, and ALDHs. Gene polymorphisms in XMEs encoding genes can compromise their metabolizing capacity to detoxify ingested carcinogens (PAHs etc.) that may lead to prolong and elevated exposure to ingested toxicants and may consequently lead to cancer. Moreover, PAHs can induce cancer through reprograming XMEs' gene functions by altering their epigenetic markers. This review article discusses possible interplay between individual's gene polymorphism in XMEs' genes, their altered epigenetic markers, and exposure to PAHs in cancer susceptibility in Pakistan.

In Vitro and in Vivo Efficacy of NBDHEX on Gefitinib-resistant Human Non-small Cell Lung Cancer

Gefitinib, a first-generation EGFR tyrosine kinase inhibitor (EGFR-TKI), is recommended for treatment of non-small cell lung cancer (NSCLC) patients who harbor activating EGFR mutations. However, the tumors of most patients initially sensitive to gefitinib will develop resistance within several months of therapy. Drug resistance is a major obstacle to NSCLC treatment. The novel glutathione transferase P1 (GSTPi) inhibitor 6-(7-nitro-2, 1, 3-benzoxadiazol-4-ylthio) hexanol (NBDHEX) has recently been shown to be active against tumors. In this study, we investigated the in vitro and in vivo efficacy of NBDHEX against NSCLC. Treatment with NBDHEX inhibited GSTpi enzymatic activity and promoted apoptosis of gefinitb-resistant NSCLC cells. Moreover, NBDHEX reduced tumor growth in mice. These findings indicated that NBDHEX is a good candidate for treatment of NSCLC patients, and that NBDHEX offers a new approach to cancer therapy.

Possible Susceptibility Genes for Intervention against Chemotherapy-Induced Cardiotoxicity

Recent therapeutic advances have significantly improved the short- and long-term survival rates in patients with heart disease and cancer. Survival in cancer patients may, however, be accompanied by disadvantages, namely, increased rates of cardiovascular events. Chemotherapy-related cardiac dysfunction is an important side effect of anticancer therapy. While advances in cancer treatment have increased patient survival, treatments are associated with cardiovascular complications, including heart failure (HF), arrhythmias, cardiac ischemia, valve disease, pericarditis, and fibrosis of the pericardium and myocardium. The molecular mechanisms of cardiotoxicity caused by cancer treatment have not yet been elucidated, and they may be both varied and complex. By identifying the functional genetic variations responsible for this toxicity, we may be able to improve our understanding of the potential mechanisms and pathways of treatment, paving the way for the development of new therapies to target these toxicities. Data from studies on genetic defects and pharmacological interventions have suggested that many molecules, primarily those regulating oxidative stress, inflammation, autophagy, apoptosis, and metabolism, contribute to the pathogenesis of cardiotoxicity induced by cancer treatment. Here, we review the progress of genetic research in illuminating the molecular mechanisms of cancer treatment-mediated cardiotoxicity and provide insights for the research and development of new therapies to treat or even prevent cardiotoxicity in patients undergoing cancer treatment. The current evidence is not clear about the role of pharmacogenomic screening of susceptible genes. Further studies need to done in chemotherapy-induced cardiotoxicity.

Therapeutic effect of hydrogen peroxide via altered expression of glutathione S-transferase and peroxiredoxin-2 in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) has a high incidence and mortality that epitomizes one of the prominent causes of cancer-related death globally. Novel therapeutic approaches are therefore required. Reactive oxygen species (ROS) are necessary for maintaining cell cycle. Although ROS is involved in HCC progression, hydrogen peroxide (H₂O₂) has anti-proliferative effect on HCC.

METHOD

HCC Huh-7 cells were cultured and incubated with various concentrations of H₂O₂. Paraoxonase activity, levels of malondialdehyde, glutathione and protein oxidation were measured in treated and untreated Huh-7 cells. Furthermore, untreated and treated Huh-7 cells were subjected to two dimensional gel electrophoresis and identified protein spots which were differentially expressed by LC-MS/MS analysis. qRT-PCR was performed to validate the identified proteins.

RESULTS

H₂O₂ depleted glutathione (GSH) with the concomitant up-regulation of GSTP1 and Prx2. H₂O₂ also increased malondialdehyde and protein oxidation, decreased the activity of paraoxonase in Huh-7 cells.

CONCLUSION

H₂O₂ could be used as a novel therapeutic agent that might be beneficial in inducing cell cytotoxicity and hence suppress HCC proliferation.

Proteomic landscape of liver tissue in old male mice that are long-term treated with polysaccharides from Sargassum fusiforme

Sargassum fusiforme is a type of brown algae and well known as a longevity promoting vegetable in Northeastern Asia. The polysaccharides derived from Sargassum fusiforme (SFPs) have been suggested as an antioxidant component for anti-aging function. However, global molecular changes in vivo by SFPs have not been fully elucidated. Here, we present a proteomics study using liver tissues of aged male mice that were fed with SFPs. Of forty-nine protein spots, thirty-eight were up-regulated and eleven were down-regulated, showing significant changes in abundance by two-dimensional gel electrophoresis. These differentially expressed proteins were mainly involved in oxidation-reduction, amino acid metabolism, and energy metabolism. Forty-six proteins were integrated into a unified network, with catalase (Cat) at the center. Intriguingly, most of the proteins were speculated as mitochondrial-located proteins. Our findings suggested that SFPs modulated antioxidant enzymes to scavenge redundant free radicals, thus preventing oxidative damage. In conclusion, our study provides a proteomic view on how SFPs have beneficial effects on the aspects of antioxidant and energy metabolism during the aging process. This study facilitates the understanding of anti-aging molecular mechanisms in polysaccharides derived from Sargassum fusiforme.

In vitro interaction of glutathione S-transferase-pi enzyme with glutathione-coated silver sulfide quantum dots: A novel method for biodetection of glutathione S-transferase enzyme

Quantum dots (QD) are being evaluated as inorganic nanoparticles for both in vitro and in vivo optical imaging. They are also used as sensors or vehicles for targeted drug delivery combined with optical imaging. In this study, we demonstrated that glutathione-coated Ag₂ S QDs (GSH-Ag₂ S QDs) act as a substrate analogue of glutathione S-transferase (GST) enzymes for the first time in the literature. The GSTs belong to a major group of detoxification enzymes involved in the detoxification metabolism responsible for the protection of cells against reactive oxygen species (ROS) or electrophiles. GST isozymes are impaired in the various diseases such as neurological diseases and cancer. We evaluated the interaction of GST-pi enzyme with GSH-Ag₂ S QDs, which have never been studied in the literature before, using both fluorometric and spectrophotometric methods. Our data showed that GSH-Ag₂ S QDs gave reaction with GST enzyme as a substrate analogue. In conclusion, our data may help to guide researchers for further development of sensing systems for GST activity which is impaired in various diseases including cancer.

Glutathione S-transferase genes variants and glioma risk: A case-control and meta-analysis study

Background: The glutathione S-transferase (GST) genes encode enzymes that metabolize carcinogenic compounds, and their variants, GSTP1 (Ile105Val and Ala114Val), GSTT1 (null/present), and GSTM1 (null/present), reduce enzyme activity that may affect the risk of developing cerebral glioma. This study undertook a case-control study and a meta-analysis to evaluate associations between these GST gene variants and the risk of glioma. Methods: The study enrolled 384 glioma patients (194 men and 190 women; mean age, 48.3 ± 9.2 years) and 340 healthy controls (174 men and 166 women; mean age, 46.5 ± 9.8 years). The amplification refractory mutation system assay was performed to identify GST gene variants of all 724 subjects. A meta-analysis enrolled 15 studies (including our case-control results) was performed. Results: Our case-control study found that the frequency of GSTP1 Ile105Val Val/Val genotype was significantly higher in the glioma group than that in the healthy controls (11.7% vs. 6.4%) (OR=1.50; 95% CI=1.05-2.04; P=0.01); the frequency of the Val/Ile + Ile/Ile genotypes was different from glioma patients and controls (88.3% vs. 93.6%) (OR=1.47(1.04-2.10); P=0.015); there were no associations between GSTP1 Ala114Val, GSTT1 (null/present) and GSTM1 (null/present) variants and glioma risk. Our meta-analysis confirmed that the GSTP1 Ile105Val variant was associated with an overall increased glioma risk. Moreover, our meta-analysis also confirmed the GSTP1 Ala114Val and GSTT1 null/present variants were associated with an increased glioma risk in the Caucasian population, rather than the Asian population. Conclusions: This study showed that GST gene variants were associated with an increased risk of glioma with ethnic differences. Future large-scale, multi center, controlled, prospective studies are required to support these findings and to determine how these GST gene variants may affect the pathogenesis of glioma.

GSTO1 acts as a mediator in sodium fluoride-induced alterations of learning and memory related factors expressions in the hippocampus cell line

The mechanism of GSTO1, as a high-risk factor for neurological damage, in sodium fluoride (NaF)-induced learning and memory impairment remained still unclear. Hence, in this study, we used the siRNA-GSTO1 HT22 model to explore the effect of NaF and siRNA-GSTO1 on the viability, and proliferation rate of HT22 cells, as well as the mRNA and protein expression levels of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB), neural cell adhesion molecule (NCAM), stem cell factor (SCF) and brain-derived neurotrophic factor (BDNF). The results of MTT showed that 10^-3, 10^-4, and 10^-5 moL/L sodium fluoride (NaF) exposure could significantly promote the proliferation of HT22 cells at 24 h, 36 h, and 48 h, respectively. In addition, our results showed that exposure to 10^-3, 10^-4, and 10^-5 moL/l NaF increased GSTO1 mRNA and protein expression, but decreased CREB and BDNF expression levels in a dose and time-dependent manner. The mRNA and protein expressions of GSTO1, CREB and BDNF were significantly decreased in the siRNA-GSTO1 and NaF + siRNA-GSTO1 group (P < 0.05). We have shown that various NaF doses affected the learning and memory ability by down-regulation the expressions of CREB, BDNF, NCAM and SCF. In summary, we concluded that GSTO1 plays a mediator role in NaF-induced neurological damage.

Progressive obesity alters ovarian insulin, phosphatidylinositol-3 kinase, and chemical metabolism signaling pathways and potentiates ovotoxicity induced by phosphoramide mustard in mice

Mechanisms underlying obesity-associated reproductive impairment are ill defined. Hyperinsulinemia is a metabolic perturbation often observed in obese subjects. Insulin activates phosphatidylinositol 3-kinase (PI3K) signaling, which regulates ovarian folliculogenesis, steroidogenesis, and xenobiotic metabolism. The impact of progressive obesity on ovarian genes encoding mRNA involved in insulin-mediated PI3K signaling and xenobiotic biotransformation [insulin receptor (Insr), insulin receptor substrate 1 (Irs1), 2 (Irs2), and 3 (Irs3); kit ligand (Kitlg), stem cell growth factor receptor (Kit), protein kinase B (AKT) alpha (Akt1), beta (Akt2), forkhead transcription factor (FOXO) subfamily 1 (Foxo1), and subfamily 3 (Foxo3a), microsomal epoxide hydrolase (Ephx1), cytochrome P450 family 2, subfamily E, polypeptide 1 (Cyp2e1), glutathione S-transferase (GST) class Pi (Gstp1) and class mu 1 (Gstm1)] was determined in normal wild-type nonagouti (a/a; lean) and lethal yellow mice (KK.CG-Ay/J; obese) at 6, 12, 18, or 24 weeks of age. At 6 weeks, ovaries from obese mice had increased (P < 0.05) Insr and Irs3 but decreased (P < 0.05) Kitlg, Foxo1, and Cyp2e1 mRNA levels. Interestingly, at 12 weeks, an increase (P < 0.05) in Kitlg and Kit mRNA, pIRS1Ser302, pAKTThr308, EPHX1, and GSTP1 protein level was observed due to obesity, while Cyp2e1 mRNA and protein were reduced. A phosphoramide mustard (PM) challenge increased (P < 0.05) ovarian EPHX1 protein abundance in lean but not obese females. In addition, lung tissue from PM-exposed animals had increased (P < 0.05) EPHX1 protein with no impact of obesity thereon. Taken together, progressive obesity affected ovarian signaling pathways potentially involved in obesity-associated reproductive disorders.

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.

Glutathione transferases: substrates, inihibitors and pro-drugs in cancer and neurodegenerative diseases

Glutathione transferase classical GSH conjugation activity plays a critical role in cellular detoxification against xenobiotics and noxious compounds as well as against oxidative stress. However, this feature is also exploited by cancer cells to acquire drug resistance and improve their survival. As a result, various members of the family were found overexpressed in a number of different cancers. Moreover several GST polymorphisms, ranging from null phenotypes to point mutations, were detected in members of the family and found to correlate with the onset of neuro-degenerative diseases. In the last decades, a great deal of research aimed at clarifying the role played by GSTs in drug resistance, at developing inhibitors to counteract this activity but also at exploiting GSTs for prodrugs specific activation in cancer cells. Here we summarize some of the most important achievements reached in this lively area of research.

GSTP1 polymorphism predicts treatment outcome and toxicities for breast cancer

This study aimed to investigate the association of the GSTP1 gene polymorphism with the outcomes and toxicities of treatments in breast cancer. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated for the association of GSTP1 polymorphism with tumour response and toxicities, and the hazard ratios (HRs) and 95% CIs were calculated for the association between GSTP1 polymorphism and overall survival (OS). The statistical analysis showed that the GSTP1 polymorphism was not associated with tumour response or OS. A significant increase in the incidence of toxicities was observed (GA vs. AA OR = 1.45, 95% CI = 1.04–2.01, P = 0.028; GG vs. AA OR = 1.47, 95% CI = 1.03–2.10, P = 0.036; recessive model OR = 1.54, 95% CI = 1.13–2.09, P = 0.006; and allele model OR = 1.35, 95% CI = 1.07–1.71, P = 0.011), especially in the chemotherapy ± surgery group (GA vs. AA OR = 1.64, 95% CI = 1.05–2.56, P = 0.030; recessive model OR = 1.72, 95% CI = 1.17–2.54, P = 0.006; and allele model OR = 1.57, 95% CI = 1.11–2.21, P = 0.010). Our results indicate that the GSTP1 polymorphism may be associated with increased toxicity, especially in patients treated with chemotherapy ± surgery.

Glutathione-s-transferase A 4 (GSTA4) suppresses tumor growth and metastasis of human hepatocellular carcinoma by targeting AKT pathway

Hepatocellular carcinoma (HCC) is one of the most lethal malignancies of cancers and its prognosis remains dismal due to the paucity of effective therapeutic targets. Up-regulation of glutathione-s-transferase A 4 (GSTA4) is associated with poor prognosis of HCC, but its functional mechanism in HCC remains unclear. In this study, we investigated the roles of GSTA4 in tumor growth and metastasis of HCC and found that GSTA4 was frequently up-regulated in HCC tissues. Through gain- and loss-of-function studies, GSTA4 was demonstrated to significantly regulate cell proliferation, migration, and invasion in vitro. Furthermore, GSTA4 overexpressing significantly promoted the tumorigenicity and metastasis of HCC cells in nude mice models bearing human HCC, whereas silencing endogenous GSTA4 caused an opposite outcome. Moreover, we demonstrated that GSTA4 enhanced HCC aggressiveness by activating protein kinase B (AKT) signaling. In multivariate analysis, our results GSTA4 overexpression promotes the progression of hepatocellular carcinoma and might represent a novel therapeutic target for its treatment.

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.

Metabolomics Analysis of Hormone-Responsive and Triple-Negative Breast Cancer Cell Responses to Paclitaxel Identify Key Metabolic Differences

To date, no targeted therapies are available to treat triple negative breast cancer (TNBC), while other breast cancer subtypes are responsive to current therapeutic treatment. Metabolomics was conducted to reveal differences in two hormone receptor-negative TNBC cell lines and two hormone receptor-positive Luminal A cell lines. Studies were conducted in the presence and absence of paclitaxel (Taxol). TNBC cell lines had higher levels of amino acids, branched-chain amino acids, nucleotides, and nucleotide sugars and lower levels of proliferation-related metabolites like choline compared with Luminal A cell lines. In the presence of paclitaxel, each cell line showed unique metabolic responses, with some similarities by type. For example, in the Luminal A cell lines, levels of lactate and creatine decreased while certain choline metabolites and myo-inositol increased with paclitaxel. In the TNBC cell lines levels of glutamine, glutamate, and glutathione increased, whereas lysine, proline, and valine decreased in the presence of drug. Profiling secreted inflammatory cytokines in the conditioned media demonstrated a greater response to paclitaxel in the hormone-positive Luminal cells compared with a secretion profile that suggested greater drug resistance in the TNBC cells. The most significant differences distinguishing the cell types based on pathway enrichment analyses were related to amino acid, lipid and carbohydrate metabolism pathways, whereas several biological pathways were differentiated between the cell lines following treatment.

Association of glutathione S-transferases M1, T1 and P1 gene polymorphisms with attention deficit and hyperactivity disorder in Korean children

Attention deficit and hyperactivity disorder (ADHD) is highly heritable disorder and common in school-age children characterized by inattention, hyperactivity and impulsivity. Although its heritability was estimated at 80-90% from family, adoption and twin studies, the molecular etiology of this disorder has not elucidated. Meanwhile, an impaired balance of oxidant-antioxidant status and increased oxidative stress is observed in ADHD, and it may imply a possible relationship between oxidative stress and etiology of ADHD. Glutathione S-transferase (GST) is antioxidant enzymes that play a key role in the cellular detoxification. In the present study, we examined the association between the genetic polymorphisms of GSTM1, GSTP1 and GSTT1, and ADHD in Korean children. Case-control study was conducted with 243 ADHD children and 327 controls. There were no significant associations between the polymorphisms and the incidence of ADHD (p>0.05). However, significant associations were observed in the stratified analyses. The frequency of GSTP1 Ile/Ile genotype is reached to the significant level in the hyperactivity subtype (88.2%) compared to controls (64.8%) (p=0.035) and the frequency of GSTT1-null genotype is significantly higher in the inattentive boys (p=0.005). Similarly, GSTT1-null genotype showed significant associations in combined subtype (p=0.016) and hyperactivity subtype (p=0.036) of the ADHD girls. Thus our result imply that the polymorphisms in the GST genes may affect ADHD, however, replication study for larger sample set and functional studies are crucial to confirm these findings.

Effects of Ethacrynic Acid Addition to Diet on Fitness and Development in the Psocid Liposcelis bostrychophila Badonnel

Fertility life table provides a comprehensive description of arthropod population dynamics by the estimation of parameters about arthropod population growth potential. It can also clarify the sublethal effects of chemicals on insects. Ethacrynic acid (EA), an inhibitor of glutathione S-transferases, is a diuretic compound that has been confirmed to modulate drug resistance in organisms. In this study, the effects of EA on growth and development of Liposcelis bostrychophila Badonnel were investigated in the laboratory to explore the potential possibilities of EA as an active agent to manage insecticide-resistant psocids. The treatment of psocids was obtained by feeding on the routine diet containing 3% EA for three successive generations, and psocids on routine diet served as control. The results indicated that EA possessed some negative effects on the life-table parameters of the psocid in F1 and F2 generations. The addition of EA to diet stunted psocids growth by lengthening development time and increasing mortality with a greater effect in the F2 generation. In the third generation of psocids on EA diet, it seemed there was a return to normal. Psocid fitness was influenced by addition of EA to standard diet. Using rm values, the fitness for EA diet in F1, F2, and F3 compared with the counterpart of routine diet was calculated as 0.80, 0.74, and 0.87, respectively.

Copper-Induced Inactivation of Camel Liver Glutathione S-Transferase

Glutathione S-transferases (GSTs) are multifunctional enzymes and play an important role in detoxification of xenobiotics and protection against oxidative stress. Camel liver glutathione transferase (cGST) was recently isolated and characterized in our lab. In this study, we have evaluated the effect of monovalent, divalent, and trivalent cations on its activity and stability. Cu(++) was found to be the potent inhibitor of GST activity which loses complete activity at 0.5-mM concentration. Other metal ions did not inhibit GST even at higher concentration of 2 mM. GST incubated with Cu(++) (0.1 mM) resulted decrease in free sulfhydryl groups by 55%, whereas other metal ions did not show any effect on free thiol content. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed formation of GST aggregates instantly in the presence of Cu(++), which further increased in molecular size with increase in time of incubation. DTT treatment resulted in de-aggregation of GST oligomers to its monomeric form. However, the GST activity was not recovered completely after de-aggregation. Cu(++) was found to inhibit GST activity by accelerating the inter- and intra-disulfide bond formation. Far-UV circular dichroism (CD) results showed that Cu(++)-catalyzed air oxidation of sulfhydryl groups leads to minor conformational changes in the GST.

Curcumin-induced downregulation of Axl receptor tyrosine kinase inhibits cell proliferation and circumvents chemoresistance in non-small lung cancer cells

Lung cancer is still in the first place in terms of both incidence and mortality. In the present study, we demonstrated the effect of curcumin, a phytochemical of the plant Curcuma longa, on expression and activation of Axl receptor tyrosine kinase (RTK) which plays an important role in cell survival, proliferation and anti-apoptosis. Curcumin treatment of non-small cell lung cancer (NSCLC) A549 and H460 cells, was found to decrease Axl protein as well as mRNA levels in a dose- and time-dependent manner. Axl promoter activity was also reduced by curcumin, indicating that curcumin downregulates Axl expression at the transcriptional level. Moreover, Axl phosphorylation in response to binding of its ligand, Gas6, was abrogated by curcumin, suggesting the inhibitory effect of curcumin on Gas6-induced Axl activation. We next found cytotoxic effect of cucumin on both the parental A549 and H460 cells, and their variants which are resistant to cisplatin (A549/CisR and H460/CisR) and paclitaxel (A549/TR and H460/TR). Exposure of these cells to curcumin resulted in dose-dependent decline of cell viability and clonogenic ability. It is further observed that the anti-proliferative effect of curcumin on A549 cells overexpressing Axl protein was reduced, while that on H460 cells transfected Axl specific siRNA was augmented, confirming that curcumin inhibits cell proliferation via downregulation of Axl expression. In addition, curcumin was found to cause the induction of p21, a cyclin-dependent kinase inhibitor, and reduction of X-linked inhibitor of apoptosis protein (XIAP), an anti-apoptotic molecule, in parental H460 cells as well as chemoresistant cells, H460/CisR and H460/TR. Taken together, our data imply that Axl RTK is a novel target of curcumin through which it exerts anti-proliferative effect in both parental and chemoresistant NSCLC cells.

Pleiotropic functions of glutathione S-transferase P

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

Glutathione S-transferase expression in upper urinary tract urothelial carcinomas: a Taiwan study

OBJECTIVES

Glutathione S-transferase (GST) isoenzymes play important roles in resistance to cell apoptosis and carcinogenesis. We aimed to establish the relationship between GST expression and the prognosis of upper urinary tract urothelial carcinoma (UTT-UC) in Taiwan.

METHODS

This study retrospectively reviewed 46 patients with pathologically confirmed UUT-UC at Kaohsiung Medical University Hospital. In each patient, expression of GSTT1 and GSTP1 was compared between urothelial carcinoma and normal urothelial cells by Western blotting.

RESULTS

GSTP1 expression in the UUT-UC cells was significantly higher than that in normal urothelial cells (1.6 fold, p<0.001). Expression of GSTT1 was significantly associated with the invasiveness of the carcinoma (p=0.006).

CONCLUSIONS

In UUT-UC, GSTP1 might be a potential tumor marker, whereas high GSTT1 expression could be used as an indicator of cancer progression. This study is the first to demonstrate potential applications of different GST isoenzymes for biomolecular analysis of UUT-UCs in Taiwan.

Genetic polymorphisms in Glutathione S-transferase Omega (GSTO) and cancer risk: a meta-analysis of 20 studies

Glutathione S-transferase Omega (GSTO) plays an important role in the development of cancer. Recently, a number of studies have investigated the association between single nucleotide polymorphisms on GSTO and susceptibility to cancer; however, the results remain inconclusive. We performed a meta-analysis of 20 studies, involving 4770 cases and 5701 controls to identify the strength of association by pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs). Overall, the pooled results revealed a significantly increased risk of susceptibility for GSTO2 polymorphism (GG vs. AA: OR = 1.20, 95%CI: 1.02-1.41, Pheterogeneity = 0.116), but no significant association was found for GSTO1 polymorphism. Subgroup analysis showed that GSTO2 polymorphism significantly increased cancer risk in Caucasian population (GG vs. AA: OR = 1.32, 95%CI 1.06-1.64, Pheterogeneity = 0.616) and GSTO2 polymorphism was significantly associated with elevated risk of breast cancer (GG vs. AA OR = 1.37, 95%CI: 1.06-1.77; Pheterogeneity = 0.281). This meta-analysis demonstrates that GSTO2 polymorphism may significantly increase cancer risk in Caucasian population and is associated with elevated risk of breast cancer; while GSTO1 polymorphism is not associated with cancer risk.

Cytoprotective and regulatory functions of glutathione S-transferases in cancer cell proliferation and cell death

PURPOSE

Glutathione S-transferases (GSTs) family of enzymes is best known for their cytoprotective role and their involvement in the development of anticancer drug resistance. Recently, emergence of non-detoxifying properties of GSTs has provided them with significant biological importance. Addressing the complex interactions of GSTs with regulatory kinases will help in understanding its precise role in tumor pathophysiology and in designing GST-centered anticancer strategies.

METHODS

We reviewed all published literature addressing the detoxification and regulatory roles of GSTs in the altered biology of cancer and evaluating novel agents targeting GSTs for cancer therapy.

RESULTS

The role of GSTs, especially glutathione S-transferase P1 isoform in tumoral drug resistance, has been the cause of intense debate. GSTs have been demonstrated to interact with different protein partners and modulate signaling pathways that control cell proliferation, differentiation and apoptosis. These specific functions of GSTs could lead to the development of new therapeutic approaches and to the identification of some interesting candidates for preclinical and clinical development. This review focuses on the crucial role played by GSTs in the development of resistance to anticancer agents and the major findings regarding the different modes of action of GSTs to regulate cell signaling.

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

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

Genetic polymorphism of glutathione S-transferase P1 (GSTP1) in Delhi population and comparison with other global populations

Glutathione S-transferases (GSTs) belong to a super family of phase II detoxification enzymes, which play an important role in protecting cells from damage caused by endogenous and exogenous compounds by conjugating reactive intermediates with glutathione to produce less reactive water-soluble compounds. In the present study, we determined the frequencies of two polymorphisms in exon 5 and exon 6 of GSTP1 gene in 500 normal individuals from Delhi. GSTP1 polymorphism was analysed by PCR-RFLP using amplification refractory mutation system (ARMS) assay. Two polymorphic sites in GSTP1 (Ile105 → Val105; Ala114 → Val114) have been analysed simultaneously, which results in four alleles: GSTP1*A (wild-type Ile105; Ala114), GSTP1*B (Val105; Ala114), GSTP1*C (Val105; Val114) and GSTP1*D (Ile105; Val114). The GSTP1 allele frequency in Delhi population was 0.663, 0.248, 0.069, and 0.020 for GSTP1*A, GSTP1*B, GSTP1*C, and GSTP1*D respectively. The frequency of Ile105 and Val105 allele was 0.683 and 0.317 respectively and it was calculated for the purpose of comparison with published data where all the four alleles were not analysed. GSTP1 alleles from Delhi population were compared with reported frequencies from all over India, and from other ethnic groups worldwide. This study would provide a basic database for future genetic studies.

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.

Glutathione S-transferase homozygous deletions and relapse in childhood acute lymphoblastic leukemia: a novel study design in a large Italian AIEOP cohort

Aim: In the AIEOP-BFM 2000 trial, 15% of pediatric patients treated according to risk-adapted polychemotherapeutic regimens relapsed. The present study aimed to investigate the influence of GST-M1 and GST-T1 deletions on clinical outcome of children with acute lymphoblastic leukemia treated according to the AIEOP-BFM ALL 2000 study protocol. Materials & methods: A novel-design, two-phase study was applied to select a subsample of 614 children to be genotyped for the deletions of GST genes. Cumulative incidence of relapse was then estimated by weighted Kaplan–Meier analysis, and the Cox model was applied to evaluate the effect of GST-M1 and GST-T1 isoenzyme deletions on relapse. Results: No overall effect was found, but the GST-M1 deletion was associated with better clinical outcome within prednisone poor-responder patients (hazard ratio [HR]: 0.45; 95% CI: 0.23–0.91; p = 0.026), whereas the GST-T1 deletion was associated with worse outcome in the standard-risk group (HR: 4.62; 95% CI: 1.04–20.6; p = 0.045) and within prednisone good responders (HR: 1.62; 95% CI: 1.02–2.58; p = 0.041). Conclusion: Our results show that GST-M1 and GST-T1 homozygous deletions have opposite correlation with relapse, the former being protective and the latter unfavourable in specific subsets of acute lymphoblastic leukemia patients.

Original submitted 1 August 2012; Revision submitted 27 September 2012