Glutathione S-conjugates as prodrugs to target drug-resistant tumors

Nrf2 pathways in neuroprotection: Alleviating mitochondrial dysfunction and cognitive impairment in aging

Mitochondrial dysfunction and cognitive impairment are widespread phenomena among the elderly, being crucial factors that contribute to neurodegenerative diseases. Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important regulator of cellular defense systems, including that against oxidative stress. As such, increased Nrf2 activity may serve as a strategy to avert mitochondrial dysfunction and cognitive decline. Scientific data on Nrf2-mediated neuroprotection was collected from PubMed, Google Scholar, and Science Direct, specifically addressing mitochondrial dysfunction and cognitive impairment in older people. Search terms included "Nrf2", "mitochondrial dysfunction," "cognitive impairment," and "neuroprotection." Studies focusing on in vitro and in vivo models and clinical investigations were included to review Nrf2's therapeutic potential comprehensively. The relative studies have demonstrated that increased Nrf2 activity could improve mitochondrial performance, decrease oxidative pressure, and mitigate cognitive impairment. To a large extent, this is achieved through the modulation of critical cellular signalling pathways such as the Keap1/Nrf2 pathway, mitochondrial biogenesis, and neuroinflammatory responses. The present review summarizes the recent progress in comprehending the molecular mechanisms regarding the neuroprotective benefits mediated by Nrf2 through its substantial role against mitochondrial dysfunction and cognitive impairment. This review also emphasizes Nrf2-target pathways and their contribution to cognitive function improvement and rescue from mitochondria-related abnormalities as treatment strategies for neurodegenerative diseases that often affect elderly individuals.

A novel, glutathione-activated prodrug of pimasertib loaded in liposomes for targeted cancer therapy

Pimasertib, a potent antiproliferative drug, has been extensively studied for treating cancers characterized by dysregulation in the ERK/MAPK signaling pathway, such as melanoma. However, its therapeutic efficacy would greatly benefit from an increased selectivity for tumour cells and a longer half-life. Such improvements may be achieved by combining the rational design of a prodrug with its encapsulation in a potential nanodelivery system. For this reason, we synthesized a glutathione (GSH)-responsive putative prodrug of pimasertib (PROPIMA), which contains a redox-sensitive disulphide linker that can be processed by GSH to activate pimasertib. The synthesis of PROPIMA and its in vitro biological activity on a human melanoma cell line as a model are described. The results showed that PROPIMA, either free or embedded in liposomes, selectively inhibits cell proliferation and cell viability, reducing by about 5-fold the levels of pERK. Additionally, PROPIMA shows stronger inhibition of the cancer cell migration than the parent drug.

Setdb1 protects genome integrity in murine muscle stem cells to allow for regenerative myogenesis and inflammation

The histone H3 lysine 9 methyltransferase SETDB1 controls transcriptional repression to direct stem cell fate. Here, we show that Setdb1 expression by adult muscle stem cells (MuSCs) is required for skeletal muscle regeneration. We find that SETDB1 represses the expression of endogenous retroviruses (ERVs) in MuSCs. ERV de-repression in Setdb1-null MuSCs prevents their amplification following exit from quiescence and promotes cell death. Multi-omics profiling shows that chromatin decompaction at ERV loci activates the DNA-sensing cGAS-STING pathway, entailing cytokine expression by Setdb1-null MuSCs. This is followed by aberrant infiltration of inflammatory cells, including pathological macrophages. The ensuing histiocytosis is accompanied by myofiber necrosis, which, in addition to progressive MuSCs depletion, completely abolishes tissue repair. In contrast, loss of Setdb1 in fibro-adipogenic progenitors (FAPs) does not impact immune cells. In conclusion, genome maintenance by SETDB1 in an adult somatic stem cell is necessary for both its regenerative potential and adequate reparative inflammation.

Glutathione‑degrading enzymes in the complex landscape of tumors (Review)

Glutathione (GSH)‑degrading enzymes are essential for starting the first stages of GSH degradation. These enzymes include extracellular γ‑glutamyl transpeptidase (GGT) and intracellular GSH‑specific γ‑glutamylcyclotransferase 1 (ChaC1) and 2. These enzymes are essential for cellular activities, such as immune response, differentiation, proliferation, homeostasis regulation and programmed cell death. Tumor tissue frequently exhibits abnormal expression of GSH‑degrading enzymes, which has a key impact on the development and spread of malignancies. The present review summarizes gene and protein structure, catalytic activity and regulation of GSH‑degrading enzymes, their vital roles in tumor development (including regulation of oxidative and endoplasmic reticulum stress, control of programmed cell death, promotion of inflammation and tumorigenesis and modulation of drug resistance in tumor cells) and potential role as diagnostic biomarkers and therapeutic targets.

In vitro Antibacterial Activity and Secondary Metabolite Profiling of Endolichenic Fungi Isolated from Genus Parmotrema

The endolichenic fungi are an unexplored group of organisms for the production of bioactive secondary metabolites. The aim of the present study is to determine the antibacterial potential of endolichenic fungi isolated from genus Parmotrema. The study is continuation of our previous work, wherein a total of 73 endolichenic fungi were isolated from the lichenized fungi, which resulted in 47 species under 23 genera. All the isolated endolichenic fungi were screened for preliminary antibacterial activity. Five endolichenic fungi-Daldinia eschscholtzii, Nemania diffusa, Preussia sp., Trichoderma sp. and Xylaria feejeensis, were selected for further antibacterial activity by disc diffusion method. The zone of inhibition ranged from 14.3 ± 0.1 to 23.2 ± 0.1. The chemical composition of the selected endolichenic fungi was analysed through GC-MS, which yielded a total of 108 compounds from all the selected five endolichenic fungi. Diethyl phthalate, 1-hexadecanol, dibutyl phthalate, n-tetracosanol-1, 1-nonadecene, pyrrol[1,2-a] pyrazine-1,4-dione, hexahydro-3-(2-methyl) and tetratetracontane were found to be common compounds among one or the other endolichenic fungi, which possibly were responsible for antibacterial activity. GC-MS data were further analysed through Principal Component Analysis which showed D. eschscholtzii to be with unique pattern of expression of metabolites. Compound confirmation test revealed coumaric acid to be responsible for antibacterial activity in D. eschscholtzii. So, the study proves that endolichenic fungi that inhabit lichenized fungal thalli could be a source of potential antibacterial compounds.

Glutathione-triggered prodrugs: Design strategies, potential applications, and perspectives

The burgeoning prodrug strategy offers a promising avenue toward improving the efficacy and specificity of cytotoxic drugs. Elevated intracellular levels of glutathione (GSH) have been regarded as a hallmark of tumor cells and characteristic feature of the tumor microenvironment. Considering the pivotal involvement of elevated GSH in the tumorigenic process, a diverse repertoire of GSH-triggered prodrugs has been developed for cancer therapy, facilitating the attenuation of deleterious side effects associated with conventional chemotherapeutic agents and/or the attainment of more efficacious therapeutic outcomes. These prodrug formulations encompass a spectrum of architectures, spanning from small molecules to polymer-based and organic-inorganic nanomaterial constructs. Although the GSH-triggered prodrugs have been gaining increasing interests, a comprehensive review of the advancements made in the field is still lacking. To fill the existing lacuna, this review undertakes a retrospective analysis of noteworthy research endeavors, based on a categorization of these molecules by their diverse recognition units (i.e., disulfides, diselenides, Michael acceptors, and sulfonamides/sulfonates). This review also focuses on explaining the distinct benefits of employing various chemical architecture strategies in the design of these prodrug agents. Furthermore, we highlight the potential for synergistic functionality by incorporating multiple-targeting conjugates, theranostic entities, and combinational treatment modalities, all of which rely on the GSH-triggering. Overall, an extensive overview of the emerging field is presented in this review, highlighting the obstacles and opportunities that lie ahead. Our overarching goal is to furnish methodological guidance for the development of more efficacious GSH-triggered prodrugs in the future. By assessing the pros and cons of current GSH-triggered prodrugs, we expect that this review will be a handful reference for prodrug design, and would provide a guidance for improving the properties of prodrugs and discovering novel trigger scaffolds for constructing GSH-triggered prodrugs.

Natural products for combating multidrug resistance in cancer

Cancer cells frequently develop resistance to chemotherapeutic therapies and targeted drugs, which has been a significant challenge in cancer management. With the growing advances in technologies in isolation and identification of natural products, the potential of natural products in combating cancer multidrug resistance has received substantial attention. Importantly, natural products can impact multiple targets, which can be valuable in overcoming drug resistance from different perspectives. In the current review, we will describe the well-established mechanisms underlying multidrug resistance, and introduce natural products that could target these multidrug resistant mechanisms. Specifically, we will discuss natural compounds such as curcumin, resveratrol, baicalein, chrysin and more, and their potential roles in combating multidrug resistance. This review article aims to provide a systematic summary of recent advances of natural products in combating cancer drug resistance, and will provide rationales for novel drug discovery.

Sedanolide Activates KEAP1-NRF2 Pathway and Ameliorates Hydrogen Peroxide-Induced Apoptotic Cell Death

Sedanolide is a bioactive compound with anti-inflammatory and antitumor activities. Although it has been recently suggested that sedanolide activates the nuclear factor E2-related factor 2 (NRF2) pathway, there is little research on its effects on cellular resistance to oxidative stress. The objective of the present study was to investigate the function of sedanolide in suppressing hydrogen peroxide (H2O2)-induced oxidative damage and the underlying molecular mechanisms in human hepatoblastoma cell line HepG2 cells. We found that sedanolide activated the antioxidant response element (ARE)-dependent transcription mediated by the nuclear translocation of NRF2. Pathway enrichment analysis of RNA sequencing data revealed that sedanolide upregulated the transcription of antioxidant enzymes involved in the NRF2 pathway and glutathione metabolism. Then, we further investigated whether sedanolide exerts cytoprotective effects against H2O2-induced cell death. We showed that sedanolide significantly attenuated cytosolic and mitochondrial reactive oxygen species (ROS) generation induced by exposure to H2O2. Furthermore, we demonstrated that pretreatment with sedanolide conferred a significant cytoprotective effect against H2O2-induced cell death probably due to preventing the decrease in the mitochondrial membrane potential and the increase in caspase-3/7 activity. Our study demonstrated that sedanolide enhanced cellular resistance to oxidative damage via the activation of the Kelch-like ECH-associated protein 1 (KEAP1)-NRF2 pathway.

Antioxidants of Non-Enzymatic Nature: Their Function in Higher Plant Cells and the Ways of Boosting Their Biosynthesis

Plants are exposed to a variety of abiotic and biotic stresses leading to increased formation of reactive oxygen species (ROS) in plant cells. ROS are capable of oxidizing proteins, pigments, lipids, nucleic acids, and other cell molecules, disrupting their functional activity. During the process of evolution, numerous antioxidant systems were formed in plants, including antioxidant enzymes and low molecular weight non-enzymatic antioxidants. Antioxidant systems perform neutralization of ROS and therefore prevent oxidative damage of cell components. In the present review, we focus on the biosynthesis of non-enzymatic antioxidants in higher plants cells such as ascorbic acid (vitamin C), glutathione, flavonoids, isoprenoids, carotenoids, tocopherol (vitamin E), ubiquinone, and plastoquinone. Their functioning and their reactivity with respect to individual ROS will be described. This review is also devoted to the modern genetic engineering methods, which are widely used to change the quantitative and qualitative content of the non-enzymatic antioxidants in cultivated plants. These methods allow various plant lines with given properties to be obtained in a rather short time. The most successful approaches for plant transgenesis and plant genome editing for the enhancement of biosynthesis and the content of these antioxidants are discussed.

Polymorphism of glutathione S-transferase P1 of dogs with mammary tumours

Mammary tumours constitute more than half of neoplasms in female dogs from different countries. Genome sequences are associated with cancer susceptibility but there is little information available about genetic polymorphisms of glutathione S-transferase P1 (GSTP1) in canine cancers. The aim of this study was to find single nucleotide polymorphisms (SNPs) in GSTP1 of dogs (Canis lupus familiaris) with mammary tumours compared to healthy dogs and to determine the association between GSTP1 polymorphisms and the occurrence of these tumours. The study population included 36 client-owned female dogs with mammary tumours and 12 healthy female dogs, with no previous diagnosis of cancer. DNA was extracted from blood and amplified by PCR assay. PCR-products were sequenced by Sanger method and analysed manually. The 33 polymorphisms were found in GSTP1: 1 coding SNP (exon 4), 24 non-coding SNPs (9 in exon 1), 7 deletions and 1 insertion. The 17 polymorphisms have been found in introns 1, 4, 5 and 6. The dogs with mammary tumours have significant difference from healthy in SNPs I4 c.1018 + 123 T > C (OR 13.412, 95%CI 1.574-114.267, P = .001), I5 c.1487 + 27 T > C (OR 10.737, 95%CI 1.260-91.477, P = .004), I5 c.1487 + 842 G > C (OR 4.714, 95% CI 1.086-20.472, P = .046) and I6 c.2481 + 50 A > G (OR 12.000, 95% CI 1.409-102.207, P = .002). SNP E5 c.1487 T > C and I5 c.1487 + 829 delG also differed significantly (P = .03) but not to the confidence interval. The study, for the first time, showed a positive association of SNPs in GSTP1 with mammary tumours of dogs, that can possibly be used to predict the occurrence of this pathology.

Probiotics ameliorate polyethylene microplastics-induced liver injury by inhibition of oxidative stress in Nile tilapia (Oreochromis niloticus)

Microplastic particles (MPs) are environmental pollutants that can cause varying levels of aquatic toxicity. Probiotics have been shown to reduce the negative effects of toxic substances. However, the protective effect of probiotics against the adverse effects of MPs has yet to be reported. The current study sought to determine the effects of the commercial probiotic AquaStar® Growout on polystyrene (PS)-MPs-mediated hepatic oxidative stress in Nile tilapia (Oreochromis niloticus). Fishes were assigned into four groups: the first group was the control, the second group was exposed to 1 mg/L of 0.5 μm PS-MPs, and the third and fourth groups were exposed to 1 mg/L of 0.5 μm PS-MPs and pre-fed with probiotics at levels of 3 g/kg and 6 g/kg diet, respectively. At the end of the experiment, probiotics administration reversed liver damage caused by the PS-MPs, reducing serum levels of malondialdehyde, aspartate aminotransferase, and alanine aminotransferase, and increasing the total antioxidant capacity. Furthermore, probiotics alleviated PS-MPs-induced oxidative stress by restoring antioxidant enzyme activities (superoxide dismutase, catalase, glutathione S-transferase, and glutathione peroxidase) and reducing oxidized glutathione and enhancing the redox state. Besides, probiotics supplementation decreased the transcriptional level of C-reactive protein and tumor necrosis factor-α following PS-MPs exposure. Furthermore, probiotics counteracted PS-MPs-associated reactive oxygen species production and mitogen-activated protein kinases (MAPKs) phosphorylation status. These findings suggested that probiotics could decrease liver damage caused by PS-MPs through their antioxidant properties and modulation of MAPK signaling pathways.

The Effects of BSA-Stabilized Selenium Nanoparticles and Sodium Selenite Supplementation on the Structure, Oxidative Stress Parameters and Selenium Redox Biology in Rat Placenta

The chemical element selenium (Se) is a nonmetal that is in trace amounts indispensable for normal cellular functioning. During pregnancy, a low Se status can increase the risk of oxidative stress. However, elevated concentrations of Se in the body can also cause oxidative stress. This study aimed to compare the effects of BSA-stabilized Se nanoparticles (SeNPs, Se0) (BSA-bovine serum albumin) and inorganic sodium selenite (NaSe, Se+4) supplementation on the histological structure of the placenta, oxidative stress parameters and the total placental Se concentration of Wistar rats during pregnancy. Pregnant females were randomized into four groups: (i) intact controls; (ii) controls that were dosed by daily oral gavage with 8.6% bovine serum albumin (BSA) and 0.125 M vit C; (iii) the SeNP group that was administered 0.5 mg of SeNPs stabilized with 8.6% BSA and 0.125 M vit C/kg bw/day by oral gavage dosing; (iv) the NaSe group, gavage dosed with 0.5 mg Na2SeO3/kg bw/day. The treatment of pregnant females started on gestational day one, lasted until day 20, and on day 21 of gestation, the fetuses with the placenta were removed from the uterus. Our findings show that the mode of action of equivalent concentrations of Se in SeNPs and NaSe depended on its redox state and chemical structure. Administration of SeNPs (Se0) increased fetal lethality and induced changes in the antioxidative defense parameters in the placenta. The accumulation of Se in the placenta was highest in SeNP-treated animals. All obtained data indicate an increased bioavailability of Se in its organic nano form and Se0 redox state in comparison to its inorganic sodium selenite form and Se+4 redox state.

Pi-class Glutathione S-transferase (GSTP1)-selective fluorescent probes for multicolour imaging with various cancer-associated enzymes

Pi-class glutathione S-transferase (GSTP1) is highly expressed in a wide variety of human cancer tissues compared to the corresponding normal counterpart. Therefore, GSTP1 is a potential target enzyme for overcoming resistance to chemotherapeutic agents or visualizing specific lesions such as cancer. Here, we present orange and red fluorescence-emitting probes selective for GSTP1. Carbofluorescein and TokyoMagenta fluorophores were modified with a previously described GSTP1-selective chromogenic compound to generate orange and red fluorescence probes, respectively. Of these probes, Ps-CF , the orange fluorescence-emitting probe, was confirmed to be highly specific for detecting GSTP1 exogenously or endogenously expressed in various cancer cells. Additionally, it was demonstrated that Ps-CF is applicable for the simultaneous detection of GSTP1 and another cancer-associated enzymes by using a green fluorescence emitting γ-glutamyl transpeptidase (GGT) probe. In conclusion, the fluorescent probes developed in this study enable the simultaneous detection of multiple tumour markers such as GSTP1 with other cancer-associated enzymes by the concurrent use of spectrally distinguished fluorescent probes, potentially broadening the scope of cancer detection.

Glutathione-Mediated Conjugation of Anticancer Drugs: An Overview of Reaction Mechanisms and Biological Significance for Drug Detoxification and Bioactivation

The effectiveness of many anticancer drugs depends on the creation of specific metabolites that may alter their therapeutic or toxic properties. One significant route of biotransformation is a conjugation of electrophilic compounds with reduced glutathione, which can be non-enzymatic and/or catalyzed by glutathione-dependent enzymes. Glutathione usually combines with anticancer drugs and/or their metabolites to form more polar and water-soluble glutathione S-conjugates, readily excreted outside the body. In this regard, glutathione plays a role in detoxification, decreasing the likelihood that a xenobiotic will react with cellular targets. However, some drugs once transformed into thioethers are more active or toxic than the parent compound. Thus, glutathione conjugation may also lead to pharmacological or toxicological effects through bioactivation reactions. My purpose here is to provide a broad overview of the mechanisms of glutathione-mediated conjugation of anticancer drugs. Additionally, I discuss the biological importance of glutathione conjugation to anticancer drug detoxification and bioactivation pathways. I also consider the potential role of glutathione in the metabolism of unsymmetrical bisacridines, a novel prosperous class of anticancer compounds developed in our laboratory. The knowledge on glutathione-mediated conjugation of anticancer drugs presented in this review may be noteworthy for improving cancer therapy and preventing drug resistance in cancers.

Response of Fusarium pseudograminearum to Biocontrol Agent Bacillus velezensis YB-185 by Phenotypic and Transcriptome Analysis

The use of biological control agents (BCAs) is a promising alternative control measure for Fusarium crown rot (FCR) of wheat caused by Fusarium pseudograminearum. A bacterial strain, YB-185, was isolated from the soil of wheat plants with FCR and identified as Bacillus velezensis. YB-185 exhibited strong inhibition of F. pseudograminearum mycelial growth and conidial germination in culture. Seed treatment with YB-185 in greenhouse and field resulted in reductions in disease by 66.1% and 57.6%, respectively, along with increased grain yield. Microscopy of infected root tissues confirmed that YB-185 reduced root invasion by F. pseudograminearum. RNA-seq of F. pseudograminearum during co-cultivation with B. velezensis YB-185 revealed 5086 differentially expressed genes (DEGs) compared to the control. Down-regulated DEGs included genes for glucan synthesis, fatty acid synthesis, mechanosensitive ion channels, superoxide dismutase, peroxiredoxin, thioredoxin, and plant-cell-wall-degrading enzymes, whereas up-regulated DEGs included genes for chitin synthesis, ergosterol synthesis, glutathione S-transferase, catalase, and ABC transporters. In addition, fungal cell apoptosis increased significantly, as indicated by TUNEL staining, and the scavenging rate of 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (ABTS·+) in the fungus significantly decreased. Thus, F. pseudograminearum may be trying to maintain normal cell functions by increasing cell wall and membrane synthesis, antioxidant and anti-stress responses, detoxification of bacterial antimicrobial compounds, and transportation of damaging compounds from its cells. However, cell death and free radical accumulation still occurred, indicating that the responses were insufficient to prevent cell damage. Bacillus velezensis YB-185 is a promising BCA against FCR that acts by directly damaging F. pseudograminearum, thus reducing its ability to colonize roots and produce symptoms.

The role of polyphenols in overcoming cancer drug resistance: a comprehensive review

Chemotherapeutic drugs are used to treat advanced stages of cancer or following surgery. However, cancers often develop resistance against drugs, leading to failure of treatment and recurrence of the disease. Polyphenols are a family of organic compounds with more than 10,000 members which have a three-membered flavan ring system in common. These natural compounds are known for their beneficial properties, such as free radical scavenging, decreasing oxidative stress, and modulating inflammation. Herein, we discuss the role of polyphenols (mainly curcumin, resveratrol, and epigallocatechin gallate [EGCG]) in different aspects of cancer drug resistance. Increasing drug uptake by tumor cells, decreasing drug metabolism by enzymes (e.g. cytochromes and glutathione-S-transferases), and reducing drug efflux are some of the mechanisms by which polyphenols increase the sensitivity of cancer cells to chemotherapeutic agents. Polyphenols also affect other targets for overcoming chemoresistance in cancer cells, including cell death (i.e. autophagy and apoptosis), EMT, ROS, DNA repair processes, cancer stem cells, and epigenetics (e.g. miRNAs).

Metal- and metalloid-based compounds to target and reverse cancer multidrug resistance

Drug resistance remains the major cause of cancer treatment failure especially at the late stage of the disease. However, based on their versatile chemistry, metal and metalloid compounds offer the possibility to design fine-tuned drugs to circumvent and even specifically target drug-resistant cancer cells. Based on the paramount importance of platinum drugs in the clinics, two main areas of drug resistance reversal strategies exist: overcoming resistance to platinum drugs as well as multidrug resistance based on ABC efflux pumps. The current review provides an overview of both aspects of drug design and discusses the open questions in the field. The areas of drug resistance covered in this article involve: 1) Altered expression of proteins involved in metal uptake, efflux or intracellular distribution, 2) Enhanced drug efflux via ABC transporters, 3) Altered metabolism in drug-resistant cancer cells, 4) Altered thiol or redox homeostasis, 5) Altered DNA damage recognition and enhanced DNA damage repair, 6) Impaired induction of apoptosis and 7) Altered interaction with the immune system. This review represents the first collection of metal (including platinum, ruthenium, iridium, gold, and copper) and metalloid drugs (e.g. arsenic and selenium) which demonstrated drug resistance reversal activity. A special focus is on compounds characterized by collateral sensitivity of ABC transporter-overexpressing cancer cells. Through this approach, we wish to draw the attention to open research questions in the field. Future investigations are warranted to obtain more insights into the mechanisms of action of the most potent compounds which target specific modalities of drug resistance.

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.

The Interaction of the Microtubule Targeting Anticancer Drug Colchicine with Human Glutathione Transferases

BACKGROUND

Glutathione transferases (GSTs) are a family of Phase II detoxification enzymes that have been shown to be involved in the development of multi-drug resistance (MDR) mechanism toward chemotherapeutic agents. GST inhibitors have, therefore, emerged as promising chemosensitizers to manage and reverse MDR. Colchicine (COL) is a classical antimitotic, tubulin-binding agent (TBA) which is being explored as anticancer drug.

METHODS

In the present work, the interaction of COL and its derivative 2,3-didemethylcolchicine (2,3-DDCOL) with human glutathione transferases (hGSTA1-1, hGSTP1-1, hGSTM1-1) was investigated by inhibition analysis, molecular modelling and molecular dynamics simulations.

RESULTS

The results showed that both compounds bind reversibly to human GSTs and behave as potent inhibitors. hGSTA1-1 was the most sensitive enzyme to inhibition by COL with IC50 22 μΜ. Molecular modelling predicted that COL overlaps with both the hydrophobic (H-site) and glutathione binding site (G-site) and polar interactions appear to be the driving force for its positioning and recognition at the binding site. The interaction of COL with other members of GST family (hGSTA2-2, hGSTM3-3, hGSTM3-2) was also investigated with similar results.

CONCLUSION

The results of the present study might be useful in future drug design and development efforts towards human GSTs.

Glutathione Synthesis in Cancer Cells

Tripeptide GSH is associated not only with the control and maintenance of redox cell homeostasis, but also with the processes of detoxification, proliferation, cell differentiation, and regulation of cell death. Disruptions in GSH synthesis and changes in the GSH/GSSG ratio are common for many pathological conditions, including malignant neoplasms. Numerous data indicate the importance of GSH and the GSH/GSSG ratio in the regulation of tumor cell viability, in the initiation of tumor development, progression, and drug resistance. However, control of the mechanism of GSH synthesis in malignant tumors remains poorly understood. This review discusses the features of GSH synthesis and its regulation in tumor cells. The role of GSH in the mechanisms of apoptosis, necroptosis, ferroptosis, and autophagy is considered.

Redox and Thiols in Archaea

Low molecular weight (LMW) thiols have many functions in bacteria and eukarya, ranging from redox homeostasis to acting as cofactors in numerous reactions, including detoxification of xenobiotic compounds. The LMW thiol, glutathione (GSH), is found in eukaryotes and many species of bacteria. Analogues of GSH include the structurally different LMW thiols: bacillithiol, mycothiol, ergothioneine, and coenzyme A. Many advances have been made in understanding the diverse and multiple functions of GSH and GSH analogues in bacteria but much less is known about distribution and functions of GSH and its analogues in archaea, which constitute the third domain of life, occupying many niches, including those in extreme environments. Archaea are able to use many energy sources and have many unique metabolic reactions and as a result are major contributors to geochemical cycles. As LMW thiols are major players in cells, this review explores the distribution of thiols and their biochemistry in archaea.

Mechanisms of Multidrug Resistance in Cancer Chemotherapy

Cancer is one of the main causes of death worldwide. Despite the significant development of methods of cancer healing during the past decades, chemotherapy still remains the main method for cancer treatment. Depending on the mechanism of action, commonly used chemotherapeutic agents can be divided into several classes (antimetabolites, alkylating agents, mitotic spindle inhibitors, topoisomerase inhibitors, and others). Multidrug resistance (MDR) is responsible for over 90% of deaths in cancer patients receiving traditional chemotherapeutics or novel targeted drugs. The mechanisms of MDR include elevated metabolism of xenobiotics, enhanced efflux of drugs, growth factors, increased DNA repair capacity, and genetic factors (gene mutations, amplifications, and epigenetic alterations). Rapidly increasing numbers of biomedical studies are focused on designing chemotherapeutics that are able to evade or reverse MDR. The aim of this review is not only to demonstrate the latest data on the mechanisms of cellular resistance to anticancer agents currently used in clinical treatment but also to present the mechanisms of action of novel potential antitumor drugs which have been designed to overcome these resistance mechanisms. Better understanding of the mechanisms of MDR and targets of novel chemotherapy agents should provide guidance for future research concerning new effective strategies in cancer treatment.

Secondary Metabolites from the Culture of the Marine-derived Fungus Paradendryphiella salina PC 362H and Evaluation of the Anticancer Activity of Its Metabolite Hyalodendrin

High-throughput screening assays have been designed to identify compounds capable of inhibiting phenotypes involved in cancer aggressiveness. However, most studies used commercially available chemical libraries. This prompted us to explore natural products isolated from marine-derived fungi as a new source of molecules. In this study, we established a chemical library from 99 strains corresponding to 45 molecular operational taxonomic units and evaluated their anticancer activity against the MCF7 epithelial cancer cell line and its invasive stem cell-like MCF7-Sh-WISP2 counterpart. We identified the marine fungal Paradendryphiella salina PC 362H strain, isolated from the brown alga Pelvetia caniculata (PC), as one of the most promising fungi which produce active compounds. Further chemical and biological characterizations of the culture of the Paradendryphiella salina PC 362H strain identified (-)-hyalodendrin as the active secondary metabolite responsible for the cytotoxic activity of the crude extract. The antitumor activity of (-)-hyalodendrin was not only limited to the MCF7 cell lines, but also prominent on cancer cells with invasive phenotypes including colorectal cancer cells resistant to chemotherapy. Further investigations showed that treatment of MCF7-Sh-WISP2 cells with (-)-hyalodendrin induced changes in the phosphorylation status of p53 and altered expression of HSP60, HSP70 and PRAS40 proteins. Altogether, our study reveals that this uninvestigated marine fungal crude extract possesses a strong therapeutic potential against tumor cells with aggressive phenotypes and confirms that members of the epidithiodioxopiperazines are interesting fungal toxins with anticancer activities.

Characterizing biotransformation products and pathways of the flame retardant triphenyl phosphate in Daphnia magna using non-target screening

Triphenyl phosphate (TPHP), one of the organophosphate flame retardants, has been widely used in manufacturing, thereby causing a gradual increase in TPHP concentrations in aquatic environments. However, the information on the biotransformation mechanism of TPHP in invertebrates is lacking. The study identified the biotransformation products of TPHP in Daphnia magna, which showed particularly high toxicity in aquatic organisms, and determined the rates of depuration. Daphnia magna, a standard species for toxicity studies, was exposed to triphenyl phosphate and transferred to the pure medium. The biotransformation products of TPHP and its depuration rates were determined by liquid chromatography-high resolution mass spectrometry. Nine biotransformation products (five in the positive mode and four in the negative mode) of triphenyl phosphate were identified in D. magna. Based on the depuration ratio, the major biotransformation mechanism is estimated to be cysteine conjugation and sulfation. Certain biotransformation products (diphenyl phosphate, hydroxylated triphenyl phosphate, and thiol triphenyl phosphate) might induce toxicity in biota. The results could be used to predict main biotransformation processes and toxic products of organophosphate flame retardants in aquatic invertebrates.

Glutathione, an Antioxidant Tripeptide: Dual Roles in Carcinogenesis and Chemoprevention

Glutathione (GSH or reduced glutathione) is a tripeptide of gamma-Glutamyl-cysteinylglycine and the predominant intracellular antioxidant in many organisms including humans. GSH and associated enzymes are controlled by a transcription factor-nuclear factor-2 related erythroid factor-2 (Nrf2). In cellular milieu, GSH protects the cells essentially against a wide variety of free radicals including reactive oxygen species, lipid hydroperoxides, xenobiotic toxicants, and heavy metals. It has two forms, the reduced form or reduced glutathione (GSH) and oxidized form (GSSG), where two GSH moieties combine by sulfhydryl bonds. Glutathione peroxidase (GPx) and glutathione-s-transferase (GST) essentially perform the detoxification reactions using GSH, converting it into GSSG. Glutathione reductase (GR) operates the salvage pathway by converting GSSG to GSH with the expense of NADPH and restores the cellular GSH pool. Hence, GSH and GSH-dependent enzymes are necessary for maintaining the normal redox balance in the body and help in cell survival under stress conditions. In addition, GST removes various carcinogenic compounds offering a chemopreventive property, whereas the GSH system plays a significant role in regulating the cellular survival by offering redox stability in a variety of cancers including prostate, lung, breast, and colon cancer. Studies have also indicated that GSH inhibitors, such as buthionine sulfoximine, improve the chemo-sensitivity in cancer cells. In addition, GSH and dependent enzymes provide a survival advantage for cancer cells against chemotherapeutic drugs and radiotherapy.

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.

Correlation Between Gamma-Glutamyl Transferase Activity and Glutathione Levels in Molecular Subgroups of Breast Cancer

Objective

The gamma-glutamyl cycle catalyzed by gamma-glutamyl transferase (GGT) plays an important role in glutathione (GSH) homeostasis in the cell. In cells continuously exposed to the drug, the main phase of the enzymatic detoxification is the conjugation of the drug with GSH catalyzed by glutathione-S-transferase (GST). Conjugation of drugs with GSH is the first step in the development of chemotherapeutic drug resistance. In this study, we aimed to investigate the relationship between GGT and GSH in molecular subgroups of breast cancer patients.

Materials and Methods

Serum GGT activity and GSH levels for patients diagnosed with breast cancer (n=58) and healthy controls (n=8) were measured by a spectrophotometric method and a colorimetric kit, respectively.

Results

GGT activity was significantly higher in the total patient group and in the molecular subgroups than those in the control groups (p<0.05). Serum GSH levels were higher in the patient groups compared to controls without reaching statistical significance (p>0.05). GGT activity was positively correlated with GSH levels in the total patients and healthy controls (p<0.001 and p<0.05, respectively). There was also a positive correlation between GGT activity and GSH levels in Luminal A, HER2-positive (Human epidermal growth factor receptor 2), and Triple-negative groups (p<0.05).

Conclusion

This is the first study showing the relationship between GGT and GSH in molecular subgroups of breast cancer. An increase in GGT activity may affect intracellular GSH synthesis. Therefore, having a correlation between GGT and GSH in some molecular subgroups may affect the course of treatment in these patients.

Protective effects of hesperidin and diosmin against acrylamide-induced liver, kidney, and brain oxidative damage in rats

Acrylamide (AA) is a heat-induced toxin formed during thermal processing of many commonly consumed foods, including meat products, French fries, potato crisps, bread, cereals, cookies, and coffee. There is thus potentially high dietary exposure of humans to AA, which can induce significant oxidative stress. Hesperidin (HS) and diosmin (DS) are flavone glycosides that have antioxidant properties. The aim of this study was to investigate the protective effects of HS and DS against AA toxicity. Fifty-six adult male Wistar albino rats were divided into seven groups. The first group was orally administered 0.5% (w/v) dimethyl sulfoxide (DMSO) and considered as the control group. The second and third groups were orally administered 10 mg/kg/day of HS or DS, respectively. The fourth group received 20 mg/kg/day of AA orally for 14 days. The fifth and sixth groups were given 10 mg/kg/day of HS or DS, respectively, followed by AA. The seventh group was given both HS and DS after AA administration. AA intoxication significantly (p ≤ 0.05) increased serum levels of liver function enzymes (ALT, AST, and ALP), kidney function products (urea and creatinine), oxidative DNA damage marker (OHdG), proinflammatory markers (TNF-α, IL-1β, and IL-6), lipid peroxidation marker (malondialdehyde), and nitric oxide (NO). On the other hand, it significantly (p ≤ 0.05) decreased levels of reduced glutathione (GSH) in the liver, kidney, and brain. The activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) in the liver, kidney, and brain tissues were also reduced. HS and DS supplementation prevented lipid peroxidation, normalized the serum parameters altered by AA, and enhanced the tissue concentrations and activities of antioxidant biomarkers. It could be concluded that HS and DS have potent protective effects against oxidative stress, lipid peroxidation, and DNA damage induced by AA toxicity in rats.

Correlation of adenosine deaminase operating under nitro-oxidative stress with tumor and vascularization in patients with advanced gallbladder carcinoma

This study investigates serum redox status and adenosine catabolism markers in relation to tumor and angiogenesis, in patients with gallbladder carcinoma (GBC). The level of adenosine deaminase (ADA) and xanthine oxidase (XO) activities, nitrites (NO2^-), glutathione (GSH) and malondialdehyde (MDA) were measured in sera of 40 GBC patients and 40 healthy donors. In parallel, 15 tumors at TNM stage IV were scored for CD34 expression and microvessel density (MVD). The results showed that XO and ADA activities, nitrites and MDA levels enhanced by 1.26 (p < 0.01), 2.69, 2.0, and 3.2-fold (p < 0.001), respectively, while those of GSH decreased by 44.6% (p < 0.001). According to receiver operating characteristic (ROC) curve, the optimal cut-off for XO, ADA, MDA, GSH and nitrites were 5.41U/l, 17.02 U/l, 3.72 μM, 36.91 μM and 21.21 μM, respectively. Spearman correlation revealed that ADA activity correlated to nitrites levels (r = 0.3419, p < 0.05) and XO activity (r = 0.5487, p < 0.001). Multivariate binary logistic regression analysis revealed that MDA (OR = 5.78, p < 0.05), ADA (OR = 1.28, p < 0.001) and XO (OR = 2.81, p < 0.05) correlated positively to GBC. CD34 was up expressed in 73.3% of tumors at intermediate to high levels. Multiple regression analysis showed that ADA affected MVD (r = 0.604, p < 0.01). The results suggest that high MDA/GSH ratio is a potential biomarker of GBC. In addition, the oxidative adenosine catabolism indicated that active purine salvage pathway could support tumor progression by sustaining angiogenesis.

Prodrugs for targeted cancer therapy

Introduction: Prodrugs have been used to improve the selectivity and efficacy of cancer therapy by targeting unique abnormal markers that are overexpressed by cancer cells and are absent in normal tissues. In this context, different strategies have been exploited and new ones are being developed each year. Areas covered: In this review, an integrated view of the potential use of prodrugs in targeted cancer therapy is provided. Passive and active strategies are discussed in light of the advantages of each one and some successful examples are provided, as well as the clinical status of several prodrugs. Among them, antibody-drug conjugates (ADCs) are the most commonly used. However, several drawbacks, including limited prodrug uptake, poor pharmacokinetics, immunogenicity problems, difficulties in selective targeting and gene expression, and optimized bystander effects limit their clinical applications. Expert opinion: Despite the efforts of different companies and research groups, several drawbacks, such as the lack of relevant in vivo models, complexity of the human metabolism, and economic limitations, have hampered the development of new prodrugs for targeted cancer therapy. As a result, we believe that the combination of prodrugs with cancer nanotechnology and other newly developed approaches, such as aptamer-conjugated nanomaterials, are efficient strategies.

Association of GSTM1, GSTT1, GSTM3, and GSTP1 Genes Polymorphisms with Susceptibility to Osteosarcoma: a Case- Control Study and Meta-Analysis

Background: Some studies have investigated the association of GSTM1, GSTT1, GSTM3, and GSTP1 polymorphisms with susceptibility to osteosarcoma; however, these studies results are inconsistent and inconclusive. In order to drive a more precise estimation, the present case-control study and meta-analysis was performed to investigate association of GSTM1, GSTT1, GSTM3, and GSTP1 polymorphisms with osteosarcoma. Methods: Eligible articles were identified by a search of several electronic databases for the period up to May 5, 2018. Odds ratios were pooled using either fixed-effects or random effects models. Results: Finally, a total of 24 case-control studies with 2,405 osteosarcoma cases and 3,293 controls were included in the present meta-analysis. Overall, significantly increased osteosarcoma risk was found when all studies were pooled into the meta-analysis of GSTT1 (Null vs. Present: OR= 1.247 95% CI 1.020-1.524, P= 0.031) and GSTP1 polymorphism (B vs. A: OR= 8.899 95% CI 2.722-29.094, P≤0.001). In the stratified, significantly increased osteosarcoma risk was observed for GSTT1 polymorphism among Asians (Null vs. Present: OR= 1.300 95% CI 1.034-1.635, P= 0.025), but not among Caucasians. Conclusions: This meta-analysis demonstrated that GSTP1 and GSTT1 null genotype are associated with the risk of osteosarcoma. Future large welldesigned epidemiological studies are warranted to validate our results.

Chemotherapy Resistance Explained through Endoplasmic Reticulum Stress-Dependent Signaling

Cancers cells have the ability to develop chemotherapy resistance, which is a persistent problem during cancer treatment. Chemotherapy resistance develops through different molecular mechanisms, which lead to modification of the cancer cells signals needed for cellular proliferation or for stimulating an immune response. The endoplasmic reticulum (ER) is an important organelle involved in protein quality control, by promoting the correct folding of protein and ER-mediated degradation of unfolded or misfolded protein, namely, ER-associated degradation. Disturbances of the normal ER functions causes an accumulation of unfolded or misfolded proteins in the ER lumen, resulting in a condition called “ER stress (ERS).” ERS triggers the unfolded protein response (UPR)—also called the ERS response (ERSR)—to restore homeostasis or activate cell death. Although the ERSR is one emerging potential target for chemotherapeutics to treat cancer, it is also critical for chemotherapeutics resistance, as well. However, the detailed molecular mechanism of the relationship between the ERSR and tumor survival or drug resistance remains to be fully understood. In this review, we aim to describe the most vital molecular mechanism of the relationship between the ERSR and chemotherapy resistance. Moreover, the review also discusses the molecular mechanism of ER stress-mediated apoptosis on cancer treatments.

JS-K induces reactive oxygen species-dependent anti-cancer effects by targeting mitochondria respiratory chain complexes in gastric cancer

As a nitric oxide (NO) donor prodrug, JS‐K inhibits cancer cell proliferation, induces the differentiation of human leukaemia cells, and triggers apoptotic cell death in various cancer models. However, the anti‐cancer effect of JS‐K in gastric cancer has not been reported. In this study, we found that JS‐K inhibited the proliferation of gastric cancer cells in vitro and in vivo and triggered mitochondrial apoptosis. Moreover, JS‐K induced a significant accumulation of reactive oxygen species (ROS), and the clearance of ROS by antioxidant reagents reversed JS‐K‐induced toxicity in gastric cancer cells and subcutaneous xenografts. Although JS‐K triggered significant NO release, NO scavenging had no effect on JS‐K‐induced toxicity in vivo and in vitro. Therefore, ROS, but not NO, mediated the anti‐cancer effects of JS‐K in gastric cancer. We also explored the potential mechanism of JS‐K‐induced ROS accumulation and found that JS‐K significantly down‐regulated the core proteins of mitochondria respiratory chain (MRC) complex I and IV, resulting in the reduction of MRC complex I and IV activity and the subsequent ROS production. Moreover, JS‐K inhibited the expression of antioxidant enzymes, including copper‐zinc‐containing superoxide dismutase (SOD1) and catalase, which contributed to the decrease of antioxidant enzymes activity and the subsequent inhibition of ROS clearance. Therefore, JS‐K may target MRC complex I and IV and antioxidant enzymes to exert ROS‐dependent anti‐cancer function, leading to the potential usage of JS‐K in the prevention and treatment of gastric cancer.

Toward Multi-Targeted Platinum and Ruthenium Drugs-A New Paradigm in Cancer Drug Treatment Regimens?

While medicinal inorganic chemistry has been practised for over 5000 years, it was not until the late 1800s when Alfred Werner published his ground-breaking research on coordination chemistry that we began to truly understand the nature of the coordination bond and the structures and stereochemistries of metal complexes. We can now readily manipulate and fine-tune their properties. This had led to a multitude of complexes with wide-ranging biomedical applications. This review will focus on the use and potential of metal complexes as important therapeutic agents for the treatment of cancer. With major advances in technologies and a deeper understanding of the human genome, we are now in a strong position to more fully understand carcinogenesis at a molecular level. We can now also rationally design and develop drug molecules that can either selectively enhance or disrupt key biological processes and, in doing so, optimize their therapeutic potential. This has heralded a new era in drug design in which we are moving from a single- toward a multitargeted approach. This approach lies at the very heart of medicinal inorganic chemistry. In this review, we have endeavored to showcase how a "multitargeted" approach to drug design has led to new families of metallodrugs which may not only reduce systemic toxicities associated with modern day chemotherapeutics but also address resistance issues that are plaguing many chemotherapeutic regimens. We have focused our attention on metallodrugs incorporating platinum and ruthenium ions given that complexes containing these metal ions are already in clinical use or have advanced to clinical trials as anticancer agents. The "multitargeted" complexes described herein not only target DNA but also contain either vectors to enable them to target cancer cells selectively and/or moieties that target enzymes, peptides, and intracellular proteins. Multitargeted complexes which have been designed to target the mitochondria or complexes inspired by natural product activity are also described. A summary of advances in this field over the past decade or so will be provided.

Hypoxia-inducible factors promote breast cancer stem cell specification and maintenance in response to hypoxia or cytotoxic chemotherapy

Clinical studies have revealed that breast cancers contain regions of intratumoral hypoxia (reduced oxygen availability), which activates hypoxia-inducible factors (HIFs). The relationship between intratumoral hypoxia, distant metastasis and cancer mortality has been well established. A major mechanism by which intratumoral hypoxia contributes to disease progression is through induction of the breast cancer stem cell (BCSC) phenotype. BCSCs are a small subpopulation of cells with the capability for self-renewal. BCSCs have been implicated in resistance to chemotherapy, disease recurrence, and metastasis. In this review, we will discuss our current understanding of the molecular mechanisms underlying HIF-dependent induction of the BCSC phenotype in response to hypoxia or chemotherapy.

Glutathione Transferases: Potential Targets to Overcome Chemoresistance in Solid Tumors

Multifunctional enzymes glutathione transferases (GSTs) are involved in the development of chemoresistance, thus representing a promising target for a novel approach in cancer treatment. This superfamily of polymorphic enzymes exhibits extraordinary substrate promiscuity responsible for detoxification of numerous conventional chemotherapeutics, at the same time regulating signaling pathways involved in cell proliferation and apoptosis. In addition to upregulated GST expression, different cancer cell types have a unique GST signature, enabling targeted selectivity for isoenzyme specific inhibitors and pro-drugs. As a result of extensive research, certain GST inhibitors are already tested in clinical trials. Catalytic properties of GST isoenzymes are also exploited in bio-activation of specific pro-drugs, enabling their targeted accumulation in cancer cells with upregulated expression of the appropriate GST isoenzyme. Moreover, the latest approach to increase specificity in treatment of solid tumors is development of GST pro-drugs that are derivatives of conventional anti-cancer drugs. A future perspective is based on the design of new drugs, which would selectively target GST overexpressing cancers more prone to developing chemoresistance, while decreasing side effects in off-target cells.

Glutathione S-transferase π: a potential role in antitumor therapy

Glutathione S-transferase π (GSTπ) is a Phase II metabolic enzyme that is an important facilitator of cellular detoxification. Traditional dogma asserts that GSTπ functions to catalyze glutathione (GSH)-substrate conjunction to preserve the macromolecule upon exposure to oxidative stress, thus defending cells against various toxic compounds. Over the past 20 years, abnormal GSTπ expression has been linked to the occurrence of tumor resistance to chemotherapy drugs, demonstrating that this enzyme possesses functions beyond metabolism. This revelation reveals exciting possibilities in the realm of drug discovery, as GSTπ inhibitors and its prodrugs offer a feasible strategy in designing anticancer drugs with the primary purpose of reversing tumor resistance. In connection with the authors' current research, we provide a review on the biological function of GSTπ and current developments in GSTπ-targeting drugs, as well as the prospects of future strategies.

Molecular evaluation of glutathione S transferase family genes in patients with sporadic colorectal cancer

AIM

To evaluate the association between polymorphisms in glutathione S transferases (GSTs) and the risk of sporadic colorectal cancer (SCRC), tumor progression and the survival of patients.

METHODS

A case-control study of 970 individuals from the Brazilian population was conducted (232 individuals from the case group with colorectal cancer and 738 individuals from the control group without a history of cancer). PCR multiplex and PCR-RFLP techniques were used to genotype the GST polymorphisms. The tumors were categorized according to the TNM classification: tumor extension (T), affected lymph nodes (N), and presence of metastasis (M). Logistic regression, multiple logistic regression and survival analysis were used to analyze the data. The results are presented in terms of odds ratio (OR) and 95% confidence interval (CI). The level of significance was set at 5% (P ≤ 0.05).

RESULTS

Age equal to or over 62 years (OR = 8.79; 95%CI: 5.90-13.09, P < 0.01) and female gender (OR = 2.91; 95%CI: 1.74-4.37; P < 0.01) were associated with increased risk of SCRC. Analysis of the polymorphisms revealed an association between the GSTM1 polymorphisms and a risk of SCRC (OR = 1.45; 95%CI: 1.06-2.00; P = 0.02), as well as between GSTT1 and a reduced risk of the disease (OR = 0.65; 95%CI: 0.43-0.98; P = 0.04). An interaction between the presence of the wild-type allele of GSTP1 Ile105Val polymorphism and tobacco consumption on risk of SCRC (OR = 2.33; 95%CI: 1.34-4.05; P = 0.05) was observed. There was an association between the GSTM1 null genotype and the presence of advanced tumors (OR = 2.33; 95%CI: 1.23-4.41; P = 0.009), as well as increased risk of SCRC in the presence of a combination of GSTT1 non-null/GSTM1 null genotypes (OR = 1.50; 95%CI: 1.03-2.19; P = 0.03) and GSTT1 non-null/GSTM1 null/GSTP1 Val* (OR = 1.85; 95%CI: 1.01-3.36, P = 0.04). Combined GSTT1 non-null/GSTM1 null genotypes (OR = 2.40; 95%CI: 1.19-4.85; P = 0.01) and GSTT1 non-null/GSTM1 null/GSTP1 Val* (OR = 2.92; 95%CI: 1.05-8.12; P = 0.04) were associated with tumor progression. Polymorphisms were not associated with the survival of patients with SCRC.

CONCLUSION

Females aged 62 years or older are more susceptible to SCRC. Polymorphisms of GSTT1 and GSTM1 null genotypes modulated the susceptibility to SCRC in the population studied.

Leveraging γ-Glutamyl Transferase To Direct Cytotoxicity of Copper Dithiocarbamates against Prostate Cancer Cells

A prodrug approach is presented to direct copper-dependent cytotoxicity to prostate cancer cells. The prochelator GGTDTC requires activation by γ-glutamyl transferase (GGT) to release the metal chelator diethyldithiocarbamate from a linker that masks its thiol reactivity and metal binding properties. In vitro studies demonstrated successful masking of copper binding as well as clean liberation of the chelator by GGT. GGTDTC was stable to non-specific degradation when incubated with a series of prostate cancer and normal cell lines, with selective release of diethyldithiocarbamate only occurring in cells with measurable GGT activity. The antiproliferative efficacy of the prochelator correlated with cellular GGT activity, with 24 h inhibitory concentrations ranging from 800 nm in prostate cancer lines 22Rv1 and LNCaP to over 15 μm in normal prostate PWR-1E cells. These findings underscore a new strategy to leverage the amplified copper metabolism of prostate cancer by conditional activation of a metal-binding pharmacophore.

Identification of a co-target for enhancing efficacy of sorafenib in HCC through a quantitative modeling approach

Sorafenib (SFB), a multi-kinase inhibitor, is the only approved drug for treating hepatocellular carcinoma (HCC). However, SFB shows low efficacy in many cases. HCC related mortality therefore remains to be high worldwide. SFB, a multi-kinase inhibitor is also known to modulate the redox homeostasis in cancer cells. To understand the effect of SFB on the redox status, a quantitative understanding of the system is necessary. Kinetic modeling of the relevant pathways is a useful approach for obtaining a quantitative understanding of the pathway dynamics and to rank the individual factors based on the extent of influence they wield on the pathway. Here, we report a comprehensive model of the glutathione reaction network (GSH_net ), consisting of four modules and includes SFB-induced redox stress. We compared GSH_net simulations for HCC of six different etiologies with healthy liver, and correctly identified the expected variations in cancer. Next, we studied alterations induced in the system upon SFB treatment and observed differential H₂ O₂ dynamics in all the conditions. Using metabolic control analysis, we identified glutathione S-transferase (GST) as the enzyme with the highest selective control coefficient, making it an attractive co-target for potentiating the action of SFB across all six etiologies. As a proof-of-concept, we selected ethacrynic acid (EA), a known inhibitor of GST, and verified ex vivo that EA synergistically potentiates the cytotoxic effect of SFB. Being an FDA approved drug, EA is a promising candidate for repurposing as a combination therapy with SFB for HCC treatment.

Photo-induced anticancer activity and singlet oxygen production of prodigiosenes

The photo-induced cytotoxicity of prodigiosenes is reported. One prodigiosene represents a synthetic analogue of the natural product prodigiosin, and two are conjugated to molecules that target the estrogen receptor (ER). A comparison of incubation and irradiation frameworks for the three prodigiosenes is reported, with activity against ER- and ER+ lines explored. Furthermore, the ability of the three prodigiosenes to photosensitise the production of singlet oxygen is demonstrated, shedding mechanistic light onto possible photodynamic therapeutic effects of this class of tripyrroles.

Ligand-induced glutathione transferase degradation as a therapeutic modality: Investigation of a new metal-mediated affinity cleavage strategy for human GSTP1-1

Glutathione transferases (GST, EC. 2.5.1.18) are overexpressed in cancer cell and have been shown to be involved in cancer cell growth, differentiation and the development of multi-drug resistance (MDR) mechanism. Therefore, GST inhibitors are emerging as promising chemosensitizers to manage and reverse MDR. The present work aims to the synthesis, characterization and assessment of a new active-site chimeric inhibitor towards the MDR-involved human GSTP1-1 isoenzyme (hGSTP1-1). The inhibitor [BDA-Fe(III)] was designed to possess two functional groups: the anthraquinone moiety, as recognition element by hGSTP1-1 and a metal chelated complex [iminodiacetic acid-Fe(III)] as a reactive moiety, able to generate reactive oxygen species (ROS), through Fenton reaction. Upon binding of the BDA-Fe(III) to hGSTP1-1 in the presence of hydrogen peroxide, reactive oxygen species (ROS) are generated, which promoted the specific cleavage of hGSTP1-1 in a time and concentration-dependent manner. Electrophoretic analysis showed that each enzyme subunit is cleaved at a single site. Amino acid sequencing as well as molecular modelling studies established that the cleaved peptide bond is located between the amino acids Tyr103 and Ile104. This ligand-induced hGSTP1-1 degradation and inactivation strategy is discussed as a new approach towards chemosensitization of MDR cancer cells.