Phosphorylation of Glutathione S-Transferase P1 (GSTP1) by Epidermal Growth Factor Receptor (EGFR) Promotes Formation of the GSTP1-c-Jun N-terminal kinase (JNK) Complex and Suppresses JNK Downstream Signaling and Apoptosis in Brain Tumor Cells

Naphthalene and phenanthrene affect differentially two glutathione S-transferases (GSTs) expression, GST activity, and glutathione content in white shrimp P. vannamei

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants ubiquitous in coastal ecosystems. The white shrimp Penaeus vannamei naturally inhabits in coastal areas and is cultivated in farms located nearby the oceans. PAHs can damage shrimp health, endanger natural populations, and lower shrimp aquaculture productivity. However, crustaceans have enzymes capable of metabolizing organic xenobiotics as PAHs and to neutralize reactive oxygen species (ROS) produced during xenobiotics metabolism. An important superfamily of xenobiotic-metabolizing and antioxidant enzymes are glutathione S-transferases (GSTs). In white shrimp, some GSTs are known, but they have been scarcely studied in response to PAHs. In this study we report the molecular cloning and bioinformatic characterization of two novel nucleotide sequences corresponding to cytosolic GSTs belonging the Delta and Theta classes (GSTD and GSTT). Both proteins genes have tissue-specific patterns of expression under normal conditions, that do not necessarily relate to GST activity and glutathione content. The expression of the GSTD and GSTT, GST activity and glutathione content was analyzed in juvenile P. vannamei exposed to two PAHs, naphthalene (NAP) and phenanthrene (PHE) in sub-lethal concentrations for 96 h. GSTD expression was up-regulated by the two PAHs, while GSTT expression was only induced by NAP. In contrast, GST activity towards CDNB was only up-regulated by PHE, suggesting differential effects of PAHs at gene and protein level. On the other hand, lower reduced glutathione content (GSH) caused by PAHs indicates its utilization for detoxification or antioxidant defenses. However, the GSH/GSSG did not change by PAHs treatment, indicating that shrimp can maintain redox balance during short-term sub-lethal exposure to NAP and PHE. Despite the variations in the responses to NAP and PHE, all these results suggest that the GSTD and GSTT genes could be useful biomarkers for PAH exposure in P. vannamei.

Involvement of GSTP1 in low dose radiation-induced apoptosis in GM12878 cells

BACKGROUND

Low-dose ionizing radiation-induced protection and damage are of great significance among radiation workers. We aimed to study the role of glutathione S-transferase Pi (GSTP1) in low-dose ionizing radiation damage and clarify the impact of ionizing radiation on the biological activities of cells.

RESULTS

In this study, we collected peripheral blood samples from healthy adults and workers engaged in radiation and radiotherapy and detected the expression of GSTP1 by qPCR. We utilized γ-rays emitted from uranium tailings as a radiation source, with a dose rate of 14 μGy/h. GM12878 cells subjected to this radiation for 7, 14, 21, and 28 days received total doses of 2.4, 4.7, 7.1, and 9.4 mGy, respectively. Subsequent analyses, including flow cytometry, MTS, and other assays, were performed to assess the ionizing radiation's effects on cellular biological functions. In peripheral blood samples collected from healthy adults and radiologic technologist working in a hospital, we observed a decreased expression of GSTP1 mRNA in radiation personnel compared to the healthy controls. In cultured GM12878 cells exposed to low-dose ionizing radiation from uranium tailings, we noted significant changes in cell morphology, suppression of proliferation, delay in cell cycle progression, and increased apoptosis. These effects were partially reversed by overexpression of GSTP1. Moreover, low-dose ionizing radiation increased GSTP1 gene methylation and downregulated GSTP1 expression. Furthermore, low-dose ionizing radiation affected the expression of GSTP1-related signaling molecules.

CONCLUSIONS

This study shows that low-dose ionizing radiation damages GM12878 cells and affects their proliferation, cell cycle progression, and apoptosis. In addition, GSTP1 plays a modulating role under low-dose ionizing radiation damage conditions. Low-dose ionizing radiation affects the expression of Nrf2, JNK, and other signaling molecules through GSTP1.

A GSTP1-mediated lactic acid signaling promotes tumorigenesis through the PPP oxidative branch

Lactic acidosis is a feature of solid tumors and plays fundamental role(s) rendering cancer cells to adapt to diverse metabolic stresses, but the mechanism underlying its roles in redox homeostasis remains elusive. Here we show that G6PD is phosphorylated at tyrosine 249/322 by the SRC through the formation of a GSTP1-G6PD-SRC complex. Lactic acid attenuates this formation and the phosphorylation of G6PD by non-covalently binding with GSTP1. Furthermore, lactic acid increases the activity of G6PD and facilitates the PPP (NADPH production) through its sensor GSTP1, thereby exhibiting resistance to reactive oxygen species when glucose is scarce. Abrogating a GSTP1-mediated lactic acid signaling showed attenuated tumor growth and reduced resistance to ROS in breast cancer cells. Importantly, positive correlations between immuno-enriched SRC protein and G6PD Y249/322 phosphorylation specifically manifest in ER/PR positive or HER negative types of breast cancer. Taken together, these results suggest that GSTP1 plays a key role in tumor development by functioning as a novel lactate sensor.

NUMA1 modulates apoptosis of esophageal squamous cell carcinoma cells through regulating ASK1-JNK signaling pathway

Esophageal squamous cell carcinoma (ESCC) is a common malignancy worldwide with a low survival rate due to a lack of therapeutic targets. Here, our results showed that nuclear mitotic apparatus protein 1 (NUMA1) transcript and protein levels are significantly upregulated in ESCC patient samples and its high expression predicated poor prognosis. Knock-down of NUMA1 promoted cell apoptosis and suppressed cell proliferation and colony formation. By using cell-derived xenograft (CDX) and patient-derived xenograft (PDX) mice models, we found silencing the NUMA1 expression suppressed tumor progression. In addition, conditional knocking-out of NUMA1 reduced 4NQO-induced carcinogenesis in mice esophagus, which further confirmed the oncogenic role of NUMA1 in ESCC. Mechanistically, from the immunoprecipitation assay we revealed that NUMA1 interacted with GSTP1 and TRAF2, promoted the association of TRAF2 with GSTP1 while inhibited the interaction of TRAF2 and ASK1, thus to regulate sustained activation of JNK. In summary, our findings suggest that NUMA1 plays an important role during ESCC progression and it functions through regulating ASK1-MKK4-SAPK/JNK signaling pathway.

The GSTP1/MAPKs/BIM/SMAC modulatory actions of nitazoxanide: Bioinformatics and experimental evidence in subcutaneous solid Ehrlich carcinoma-inoculated mice

AIMS

Ehrlich ascites carcinoma and its subcutaneous inoculated solid tumour form (SEC) are reliable models for chemotherapeutic molecular targets exploration. Novel chemotherapeutic approaches are identified as molecular targets for intrinsic apoptosis, like the modulation of the second mitochondria-derived activator of caspases (SMAC). SMAC is a physiological substrate of mitogen-activated protein kinases (MAPKs). Glutathione-S-transferase P1 (GSTP1) and its close association with MAPKs play an important role in malignant cell proliferation, metastasis, and resistance to chemotherapeutics. Nitazoxanide (NTZ) is an emerging cancer therapy and its targeted GSTP1 evidence remains a knowledge need.

MAIN METHODS

In the present mice-established SEC, the chemotherapeutic roles of oral NTZ (200 mg/kg/day) and 5-fluorouracil (5-FU; 20 mg/kg/day, intraperitoneally) regimens were evaluated by measuring changes in tumour mass, the tumour MAPKs, cytochrome c, Bcl-2 interacting mediator of cell death (BIM), and SMAC signalling pathway in addition to its molecular downstream; caspases 3 and 9.

KEY FINDINGS

Computational analysis for these target protein interactions showed direct-ordered interactions. After individual therapy with NTZ and 5-FU regimens, the histological architecture of the extracted tumour discs revealed decreases in viable tumour regions with significant necrosis surrounds. These findings were consistent with gross tumour sizes. Each separate regimen lowered the remarkable GSTP1 and elevated the low MAPKs expressions, cytochrome c, BIM, SMAC, and caspases 3, and 9 in EST tissues.

SIGNIFICANCE

The chemotherapeutic activity of NTZ in SEC was proven. Additionally, NTZ possesses a SMAC modulatory activity that, following thorough research, should be taken into consideration as a chemotherapeutic approach in solid tumours.

The good Samaritan glutathione-S-transferase P1: An evolving relationship in nitric oxide metabolism mediated by the direct interactions between multiple effector molecules

Glutathione-S-transferases (GSTs) are phase II detoxification isozymes that conjugate glutathione (GSH) to xenobiotics and also suppress redox stress. It was suggested that GSTs have evolved not to enhance their GSH affinity, but to better interact with and metabolize cytotoxic nitric oxide (NO). The interactions between NO and GSTs involve their ability to bind and store NO as dinitrosyl-dithiol iron complexes (DNICs) within cells. Additionally, the association of GSTP1 with inducible nitric oxide synthase (iNOS) results in its inhibition. The function of NO in vasodilation together with studies associating GSTM1 or GSTT1 null genotypes with preeclampsia, additionally suggests an intriguing connection between NO and GSTs. Furthermore, suppression of c-Jun N-terminal kinase (JNK) activity occurs upon increased levels of GSTP1 or NO that decreases transcription of JNK target genes such as c-Jun and c-Fos, which inhibit apoptosis. This latter effect is mediated by the direct association of GSTs with MAPK proteins. GSTP1 can also inhibit nuclear factor kappa B (NF-κB) signaling through its interactions with IKKβ and Iκα, resulting in decreased iNOS expression and the stimulation of apoptosis. It can be suggested that the inhibitory activity of GSTP1 within the JNK and NF-κB pathways may be involved in crosstalk between survival and apoptosis pathways and modulating NO-mediated ROS generation. These studies highlight an innovative role of GSTs in NO metabolism through their interaction with multiple effector proteins, with GSTP1 functioning as a "good Samaritan" within each pathway to promote favorable cellular conditions and NO levels.

Activity-Based Proteomic Identification of the S-Thiolation Targets of Ajoene in MDA-MB-231 Breast Cancer Cells

Garlic is a medicinal plant and spice that has been used for millennia for its health-promoting effects. These medicinal properties are associated with low molecular weight organosulfur compounds, produced following the crushing of garlic cloves. One of these compounds, ajoene, is proposed to act by S-thioallylating cysteine residues on target proteins whose identification in cancer cells holds great promise for understanding mechanistic aspects of ajoene's cancer cell cytotoxicity. To this end, an ajoene analogue (called biotin-ajoene, BA), containing a biotin affinity tag, was designed as an activity-based probe specific for the protein targets of ajoene in MDA-MB-231 breast cancer cells. BA was synthesized via a convergent "click" strategy and found to retain its cytotoxicity against MDA-MB-231 cells compared to ajoene. Widespread biotinylation of proteins was found to occur via disulfide bond formation in a dose-dependent manner, and the biotin-ajoene probe was found to share the same protein targets as its parent compound, ajoene. The biotinylated proteins were affinity-purified from the treated MDA-MB-231 cell lysate using streptavidin-coated magnetic beads followed by an on-bead reduction, alkylation, and digestion to liberate the peptide fragments, which were analyzed by liquid chromatography tandem mass chromatography. A total of 600 protein targets were identified, among which 91% overlapped with proteins with known protein cysteine modification (PCM) sites. The specific sites were enriched for those susceptible to S-glutathionylation (-SSG) (16%), S-sulfhydration (-SSH) (20%), S-sulfenylation (-SOH) (22%), and S-nitrosylation (-SNO) (31%). As target validation, both ajoene and a dansylated ajoene (DP) were found to S-thiolate the pure recombinant forms of glutathione S-transferase pi 1 (GSTP1) and protein disulfide isomerase (PDI), and the ajoene analogue DP was found to be a more potent inhibitor than 5,5-dithio-bis-(2-nitrobenzoic acid) (DTNB). Pathway analysis elucidated that ajoene targets functional and signaling pathways that are implicated in cancer cell survival, specifically cellular processes, metabolism, and genetic information processing pathways. The results of this study provide mechanistic insights into the character of the anti-cancer activity of the natural dietary compound ajoene.

Praeruptorin B inhibits osteoclastogenesis by targeting GSTP1 and impacting on the S-glutathionylation of IKKβ

Osteoporosis a common disease in postmenopausal women which contains significant impact on the living quality of women. With the aging of the population, the number of patients suffer from osteoporosis has shown a significant increase. Given the limitations of clinical drugs for the treatment of osteoporosis, natural extracts with small side effects have a great application prospect in the treatment of osteoporosis. Praeruptorin B (Pra-B), is one of the main components found in the roots of Peucedanum praeruptorum Dunn and exhibits anti-inflammatory effects. However, there is no research on the influence of Pra-B on osteoporosis. Here, we showed that Pra-B can dose-dependently suppress osteoclastogenesis without cytotoxicity. Receptor activator of nuclear factor kappa-B (NF-κB) ligand (RANKL)-induced the nuclear import of P65 was inhibited by Pra-B, which indicated the suppressive effect of Pra-B on NF-κB signaling. Further, Pra-B enhanced the expression of Glutathione S-transferase Pi 1 (GSTP1) and promoted the S-glutathionylation of IKKβ to inhibit the nuclear translocation of P65. Moreover, in vivo experiments showed that Pra-B considerably attenuated the bone loss in ovariectomy (OVX)-induced mice. Collectively, our studies revealed that Pra-B suppress the NF-κB signaling targeting GSTP1 to rescued RANKL-induced osteoclastogenesis in vitro and OVX-induced bone loss in vivo, supporting the potential of Pra-B for treating osteoporosis in the future.

Implications of glutathione-S transferase P1 in MAPK signaling as a CRAF chaperone: In memory of Dr. Irving Listowsky

Glutathione-S transferase P1 (GSTP1) is one of the glutathione-S transferase isozymes that belong to a family of phase II metabolic isozymes. The unique feature of GSTP1 compared with other GST isozymes is its relatively high expression in malignant tissues. Thus, clinically, GSTP1 serves as a tumor marker and as a refractory factor against certain types of anticancer drugs through its primary function as a detoxifying enzyme. Additionally, recent studies have identified a chaperone activity of GSTP1 involved in the regulation the function of various intracellular proteins, including factors of the growth signaling pathway. In this review, we will first describe the function of GSTP1 and then extend the details onto its role in the mitogen-activated protein kinase signal pathway, referring to the results of our recent study that proposed a novel autocrine signal loop formed by the CRAF/GSTP1 complex in mutated KRAS and BRAF cancers. Finally, the possibilities of new therapeutic approaches for these cancers by targeting this complex will be discussed.

Identification of glutathione-S-transferase m19 and m34 among responsive GST genes against 1-chloro-2,4-dinitrobenzene treatment of Tetrahymena thermophila

Industrial xenobiotic pollutants have toxic effects on diverse organisms in their natural environments. This study aims to identify the Glutathione-S-transferases (GST) from Tetrahymena thermophila that are highly responsive to the treatment of synthetic substrate 1-chloro-2,4-dinitrobenzene (CDNB). The LD50 value of CDNB was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test as 0.079 mM at 9 h exposure. The glutathione affinity-purified 22 kDa and 23 kDa GSTs from CDNB-treated cells were identified as GSTm19 and GSTm34 with 2D-gel electrophoresis coupled MALDI-Tof MS/MS analysis. The specific activitiy of the affinity-purified GSTs was upregulated upon the treatment of 0.072 mM CDNB with the decreased cell survival. GSTm19 and GSTm34 had also upregulated the mRNA expression under the highest dose treatment. The high cell survival and elevated total GST enzyme activity at 9 h under CDNB doses could be the result of both transcriptional upregulations as well as post-translational modifications. As a result, the cell survival of Tetrahymena thermophila was significantly affected by CDNB exposure in a concentration-dependent manner with the effect of low-dose stimulation and high-dose inhibition.

Biomarkers and Mechanisms of Oxidative Stress-Last 20 Years of Research with an Emphasis on Kidney Damage and Renal Transplantation

Oxidative stress is an imbalance between pro- and antioxidants that adversely influences the organism in various mechanisms and on many levels. Oxidative damage occurring concomitantly in many cellular structures may cause a deterioration of function, including apoptosis and necrosis. The damage leaves a molecular “footprint”, which can be detected by specific methodology, using certain oxidative stress biomarkers. There is an intimate relationship between oxidative stress, inflammation, and functional impairment, resulting in various diseases affecting the entire human body. In the current narrative review, we strengthen the connection between oxidative stress mechanisms and their active compounds, emphasizing kidney damage and renal transplantation. An analysis of reactive oxygen species (ROS), antioxidants, products of peroxidation, and finally signaling pathways gives a lot of promising data that potentially will modify cell responses on many levels, including gene expression. Oxidative damage, stress, and ROS are still intensively exploited research subjects. We discuss compounds mentioned earlier as biomarkers of oxidative stress and present their role documented during the last 20 years of research. The following keywords and MeSH terms were used in the search: oxidative stress, kidney, transplantation, ischemia-reperfusion injury, IRI, biomarkers, peroxidation, and treatment.

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.

Development and biological applications of sulfur-triazole exchange (SuTEx) chemistry

Sulfur electrophiles constitute an important class of covalent small molecules that have found widespread applications in synthetic chemistry and chemical biology. Various electrophilic scaffolds, including sulfonyl fluorides and arylfluorosulfates as recent examples, have been applied for protein bioconjugation to probe ligand sites amenable for chemical proteomics and drug discovery. In this review, we describe the development of sulfonyl-triazoles as a new class of electrophiles for sulfur-triazole exchange (SuTEx) chemistry. SuTEx achieves covalent reaction with protein sites through irreversible modification of a residue with an adduct group (AG) upon departure of a leaving group (LG). A principal differentiator of SuTEx from other chemotypes is the selection of a triazole heterocycle as the LG, which introduces additional capabilities for tuning the sulfur electrophile. We describe the opportunities afforded by modifications to the LG and AG alone or in tandem to facilitate nucleophilic substitution reactions at the SO2 center in cell lysates and live cells. As a result of these features, SuTEx serves as an efficient platform for developing chemical probes with tunable bioactivity to study novel nucleophilic sites on established and poorly annotated protein targets. Here, we highlight a suite of biological applications for the SuTEx electrophile and discuss future goals for this enabling covalent chemistry.

Deactivation of the JNK Pathway by GSTP1 Is Essential to Maintain Sperm Functionality

Fifty percent of male subfertility diagnosis is idiopathic and is usually associated with genetic abnormalities or protein dysfunction, which are not detectable through the conventional spermiogram. Glutathione S-transferases (GSTs) are antioxidant enzymes essential for preserving sperm function and maintaining fertilizing ability. However, while the role of GSTP1 in cell signaling regulation via the inhibition of c-Jun N-terminal kinases (JNK) has been enlightened in somatic cells, it has never been investigated in mammalian spermatozoa. In this regard, a comprehensive approach through immunoblotting, immunofluorescence, computer-assisted sperm assessment (CASA), and flow cytometry analysis was used to characterize the molecular role of the GSTP1–JNK heterocomplex in sperm physiology, using the pig as a model. Immunological assessments confirmed the presence and localization of GSTP1 in sperm cells. The pharmacological dissociation of the GSTP1–JNK heterocomplex resulted in the activation of JNK, which led to a significant decrease in sperm viability, motility, mitochondrial activity, and plasma membrane stability, as well as to an increase of intracellular superoxides. No effects in intracellular calcium levels and acrosome membrane integrity were observed. In conclusion, the present work has demonstrated, for the first time, the essential role of GSTP1 in deactivating JNK, which is crucial to maintain sperm function and has also set the grounds to understand the relevance of the GSTP1–JNK heterocomplex for the regulation of mammalian sperm physiology.

Glutathione S-Transferase P Influences Redox Homeostasis and Response to Drugs that Induce the Unfolded Protein Response in Zebrafish

We have created a novel glutathione S-transferase π1 (gstp1) knockout (KO) zebrafish model and used it for comparative analyses of redox homeostasis and response to drugs that cause endoplasmic reticulum (ER) stress and induce the unfolded protein response (UPR). Under basal conditions, gstp1 KO larvae had higher expression of antioxidant nuclear factor erythroid 2-related factor 2 (Nrf2) accompanied by a more reduced larval environment and a status consistent with reductive stress. Compared with wild type, various UPR markers were decreased in KO larvae, but treatment with drugs that induce ER stress caused greater toxicities and increased expression of Nrf2 and UPR markers in KO. Tunicamycin and 0²-{2,4-dinitro-5-[4-(N-methylamino)benzoyloxy]phenyl}1-(N,N-dimethylamino)diazen-1-ium-1,2-diolate (PABA/nitric oxide) activated inositol-requiring protein-1/X-box binding protein 1 pathways, whereas thapsigargin caused greater activation of protein kinase-like ER kinase/activating transcription factor 4/CHOP pathways. These results suggest that this teleost model is useful for predicting how GSTP regulates organismal management of oxidative/reductive stress and is a determinant of response to drug-induced ER stress and the UPR. SIGNIFICANCE STATEMENT: A new zebrafish model has been created to study the importance of glutathione S-transferase π1 in development, redox homeostasis, and response to drugs that enact cytotoxicity through endoplasmic reticulum stress and induction of the unfolded protein response.

A CRAF/glutathione-S-transferase P1 complex sustains autocrine growth of cancers with KRAS and BRAF mutations

A strategy to overcome therapeutic obstacles of mKRAS and mBRAF cancers is devised based on the finding, here, that the RAF/MEK/ERK cascade is by-passed by an autocrine signal loop established by interaction of CRAF with GSTP1. The interaction evokes stabilization of CRAF from proteosomal degradation and facilitation of RAF-dimer formation. Thus, blocking CRAF/GSTP1 interactions should generate additive antiproliferative effects.

The Ras/RAF/MEK/ERK pathway is an essential signaling cascade for various refractory cancers, such as those with mutant KRAS (mKRAS) and BRAF (mBRAF). However, there are unsolved ambiguities underlying mechanisms for this growth signaling thereby creating therapeutic complications. This study shows that a vital component of the pathway CRAF is directly impacted by an end product of the cascade, glutathione transferases (GST) P1 (GSTP1), driving a previously unrecognized autocrine cycle that sustains proliferation of mKRAS and mBRAF cancer cells, independent of oncogenic stimuli. The CRAF interaction with GSTP1 occurs at its N-terminal regulatory domain, CR1 motif, resulting in its stabilization, enhanced dimerization, and augmented catalytic activity. Consistent with the autocrine cycle scheme, silencing GSTP1 brought about significant suppression of proliferation of mKRAS and mBRAF cells in vitro and suppressed tumorigenesis of the xenografted mKRAS tumor in vivo. GSTP1 knockout mice showed significantly impaired carcinogenesis of mKRAS colon cancer. Consequently, hindering the autocrine loop by targeting CRAF/GSTP1 interactions should provide innovative therapeutic modalities for these cancers.

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.

GSTP1 and cancer: Expression, methylation, polymorphisms and signaling (Review)

Glutathione S‑transferase Pi (GSTP1) is an isozyme encoded by the GST pi gene that plays an important regulatory role in detoxification, anti‑oxidative damage, and the occurrence of various diseases. The aim of the present study was to review the association between the expression of GSTP1 and the development and treatment of various cancers, and discuss GSTP1 methylation in several malignant tumors, such as prostate, breast and lung cancer, as well as hepatocellular carcinoma; to review the association between polymorphism of the GSTP1 gene and various diseases; and to review the effects of GSTP1 on electrophilic oxidative stress, cell signal transduction, and the regulation of carcinogenic factors. Collectively, GSTP1 plays a major role in the development of various diseases.

Selective inhibitors for JNK signalling: a potential targeted therapy in cancer

c-Jun N-terminal kinase (JNK) signalling regulates both cancer cell apoptosis and survival. Emerging evidence show that JNK promoted tumour progression is involved in various cancers, that include human pancreatic-, lung-, and breast cancer. The pro-survival JNK oncoprotein functions in a cell context- and cell type-specific manner to affect signal pathways that modulate tumour initiation, proliferation, and migration. JNK is therefore considered a potential oncogenic target for cancer therapy. Currently, designing effective and specific JNK inhibitors is an active area in the cancer treatment. Some ATP-competitive inhibitors of JNK, such as SP600125 and AS601245, are widely used in vitro; however, this type of inhibitor lacks specificity as they indiscriminately inhibit phosphorylation of all JNK substrates. Moreover, JNK has at least three isoforms with different functions in cancer development and identifying specific selective inhibitors is crucial for the development of targeted therapy in cancer. Some selective inhibitors of JNK are identified; however, their clinical studies in cancer are relatively less conducted. In this review, we first summarised the function of JNK signalling in cancer progression; there is a focus on the discussion of the novel selective JNK inhibitors as potential targeting therapy in cancer. Finally, we have offered a future perspective of the selective JNK inhibitors in the context of cancer therapies. We hope this review will help to further understand the role of JNK in cancer progression and provide insight into the design of novel selective JNK inhibitors in cancer treatment.

FBX8 degrades GSTP1 through ubiquitination to suppress colorectal cancer progression

F-box only protein 8 (FBX8), as a critical component of the SKP1-CUL1-F-box (SCF) E3 ubiquitin ligases, has been associated with several malignancies through interacting with a member of proteins. However, the substrates of FBX8 for destruction in the progression of colorectal carcinoma (CRC) need to be explored. Here, we show that loss of FBX8 accelerates chemical-induced colon tumorigenesis. FBX8 directly targets GSTP1 for ubiquitin-mediated proteasome degradation in CRC. GSTP1 promotes the proliferation, invasion, and metastasis of CRC cells. Furthermore, GSTP1 is upregulated in CRC tissue samples and predicts poor prognosis of CRC patients. The inactivation of FBX8 negatively correlated with increased levels and stability of GSTP1 in clinical CRC tissues and FBX8 knockout transgenic mice. These findings identify a novel ubiquitination pathway as FBX8-GSTP1 axis that regulates the progression of CRC, which might be a potential prognostic biomarker for CRC patients.

Dysregulated Redox Regulation Contributes to Nuclear EGFR Localization and Pathogenicity in Lung Cancer

Lung cancers are frequently characterized by inappropriate activation of epidermal growth factor receptor (EGFR)-dependent signaling and epigenetic silencing of the NADPH oxidase (NOX) enzyme DUOX1, both potentially contributing to worse prognosis. Based on previous findings linking DUOX1 with redox-dependent EGFR activation, the present studies were designed to evaluate whether DUOX1 silencing in lung cancers may be responsible for altered EGFR regulation. In contrast to normal epithelial cells, EGF stimulation of lung cancer cell lines that lack DUOX1 promotes EGF-induced EGFR internalization and nuclear localization, associated with induction of EGFR-regulated genes and related tumorigenic outcomes. Each of these outcomes could be reversed by overexpression of DUOX1 or enhanced by shRNA-dependent DUOX1 silencing. EGF-induced nuclear EGFR localization in DUOX1-deficient lung cancer cells was associated with altered dynamics of cysteine oxidation of EGFR, and an overall reduction of EGFR cysteines. These various outcomes could also be attenuated by silencing of glutathione S-transferase P1 (GSTP1), a mediator of metabolic alterations and drug resistance in various cancers, and a regulator of cysteine oxidation. Collectively, our findings indicate DUOX1 deficiency in lung cancers promotes dysregulated EGFR signaling and enhanced GSTP1-mediated turnover of EGFR cysteine oxidation, which result in enhanced nuclear EGFR localization and tumorigenic properties.

A Covalent Inhibitor for Glutathione S-Transferase Pi (GSTP1-1 ) in Human Cells

Glutathione S-transferase π (GSTP_1-1 ) is overexpressed in many types of cancer and is involved in drug resistance. Therefore, GSTP_1-1 is an important target in cancer therapy, and many GST inhibitors have been reported. We had previously developed an irreversible inhibitor, GS-ESF, as an effective GST inhibitor; however, its cellular permeability was too low for it to be used in inhibiting intracellular GST. We have now developed new irreversible inhibitors by introducing sulfonyl fluoride (SF) into chloronitrobenzene (CNB). The mechanism of action was revealed to be that CNBSF first reacts with glutathione (GSH) through an aromatic substitution in the cell, then the sulfonyl group on the GSH conjugate with CNBSF reacts with Tyr108 of GST to form a sulfonyl ester bond. Our new inhibitor irreversible inhibited GSTP_1-1 both in vitro and in cellulo with a long duration of action.

Stra8 may inhibit apoptosis during mouse spermatogenesis via the AKT signaling pathway

Stimulated by retinoic acid 8 (Stra8), one of genes induced by retinoic acid (RA), is required for the meiotic initiation of male spermatogenesis. The present study found that Stra8 inhibited apoptosis in male Stra8‑knockout mice, and in mice with vitamin A deficiency and vitamin A recovery in vivo. This phenotype was also verified in GC1 spermatogonia (spg) cells overexpressing Stra8. In addition, microarray analysis identified that there were nine differentially expressed genes (DEGs) in the Stra8‑overexpressed GC1 spg cells compared with the control groups; the expression of these nine genes was verified via mRNA expression levels. The DEGs were as follows: Phosphatidylinositol‑dependent kinase 1 (PDK1), a key gene upstream of protein kinase B (AKT); angiopoietin 2, a B‑cell lymphoma 2 (Bcl‑2)‑inhibited gene; transcription factor 4, glutathione S‑transferase P91 and ubiquitin‑specific protease 33, mitogen‑activated protein kinase (MAPK)‑related genes; oxidative stress induced growth inhibitor 1, related to the P53 pathway; Bcl‑2, P53, ERK (MAPK1/3), c‑Jun N‑terminal kinase (MAPK8/9), and P38 (MAPK14), all of which are key genes involved in the AKT signaling pathway. Therefore, the present study further verified these genes and found that the mRNA and protein expression levels of PDK1, AKT, Bcl‑2 and ERK were increased. Although the mRNA expression level of P53 was decreased, there was no significant difference in the protein expression level in Stra8‑overexpressing GC1 spg cells compared with controls. In addition, Caspase 3, one of the executioner caspases, was decreased in Stra8‑overexpressing GC1 spg cells compared with the control groups. Therefore, it was suggested that Stra8 may directly or indirectly inhibit caspases through the AKT signaling pathway and ultimately exert an anti‑apoptotic effect in the male reproductive system.

The multifaceted role of glutathione S-transferases in cancer

Glutathione S-transferases (GSTs) are phase II detoxifying enzymes involved in the maintenance of cell integrity, oxidative stress and protection against DNA damage by catalyzing the conjugation of glutathione to a wide variety of electrophilic substrates. Though enzymes of the glutathione synthesis and salvage pathways have been well characterized in the past, there is still a lack of comprehensive understanding of their independent and coordinate regulatory mechanisms in carcinogenesis. The present review discusses implication of GST in cancer development and progression, gene polymorphism, drug resistance, signaling and epigenetic regulation involving their role in cancer. It is anticipated that GST especially the GSTP1 class can be developed as a biomarker either used alone or in combination with other biomarkers for early cancer detection and/or diagnosis as well as for future targeted preventive and therapeutic interventions with dietary agents.

A tyrosine-reactive irreversible inhibitor for glutathione S-transferase Pi (GSTP1)

Glutathione S-transferase Pi (GSTP1) mediates cellular defense against reactive electrophiles. Here, we report LAS17, a dichlorotriazine-containing compound that irreversibly inhibits GSTP1 and is selective for GSTP1 within cellular proteomes. Mass spectrometry and mutational studies identified Y108 as the site of modification, providing a unique mode of GSTP1 inhibition.

ErbB Family Signalling: A Paradigm for Oncogene Addiction and Personalized Oncology

ErbB family members represent important biomarkers and drug targets for modern precision therapy. They have gained considerable importance as paradigms for oncoprotein addiction and personalized medicine. This review summarizes the current understanding of ErbB proteins in cell signalling and cancer and describes the molecular rationale of prominent cases of ErbB oncoprotein addiction in different cancer types. In addition, we have highlighted experimental technologies for the development of innovative cancer cell models that accurately predicted clinical ErbB drug efficacies. In the future, such cancer models might facilitate the identification and validation of physiologically relevant novel forms of oncoprotein and non-oncoprotein addiction or synthetic lethality. The identification of genotype-drug response relationships will further advance personalized oncology and improve drug efficacy in the clinic. Finally, we review the most important drugs targeting ErbB family members that are under investigation in clinical trials or that made their way already into clinical routine. Taken together, the functional characterization of ErbB oncoproteins have significantly increased our knowledge on predictive biomarkers, oncoprotein addiction and patient stratification and treatment.

Estrogen inhibits starvation-induced apoptosis in osteocytes by a redox-independent process involving association of JNK and glutathione S-transferase P1-1

Estrogen deficiency causes bone loss as a result of microdamage, oxidative stress, and osteocyte apoptosis. A relationship between oxidative stress‐induced apoptosis, c‐Jun N‐terminal kinase (JNK) activation, and expression of factors involved in bone remodeling has been demonstrated in osteocytes. However, the molecular regulation of these events in osteocytes treated with 17β‐estradiol (17β‐E2) remains unexplored. The MLO‐Y4 murine osteocyte‐like cell line was used as a model to study starvation‐induced apoptosis and ROS production during 17β‐E2 treatment. Expression of glutathione S‐transferase P1‐1 (GSTP1‐1), receptor activator kB ligand (RANKL), osteoprotegerin (OPG), sclerostin, and kinases activation were measured by western blot. In addition, the GSTP1‐1/JNK association was assessed by immunoprecipitation, and GSTP1‐1 involvement in the osteocyte response to 17β‐E2 was detected by specific siRNA transfection. 17β‐E2 prevents starvation‐induced apoptosis (DNA fragmentation and caspase activation), the increase in sclerostin expression and the RANKL/OPG ratio, which are all related to JNK activation due to oxidative stress in osteocytes. This occurs through GSTP1‐1 overexpression, which can inhibit JNK activation by formation of a GSTP1‐1/JNK complex. No early antioxidant action of 17β‐E2 has been found but the estrogen effect is similar to N‐acetylcysteine which, by increasing the intracellular redox state, maintains JNK bound to GSTP1‐1. Thus, the antiapoptotic and osteogenic effect of 17β‐E2 in MLO‐Y4 occurs by a redox‐independent process involving GSTP1‐1/JNK association. This study clarifies at molecular level the effect of 17β‐E2 on osteocyte activity and identifies a possible role of GSTP1‐1 and JNK activity in bone remodeling and repair mechanisms.

A covalent G-site inhibitor for glutathione S-transferase Pi (GSTP1-1)

We herein report the first covalent G-site-binding inhibitor for GST, GS-ESF (1), which irreversibly inhibited the GSTP_1-1 function.

Carboxyl terminus-truncated α1D-adrenoceptors inhibit the ERK pathway

Human α1D-adrenoceptors are G protein-coupled receptors that mediate adrenaline/noradrenaline actions. There is a growing interest in identifying regulatory domains in these receptors and determining how they function. In this work, we show that the absence of the human α1D-adrenoceptor carboxyl tail results in altered ERK (extracellular signal-regulated kinase) and p38 phosphorylation states. Amino terminus-truncated and both amino and carboxyl termini-truncated α1D-adrenoceptors were transfected into Rat-1, HEK293, and B103 cells, and changes in the phosphorylation state of extracellular signal-regulated kinase was assessed using biochemical and biophysical approaches. The phosphorylation state of other protein kinases (p38, MEK1, and Raf-1) was also studied. Noradrenaline-induced ERK phosphorylation in Rat-1 fibroblasts expressing amino termini-truncated α1D-adrenoceptors. However, in cells expressing receptors with both amino and carboxyl termini truncations, noradrenaline-induced activation was abrogated. Interestingly, ERK phosphorylation that normally occurs through activation of endogenous G protein-coupled receptors, EGF receptors, and protein kinase C, was also decreased, suggesting that downstream steps in the mitogen-activated protein kinase pathway were affected. A similar effect was observed in B103 cells but not in HEK 293 cells. Phosphorylation of Raf-1 and MEK1 was also diminished in Rat-1 fibroblasts expressing amino- and carboxyl-truncated α1D-adrenoceptors. Our data indicate that expression of carboxyl terminus-truncated α1D-adrenoceptors alters ERK and p38 phosphorylation state.