Targeting the Selenoprotein Thioredoxin Reductase 1 for Anticancer Therapy

Inhibition of thioredoxin reductase 1 sensitizes glucose-starved glioblastoma cells to disulfidptosis

Disulfidptosis is a recently identified form of cell death characterized by the aberrant accumulation of cellular disulfides. This process primarily occurs in glucose-starved cells expressing higher levels of SLC7A11 and has been proposed as a therapeutic strategy for cancers with hyperactive SCL7A11. However, the potential for inducing disulfidptosis through other mechanisms in cancers remains unclear. Here, we found that inhibiting thioredoxin reductase 1 (TrxR1), a key enzyme in the thioredoxin system, induces disulfidptosis in glioblastoma (GBM) cells. TrxR1 expression is elevated in GBM with activated transcriptional coactivator with PDZ-binding motif (TAZ) and correlates with poor prognosis. TrxR1 inhibitors induced GBM cell death that can be rescued by disulfide reducers but not by ROS scavengers or inhibitors of apoptosis, ferroptosis, or necroptosis. Glucose-starved cells, but not those deprived of oxygen or glutamine, increased TrxR1 expression in an NRF2-dependent manner and were more sensitive to TrxR1 inhibition-induced cell death. The dying cells initially exhibited highly dynamic lamellipodia, followed by actin cytoskeleton collapse. This process involved the accumulation of cytosolic peroxisomes and micropinocytic caveolae, as well as small gaps in the plasma membrane. Depletion of the WAVE complex component NCKAP1 partially rescued the cells, whereas Rac inhibition enhanced cell death. In an orthotopic xenograft GBM mouse model, TrxR1 depletion inhibited tumor growth and improved survival. Furthermore, cells undergoing TrxR1 inhibition exhibited features of immunogenic cell death. Therefore, this study suggests the potential of targeting TrxR1 as a therapeutic strategy in GBM.

Cellular activity of the cytosolic selenoprotein thioredoxin reductase 1 (TXNRD1) is modulated by copper and zinc levels in the cell culture medium

BACKGROUND

Selenium (Se), Copper (Cu) and Zinc (Zn) are essential trace elements, required for several cellular functions, showcasing toxicity in either insufficient or excessive concentrations. The selenoprotein thioredoxin reductase 1 (TXNRD1) is directly affected by Se availability and here we hypothesized that it may also be affected by high Cu and Zn concentrations.

METHODS AND RESULTS

Using an optimized protocol for the highly selective TXNRD1 activity probe, RX1, we discovered a direct inhibitory effect of Zn on the intracellular TXNRD1 activity, using two different commonly used human cancer cell lines, A549 lung carcinoma and HeLa cervical carcinoma cells. Subsequently, after initial inhibition by Zn, the TXNRD1 activity recovered in both cell lines, in HeLa cells concomitantly with activation of the redox regulatory transcription factor NRF2. High extracellular Cu concentrations did not induce an immediate decrease of intracellular TXNRD1 activity, but decreased its activity upon long-term exposure. While the expression levels of TXNRD1 did not change upon long-term Cu exposure, the selenoprotein glutathione peroxidase 1 (GPX1), that is more dependent upon selenocysteine incorporation, was downregulated, suggesting that higher Cu exposure generally impaired selenoprotein synthesis.

CONCLUSION

Our findings support the importance of understanding trace element exposure and availability in basic research, especially in redox biology research, as well as considering Cu and Zn as potential modulators of the cellular capacity of the thioredoxin system and other selenoproteins.

Recent Advances in Aging and Immunosenescence: Mechanisms and Therapeutic Strategies

Cellular senescence is an irreversible state of cell cycle arrest. Senescent cells (SCs) accumulate in the body with age and secrete harmful substances known as the senescence-associated secretory phenotype (SASP), causing chronic inflammation; at the same time, chronic inflammation leads to a decrease in immune system function, known as immunosenescence, which further accelerates the aging process. Cellular senescence and immunosenescence are closely related to a variety of chronic diseases, including cardiovascular diseases, metabolic disorders, autoimmune diseases, and neurodegenerative diseases. Studying the mechanisms of cellular senescence and immunosenescence and developing targeted interventions are crucial for improving the immune function and quality of life of elderly people. Here, we review a series of recent studies focusing on the molecular mechanisms of cellular senescence and immunosenescence, the regulation of aging by the immune system, and the latest advances in basic and clinical research on senolytics. We summarize the cellular and animal models related to aging research, as well as the mechanisms, strategies, and future directions of aging interventions from an immunological perspective, with the hope of laying the foundation for developing novel and practical anti-aging therapies.

Plasma Thioredoxin Reductase as a Potential Diagnostic Biomarker for Breast Cancer

BACKGROUND

Early diagnosis of breast cancer is critical to the treatment and prognosis of breast cancer patients. Our aim is to explore more practical and effective diagnostic methods to facilitate early treatment and improve prognosis for breast cancer patients.

MATERIALS AND METHODS

The Mann-Whitney U test, receiver operating characteristic curve, Youden index, Chi-square test, and Fisher's exact test were used to determine whether plasma thioredoxin reductase (TrxR) could be used for the clinical diagnosis of breast cancer. The Wilcoxon signed-rank test was used to validate the prognostic potential of plasma TrxR activity assessment.

RESULTS

A total of 761 patients were included, including 537 cases of breast cancer and 224 cases of benign breast diseases. Plasma TrxR activity in the breast cancer group [8.0 (6.0, 9.45) U/mL] was significantly higher than that in the benign group [3.05 (1.20, 6.275) U/mL]. The diagnostic efficiency of TrxR for breast cancer was higher than that of other conventional breast cancer biomarkers, with an area under the curve of 0.821 (95% CI = 0.791-0.852). In addition, TrxR can be used in combination with conventional tumor markers to further improve the diagnostic efficiency. The optimal TrxR threshold for identifying benign and malignant diseases is 7.45 U/mL. We detected plasma TrxR activity and serum tumor markers before and after antitumor therapies in 333 breast cancer patients and found that their trends were basically the same, with a significant decrease in plasma TrxR activity after treatment.

CONCLUSION

Plasma TrxR activity can be used as a suitable biomarker for breast cancer diagnosis and efficacy assessment.

Diffractaic acid exerts anti-cancer effects on hepatocellular carcinoma HepG2 cells by inducing apoptosis and suppressing migration through targeting thioredoxin reductase 1

Hepatocellular carcinoma (HCC) represents one of the most common malignant tumors worldwide. Due to the limited number of available drugs and their side effects, the development of new chemotherapeutic strategies for HCC treatment has become increasingly important. This study is aimed at investigating whether diffractaic acid (DA), one of the secondary metabolites of lichen, exhibits a potential anticancer effect on HepG2 cells and whether its anticancer effect is mediated by inhibition of thioredoxin reductase 1 (TRXR1), which is a target of chemotherapeutic strategies due to overexpression in tumor cells including HCC. XTT assay results showed that DA exhibited strong cytotoxicity on HepG2 cells with an IC50 value of 78.07 µg/mL at 48 h. Flow cytometric analysis results revealed that DA displayed late apoptotic and necrotic effects on HepG2 cells. Consistent with these findings, real-time PCR results showed that DA did not alter the BAX/BCL2 ratio in HepG2 cells but upregulated the P53 gene. Moreover, the wound healing assay results revealed a strong anti-migratory effect of DA in HepG2 cells. Real-time PCR and Western blot analyses demonstrated that DA increased TRXR1 gene and protein expression levels, whereas enzyme activity studies disclosed that DA inhibited TRXR1. These findings suggest that DA has an anticancer effect on HepG2 cells by targeting the enzymatic inhibition of TRXR1. In conclusion, DA as a TRXR1 inhibitor can be considered an effective chemotherapeutic agent which may be a useful lead compound for the treatment of HCC.

The diagnostic potential role of thioredoxin reductase and TXNRD1 in early lung adenocarcinoma: A cohort study

BACKGROUND

Lung adenocarcinoma (LUAD) is the primary form of lung cancer, yet the reliable biomarkers for early diagnosis remain insufficient. Thioredoxin reductase (TrxR) is strongly linked to the occurrence, development, and drug resistance of lung cancer, making it a potential biomarker. However, further research is required to assess its diagnostic value in LUAD.

METHODS

A retrospective analysis was performed on patients who underwent pulmonary nodule resection at our center from 2018 to 2022. Clinical data, including preoperative TrxR levels, imaging, and laboratory characteristics, were identified as study variables. Two prediction models were constructed using multiple logistic regression, and their prediction performance was evaluated comprehensively. Besides, bioinformatics analyses of TrxR coding genes including differential expression, functional enrichment, immune infiltration, drug sensitivity, and single-cell landscape were performed based on TCGA database, which were subsequently validated by Human Protein Atlas.

RESULTS

A total of 506 eligible patients (72 benign lesions, 77 AISs, 185 MIAs and 172 IACs) were identified in the clinical cohort. Two TrxR-based models were developed, which were able to distinguish between benign and malignant pulmonary nodules, as well as pathological subtypes of LUAD, respectively. The models exhibited good predictive ability with all AUC values ranging from 0.7 to 0.9. Based on calibration curves and clinical decision analysis, the nomogram models showed high reliability. Functional analysis indicated that TXNRD1 primarily participated in cell cycle and lipid metabolism. Immune infiltration analysis showed that TXNRD1 has a strong association with immune cells and could impact immunotherapy. Then, we identified small molecular compounds that inhibit TXNRD1 and confirmed TXNRD1 expression by single-cell landscape and immunohistochemistry.

CONCLUSION

This study validated the diagnostic value of TrxR and TXNRD1 in clinical cohorts and transcriptional data, respectively. TrxR and TXNRD1 could be used in the risk diagnosis of early LUAD and facilitate personalized treatment strategies.

Selenium as a Modulator of Redox Reactions in the Prevention and Treatment of Cardiovascular Diseases

Cardiovascular diseases stand as the predominant global cause of mortality, exerting a profound impact on both life expectancy and its quality. Given their immense public health burden, extensive efforts have been dedicated to comprehending the underlying mechanisms and developing strategies for prevention and treatment. Selenium, a crucial participant in redox reactions, emerges as a notable factor in maintaining myocardial cell homeostasis and influencing the progression of cardiovascular disorders. Some disorders, such as Keshan disease, are directly linked with its environmental deficiency. Nevertheless, the precise extent of its impact on the cardiovascular system remains unclear, marked by contradictory findings in the existing literature. High selenium levels have been associated with an increased risk of developing hypertension, while lower concentrations have been linked to heart failure and atrial fibrillation. Although some trials have shown its potential effectiveness in specific groups of patients, large cohort supplementation attempts have generally yielded unsatisfactory outcomes. Consequently, there persists a significant need for further research aimed at delineating specific patient cohorts and groups of diseases that would benefit from selenium supplementation.

HyPer as a tool to determine the reductive activity in cellular compartments

A multitude of cellular metabolic and regulatory processes rely on controlled thiol reduction and oxidation mechanisms. Due to our aerobic environment, research preferentially focuses on oxidation processes, leading to limited tools tailored for investigating cellular reduction. Here, we advocate for repurposing HyPer1, initially designed as a fluorescent probe for H2O2 levels, as a tool to measure the reductive power in various cellular compartments. The response of HyPer1 depends on kinetics between thiol oxidation and reduction in its OxyR sensing domain. Here, we focused on the reduction half-reaction of HyPer1. We showed that HyPer1 primarily relies on Trx/TrxR-mediated reduction in the cytosol and nucleus, characterized by a second order rate constant of 5.8 × 102 M-1s-1. On the other hand, within the mitochondria, HyPer1 is predominantly reduced by glutathione (GSH). The GSH-mediated reduction rate constant is 1.8 M-1s-1. Using human leukemia K-562 cells after a brief oxidative exposure, we quantified the compartmentalized Trx/TrxR and GSH-dependent reductive activity using HyPer1. Notably, the recovery period for mitochondrial HyPer1 was twice as long compared to cytosolic and nuclear HyPer1. After exploring various human cells, we revealed a potent cytosolic Trx/TrxR pathway, particularly pronounced in cancer cell lines such as K-562 and HeLa. In conclusion, our study demonstrates that HyPer1 can be harnessed as a robust tool for assessing compartmentalized reduction activity in cells following oxidative stress.

TXNRD1 drives the innate immune response in senescent cells with implications for age-associated inflammation

Sterile inflammation, also known as 'inflammaging', is a hallmark of tissue aging. Cellular senescence contributes to tissue aging, in part, through the secretion of proinflammatory factors collectively known as the senescence-associated secretory phenotype (SASP). The genetic variability of thioredoxin reductase 1 (TXNRD1) is associated with aging and age-associated phenotypes such as late-life survival, activity of daily living and physical performance in old age. TXNRD1's role in regulating tissue aging has been attributed to its enzymatic role in cellular redox regulation. Here, we show that TXNRD1 drives the SASP and inflammaging through the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) innate immune response pathway independently of its enzymatic activity. TXNRD1 localizes to cytoplasmic chromatin fragments and interacts with cGAS in a senescence-status-dependent manner, which is necessary for the SASP. TXNRD1 enhances the enzymatic activity of cGAS. TXNRD1 is required for both the tumor-promoting and immune surveillance functions of senescent cells, which are mediated by the SASP in vivo in mouse models. Treatment of aged mice with a TXNRD1 inhibitor that disrupts its interaction with cGAS, but not with an inhibitor of its enzymatic activity alone, downregulated markers of inflammaging in several tissues. In summary, our results show that TXNRD1 promotes the SASP through the innate immune response, with implications for inflammaging. This suggests that the TXNRD1-cGAS interaction is a relevant target for selectively suppressing inflammaging.

Synthesis, cytotoxicity, antioxidant activity and molecular modeling of new NSAIDs-EBS derivatives

Two series of NSAIDs-EBS derivatives (5a-j and 9a-i) based on the hybridization of nonsteroidal anti-inflammatory drugs (NSAIDs) skeleton and Ebselen moiety were synthesized. Their cytotoxicity was evaluated against five types of human cancer cell lines, BGC-823 (human gastric cancer cell line), SW480 (human colon adenocarcinoma cells), MCF-7 (human breast adenocarcinoma cells), HeLa (human cervical cancer cells), A549 (human lung carcinoma cells). Moreover, the most active compound 5j showed IC50 values below 3 μM in all cancer cell lines and with remarkable anticancer activity against MCF-7 (1.5 μM) and HeLa (1.7 μM). The redox properties of the NSAIDs-EBS derivatives prepared herein were conducted by 2, 2-didiphenyl-1-picrylhydrazyl (DPPH), bleomycin dependent DNA damage and glutathione peroxidase (GPx)-like assays. Finally, TrxR1 inhibition activity assay and molecular docking study revealed NSAIDs-EBS derivatives could serve as potential TrxR1 inhibitor.

Effect of evernic acid on human breast cancer MCF-7 and MDA-MB-453 cell lines via thioredoxin reductase 1: A molecular approach

Thioredoxin reductase 1 (TrxR1) has emerged as an important target for anticancer drug development due to its overexpression in many human tumors including breast cancer. Due to the serious side effects of currently used commercial anticancer drugs, new natural compounds with very few side effects and high efficacy are of great importance in cancer treatment. Lichen secondary metabolites, known as natural compounds, have diverse biological properties, including antioxidant and anticancer activities. Herein, we aimed to determine the potential antiproliferative, antimigratory, and apoptotic effects of evernic acid, a lichen secondary metabolite, on breast cancer MCF-7 and MDA-MB-453 cell lines and afterward to investigate whether its anticancer effect is exerted by TrxR1-targeting. The cytotoxicity results indicated that evernic acid suppressed the proliferation of MCF-7 and MDA-MB-453 cells in a dose-dependent manner and the IC₅₀ values were calculated as 33.79 and 121.40 μg/mL, respectively. Migration assay results revealed the notable antimigratory ability of evernic acid against both cell types. The expression of apoptotic markers Bcl2 associated X, apoptosis regulator, Bcl2 apoptosis regulator, and tumor protein p53 by quantitative real-time polymerase chain reaction and western blot analysis showed that evernic acid did not induce apoptosis in both cell lines, consistent with flow cytometry results. Evernic acid showed its anticancer effect via inhibiting TrxR1 enzyme activity rather than mRNA and protein expression levels in both cell lines. In conclusion, these findings suggest that evernic acid has the potential to be evaluated as a therapeutic agent in breast cancer treatment.

Prognosis stratification in breast cancer and characterization of immunosuppressive microenvironment through a pyrimidine metabolism-related signature

Pyrimidine metabolism is a hallmark of cancer and will soon become an essential part of cancer therapy. In the tumor microenvironment, cells reprogram pyrimidine metabolism intrinsically and extracellularly, thereby promoting tumorigenesis. Metabolites in pyrimidine metabolism have a significant impact on promoting cancer advancement and modulating immune system responses. In preclinical studies and practical clinical applications, critical targets in pyrimidine metabolism are acted upon by drugs to exert promising therapeutic effects on tumors. However, the pyrimidine metabolism in breast cancer (BC) is still largely underexplored. In this study, 163 credible pyrimidine metabolism-related genes (PMGs) were retrieved, and their somatic mutations and expression levels were determined. In addition, by using The Cancer Genome Atlas (TCGA) and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) databases, 12 PMGs related to the overall survival (OS) were determined using the univariate Cox regression analysis. Subsequently, by performing the LASSO Cox hazards regression analysis in the 12 PMGs in TCGA-BRCA dataset, we developed a prognosis nomogram using eight OS-related PMGs and then verified the same in the METABRIC, GSE96058, GSE20685, GSE42568 and GSE86166 data. Moreover, we validated relationships between the pyrimidine metabolism index (PMI) and the survival probability of patients, essential clinical parameters, including the TNM stage and the PAM50 subtypes. Next, we verified the predictive capability of the optimum model, including the signature, the PAM50 subtype, and age, using ROC analysis and calibration curve, and compared it with other single clinical factors for the predictive power of benefit using decision curve analysis. Finally, we investigated the potential effects of pyrimidine metabolism on immune checkpoints, tumor-infiltrating immune cells, and cytokine levels and determined the potential implications of pyrimidine metabolism in BC immunotherapy. In conclusion, our findings suggest that pyrimidine metabolism has underlying prognostic significance in BC and can facilitate a new management approach for patients with different prognoses and more precise immunotherapy.

USF2-mediated upregulation of TXNRD1 contributes to hepatocellular carcinoma progression by activating Akt/mTOR signaling

Thioredoxin reductase 1 (TXNRD1) is one of the major redox regulators in mammalian cells, which has been reported to be involved in tumorigenesis. However, its roles and regulatory mechanism underlying the progression of HCC remains poorly understood. In this study, we demonstrated that TXNRD1 was significantly upregulated in HCC tumor tissues and correlated with poor survival in HCC patients. Functional studies indicated TXNRD1 knockdown substantially suppressed HCC cell proliferation and metastasis both in vitro and in vivo, and its overexpression showed opposite effects. Mechanistically, TXNRD1 attenuated the interaction between Trx1 and PTEN which resulting in acceleration of PTEN degradation, thereby activated Akt/mTOR signaling and its target genes which conferred to elevated HCC cell mobility and metastasis. Moreover, USF2 was identified as a transcriptional suppressor of TXNRD1, which directly interacted with two E-box sites in TXNRD1 promoter. USF2 functioned as tumor suppressor through the downstream repression of TXNRD1. Further clinical data revealed negative co-expression correlations between USF2 and TXNRD1. In conclusion, our findings reveal that USF2-mediated upregulation of TXNRD1 contributes to hepatocellular carcinoma progression by activating Akt/mTOR signaling.

Ferrocifen stealth LNCs and conventional chemotherapy: A promising combination against multidrug-resistant ovarian adenocarcinoma

Ovarian cancer is one of the deadliest epithelial malignancies in women, owing to the multidrug resistance that restricts the success of conventional chemotherapy, carboplatin and paclitaxel. High grade serous ovarian carcinoma can be classified into two subtypes, the chemosensitive High OXPHOS and the Low OXPHOS tumour, less sensitive to chemotherapy. This difference of treatment efficacy could be explained by the redox status of these tumours, High OXPHOS exhibiting a chronic oxidative stress and an accumulation of reactive oxygen species. Ferrocifens, bio-organometallic compounds, are believed to be ROS producers with a good cytotoxicity on ovarian cancer cell lines. The aim of this study was to evaluate the in vivo efficacy of ferrocifen stealth lipid nanocapsules on High and Low OXPHOS ovarian Patient-Derived Xenograft models, alone or in combination to standard chemotherapy. Accordingly, two ferrocifens, P53 and P722, were encapsulated in stealth LNCs. The treatment by stealth P722-LNCs in combination with standard chemotherapy induced, with a concentration eight time lower than in stealth P53-LNCs, similar tumour reduction on a Low OXPHOS model, allowing us to conclude that P722 could be a leading ferrocifen to treat ovarian cancer. This combination of treatments may represent a promising synergistic approach to treat resistant ovarian adenocarcinoma.

Delivery of the selenoprotein thioredoxin reductase 1 to mammalian cells

Over-expression of genetically encoded thioredoxin reductase 1 (TrxR1) TrxR1 can be toxic to cells due to the formation of a truncated version of the enzyme. We developed a new mammalian cell-based model to investigate TrxR1 activity. Fusion of the HIV-derived cell penetrating peptide (TAT) enabled efficient cellular uptake of purified TrxR1 containing 21 genetically encoded amino acids, including selenocysteine. The TAT peptide did not significantly alter the catalytic activity of TrxR1 in vitro. We monitored TrxR1-dependent redox activity in human cells using a TrxR1-specific red fluorescent live-cell reporter. Using programmed selenocysteine incorporation in Escherichia coli, our approach allowed efficient production of active recombinant human selenoprotein TrxR1 for delivery to the homologous context of the mammalian cell. The delivered TAT-TrxR1 showed robust activity in live cells and provided a novel platform to study TrxR1 biology in human cells.

Revealing PACMA 31 as a new chemical type TrxR inhibitor to promote cancer cell apoptosis

Thioredoxin reductase (TrxR) is a pivotal regulator of redox homeostasis, while dysregulation of redox homeostasis is a hallmark for cancer cells. Thus, there is considerable potential to inhibit the aberrantly upregulated TrxR in cancer cells to discover selective cancer therapeutic agents. Nevertheless, the structural types of TrxR inhibitors presented currently are still relatively limited. We herein report that PACMA 31, previously reported to inhibit protein disulfide isomerase (PDI), is a potent TrxR inhibitor. PACMA 31 possesses a pharmacophore scaffold that is structurally different from the announced TrxR inhibitors and exhibits effective cytotoxicity against cervical cancer cells. Our results reveal that PACMA 31 selectively inhibits TrxR over the related glutathione reductase (GR) and in the presence of reduced glutathione (GSH). Further studies with mutant enzyme and molecular docking suggest that the propynamide fragment of PACMA 31 interacts covalently with the selenocysteine residue of TrxR. Moreover, PACMA 31 effectively and selectively curbs TrxR activity in cells and further stimulates the production of reactive oxygen species (ROS) at low micromolar concentrations, which in turn triggers the accumulation of oxidized thioredoxin (Trx) and GSSG in cells. Follow-up studies demonstrate that PACMA 31 targets TrxR in cells to induce oxidative stress-mediated cancer cell apoptosis. Our results provide a new structural type of TrxR inhibitor that may serve as a useful probe for investigating the biology of TrxR-implicated pathways, and uncover a new target of PACMA 31 that contributes to it becoming a candidate for cancer treatment.

Thioredoxin reductase selenoproteins from different organisms as potential drug targets for treatment of human diseases

Human thioredoxin reductase (TrxR) is a selenoprotein with a central role in cellular redox homeostasis, utilizing a highly reactive and solvent-exposed selenocysteine (Sec) residue in its active site. Pharmacological modulation of TrxR can be obtained with several classes of small compounds showing different mechanisms of action, but most often dependent upon interactions with its Sec residue. The clinical implications of TrxR modulation as mediated by small compounds have been studied in diverse diseases, from rheumatoid arthritis and ischemia to cancer and parasitic infections. The possible involvement of TrxR in these diseases was in some cases serendipitously discovered, by finding that existing clinically used drugs are also TrxR inhibitors. Inhibiting isoforms of human TrxR is, however, not the only strategy for human disease treatment, as some pathogenic parasites also depend upon Sec-containing TrxR variants, including S. mansoni, B. malayi or O. volvulus. Inhibiting parasite TrxR has been shown to selectively kill parasites and can thus become a promising treatment strategy, especially in the context of quickly emerging resistance towards other drugs. Here we have summarized the basis for the targeting of selenoprotein TrxR variants with small molecules for therapeutic purposes in different human disease contexts. We discuss how Sec engagement appears to be an indispensable part of treatment efficacy and how some therapeutically promising compounds have been evaluated in preclinical or clinical studies. Several research questions remain before a wider application of selenoprotein TrxR inhibition as a first-line treatment strategy might be developed. These include further mechanistic studies of downstream effects that may mediate treatment efficacy, identification of isoform-specific enzyme inhibition patterns for some given therapeutic compounds, and the further elucidation of cell-specific effects in disease contexts such as in the tumor microenvironment or in host-parasite interactions, and which of these effects may be dependent upon the specific targeting of Sec in distinct TrxR isoforms.

Thioredoxin-Interacting Protein in Cancer and Diabetes

Significance: Thioredoxin-interacting protein (Txnip) is an α-arrestin protein that acts as a cancer suppressor. Txnip is simultaneously a critical regulator of energy metabolism. Other alpha-arrestin proteins also play key roles in cell biology and cancer. Recent Advances: Txnip expression is regulated by multilayered mechanisms, including transcriptional regulation, microRNA, messenger RNA (mRNA) stabilization, and protein degradation. The Txnip-based connection between cancer and metabolism has been widely recognized. Meanwhile, new aspects are proposed for the mechanism of action of Txnip, including the regulation of RNA expression and autophagy. Arrestin domain containing 3 (ARRDC3), another α-arrestin protein, regulates endocytosis and signaling, whereas ARRDC1 and ARRDC4 regulate extracellular vesicle formation. Critical Issues: The mechanism of action of Txnip is yet to be elucidated. The regulation of intracellular protein trafficking by arrestin family proteins has opened an emerging field of biology and medical research, which needs to be examined further. Future Directions: A fundamental understanding of the mechanism of action of Txnip and other arrestin family members needs to be explored in the future to combat diseases such as cancer and diabetes. Antioxid. Redox Signal. 36, 1001-1022.

Identification of the Signature Genes and Network of Reactive Oxygen Species Related Genes and DNA Repair Genes in Lung Adenocarcinoma

Reactive Oxygen Species (ROS) are present in excess amounts in patients with tumors, and these ROS can kill and destroy tumor cells. Therefore, tumor cells upregulate ROS-related genes to protect them and reduce their destructing effects. Cancer cells already damaged by ROS can be repaired by expressing DNA repair genes consequently promoting their proliferation. The present study aimed to identify the signature genes of and regulating network of ROS-related genes and DNA repair genes in lung adenocarcinoma (LUAD) using transcriptomic data of public databases. The LUAD transcriptome data in the TCGA database and gene expressions from Gene Expression Omnibus (GEO) were analyzed and samples were clustered into 5 ROS-related categories and 6 DNA repair categories. Survival analysis revealed a significant difference in patient survival between the two classification methods. In addition, the samples corresponding to the two categories overlap, thus, the gene expression profile of the same sample with different categories and survival prognosis was further explored, and the connection between ROS-related and DNA repair genes was investigated. The interactive sample recombination classification was used, revealing that the patient's prognosis was worse when the ROS-related and DNA repair genes were expressed at the same time. The further research on the potential regulatory network of the two categories of genes and the correlation analysis revealed that ROS-related genes and DNA repair genes have a mutual regulatory relationship. The ROS-related genes namely NQO1, TXNRD1, and PRDX4 could establish links with other DNA repair genes through the DNA repair gene NEIL3, thereby balancing the level of ROS. Therefore, targeting ROS-related genes and DNA repair genes might be a promising strategy in the treatment of LUAD. Finally, a survival prognostic model of ROS-related genes and DNA repair genes was established (TERT, PRKDC, PTTG1, SMUG1, TXNRD1, CAT, H2AFX, and PFKP). The risk score obtained from our survival prognostic model could be used as an independent prognostic factor in LUAD patients.

A novel mTOR-associated gene signature for predicting prognosis and evaluating tumor immune microenvironment in lung adenocarcinoma

BACKGROUND

The mechanistic target of rapamycin (mTOR) was proven to have great impact on apoptosis, cell proliferation, autophagy, and many other fundamental cellular processes; moreover, it closely correlates with tumor occurrence and development. However, few studies have constructed signatures based on mTOR-associated genes to assess multiple indicators of prognosis in lung adenocarcinoma (LUAD) patients.

METHODS

mTOR-associated gene sets, whole mRNA expression matrices, and clinical information of LUAD patients in training and validation cohorts were obtained from multiple public databases. Multiple methods were used to screen candidate genes, construct signatures, validate internally and externally, and conduct further studies: differentially expressed gene analysis, LASSO Cox regression analysis, Cox regression analysis, risk factor analysis, nomogram analysis, functional enrichment analysis, analyses in tumor immune microenvironment, and therapy.

RESULTS

A prognostic signature containing 8 genes (LDHA, SLA, WNT7A, PLK1, CCT6A, BTG2, TXNRD1, and DDIT4) was constructed. It performed well in both internal and external validation. Subsequent analysis found that the prognostic signature was of great significance in evaluating the tumor immune microenvironment and could guide the treatment of patients with LUAD to a certain extent.

CONCLUSION

The constructed mTOR-associated gene signature accurately predicted the prognostic pattern of patients with LUAD and is expected to be extremely useful in guiding LUAD therapy.

Natural diterpenoid eriocalyxin B covalently modifies glutathione and selectively inhibits thioredoxin reductase inducing potent oxidative stress-mediated apoptosis in colorectal carcinoma RKO cells

Increasing evidence suggests the significant contribution of high levels of thioredoxin reductase (TrxR) in various stages of tumorigenesis and resistance to tumor chemotherapy. Thus, inhibition of TrxR with small molecules is an attractive strategy for cancer therapy. Eriocalyxin B (EriB), a naturally occurring diterpenoid extracted from Isodon eriocalyx, has reflected potential anticancer activities through numerous pathways. Here, we describe that EriB covalently modifies GSH and selectively inhibits TrxR activity by targeting the Sec residue of the enzyme. Pharmacological inhibition of TrxR by EriB results in elevated ROS levels, reduced total GSH and thiols content, which ultimately induced potent RKO cell apoptosis mediated by oxidative stress. Importantly, EriB indicates potent synthetic lethality with GSH inhibitors, BSO, in RKO cells. In summary, our results highlight that targeting TrxR by EriB explores a novel mechanism for the biological action of EriB. This opened up a new therapeutic indication for using EriB to combat cancers.

Onopordopicrin from the new genus Shangwua as a novel thioredoxin reductase inhibitor to induce oxidative stress-mediated tumor cell apoptosis

Isolation and identification of natural products from plants is an essential approach for discovering drug candidates. Herein we report the characterization of three sesquiterpene lactones from a new genus Shangwua, e.g. onopordopicrin (ONP), C2, and C3, and evaluation of their pharmacological functions in interfering cellular redox signaling. Compared to C2 and C3, ONP shows the most potency in killing cancer cells. Further experiments demonstrate that ONP robustly inhibits thioredoxin reductase (TrxR), which leads to perturbation of cellular redox homeostasis with the favor of oxidative stress. Knockdown of the TrxR sensitizes cells to the ONP treatment while overexpression of the enzyme reduces the potency of ONP, underpinning the correlation of TrxR inhibition to the cytotoxicity of ONP. The discovery of ONP expands the library of the natural TrxR inhibitors, and the disclosure of the action mechanism of ONP provides a foundation for the further development of ONP as an anticancer agent.

The role of ferroptosis-related genes for overall survival prediction in breast cancer

Background

Ferroptosis is a novel iron‐dependent form of cell death, which is implicated in various diseases including cancers. However, the influence of ferroptosis‐related genes on the prognosis of breast cancer remains unclear.

Methods

RNA sequencing data of 1053 breast cancer tissue samples and 111 normal tissue samples from The Cancer Genome Atlas (TCGA) were analyzed. Expression levels of 259 ferroptosis‐related genes were compared. Gene Ontology (GO) and the Kyoto Gene and Genomic Encyclopedia (KEGG) analyses were conducted on differentially expressed genes. Cox univariate analysis was conducted to explore the potential prognostic biomarkers of breast cancer. Infiltrating immune cell status was assessed.

Results

A total of 66 ferroptosis‐related genes were differentially expressed in breast cancer tissues. The enriched GO terms included Biological Process (mainly included response to oxidative stress, cellular response to chemical stress, multicellular organismal homeostasis, cofactor metabolic process, response to metal ion, response to steroid hormone, cellular response to oxidative stress, transition metal ion homeostasis, iron ion homeostasis, and cellular iron ion homeostasis), Cellular Component (mainly included apical plasma membrane, early endosome, apical part of cell, lipid droplet, basolateral plasma membrane, blood microparticle, clathrin‐coated pit, caveola, astrocyte projection, and pronucleus) and Molecular Function (mainly included iron ion binding, ubiquitin protein ligase binding, oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen, oxidoreductase activity, acting on the CH−OH group of donors, NAD or NADP as acceptor, ferric iron binding, aldo−keto reductase (NADP) activity, oxidoreductase activity, acting on single donors with incorporation of molecular oxygen, steroid dehydrogenase activity, alditol:NADP+1−oxidoreductase activity, and alcohol dehydrogenase (NADP+) activity). The enriched KEGG pathway mainly included the HIF‐1 signaling pathway, NOD‐like receptor signaling pathway, ferroptosis, IL‐17 signaling pathway, central carbon metabolism in cancer, PPAR signaling pathway, PD‐L1 expression, and PD‐1 checkpoint pathway in cancer. Among them, 38 ferroptosis‐related genes were significantly associated with the prognosis of breast cancer. The prognostic model was constructed, and breast cancer patients in low‐risk group had a better prognosis. In addition, risk score of ferroptosis prognostic model was negatively correlated with B cells (r = −0.063, p = 0.049), CD8+ T cells (r = −0.083, p = 0.010), CD4+ T cells (r = −0.097, p = 0.002), neutrophils (r = −0.068, p = 0.033), and dendritic cells (r = 0.088, p = 0.006).

Conclusions

The ferroptosis pathway plays a key role in breast cancer. Some differentially expressed ferroptosis‐related genes can be used as prognostic biomarkers for breast cancer.

The gold complex auranofin: new perspectives for cancer therapy

Advanced stages of cancer are highly associated with short overall survival in patients due to the lack of long-term treatment options following the standard form of care. New options for cancer therapy are needed to improve the survival of cancer patients without disease recurrence. Auranofin is a clinically approved agent against rheumatoid arthritis that is currently enrolled in clinical trials for potential repurposing against cancer. Auranofin mainly targets the anti-oxidative system catalyzed by thioredoxin reductase (TrxR), which protects the cell from oxidative stress and death in the cytoplasm and the mitochondria. TrxR is over-expressed in many cancers as an adaptive mechanism for cancer cell proliferation, rendering it an attractive target for cancer therapy, and auranofin as a potential therapeutic agent for cancer. Inhibiting TrxR dysregulates the intracellular redox state causing increased intracellular reactive oxygen species levels, and stimulates cellular demise. An alternate mechanism of action of auranofin is to mimic proteasomal inhibition by blocking the ubiquitin-proteasome system (UPS), which is critically important in cancer cells to prevent cell death when compared to non-cancer cells, because of its role on cell cycle regulation, protein degradation, gene expression, and DNA repair. This article provides new perspectives on the potential mechanisms used by auranofin alone, in combination with diverse other compounds, or in combination with platinating agents and/or immune checkpoint inhibitors to combat cancer cells, while assessing the feasibility for its repurposing in the clinical setting.

Inhibition of Thioredoxin Reductase by Santamarine Conferring Anticancer Effect in HeLa Cells

Natural products frequently have unique physiological activities and new action mechanisms due to their structural diversity and novelty, and are an important source for innovative drugs and lead compounds. We present herein that natural product santamarine targeted thioredoxin reductase (TrxR) to weaken its antioxidative function in cells, accompanied by accumulation of high levels of reactive oxygen species (ROS), and finally induced a new mechanism of tumor cell oxidative stress-mediated apoptosis. TrxR knockdown or overexpression cell lines were employed to further evaluate the cytotoxicity of santamarine regulated by TrxR, demonstrated that TrxR played a key role in the physiological effect of santamarine on cells. Santamarine targeting TrxR reveals its previously unrecognized mechanism of antitumor and provides a basis for the further development of santamarine as a potential cancer therapeutic agent.

Thioredoxin Reductase Inhibition for Cancer Therapy

The cytosolic selenoprotein thioredoxin reductase 1 (TrxR1, TXNRD1), and to some extent mitochondrial TrxR2 (TXNRD2), can be inhibited by a wide range of electrophilic compounds. Many such compounds also yield cytotoxicity toward cancer cells in culture or in mouse models, and most compounds are likely to irreversibly modify the easily accessible selenocysteine residue in TrxR1, thereby inhibiting its normal activity to reduce cytosolic thioredoxin (Trx1, TXN) and other substrates of the enzyme. This leads to an oxidative challenge. In some cases, the inhibited forms of TrxR1 are not catalytically inert and are instead converted to prooxidant NADPH oxidases, named SecTRAPs, thus further aggravating the oxidative stress, particularly in cells expressing higher levels of the enzyme. In this review, the possible molecular and cellular consequences of these effects are discussed in relation to cancer therapy, with a focus on outstanding questions that should be addressed if targeted TrxR1 inhibition is to be further developed for therapeutic use. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Discovery of hydroxytyrosol as thioredoxin reductase 1 inhibitor to induce apoptosis and G1/S cell cycle arrest in human colorectal cancer cells via ROS generation

Colorectal cancer (CRC) is one of the most common cancer types and a leading cause of cancer-associated mortality in China. Increased thioredoxin reductase 1 (TrxR1) levels have been previously identified as possible target for CRC. The present study revealed that the natural product hydroxytyrosol (HT), which exhibits a polyphenol scaffold, is a potent inhibitor of TrxR1. Inhibition of TrxR1 was indicated to result in accumulation of reactive oxygen species, inhibit proliferation and induce apoptosis and G1/S cell cycle arrest of CRC cells. Using a C-terminal mutant TrxR1 enzyme activity assay, TrxR1 RNA interference assay and HT binding model assay, the present study demonstrated the core character of the selenocysteine residue in the interaction between HT and TrxR1. HT can serve as polyphenol scaffold to develop novel TrxR1 inhibitors for CRC treatment in the future.

Probing the Surface of a Parasite Drug Target Thioredoxin Glutathione Reductase Using Small Molecule Fragments

Fragment screening is a powerful drug discovery approach particularly useful for enzymes difficult to inhibit selectively, such as the thiol/selenol-dependent thioredoxin reductases (TrxRs), which are essential and druggable in several infectious diseases. Several known inhibitors are reactive electrophiles targeting the selenocysteine-containing C-terminus and thus often suffering from off-target reactivity in vivo. The lack of structural information on the interaction modalities of the C-terminus-targeting inhibitors, due to the high mobility of this domain and the lack of alternative druggable sites, prevents the development of selective inhibitors for TrxRs. In this work, fragments selected from actives identified in a large screen carried out against Thioredoxin Glutathione Reductase from Schistosoma mansoni (SmTGR) were probed by X-ray crystallography. SmTGR is one of the most promising drug targets for schistosomiasis, a devastating, neglected disease. Utilizing a multicrystal method to analyze electron density maps, structural analysis, and functional studies, three binding sites were characterized in SmTGR: two sites are close to or partially superposable with the NADPH binding site, while the third one is found between two symmetry related SmTGR subunits of the crystal lattice. Surprisingly, one compound bound to this latter site stabilizes, through allosteric effects mediated by the so-called guiding bar residues, the crucial redox active C-terminus of SmTGR, making it finally visible at high resolution. These results further promote fragments as small molecule probes for investigating functional aspects of the target protein, exemplified by the allosteric effect on the C-terminus, and providing fundamental chemical information exploitable in drug discovery.

High Density of NRF2 Expression in Malignant Cells Is Associated with Increased Risk of CNS Metastasis in Early-Stage NSCLC

Simple Summary

We retrospectively analyzed 304 patients with surgically removed non-small cell lung cancer (NSCLC). Multiplex antibody staining of nuclear factor erythroid 2-related factor 2 (NRF2) and thioredoxin reductase 1 (TrxR1) was conducted and scored in cytokeratin-positive (CK+) cells within the whole-tissue core as well as the tumor and stromal compartments of each tissue microarray (TMA) core. A high density of NRF2+/CK+ cells in the whole-tissue core compartment was an independent prognostic factor, with an eightfold increase in odds regarding the risk of relapse in the central nervous system (CNS). This is the first study to report a tumor-cell-associated protein biomarker for CNS relapse in early-stage lung cancer and the first trial to report the correlation between NRF2 expression and risk of CNS relapse. The results of our study may have an impact on the follow-up strategy for early-stage NSCLC patients and eventually improve their prognosis.

Abstract

Nuclear factor erythroid 2-related factor 2 (NRF2) protein expression promotes cancer progression in non-small cell lung cancer (NSCLC). However, its role in the clinical setting has not been established. We retrospectively analyzed data from 304 patients with surgically removed NSCLC. Multiplex antibody staining of NRF2 and thioredoxin reductase 1 (TrxR1) was conducted and scored in cytokeratin-positive (CK+) cells within the whole-tissue core as well as the tumor and stromal compartments of each tissue microarray (TMA) core. A high density of NRF2+/CK+ cells in the whole-tissue core compartment was correlated with a higher risk of central nervous system (CNS) relapse OR = 7.36 (95% CI: 1.64–33.06). The multivariate analysis showed an OR = 8.00 (95% CI: 1.70–37.60) for CNS relapse in NRF2+/CK+ high-density cases. The density of TrxR1+/CK+ cells failed to show any statistically significant risk of relapse. The OS analyses for NRF2+/CK+ and TrxR1+/CK+ cell density failed to show any statistical significance. This is the first study to report a correlation between NRF2+/CK+ cell density and the risk of CNS relapse in early-stage NSCLC. The results of our study may impact the follow-up strategy for early-stage NSCLC patients and eventually improve their prognosis.

Natural Molecules Targeting Thioredoxin System and Their Therapeutic Potential

Significance: Thioredoxin (Trx) and thioredoxin reductase are two core members of the Trx system. The system bridges the gap between the universal reducing equivalent NADPH and various biological molecules and plays an essential role in maintaining cellular redox homeostasis and regulating multiple cellular redox signaling pathways. Recent Advance: In recent years, the Trx system has been well documented as an important regulator of many diseases, especially tumorigenesis. Thus, the development of potential therapeutic molecules targeting the system is of great significance for disease treatment. Critical Issues: We herein first discuss the physiological functions of the Trx system and the role that the Trx system plays in various diseases. Then, we focus on the introduction of natural small molecules with potential therapeutic applications, especially the anticancer activity, and review their mechanisms of pharmacological actions via interfering with the Trx system. Finally, we further discuss several natural molecules that harbor therapeutic potential and have entered different clinical trials. Future Directions: Further studies on the functions of the Trx system in multiple diseases will not only improve our understanding of the pathogenesis of many human disorders but also help develop novel therapeutic strategies against these diseases. Antioxid. Redox Signal. 34, 1083-1107.

Potential therapeutic targets shared between leishmaniasis and cancer

The association of leishmaniasis and malignancies in human and animal models has been highlighted in recent years. The misdiagnosis of coexistence of leishmaniasis and cancer and the use of common drugs in the treatment of such diseases prompt us to further survey the molecular biology of Leishmania parasites and cancer cells. The information regarding common expressed proteins, as possible therapeutic targets, in Leishmania parasites and cancer cells is scarce. Therefore, the current study reviews proteins, and investigates the regulation and functions of several key proteins in Leishmania parasites and cancer cells. The up- and down-regulations of such proteins were mostly related to survival, development, pathogenicity, metabolic pathways and vital signalling in Leishmania parasites and cancer cells. The presence of common expressed proteins in Leishmania parasites and cancer cells reveals valuable information regarding the possible shared mechanisms of pathogenicity and opportunities for therapeutic targeting in leishmaniasis and cancers in the future.

Keshan Disease: A Potentially Fatal Endemic Cardiomyopathy in Remote Mountains of China

Keshan disease (KD) as an endemic, highly lethal cardiomyopathy, first reported in northeast China's Keshan County in 1935. The clinical manifestations of patients with KD include primarily congestive heart failure, acute heart failure, and cardiac arrhythmia. Even though some possible etiologies, such as viral infection, fungal infection, microelement deficiency, and malnutrition, have been reported, the exact causes of KD remain poorly known. The endemic areas where KD is found are remote and rural, and many are poor and mountainous places where people are the most socioeconomically disadvantaged in terms of housing, income, education, transportation, and utilization of health services. To date, KD is a huge burden to and severely restricts the economic development of the local residents and health systems of the endemic areas. Although efforts have been made by the government to control, treat, and interrupt disease transmission, the cure for or complete eradication of KD still requires global attention. For this reason, in this review, we systematically describe the etiological hypothesis, clinical manifestations, incidence characteristics, and treatment of KD, to facilitate the better understanding of and draw more attention to this non-representative cardiovascular disease, with the aim of accelerating its elimination.

Isodeoxyelephantopin Inactivates Thioredoxin Reductase 1 and Activates ROS-Mediated JNK Signaling Pathway to Exacerbate Cisplatin Effectiveness in Human Colon Cancer Cells

Colon cancer is one of the leading causes of cancer-related death in the world. The development of new drugs and therapeutic strategies for patients with colon cancer are urgently needed. Isodeoxyelephantopin (ESI), a sesquiterpene lactone isolated from the medicinal plant Elephantopus scaber L., has been reported to exert antitumor effects on several cancer cells. However, the molecular mechanisms underlying the action of ESI is still elusive. In the present study, we found that ESI potently suppressed cell proliferation in human colon cancer cells. Furthermore, our results showed that ESI treatment markedly increased cellular reactive oxygen species (ROS) levels by inhibiting thioredoxin reductase 1 (TrxR1) activity, which leads to activation of the JNK signaling pathway and eventually cell death in HCT116 and RKO cells. Importantly, we found that ESI markedly enhanced cisplatin-induced cytotoxicity in HCT116 and RKO cells. Combination of ESI and cisplatin significantly increased the production of ROS, resulting in activation of the JNK signaling pathway in HCT116 and RKO cells. In vivo, we found that ESI combined with cisplatin significantly suppressed tumor growth in HCT116 xenograft models. Together, our study provide a preclinical proof-of-concept for ESI as a potential strategy for colon cancer treatment.

Identification and targeting of selective vulnerability rendered by tamoxifen resistance

BACKGROUND

The estrogen receptor (ER)-positive breast cancer represents over 80% of all breast cancer cases. Even though adjuvant hormone therapy with tamoxifen (TMX) is saving lives of patients with ER-positive breast cancer, the acquired resistance to TMX anti-estrogen therapy is the main hurdle for successful TMX therapy. Here we address the mechanism for TMX resistance and explore the ways to eradicate TMX-resistant breast cancer in both in vitro and ex vivo experiments.

EXPERIMENTAL DESIGN

To identify compounds able to overcome TMX resistance, we used short-term and long-term viability assays in cancer cells in vitro and in patient samples in 3D ex vivo, analysis of gene expression profiles and cell line pharmacology database, shRNA screen, CRISPR-Cas9 genome editing, real-time PCR, immunofluorescent analysis, western blot, measurement of oxidative stress using flow cytometry, and thioredoxin reductase 1 enzymatic activity.

RESULTS

Here, for the first time, we provide an ample evidence that a high level of the detoxifying enzyme SULT1A1 confers resistance to TMX therapy in both in vitro and ex vivo models and correlates with TMX resistance in metastatic samples in relapsed patients. Based on the data from different approaches, we identified three anticancer compounds, RITA (Reactivation of p53 and Induction of Tumor cell Apoptosis), aminoflavone (AF), and oncrasin-1 (ONC-1), whose tumor cell inhibition activity is dependent on SULT1A1. We discovered thioredoxin reductase 1 (TrxR1, encoded by TXNRD1) as a target of bio-activated RITA, AF, and ONC-1. SULT1A1 depletion prevented the inhibition of TrxR1, induction of oxidative stress, DNA damage signaling, and apoptosis triggered by the compounds. Notably, RITA efficiently suppressed TMX-unresponsive patient-derived breast cancer cells ex vivo.

CONCLUSION

We have identified a mechanism of resistance to TMX via hyperactivated SULT1A1, which renders selective vulnerability to anticancer compounds RITA, AF, and ONC-1, and provide a rationale for a new combination therapy to overcome TMX resistance in breast cancer patients. Our novel findings may provide a strategy to circumvent TMX resistance and suggest that this approach could be developed further for the benefit of relapsed breast cancer patients.

Sanguinarine as a new chemical entity of thioredoxin reductase inhibitor to elicit oxidative stress and promote tumor cell apoptosis

The alteration of redox homeostasis is a hallmark of cancer cells. As a critical player in regulating cellular redox signaling, thioredoxin reductase (TrxR) enzymes are increasingly recognized as attractive targets for anticancer drug development. We reported herein the natural product sanguinarine (SAN) as a potent inhibitor of TrxR with a new chemical scaffold. Inhibition of TrxR leads to accumulation of the oxidized thioredoxin, elicits oxidative stress, and finally promotes apoptosis of cancer cells. Further synthesis of different model compounds of SAN demonstrated that the phenanthridinium unit is responsible for the TrxR inhibition. The core structure of SAN, e.g., the phenanthridinium moiety, is different from those of known TrxR inhibitors, and thus SAN is a new chemical entity of TrxR inhibitors and may serve a lead for further development. In addition, as the phenanthridinium scaffold is widely present in natural products, the disclosure of TrxR inhibition by such unit sheds light in understanding the pharmacological actions of these molecules.

Downregulation of thioredoxin-1-dependent CD95 S-nitrosation by Sorafenib reduces liver cancer

Hepatocellular carcinoma (HCC) represents 80% of the primary hepatic neoplasms. It is the sixth most frequent neoplasm, the fourth cause of cancer-related death, and 7% of registered malignancies. Sorafenib is the first line molecular targeted therapy for patients in advanced stage of HCC. The present study shows that Sorafenib exerts free radical scavenging properties associated with the downregulation of nuclear factor E2-related factor 2 (Nrf2)-regulated thioredoxin 1 (Trx1) expression in liver cancer cells. The experimental downregulation and/or overexpression strategies showed that Trx1 induced activation of nitric oxide synthase (NOS) type 3 (NOS3) and S-nitrosation (SNO) of CD95 receptor leading to an increase of caspase-8 activity and cell proliferation, as well as reduction of caspase-3 activity in liver cancer cells. In addition, Sorafenib transiently increased mRNA expression and activity of S-nitrosoglutathione reductase (GSNOR) in HepG2 cells. Different experimental models of hepatocarcinogenesis based on the subcutaneous implantation of HepG2 cells in nude mice, as well as the induction of HCC by diethylnitrosamine (DEN) confirmed the relevance of Trx1 downregulation during the proapoptotic and antiproliferative properties induced by Sorafenib. In conclusion, the induction of apoptosis and antiproliferative properties by Sorafenib were related to Trx1 downregulation that appeared to play a relevant role on SNO of NOS3 and CD95 in HepG2 cells. The transient increase of GSNOR might also participate in the deactivation of CD95-dependent proliferative signaling in liver cancer cells.

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Sorafenib induces mitochondrial ROS generation, but also acts as nucleophilic scavenger.

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Sorafenib reduces Nrf2-depenent Trx1 expression, and SNO–NOS3 and SNO-CD95 ratios.

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Sorafenib-related antitumoral in vivo activity involves diminution of Trx1 and SNO-CD95.

Allylated Curcumin Analog CA6 Inhibits TrxR1 and Leads to ROS-Dependent Apoptotic Cell Death in Gastric Cancer Through Akt-FoxO3a

Background

Gastric cancer is one of the leading causes of cancer-related deaths. Allylated monocarbonyl analogs of curcumin (MACs) have been reported to selectively inhibit a broad range of human cancers including gastric cancer. However, the precise molecular mechanisms underlying the inhibitory activities of MACs are not fully known.

Methods

In this study, we examined the anti-tumor activities of an allylated MAC, CA6, on gastric cancer cells and gastric cancer xenograft mouse model. The potential molecular anti-tumor mechanisms of CA6 were also elucidated.

Results

Our data show that CA6 exhibited significant cytotoxicity in gastric cancer cells, which was seen as an induction of G2/M cell cycle arrest and apoptosis. These activities were mediated through an elaboration of ROS levels in gastric cancer cells and induction of endoplasmic reticulum stress. CA6 increased ROS levels through directly binding to and inhibiting thioredoxin reductase R1 (TrxR1). Also, CA6-generated ROS inhibited Akt and activated forkhead O3A (FoxO3a), causing cytotoxicity in gastric cancer cells. Finally, CA6 treatment dose-dependently reduced the growth of gastric cancer xenografts in tumor-bearing mice, which was associated with reduced TrxR1 activity and increased ROS in the tumor.

Conclusion

In summary, our studies demonstrate that CA6 inhibited gastric cancer growth by inhibiting TrxR1 and increasing ROS, which in turn activated FoxO3a through suppressing Akt. CA6 is a potential candidate for the treatment of gastric cancer.

Plasma activity of Thioredoxin Reductase as a Novel Biomarker in Gastric Cancer

Gastric cancer (GC) is one of the leading malignancies around the world. Identification of novel and efficient biomarkers for GC diagnosis and evaluation of therapeutic efficiency could improve the therapeutic strategy in future clinical application. This study aims to evaluate the levels of plasma thioredoxin reductase (TrxR) activity in GC patients to confirm its validity and efficacy in GC diagnosis and evaluation of therapeutic efficiency. 923 cases were enrolled in the current study. In the group of GC patients before clinical intervention, plasma TrxR activity [9.09 (7.96, 10.45) U/mL] was significantly higher than in healthy controls [3.69 (2.38, 5.32) U/mL]. The threshold of TrxR activity for GC diagnosis was set at 7.34 U/mL with a sensitivity of 85.5% and a specificity of 97.9%. In GC patients after chemotherapy, plasma TrxR activity was remarkably higher in patients with progressive disease or uncontrolled condition [10.07 (8.19, 11.02) U/mL] compared with patients with complete or partial response [7.12 (6.08, 8.37) U/mL] in response to chemotherapy. TrxR activity displayed the higher efficiency to distinguish between GC patients with two distinct clinical outcomes than carcinoembryonic antigen (CEA), cancer antigen 72-4 (CA72-4) and cancer antigen 19-9 (CA19-9). Moreover, combination of TrxR, CEA, CA72-4 and CA19-9 was demonstrated to be more effective in both GC diagnosis and evaluation of therapeutic efficiency than was each biomarker individually. Together, plasma TrxR activity was identified as a novel and efficient biomarker of GC, both in diagnosis and monitoring of therapeutic efficiency in response to chemotherapy.

Piperlongumine, a Novel TrxR1 Inhibitor, Induces Apoptosis in Hepatocellular Carcinoma Cells by ROS-Mediated ER Stress

Hepatocellular carcinoma (HCC) is the sixth most common cancer and the third leading cause of cancer-related deaths globally. Despite advances in diagnosis and treatment, the incidence and mortality of HCC continue to rise. Piperlongumine (PL), an alkaloid isolated from the fruit of the long pepper, is known to selectively kill tumor tissues while sparing their normal counterparts. However, the killing effects of PL on HCC and the underlying mechanism of PL are not clear. We report that PL may interact with thioredoxin reductase 1 (TrxR1), an important selenocysteine (Sec)-containing antioxidant enzyme, and induce reactive oxygen species (ROS)-mediated apoptosis in HCC cells. Our results suggest that PL induces a lethal endoplasmic reticulum (ER) stress response in HCC cells by targeting TrxR1 and increasing intracellular ROS levels. Notably, PL treatment reduces TrxR1 activity and tumor cell burden in vivo. Additionally, TrxR1 is significantly upregulated in existing HCC databases and available HCC clinical specimens. Taken together, these results suggest PL as a novel anticancer candidate for the treatment of HCC. More importantly, this study reveals that TrxR1 might be an effective target in treating HCC.

Dietary intakes and biomarker patterns of folate, vitamin B6, and vitamin B12 can be associated with cognitive impairment by hypermethylation of redox-related genes NUDT15 and TXNRD1

BACKGROUND

B vitamins in the one-carbon metabolism pathway (folate, vitamin B₆, and vitamin B₁₂) have been implicated in DNA methylation, and their deficiency may contribute to cognitive decline through increased homocysteine (Hcy) levels and subsequent oxidative damage. The aim of this study was to investigate whether B vitamin deficiency and increased Hcy could interact with DNA methylation of oxidative-related genes and exacerbate cognitive impairment.

METHODS

Participants were selected from a large cohort study entitled the Effects and Mechanism Investigation of Cholesterol and Oxysterol on Alzheimer's disease (EMCOA) study. We included 2533 participants who completed a selection of comprehensive cognitive tests and a semiquantitative food frequency questionnaire (FFQ) and were followed for an average of 2.3 years. The longitudinal effects of B vitamin intake on cognitive decline were examined using linear mixed-effect models. Seven mild cognitive impairment (MCI) patients, in the predementia stage of Alzheimer's disease (AD), and fivev healthy controls were selected for the discovery of genome-wide differentially methylated CpG sites. Candidate oxidative stress-related genes significantly correlated with serum levels of B vitamins were selected for validation in 102 MCI patients and 68 controls. The correlations between DNA methylation levels and serum concentrations of B vitamins and oxidative biomarkers were analyzed with Spearman's correlation. The interactive effects of DNA methylation and B vitamins on cognitive performance were further evaluated by multiple linear regression.

RESULTS

In the prospective analysis, inadequate dietary intake of vitamin B₁₂ was significantly associated with accelerated cognitive decline, whereas adequate folate, vitamin B₆, and vitamin B₁₂ intakes were significantly associated with better cognitive reserve. In the case-control analysis, the DNA methylation levels of NUDT15 and TXNRD1 were examined, and significantly hypermethylated sites were identified in MCI patients. Significant correlations of hypermethylated sites with serum levels of folate, homocysteine (Hcy), and oxidative biomarkers were observed, and interactive effects of B vitamins and hypermethylated sites were significantly associated with cognitive performance.

CONCLUSION

Adequate dietary folate at baseline predicted a better cognitive reserve, while decreased serum levels of B vitamins may contribute to cognitive impairment by affecting methylation levels of specific redox-related genes.

TRIAL REGISTRATION

EMCOA, ChiCTR-OOC-17011882, Registered 5th, July 2017-Retrospectively registered, http://www.medresman.org/uc/project/projectedit.aspx?proj=2610.

Which Antioxidant System Shapes Intracellular H2O2 Gradients?

Cellular antioxidant systems control the levels of hydrogen peroxide (H₂O₂) within cells. Multiple theoretical models exist that predict the diffusion properties of H₂O₂ depending on the rate of H₂O₂ generation and amount and reaction rates of antioxidant machinery components. Despite these theoretical predictions, it has remained unknown how antioxidant systems shape intracellular H₂O₂ gradients. The relative role of thioredoxin (Trx) and glutathione systems in H₂O₂ pattern formation and maintenance is another disputed question. Here, we visualized cellular antioxidant activity and H₂O₂ gradients formation by exploiting chemogenetic approaches to generate compartmentalized intracellular H₂O₂ and using the H₂O₂ biosensor HyPer to analyze the resulting H₂O₂ distribution in specific subcellular compartments. Using human HeLa cells as a model system, we propose that the Trx system, but not the glutathione system, regulates intracellular H₂O₂ gradients. Antioxid. Redox Signal. 31, 664-670.

The role of thioredoxin system in cancer: strategy for cancer therapy

PURPOSE

Cancer, a major public health problem, exhibits significant redox alteration. Thioredoxin (Trx) system, including Trx and Trx reductase (TrxR), as well as Trx-interacting protein (TXNIP) play important roles in controlling the cellular redox balance in cancer cells. In most cancers, Trx and TrxR are usually overexpressed and TXNIP is underexpressed. In recent years, some agents targeting Trx, TrxR, and TXNIP were used to explore a therapy approach for cancer patients.

METHODS

A systematic search of PMC and the PubMed Database was conducted to summarize the potential of Trx system inhibitors for cancer treatment.

RESULTS

In this article, we first summarize the functions of Trx, TrxR, and TXNIP in cancers. We also review some small molecule inhibitors of Trx/TrxR and D-allose (TXNIP inducer) and discuss their antitumor mechanisms. We highlight the combined inhibition of Trx system and GSH system in cancer therapy. We expect that a highly specific and selective antitumor agent with no cytotoxicity on human normal cells could be developed in the future.

CONCLUSION

In conclusion, Trx system may be very promising for clinical therapy of cancer in the future.

Cytotoxic unsaturated electrophilic compounds commonly target the ubiquitin proteasome system

A large number of natural products have been advocated as anticancer agents. Many of these compounds contain functional groups characterized by chemical reactivity. It is not clear whether distinct mechanisms of action can be attributed to such compounds. We used a chemical library screening approach to demonstrate that a substantial fraction (~20%) of cytotoxic synthetic compounds containing Michael acceptor groups inhibit proteasome substrate processing and induce a cellular response characteristic of proteasome inhibition. Biochemical and structural analyses showed binding to and inhibition of proteasome-associated cysteine deubiquitinases, in particular ubiquitin specific peptidase 14 (USP14). The results suggested that compounds bind to a crevice close to the USP14 active site with modest affinity, followed by covalent binding. A subset of compounds was identified where cell death induction was closely associated with proteasome inhibition and that showed significant antineoplastic activity in a zebrafish embryo model. These findings suggest that proteasome inhibition is a relatively common mode of action by cytotoxic compounds containing Michael acceptor groups and help to explain previous reports on the antineoplastic effects of natural products containing such functional groups.

A fast and specific fluorescent probe for thioredoxin reductase that works via disulphide bond cleavage

Small molecule probes are indispensable tools to explore diverse cellular events. However, finding a specific probe of a target remains a high challenge. Here we report the discovery of Fast-TRFS, a specific and superfast fluorogenic probe of mammalian thioredoxin reductase, a ubiquitous enzyme involved in regulation of diverse cellular redox signaling pathways. By systematically examining the processes of fluorophore release and reduction of cyclic disulfides/diselenides by the enzyme, structural factors that determine the response rate and specificity of the probe are disclosed. Mechanistic studies reveal that the fluorescence signal is switched on by a simple reduction of the disulfide bond within the probe, which is in stark contrast to the sensing mechanism of published probes. The favorable properties of Fast-TRFS enable development of a high-throughput screening assay to discover inhibitors of thioredoxin reductase by using crude tissue extracts as a source of the enzyme.