Glutathione peroxidases in different stages of carcinogenesis

Synergistic Effect of Layered Double Hydroxides Nanodosage Form to Induce Apoptosis and Ferroptosis in Breast Cancer

Background

Breast cancer is the most common cancer in women and one of the leading causes of cancer death worldwide. Ferroptosis, a promising mechanism of killing cancer cells, has become a research hotspot in cancer therapy. Simvastatin (SIM), as a potential new anti-breast cancer drug, has been shown to cause ferroptosis of cancer cells and inhibit breast cancer metastasis and recurrence. The purpose of this study is to develop a novel strategy boosting ferroptotic cascade for synergistic cancer therapy.

Methods

In this paper, iron base form of layered double hydroxide supported simvastatin (LDHs-SIM) was synthesized by hydrothermal co-precipitation method. The characterization of LDHs-SIM were assessed by various analytical techniques, including ultraviolet-visible (UV-vis) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). Biological activity, ferroptosis mechanism and biocompatibility were analyzed through in vivo and in vitro analysis, so as to evaluate its therapeutic effect on breast cancer.

Results

The constructed LDHs-SIM nanosystem can not only release SIM through mevalonate (MVA) pathway, inhibit the expression of glutathione peroxidase 4 (GPX4), inhibit the expression of SLC7A11 and reduce the synthesis efficiency of GSH, but also promote the accumulation of Fe2+ in cells through the release of Fe3+, and increase the intracellular ROS content. In addition, LDHs-SIM nanosystem can induce apoptosis of breast cancer cells to a certain extent, and achieve the synergistic effect of apoptosis and ferroptosis.

Conclusion

In the present study, we demonstrated that nanoparticles of layered double hydroxides (LDHs) loaded with simvastatin were more effective than a free drug at inhibiting breast cancer cell growth, In addition, superior anticancer therapeutic effects were achieved with little systemic toxicity, indicating that LDHs-SIM could serve as a safe and high-performance platform for ferroptosis-apoptosis combined anticancer therapy.

PI3K/AKT pathway as a pivotal regulator of epithelial-mesenchymal transition in lung tumor cells

Lung cancer, as the leading cause of cancer related deaths, is one of the main global health challenges. Despite various progresses in diagnostic and therapeutic methods, there is still a high rate of mortality among lung cancer patients, which can be related to the lack of clinical symptoms to differentiate lung cancer from the other chronic respiratory disorders in the early tumor stages. Most lung cancer patients are identified in advanced and metastatic tumor stages, which is associated with a poor prognosis. Therefore, it is necessary to investigate the molecular mechanisms involved in lung tumor progression and metastasis in order to introduce early diagnostic markers as well as therapeutic targets. Epithelial-mesenchymal transition (EMT) is considered as one of the main cellular mechanisms involved in lung tumor metastasis, during which tumor cells gain the metastatic ability by acquiring mesenchymal characteristics. Since, majority of the oncogenic signaling pathways exert their role in tumor cell invasion by inducing the EMT process, in the present review we discussed the role of PI3K/AKT signaling pathway in regulation of EMT process during lung tumor metastasis. It has been reported that the PI3K/AKT acts as an inducer of EMT process through the activation of EMT-specific transcription factors in lung tumor cells. MicroRNAs also exerted their inhibitory effects during EMT process by inhibition of PI3K/AKT pathway. This review can be an effective step towards introducing the PI3K/AKT pathway as a suitable therapeutic target to inhibit the EMT process and tumor metastasis in lung cancer patients.

Several lines of antioxidant defense against oxidative stress: antioxidant enzymes, nanomaterials with multiple enzyme-mimicking activities, and low-molecular-weight antioxidants

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are well recognized for playing a dual role, since they can be either deleterious or beneficial to biological systems. An imbalance between ROS production and elimination is termed oxidative stress, a critical factor and common denominator of many chronic diseases such as cancer, cardiovascular diseases, metabolic diseases, neurological disorders (Alzheimer's and Parkinson's diseases), and other disorders. To counteract the harmful effects of ROS, organisms have evolved a complex, three-line antioxidant defense system. The first-line defense mechanism is the most efficient and involves antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). This line of defense plays an irreplaceable role in the dismutation of superoxide radicals (O2•-) and hydrogen peroxide (H2O2). The removal of superoxide radicals by SOD prevents the formation of the much more damaging peroxynitrite ONOO- (O2•-  + NO• → ONOO-) and maintains the physiologically relevant level of nitric oxide (NO•), an important molecule in neurotransmission, inflammation, and vasodilation. The second-line antioxidant defense pathway involves exogenous diet-derived small-molecule antioxidants. The third-line antioxidant defense is ensured by the repair or removal of oxidized proteins and other biomolecules by a variety of enzyme systems. This review briefly discusses the endogenous (mitochondria, NADPH, xanthine oxidase (XO), Fenton reaction) and exogenous (e.g., smoking, radiation, drugs, pollution) sources of ROS (superoxide radical, hydrogen peroxide, hydroxyl radical, peroxyl radical, hypochlorous acid, peroxynitrite). Attention has been given to the first-line antioxidant defense system provided by SOD, CAT, and GPx. The chemical and molecular mechanisms of antioxidant enzymes, enzyme-related diseases (cancer, cardiovascular, lung, metabolic, and neurological diseases), and the role of enzymes (e.g., GPx4) in cellular processes such as ferroptosis are discussed. Potential therapeutic applications of enzyme mimics and recent progress in metal-based (copper, iron, cobalt, molybdenum, cerium) and nonmetal (carbon)-based nanomaterials with enzyme-like activities (nanozymes) are also discussed. Moreover, attention has been given to the mechanisms of action of low-molecular-weight antioxidants (vitamin C (ascorbate), vitamin E (alpha-tocopherol), carotenoids (e.g., β-carotene, lycopene, lutein), flavonoids (e.g., quercetin, anthocyanins, epicatechin), and glutathione (GSH)), the activation of transcription factors such as Nrf2, and the protection against chronic diseases. Given that there is a discrepancy between preclinical and clinical studies, approaches that may result in greater pharmacological and clinical success of low-molecular-weight antioxidant therapies are also subject to discussion.

GPX4, ferroptosis, and diseases

GPX4 (Glutathione peroxidase 4) serves as a crucial intracellular regulatory factor, participating in various physiological processes and playing a significant role in maintaining the redox homeostasis within the body. Ferroptosis, a form of iron-dependent non-apoptotic cell death, has gained considerable attention in recent years due to its involvement in multiple pathological processes. GPX4 is closely associated with ferroptosis and functions as the primary inhibitor of this process. Together, GPX4 and ferroptosis contribute to the pathophysiology of several diseases, including sepsis, nervous system diseases, ischemia reperfusion injury, cardiovascular diseases, and cancer. This review comprehensively explores the regulatory roles and impacts of GPX4 and ferroptosis in the development and progression of these diseases, with the aim of providing insights for identifying potential therapeutic strategies in the future.

Single-Cell RNA Sequencing Reveals Cardiac Fibroblast-Specific Transcriptomic Changes in Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is the most common cause of heart failure, with a complex aetiology involving multiple cell types. We aimed to detect cell-specific transcriptomic alterations in DCM through analysis that leveraged recent advancements in single-cell analytical tools. Single-cell RNA sequencing (scRNA-seq) data from human DCM cardiac tissue were subjected to an updated bioinformatic workflow in which unsupervised clustering was paired with reference label transfer to more comprehensively annotate the dataset. Differential gene expression was detected primarily in the cardiac fibroblast population. Bulk RNA sequencing was performed on an independent cohort of human cardiac tissue and compared with scRNA-seq gene alterations to generate a stratified list of higher-confidence, fibroblast-specific expression candidates for further validation. Concordant gene dysregulation was confirmed in TGFβ-induced fibroblasts. Functional assessment of gene candidates showed that AEBP1 may play a significant role in fibroblast activation. This unbiased approach enabled improved resolution of cardiac cell-type-specific transcriptomic alterations in DCM.

Immunohistochemical Expression of Glutathione Peroxidase-2 (Gpx-2) and Its Clinical Relevance in Colon Adenocarcinoma Patients

Glutathione peroxidase 2 (Gpx-2) is a selenoenzyme with antioxidant capabilities that may play a role in cancer development. Hence, we investigated the immunohistochemical expression of Gpx-2 protein in colon adenocarcinoma samples derived from patients with colon adenocarcinoma who did not receive any form of treatment prior to the surgical procedure. The associations between the immunohistochemical expression of Gpx-2 and clinical parameters were analysed using the Chi2 test and Fisher's exact test. A Kaplan-Meier analysis and the log-rank test were used to verify the relationship between the intensity of Gpx-2 expression and the 5-year survival rate of patients. In total, 101 (80.80%) samples had strong Gpx-2 protein expression and 24 (19.20%) samples were characterized with low expression. The high expression of Gpx-2 was correlated with the histological grade of the tumour (p < 0.001), PCNA immunohistochemical expression (p < 0.001), depth of invasion (p = 0.001) and angioinvasion (p < 0.001). We can conclude that high expression of Gpx-2 is correlated with reduced survival of colon adenocarcinoma patients (log-rank, p < 0.001).

Nrf2 signaling pathway: current status and potential therapeutic targetable role in human cancers

Cancer is a borderless global health challenge that continues to threaten human health. Studies have found that oxidative stress (OS) is often associated with the etiology of many diseases, especially the aging process and cancer. Involved in the OS reaction as a key transcription factor, Nrf2 is a pivotal regulator of cellular redox state and detoxification. Nrf2 can prevent oxidative damage by regulating gene expression with antioxidant response elements (ARE) to promote the antioxidant response process. OS is generated with an imbalance in the redox state and promotes the accumulation of mutations and genome instability, thus associated with the establishment and development of different cancers. Nrf2 activation regulates a plethora of processes inducing cellular proliferation, differentiation and death, and is strongly associated with OS-mediated cancer. What's more, Nrf2 activation is also involved in anti-inflammatory effects and metabolic disorders, neurodegenerative diseases, and multidrug resistance. Nrf2 is highly expressed in multiple human body parts of digestive system, respiratory system, reproductive system and nervous system. In oncology research, Nrf2 has emerged as a promising therapeutic target. Therefore, certain natural compounds and drugs can exert anti-cancer effects through the Nrf2 signaling pathway, and blocking the Nrf2 signaling pathway can reduce some types of tumor recurrence rates and increase sensitivity to chemotherapy. However, Nrf2's dual role and controversial impact in cancer are inevitable consideration factors when treating Nrf2 as a therapeutic target. In this review, we summarized the current state of biological characteristics of Nrf2 and its dual role and development mechanism in different tumor cells, discussed Keap1/Nrf2/ARE signaling pathway and its downstream genes, elaborated the expression of related signaling pathways such as AMPK/mTOR and NF-κB. Besides, the main mechanism of Nrf2 as a cancer therapeutic target and the therapeutic strategies using Nrf2 inhibitors or activators, as well as the possible positive and negative effects of Nrf2 activation were also reviewed. It can be concluded that Nrf2 is related to OS and serves as an important factor in cancer formation and development, thus provides a basis for targeted therapy in human cancers.

The selenoprotein P-LRP5/6-WNT3A complex promotes tumorigenesis in sporadic colorectal cancer

Some studies suggest that the trace element selenium protects against colorectal cancer (CRC). However, the contribution of selenoprotein P (SELENOP), a unique selenocysteine-containing protein, to sporadic colorectal carcinogenesis challenges this paradigm. SELENOP is predominately secreted by the liver but is also expressed in various cells of the small intestine and colon in mice and humans. In this issue of the JCI, Pilat et al. demonstrate that increased SELENOP expression promoted the progression of conventional adenomas to carcinoma. SELENOP functioned as a modulator of canonical WNT signaling activity through interactions with WNT3A and its coreceptor LDL receptor-related protein 5/6 (LRP5/6). Secreted SELENOP formed a concentration gradient along the gut crypt axis, which might amplify WNT signaling activity by binding to LRPL5/6. The mechanism for WNT control via SELENOP may affect colorectal tumorigenesis and provide therapeutic targets for CRC.

GPX2 promotes EMT and metastasis in non-small cell lung cancer by activating PI3K/AKT/mTOR/Snail signaling axis

Lung cancer, with non-small cell lung cancer (NSCLC) being the main subtype, is the leading cause of cancer death worldwide, which is mainly due to the cancer metastasis. Glutathione peroxidase 2 (GPX2), an antioxidant enzyme, is involved in tumor progression and metastasis. Nevertheless, the role of GPX2 in NSCLC metastasis has not been clarified. In this study, we found that GPX2 expression was elevated in NSCLC tissues and high GPX2 expression was correlated with poor prognosis in patients with NSCLC. In addtion, GPX2 expression was related to the patient's clinicopathological features, including lymph node metastasis, tumor size, and TNM stage. Overexpression of GPX2 promoted epithelial-mesenchymal transition (EMT), migration, and invasion of NSCLC cells in vitro. Knockdown of GPX2 showed the opposite effects in vitro and inhibited the metastasis of NSCLC cells in nude mice. Furthermore, GPX2 reduced reactive oxygen species (ROS) accumulation and activated the PI3K/AKT/mTOR/Snail signaling axis. Therefore, our results indicate that GPX2 promotes EMT and metastasis of NSCLC cells by activating the PI3K/AKT/mTOR/Snail signaling axis via the removal of ROS. GPX2 may be an effective diagnostic and prognostic biomarker for NSCLC.

Development of an assay pipeline for the discovery of novel small molecule inhibitors of human glutathione peroxidases GPX1 and GPX4

Selenoprotein glutathione peroxidases (GPX), like ubiquitously expressed GPX1 and the ferroptosis modulator GPX4, enact antioxidant activities by reducing hydroperoxides using glutathione. Overexpression of these enzymes is common in cancer and can be associated with the development of resistance to chemotherapy. GPX1 and GPX4 inhibitors have thus shown promise as anti-cancer agents, and targeting other GPX isoforms may prove equally beneficial. Existing inhibitors are often promiscuous, or modulate GPXs only indirectly, so novel direct inhibitors identified through screening against GPX1 and GPX4 could be valuable. Here, we developed optimized glutathione reductase (GR)-coupled GPX assays for the biochemical high-throughput screen (HTS) of almost 12,000 compounds with proposed mechanisms of action. Initial hits were triaged using a GR counter-screen, assessed for isoform specificity against an additional GPX isoform, GPX2, and were assessed for general selenocysteine-targeting activity using a thioredoxin reductase (TXNRD1) assay. Importantly, 70% of the GPX1 inhibitors identified in the primary screen, including several cephalosporin antibiotics, were found to also inhibit TXNRD1, while auranofin, previously known as a TXNRD1 inhibitor, also inhibited GPX1 (but not GPX4). Additionally, every GPX1 inhibitor identified (including omapatrilat, tenatoprazole, cefoxitin and ceftibuten) showed similar inhibitory activity against GPX2. Some compounds inhibiting GPX4 but not GPX1 or GPX2, also inhibited TXNRD1 (26%). Compounds only inhibiting GPX4 included pranlukast sodium hydrate, lusutrombopag, brilanestrant, simeprevir, grazoprevir (MK-5172), paritaprevir, navitoclax, venetoclax and VU0661013. Two compounds (metamizole sodium and isoniazid sodium methanesulfate) inhibited all three GPXs but not TXNRD1, while 2,3-dimercaptopropanesulfonate, PI4KIII beta inhibitor 3, SCE-2174 and cefotetan sodium inhibited all tested selenoproteins (but not GR). The detected overlaps in chemical space suggest that the counter screens introduced here should be imperative for identification of specific GPX inhibitors. With this approach, we could indeed identify novel GPX1/GPX2- or GPX4-specific inhibitors, thus presenting a validated pipeline for future identification of specific selenoprotein-targeting agents. Our study also identified GPX1/GPX2, GPX4 and/or TXNRD1 as targets for several previously developed pharmacologically active compounds.

Ferroptosis in acute leukemia

ABSTRACT

Ferroptosis is an iron-dependent cell death pathway that is different from apoptosis, pyroptosis, and necrosis. The main characteristics of ferroptosis are the Fenton reaction mediated by intracellular free divalent iron ions, lipid peroxidation of cell membrane lipids, and inhibition of the anti-lipid peroxidation activity of intracellular glutathione peroxidase 4 (GPX4). Recent studies have shown that ferroptosis can be involved in the pathological processes of many disorders, such as ischemia-reperfusion injury, nervous system diseases, and blood diseases. However, the specific mechanisms by which ferroptosis participates in the occurrence and development of acute leukemia still need to be more fully and deeply studied. This article reviews the characteristics of ferroptosis and the regulatory mechanisms promoting or inhibiting ferroptosis. More importantly, it further discusses the role of ferroptosis in acute leukemia and predicts a change in treatment strategy brought about by increased knowledge of the role of ferroptosis in acute leukemia.

PHKG2 regulates RSL3-induced ferroptosis in Helicobacter pylori related gastric cancer

Ferroptosis is a newly discovered form of regulatory cell death induced by iron-dependent lipid peroxidation. Infection with Helicobacter pylori (H. pylori) is regarded as a high-risk factor for the development of gastric cancer (GC) and is associated with an increase in the levels of reactive oxygen species with activation of oncogenic signaling pathways. However, whether GC arising in the context of infection with H. pylori is correlated with ferroptosis is still unknown. In this study, we demonstrate that H. pylori infection increased the sensitivity of GC cells to RSL3 (RAS-selective lethal3)-induced ferroptosis. The molecular subtypes mediated by ferroptosis-related genes are associated with tumor microenvironment (TME) cell infiltration and patient survival. Importantly, we identified that the expression of phosphorylase kinase G2 (PHKG2) was remarkably correlated with H. pylori infection, metabolic biological processes, patient survival and therapy response. We further found the mechanism of H. pylori-induced cell sensitivity to ferroptosis, which involves PHKG2 regulation of the lipoxygenase enzyme Arachidonate 5-Lipoxygenase (ALOX5). In conclusion, PHKG2 facilitates RSL3-induced ferroptosis in H. pylori-positive GC cells by promoting ALOX5 expression. These findings may contribute to a better understanding of the unique pathogenesis of H. pylori-induced GC and allow for maximum efficacy of genetic, cellular, and immune therapies for controlling ferroptosis in diverse contexts.

GPX4: The hub of lipid oxidation, ferroptosis, disease and treatment

Glutathione peroxidase 4 (GPx4) moonlights as structural protein and antioxidase that powerfully inhibits lipid oxidation. In the past years, it is considered as a key regulator of ferroptosis, which takes role in the lipid and amine acid metabolism and influences the cell aging, oncogenesis, and cell death. More and more evidences show that targeting GPX4-induced ferroptosis is a promising strategy for disease therapy, especially cancer treatment. In view of these, we generalize the function of GPX4 and regulatory mechanism between GPX4 and ferroptosis, discuss its roles in the disease pathology, and focus on the recent advances of disease therapeutic potential.

Antidiabetic and Anticancer Potentials of Mangifera indica L. from Different Geographical Origins

Mango fruit is well known for its nutritional and health benefits due to the presence of a plethora of phytochemical classes. The quality of mango fruit and its biological activities may change depending upon the variation in geographical factors. For the first time, this study comprehensively screened the biological activities of all four parts of the mango fruit from twelve different origins. Various cell lines (MCF7, HCT116, HepG2, MRC5) were used to screen the extracts for their cytotoxicity, glucose uptake, glutathione peroxidase activity, and α-amylase inhibition. MTT assays were carried out to calculate the IC50 values for the most effective extracts. The seed part from Kenya and Sri Lanka origins exhibited an IC50 value of 14.44 ± 3.61 (HCT116) and 17.19 ± 1.60 (MCF7). The seed part for Yemen Badami (119 ± 0.08) and epicarp part of Thailand (119 ± 0.11) mango fruit showed a significant increase in glucose utilization (50 μg/mL) as compared to the standard drug metformin (123 ± 0.07). The seed extracts of Yemen Taimoor seed (0.46 ± 0.05) and Yemen Badami (0.62 ± 0.13) produced a significant reduction in GPx activity (50 μg/mL) compared to the control cells (100 μg/mL). For α-amylase inhibition, the lowest IC50 value was observed for the endocarp part of Yemen Kalabathoor (108.8 ± 0.70 μg/mL). PCA, ANOVA, and Pearson’s statistical models revealed a significant correlation for the fruit part vs. biological activities, and seed part vs. cytotoxicity and α-amylase activity (p = 0.05). The seed of mango fruit exhibited significant biological activities; hence, further in-depth metabolomic and in vivo studies are essential to effectively utilize the seed part for the treatment of various diseases.

Identification of Prognostic and Predictive Biomarkers and Druggable Targets among 205 Antioxidant Genes in 21 Different Tumor Types via Data-Mining

(1) Background: Oxidative stress is crucial in carcinogenesis and the response of tumors to treatment. Antioxidant genes are important determinants of resistance to chemotherapy and radiotherapy. We hypothesized that genes involved in the oxidative stress response may be valuable as prognostic biomarkers for the survival of cancer patients and as druggable targets. (2) Methods: We mined the KM Plotter and TCGA Timer2.0 Cistrome databases and investigated 205 antioxidant genes in 21 different tumor types within the context of this investigation. (3) Results: Of 4347 calculations with Kaplan-Meier statistics, 84 revealed statistically significant correlations between high gene expression and worse overall survival (p < 0.05; false discovery rate ≤ 5%). The tumor types for which antioxidant gene expression was most frequently correlated with worse overall survival were renal clear cell carcinoma, renal papillary cell carcinoma, and hepatocellular carcinoma. Seventeen genes were clearly overexpressed in tumors compared to their corresponding normal tissues (p < 0.001), possibly qualifying them as druggable targets (i.e., ALOX5, ALOX5AP, EPHX4, G6PD, GLRX3, GSS, PDIA4, PDIA6, PRDX1, SELENOH, SELENON, STIP1, TXNDC9, TXNDC12, TXNL1, TXNL4A, and TXNRD1). (4) Conclusions: We concluded that a sub-set of antioxidant genes might serve as prognostic biomarkers for overall survival and as druggable targets. Renal and liver tumors may be the most suitable entities for this approach.

Potential Role of ROS in Butyrate- and Dietary Fiber-Mediated Growth Inhibition and Modulation of Cell Cycle-, Apoptosis- and Antioxidant-Relevant Proteins in LT97 Colon Adenoma and HT29 Colon Carcinoma Cells

The aim of the present study was to examine whether reactive oxygen species (ROS) contribute to chemopreventive effects of fermentation supernatants (FS) of different dietary fibers (Synergy1^®, oat-, barley-, yeast β-glucan, Curdlan) and butyrate as a fermentation metabolite. LT97 and HT29 cells were treated with butyrate and FS alone or with N-acetyl-cysteine (NAC) and their impact on ROS formation, cell growth, and protein expression (Cyclin D2, p21, PARP, Bid, GPx2) was investigated. Butyrate and FS significantly decreased cell growth. ROS levels were significantly increased, particularly in LT97 cells, while co-treatment with NAC decreased ROS formation and growth inhibitory effects in both cell lines. After treatment with butyrate and FS, Cyclin D2 expression was reduced in LT97 cells and p21 expression was increased in both cell lines. Levels of full-length PARP and Bid were decreased, while levels of cleaved PARP were enhanced. GPx2 expression was significantly reduced by fiber FS in HT29 cells. A notable effect of NAC on butyrate- and FS-modulated protein expression was observed exclusively for PARP and Bid in HT29 cells. From the present results, a contribution of ROS to growth inhibitory and apoptotic effects of butyrate and FS on LT97 and HT29 cells cannot be excluded.

Antitumor effect of selenium-rich Brazil nuts and selenomethionine dietary supplementation on pre-existing 4T1 mammary tumor growth in mice

Selenium (Se) is an essential micronutrient known to play an important role in the antioxidant system that can potentially influence tumor growth. We aimed to investigate the effects of dietary Se supplementation after detection of 4T1 mammary tumor growth in BALB/c mice. Thirty female mice received subcutaneous inoculation of 4T1 cells. After five days, all animals presenting palpable tumors were randomly assigned to three groups: a control group (Se-control) receiving a diet with adequate Se (0.15 mg/kg) and two other groups that received Se-supplemented diets (1.4 mg/kg of total Se) with either Brazilian nuts (Se-Nuts) or selenomethionine (SeMet). Data were assessed by either One or Two-way ANOVA followed by Tukey's HSD or Bonferroni's post hoc tests, respectively. Both Se-supplemented diets reduced tumor volume from the thirteenth day of feeding compared with the Se-adequate (control) diet (p < 0.05). The SeMet group presented a higher Se blood concentration (p < 0.05) than the Se-control group, with the Se-Nuts group presenting intermediate values. Selenoprotein P gene expression in the liver was higher in the Se-Nuts group than in the Se-control group (p < 0.05), while the SeMet group presented intermediate expression. Dietary Se supplementation, starting after detection of 4T1 palpable lesions, reduced tumor volume in mice.

Biological Screening of Glycyrrhiza glabra L. from Different Origins for Antidiabetic and Anticancer Activity

BACKGROUND

Geographical variation may affect the phytochemistry as well as the biological activities of Glycyrrhiza glabra (licorice) root. Herein, a series of biological activities were performed to evaluate the impact of geographical origin on the biological potential of eight different licorice samples.

METHODOLOGY

Cell culture studies were performed for cytotoxicity (MCF7, HCT116, HepG2, and MRC5), glucose uptake assay (HepG2), and glutathione peroxidase activity (HepG2), whereas α-amylase inhibition activity was tested for antidiabetic potential.

RESULTS

The Indian sample was observed to be more cytotoxic against MCF7 (22%) and HCT116 (43%) with an IC₅₀ value of 56.10 (±2.38) μg/mL against the MCF7 cell line. The glucose uptake was seen with a mean value of 96 (±2.82) and a range of 92-101%. For glutathione peroxidase activity (GPx), the Syrian (0.31 ± 0.11) and Pakistani samples (0.21 ± 0.08) revealed a significant activity, whereas the Palestinian (70 ± 0.09) and Indian samples (68±0.06) effectively inhibited the α-amylase activity, with the lowest IC₅₀ value (67.11 ± 0.97) μg/mL for the Palestinian sample. The statistical models of PCA (principal component analysis) and K-mean cluster analysis were performed to correlate the geographical origin, extract yield, and biological activities for the eight licorice samples of different origins.

CONCLUSION

The licorice samples exhibited significant cytotoxic, GPx, and α-amylase inhibitory activity. The samples with higher extract yield showed more potential in these biological activities.

Selenoprotein GPX1 is a prognostic and chemotherapy-related biomarker for brain lower grade glioma

OBJECTIVE

Glutathione peroxidase 1 (GPX1) is a major selenoprotein in most animal tissues, primarily expressed in the cytoplasm and mitochondria of cells and peroxidase structures of certain cells. GPX1 expression is highly correlated with carcinogenesis and disease progression. The goal of the study was to determine the association between GPX1 expression and tumor therapy, and to identify GPX1 prognostic value in various malignancies.

METHODS

The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), and Human Protein Atlas (HPA) databases were used to detect the levels of GPX1 expression in human tumor tissues and normal tissues. Indeed, correlations between GPX1 and tumor purity, tumor mutation burden (TMB), microsatellite instability (MSI), and DNA mismatch repair genes (MMRs) were explored using the TCGA cohort. Functional and enrichment analyses were performed by the GeneMANIA database and Gene Set Enrichment Analysis (GSEA), respectively. Cox regression models and Kaplan - Meier curves were used to screen for independent risk factors and estimate brain lower-grade glioma (LGG) survival probability. The Chinese Glioma Genome Atlas (CGGA) database was used to determine whether GPX1 had a race-specific effect on overall survival (OS) in LGG. The cross-interaction between GPX1 and chemoradiotherapy on LGG OS was determined by Kaplan - Meier curves. Logistic regression models of multiplicative interactions were constructed. Furthermore, the relationship between GPX1 and LGG treatment regimens was also explored through the Genomics of Drug Sensitivity in Cancer (GDSC) database.

RESULTS

GPX1 was highly expressed in various tumors, GPX1 overexpression was significantly correlated with the poor prognosis of LGG. GPX1 was found to be an independent predictive factor for LGG in both univariate and multivariate Cox models. The nomogram showed a high predictive accuracy (C-index: 0.804, 95% CI: 0.74-0.86). In addition, GPX1 was significantly associated with TMB, MSI, and MMRs in diverse cancers. GPX1 was involved in IL6/JAK/STAT3, inflammatory response, and apoptosis signaling pathways. Besides, non-radiotherapy, chemotherapy, and low GPX1 expression were important factors affecting the better prognosis of LGG. GPX1 acted as a tumor promoter, which has taken the worst effect on LGG survival, but a multiplicative interaction of GPX1*chemoradiotherapy may improve the poor clinical outcome. GPX1 was negatively correlated with the half inhibition concentration (IC50) of temozolomide (TMZ) (Spearman = -0.44, P = 4.52 ×10^-26).

CONCLUSION

In LGG patients, high GPX1 expression was linked to a shorter OS. The interaction between GPX1 and chemoradiotherapy exhibits a beneficial clinical effect and chemotherapy was recommended for LGG patients, especially for those with high GPX1 expression. Besides, high GPX1 expression can predict TMZ sensitivity in LGG, providing potential evidence for chemotherapy. On the whole, this study presents a wealth of biological as well as clinical significance for the roles of GPX1 in human tumors, particularly in LGG.

Identification of Small Airway Epithelium-Related Hub Genes in Chronic Obstructive Pulmonary Disease

Background

Pulmonary small airway epithelia are the primary site of cellular and histological alterations in chronic obstructive pulmonary disease (COPD), while the potential therapeutic hub genes of pulmonary epithelia are rarely identified to elucidate profound alterations in the progression of the disease.

Methods

Microarray dataset of GSE11906 containing small airway epithelia from 34 healthy non-smokers and 33 COPD patients was applied to screen differentially expressed genes (DEGs). Weighted gene correlation network analysis (WGCNA) was further used to identify the hub genes related to clinical features. Moreover, single-cell RNA sequencing data from GSE173896 and GSE167295 dataset were applied to explore the expression and distribution of the hub genes. The expression levels of hub genes in epithelial cells stimulated by cigarette smoke extract (CSE) were detected by RT-qPCR.

Results

Ninety-eight DEGs correlated with clinical features of COPD were identified via limma and WGCNA. Eight hub genes (including AKR1C3, ALDH3A1, AKR1C1, CYP1A1, GPX2, CBR3, AKR1B1 and GSR) that might exert an antioxidant role in COPD process were identified. Single-cell transcriptomic analysis indicated that the expressions of AKRAC3, ALDH3A1, GPX2, CBR3 and AKR1B1 were significantly increased in the COPD group when compared with the normal group. Moreover, we found that the expression of ALDH3A1 was the most abundantly expressed in ciliated cells. RT-qPCR results indicated that the majority of candidate novel genes were significantly elevated when the epithelial cells were exposed to CSE.

Conclusion

Through integrating limma, WGCNA, and protein-protein interaction (PPI) analysis, a total of eight candidate hub genes of pulmonary airway epithelia were identified in COPD. Moreover, single-cell transcriptomic analysis indicated that ALDH3A1 was enriched in ciliated cells, which may provide a new insight into the pathogenesis and treatment of COPD.

Effects of Antioxidant Gene Overexpression on Stress Resistance and Malignization In Vitro and In Vivo: A Review

Reactive oxygen species (ROS) are normal products of a number of biochemical reactions and are important signaling molecules. However, at the same time, they are toxic to cells and have to be strictly regulated by their antioxidant systems. The etiology and pathogenesis of many diseases are associated with increased ROS levels, and many external stress factors directly or indirectly cause oxidative stress in cells. Within this context, the overexpression of genes encoding the proteins in antioxidant systems seems to have become a viable approach to decrease the oxidative stress caused by pathological conditions and to increase cellular stress resistance. However, such manipulations unavoidably lead to side effects, the most dangerous of which is an increased probability of healthy tissue malignization or increased tumor aggression. The aims of the present review were to collect and systematize the results of studies devoted to the effects resulting from the overexpression of antioxidant system genes on stress resistance and carcinogenesis in vitro and in vivo. In most cases, the overexpression of these genes was shown to increase cell and organism resistances to factors that induce oxidative and genotoxic stress but to also have different effects on cancer initiation and promotion. The last fact greatly limits perspectives of such manipulations in practice. The overexpression of GPX3 and SOD3 encoding secreted proteins seems to be the "safest" among the genes that can increase cell resistance to oxidative stress. High efficiency and safety potential can also be found for SOD2 overexpression in combinations with GPX1 or CAT and for similar combinations that lead to no significant changes in H₂O₂ levels. Accumulation, systematization, and the integral analysis of data on antioxidant gene overexpression effects can help to develop approaches for practical uses in biomedical and agricultural areas. Additionally, a number of factors such as genetic and functional context, cell and tissue type, differences in the function of transcripts of one and the same gene, regulatory interactions, and additional functions should be taken into account.

Plant Glutathione Peroxidases: Non-Heme Peroxidases with Large Functional Flexibility as a Core Component of ROS-Processing Mechanisms and Signalling

Glutathione peroxidases (GPXs) are non-heme peroxidases catalyzing the reduction of H₂O₂ or organic hydroperoxides to water or corresponding alcohols using glutathione (GSH) or thioredoxin (TRX) as a reducing agent. In contrast to animal GPXs, the plant enzymes are non-seleno monomeric proteins that generally utilize TRX more effectively than GSH but can be a putative link between the two main redox systems. Because of the substantial differences compared to non-plant GPXs, use of the GPX-like (GPXL) name was suggested for Arabidopsis enzymes. GPX(L)s not only can protect cells from stress-induced oxidative damages but are crucial components of plant development and growth. Due to fine-tuning the H₂O₂ metabolism and redox homeostasis, they are involved in the whole life cycle even under normal growth conditions. Significantly new mechanisms were discovered related to their transcriptional, post-transcriptional and post-translational modifications by describing gene regulatory networks, interacting microRNA families, or identifying Lys decrotonylation in enzyme activation. Their involvement in epigenetic mechanisms was evidenced. Detailed genetic, evolutionary, and bio-chemical characterization, and comparison of the main functions of GPXs, demonstrated their species-specific roles. The multisided involvement of GPX(L)s in the regulation of the entire plant life ensure that their significance will be more widely recognized and applied in the future.

Voyage of selenium from environment to life: Beneficial or toxic?

Selenium (Se), a naturally occurring metalloid, is an essential micronutrient for life as it is incorporated as selenocysteine in proteins. Although beneficial at low doses, Se is hazardous at high concentrations and poses a serious threat to various ecosystems. Due to this contrasting 'dual' nature, Se has garnered the attention of researchers wishing to unravel its puzzling properties. In this review, we describe the impact of selenium's journey from environment to diverse biological systems, with an emphasis on its chemical advantage. We describe the uneven distribution of Se and how this affects the bioavailability of this element, which, in turn, profoundly affects the habitat of a region. Once taken up, the subsequent incorporation of Se into proteins as selenocysteine and its antioxidant functions are detailed here. The causes of improved protein function due to the incorporation of redox-active Se atom (instead of S) are examined. Subsequently, the reasons for the deleterious effects of Se, which depend on its chemical form (organo-selenium or the inorganic forms) in different organisms are elaborated. Although Se is vital for the function of many antioxidant enzymes, how the pro-oxidant nature of Se can be potentially exploited in different therapies is highlighted. Furthermore, we succinctly explain how the presence of Se in biological systems offsets the toxic effects of heavy metal mercury. Finally, the different avenues of research that are fundamental to expand our understanding of selenium biology are suggested.

Glutathione peroxidase 2 is a metabolic driver of the tumor immune microenvironment and immune checkpoint inhibitor response

BACKGROUND

The existence of immunologically 'cold tumors' frequently found across a wide spectrum of tumor types represents a significant challenge for cancer immunotherapy. Cold tumors have poor baseline pan-leukocyte infiltration, including a low prevalence of cytotoxic lymphocytes, and not surprisingly respond unfavorably to immune checkpoint (IC) inhibitors. We hypothesized that cold tumors harbor a mechanism of immune escape upstream and independent of ICs that may be driven by tumor biology rather than differences in mutational neoantigen burden.

METHODS

Using a bioinformatic approach to analyze TCGA (The Cancer Genome Atlas) RNA sequencing data we identified genes upregulated in cold versus hot tumors across four different smoking-related cancers, including squamous carcinomas from the oral cavity (OCSCC) and lung (LUSC), and adenocarcinomas of the bladder (BLCA) and lung (LUAD). Biological significance of the gene most robustly associated with a cold tumor phenotype across all four tumor types, glutathione peroxidase 2 (GPX2), was further evaluated using a combination of in silico analyses and functional genomic experiments performed both in vitro and in in vivo with preclinical models of oral cancer.

RESULTS

Elevated RNA expression of five metabolic enzymes including GPX2, aldo-keto reductase family 1 members AKR1C1, AKR1C3, and cytochrome monoxygenases (CP4F11 and CYP4F3) co-occurred in cold tumors across all four smoking-related cancers. These genes have all been linked to negative regulation of arachidonic acid metabolism-a well-established inflammatory pathway-and are also known downstream targets of the redox sensitive Nrf2 transcription factor pathway. In OCSCC, LUSC, and LUAD, GPX2 expression was highly correlated with Nrf2 activation signatures, also elevated in cold tumors. In BLCA, however, GPX2 correlated more strongly than Nrf2 signatures with decreased infiltration of multiple leukocyte subtypes. GPX2 inversely correlated with expression of multiple pro- inflammatory cytokines/chemokines and NF-kB activation in cell lines and knockdown of GPX2 led to increased secretion of prostaglandin E2 (PGE2) and interleukin-6. Conversely, GPX2 overexpression led to reduced PGE2 production in a murine OCSCC model (MOC1). GPX2 overexpressing MOC1 tumors had a more suppressive tumor immune microenvironment and responded less favorably to anti-cytotoxic T-lymphocytes-associated protein 4 IC therapy in mice.

CONCLUSION

GPX2 overexpression represents a novel potentially targetable effector of immune escape in cold tumors.

The role of glutathione peroxidase-1 in health and disease

Glutathione peroxidase 1 (GPx1) is an important cellular antioxidant enzyme that is found in the cytoplasm and mitochondria of mammalian cells. Like most selenoenzymes, it has a single redox-sensitive selenocysteine amino acid that is important for the enzymatic reduction of hydrogen peroxide and soluble lipid hydroperoxides. Glutathione provides the source of reducing equivalents for its function. As an antioxidant enzyme, GPx1 modulates the balance between necessary and harmful levels of reactive oxygen species. In this review, we discuss how selenium availability and modifiers of selenocysteine incorporation alter GPx1 expression to promote disease states. We review the role of GPx1 in cardiovascular and metabolic health, provide examples of how GPx1 modulates stroke and provides neuroprotection, and consider how GPx1 may contribute to cancer risk. Overall, GPx1 is protective against the development and progression of many chronic diseases; however, there are some situations in which increased expression of GPx1 may promote cellular dysfunction and disease owing to its removal of essential reactive oxygen species.

Recent Advances in Electrochemical Sensing of Hydrogen Peroxide (H2O2) Released from Cancer Cells

Cancer is by far the most common cause of death worldwide. There are more than 200 types of cancer known hitherto depending upon the origin and type. Early diagnosis of cancer provides better disease prognosis and the best chance for a cure. This fact prompts world-leading scientists and clinicians to develop techniques for the early detection of cancer. Thus, less morbidity and lower mortality rates are envisioned. The latest advancements in the diagnosis of cancer utilizing nanotechnology have manifested encouraging results. Cancerous cells are well known for their substantial amounts of hydrogen peroxide (H₂O₂). The common methods for the detection of H₂O₂ include colorimetry, titration, chromatography, spectrophotometry, fluorimetry, and chemiluminescence. These methods commonly lack selectivity, sensitivity, and reproducibility and have prolonged analytical time. New biosensors are reported to circumvent these obstacles. The production of detectable amounts of H₂O₂ by cancerous cells has promoted the use of bio- and electrochemical sensors because of their high sensitivity, selectivity, robustness, and miniaturized point-of-care cancer diagnostics. Thus, this review will emphasize the principles, analytical parameters, advantages, and disadvantages of the latest electrochemical biosensors in the detection of H₂O₂. It will provide a summary of the latest technological advancements of biosensors based on potentiometric, impedimetric, amperometric, and voltammetric H₂O₂ detection. Moreover, it will critically describe the classification of biosensors based on the material, nature, conjugation, and carbon-nanocomposite electrodes for rapid and effective detection of H₂O₂, which can be useful in the early detection of cancerous cells.

The Selenoprotein Glutathione Peroxidase 4: From Molecular Mechanisms to Novel Therapeutic Opportunities

The selenoprotein glutathione peroxidase 4 (GPX4) is one of the main antioxidant mediators in the human body. Its central function involves the reduction of complex hydroperoxides into their respective alcohols often using reduced Glutathione (GSH) as a reducing agent. GPX4 has become a hotspot therapeutic target in biomedical research following its characterization as a chief regulator of ferroptosis, and its subsequent recognition as a specific pharmacological target for the treatment of an extensive variety of human diseases including cancers and neurodegenerative disorders. Several recent studies have provided insights into how GPX4 is distinguished from the rest of the glutathione peroxidase family, the unique biochemical properties of GPX4, how GPX4 is related to lipid peroxidation and ferroptosis, and how the enzyme may be modulated as a potential therapeutic target. This current report aims to review the literature underlying all these insights and present an up-to-date perspective on the current understanding of GPX4 as a potential therapeutic target.

A Bioinformatic Analysis: The Overexpression and Prognostic Potential of GPX7 in Lower-Grade Glioma

Purpose

Glutathione peroxidase-7 (GPX7) is a newly discovered non-selenium-containing protein with glutathione peroxidase activity, which mainly protects the organism from oxidative damage and is very important for basic biology studies. This study aims to reveal the expression pattern of GPX7 and its prognosis potential from a pan-cancer perspective.

Methods

Expression levels of GPX7 in human tumor tissues and normal tissues were evaluated using Human Protein Atlas (HPA), the Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx) and UALCAN databases. The prognostic potential of GPX7 for 33 TCGA tumors was evaluated by Kaplan–Meier analysis and Cox regression analysis. Subsequently, the Chinese Glioma Genome Atlas (CGGA) dataset was used to further verify the expression of GPX7 and its prognostic potential in glioma. We explored the correlation between GPX7 and immune infiltration, tumor mutational burden (TMB) and microsatellite instability (MSI). Furthermore, a nomogram lower-grade glioma (LGG) was constructed to verify the prognostic outcome of patients. Finally, the relationship between GPX7 and treatment regimens for LGG was also explored.

Results

GPX7 was overexpressed in multiple tumors. Elevated expression of GPX7 was associated with poor prognosis of LGG patients (OS hazard ratio (HR) = 1.044, P < 0.0001; DFS HR = 1.035, P < 0.0001; PFS HR = 1.045, P < 0.0001). GPX7 was proved to be an independent prognostic factor of LGG through univariate and multivariate Cox analysis. The nomogram confirmed a better predictability (Concordance index (C-index): 0.845; 95% CI, 0.825–0.865). GPX7 was positively correlated with TMB in LGG. GPX7 expression was negatively correlated with half-maximal inhibitory concentration (IC50) of temozolomide (TMZ) (\documentclass[12pt]{minimal} \usepackage{wasysym} \usepackage[substack]{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage[mathscr]{eucal} \usepackage{mathrsfs} \DeclareFontFamily{T1}{linotext}{} \DeclareFontShape{T1}{linotext}{m}{n} {linotext }{} \DeclareSymbolFont{linotext}{T1}{linotext}{m}{n} \DeclareSymbolFontAlphabet{\mathLINOTEXT}{linotext} \begin{document} $$\mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\frown$}}\over \rho } $$ \end{document}_spearman= −0.59, P =1.3e-48).

Conclusion

GPX7 was upregulated in multiple tumors, and it was a potential prognostic biomarker in LGG. High-expressed GPX7 can predict the sensitivity of TMZ in LGG patients.

Calcium intake may explain the reduction of colorectal cancer odds by dietary selenium - a case-control study in Poland

Background

Colorectal cancer (CRC) has been placed among top three cancer sites in high income countries. Although there are several inconsistencies across studies it is widely accepted that diet contributes to approximately 70% of CRC. Several dietary factors have been investigated; however, the knowledge about the role of trace elements and their interplay with other dietary factors in CRC odds is limited. The aim of the study was to estimate the odds ratio of colorectal cancer associated with the content of selenium in diet, and to check whether dietary calcium is a modifier of selenium effect in the population characterized by low selenium intake.

Methods

Face-to-face interviews were used to gather data on dietary habits (by 148-item semi-quantitative food frequency questionnaire) and covariates among 683 histologically confirmed incident colorectal cancer cases and 759 hospital-based controls in a case-control study. Data was collected in a period between 2000 and 2012. Setting: Lesser Poland, Central Europe. Logistic regression models were used to assess the role of dietary selenium intake and calcium-selenium interaction in colorectal cancer odds.

Results

After the adjustment for several covariates dietary selenium was associated with the decrease of colorectal cancer odds by 8% (OR = 0.92, 95%CI: 0.84–0.99 for every 10μg Se/day increase). In individuals with lower (< 1000 mg/day) calcium content the odds of colorectal cancer was decreased by 13%(for every 10μg Se/day) and by 44% and 66% depending on the categories of selenium intake (60 to < 80 μg/day and ≥ 80 μg/day, respectively). The effect of dietary selenium was modified by dietary calcium (p for interaction < .005).

Conclusions

The study has shown a beneficial effect of dietary selenium for colorectal cancer and a modification effect of dietary calcium in a population characterized by lower levels of selenium intake. The results provide the basis for well-planned controlled trials to confirm the findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40795-022-00515-w.

The emerging role of selenium metabolic pathways in cancer: New therapeutic targets for cancer

Selenium (Se) is incorporated into the body via the selenocysteine (Sec) biosynthesis pathway, which is critical in the synthesis of selenoproteins, such as glutathione peroxidases and thioredoxin reductases. Selenoproteins, which play a key role in several biological processes, including ferroptosis, drug resistance, endoplasmic reticulum stress, and epigenetic processes, are guided by Se uptake. In this review, we critically analyze the molecular mechanisms of Se metabolism and its potential as a therapeutic target for cancer. Sec insertion sequence binding protein 2 (SECISBP2), which is a positive regulator for the expression of selenoproteins, would be a novel prognostic predictor and an alternate target for cancer. We highlight strategies that attempt to develop a novel Se metabolism-based approach to uncover a new metabolic drug target for cancer therapy. Moreover, we expect extensive clinical use of SECISBP2 as a specific biomarker in cancer therapy in the near future. Of note, scientists face additional challenges in conducting successful research, including investigations on anticancer peptides to target SECISBP2 intracellular protein.

Redox Control of Integrin-Mediated Hepatic Inflammation in Systemic Autoimmunity

Significance: Systemic autoimmunity affects 3%-5% of the population worldwide. Systemic lupus erythematosus (SLE) is a prototypical form of such condition, which affects 20-150 of 100,000 people globally. Liver dysfunction, defined by increased immune cell infiltration into the hepatic parenchyma, is an understudied manifestation that affects up to 20% of SLE patients. Autoimmunity in SLE involves proinflammatory lineage specification in the immune system that occurs with oxidative stress and profound changes in cellular metabolism. As the primary metabolic organ of the body, the liver is uniquely capable to encounter oxidative stress through first-pass derivatization and filtering of waste products. Recent Advances: The traffic of immune cells from their development through recirculation in the liver is guided by cell adhesion molecules (CAMs) and integrins, cell surface proteins that tightly anchor cells together. The surface expression of CAMs and integrins is regulated via endocytic traffic that is sensitive to oxidative stress. Reactive oxygen species (ROS) that elicit oxidative stress in the liver may originate from the mitochondria, the cytosol, or the cell membrane. Critical Issues: While hepatic ROS production is a source of vulnerability, it also modulates the development and function of the immune system. In turn, the liver employs antioxidant defense mechanisms to protect itself from damage that can be harnessed to serve as therapeutic mechanisms against autoimmunity, inflammation, and development of hepatocellular carcinoma. Future Directions: This review is aimed at delineating redox control of integrin signaling in the liver and checkpoints of regulatory impact that can be targeted for treatment of inflammation in systemic autoimmunity. Antioxid. Redox Signal. 36, 367-388.

Redox-Related Proteins in Melanoma Progression

Melanoma is the most aggressive type of skin cancer. Despite the available therapies, the minimum residual disease is still refractory. Reactive oxygen and nitrogen species (ROS and RNS) play a dual role in melanoma, where redox imbalance is involved from initiation to metastasis and resistance. Redox proteins modulate the disease by controlling ROS/RNS levels in immune response, proliferation, invasion, and relapse. Chemotherapeutics such as BRAF and MEK inhibitors promote oxidative stress, but high ROS/RNS amounts with a robust antioxidant system allow cells to be adaptive and cooperate to non-toxic levels. These proteins could act as biomarkers and possible targets. By understanding the complex mechanisms involved in adaptation and searching for new targets to make cells more susceptible to treatment, the disease might be overcome. Therefore, exploring the role of redox-sensitive proteins and the modulation of redox homeostasis may provide clues to new therapies. This study analyzes information obtained from a public cohort of melanoma patients about the expression of redox-generating and detoxifying proteins in melanoma during the disease stages, genetic alterations, and overall patient survival status. According to our analysis, 66% of the isoforms presented differential expression on melanoma progression: NOS2, SOD1, NOX4, PRX3, PXDN and GPX1 are increased during melanoma progression, while CAT, GPX3, TXNIP, and PRX2 are decreased. Besides, the stage of the disease could influence the result as well. The levels of PRX1, PRX5 and PRX6 can be increased or decreased depending on the stage. We showed that all analyzed isoforms presented some genetic alteration on the gene, most of them (78%) for increased mRNA expression. Interestingly, 34% of all melanoma patients showed genetic alterations on TRX1, most for decreased mRNA expression. Additionally, 15% of the isoforms showed a significant reduction in overall patient survival status for an altered group (PRX3, PRX5, TR2, and GR) and the unaltered group (NOX4). Although no such specific antioxidant therapy is approved for melanoma yet, inhibitors or mimetics of these redox-sensitive proteins have achieved very promising results. We foresee that forthcoming investigations on the modulation of these proteins will bring significant advances for cancer therapy.

Redox signaling by glutathione peroxidase 2 links vascular modulation to metabolic plasticity of breast cancer

Redox regulation of breast cancer underlies malignant progression. Loss of the antioxidant glutathione peroxidase 2 in breast cancer cells increases reactive oxygen species, thereby activating hypoxia inducible factor-α (HIF1α) signaling. This in turn causes vascular malfunction, resulting in hypoxia and metabolic heterogeneity. HIF1α suppresses oxidative phosphorylation and stimulates glycolysis (the Warburg effect) in most of the tumor, except for one cancer subpopulation, which was capable of using both metabolic modalities. Hence, adopting a hybrid metabolic state may allow tumor cells to survive under aerobic or hypoxic conditions, a vulnerability that may be exploited for therapeutic targeting by either metabolic or redox-based strategies.

In search of redox mechanisms in breast cancer, we uncovered a striking role for glutathione peroxidase 2 (GPx2) in oncogenic signaling and patient survival. GPx2 loss stimulates malignant progression due to reactive oxygen species/hypoxia inducible factor-α (HIF1α)/VEGFA (vascular endothelial growth factor A) signaling, causing poor perfusion and hypoxia, which were reversed by GPx2 reexpression or HIF1α inhibition. Ingenuity Pathway Analysis revealed a link between GPx2 loss, tumor angiogenesis, metabolic modulation, and HIF1α signaling. Single-cell RNA analysis and bioenergetic profiling revealed that GPx2 loss stimulated the Warburg effect in most tumor cell subpopulations, except for one cluster, which was capable of oxidative phosphorylation and glycolysis, as confirmed by coexpression of phosphorylated-AMPK and GLUT1. These findings underscore a unique role for redox signaling by GPx2 dysregulation in breast cancer, underlying tumor heterogeneity, leading to metabolic plasticity and malignant progression.

Multifunctional Flavonoid-Silica Nanohydrogel Enables Simultaneous Inhibition of Tumor Recurrence and Bacterial Infection in Post-Surgical Treatment

A strategy to synthesize water-soluble and fluorescent flavonoid-silica nanocomposites (FSiNCs) simultaneously featuring anti-tumor and anti-bacterial abilities is developed. Furthermore, it is demonstrated that the therapeutic effects of FSiNCs are associated with the selective accumulation of reactive oxide species in both tumor and bacteria cells. Following that, the resultant FSiNCs are incorporated with thrombin and fibrinogen, being sprayed onto the tumor surgical wound site to in situ form fibrin gel (FSiNCs@Fibrin). Remarkably, such FSiNCs@Fibrin results in an ≈18-fold reduction in intratumoral bacteria numbers and ≈12-fold decrease in tumor regrowth compared to equivalent free flavonoid-loaded gel.

The role of redox homeostasis biomarkers in clear cell renal cell carcinoma development and progression

The clear cell renal cell carcinoma (ccRCC) is the most frequent and the most aggresive subtype of renal cell carcinoma usually detected at an already advanced stage. It might even be observed as a metabolic disease since complex molecular changes and disturbed redox homeostasis are its hallmark. As certain changes are characteristic for tumorigenesis, while some other for metastatic disease, the identification of metabolic modifications could also point out the stage of tumor progression. Hypoxia inducible factor, as a factor regulating transcription of genes encoding glycolytic enzymes, as well as controlling lipid accumulation, has a particular place in ccRCC development. Additionaly, disturbed redox homeostasis induces the Keap1/Nrf2 pathway which further modulates the synthesis of phase-II detoxifying metabolism enzymes. The upregulation of glutathione transferases, Pi class especially, inhibits kinase-dependent apoptosis that is essential in tumor progression. Furthermore, hydrogen peroxide (H2O2) acts as a signaling molecule conveying redox signals, while superoxide dismutase, as well as glutathione peroxidase are enzymes involved in its production and degradation. Hence, the activity of these enzymes impacts hydrogen peroxide levels and consequentially the ability of ccRCC cells to evade negative effect of reactive oxygen species.

Emerging roles of mesenchymal stem cell-derived exosomes in gastrointestinal cancers

Gastrointestinal tumours are the most common solid tumours, with a poor prognosis and remain a major challenge in cancer treatment. Mesenchymal stem cells (MSC) are multipotent stromal cells with the potential to differentiate into multiple cell types. Several studies have shown that MSC-derived exosomes have become essential regulators of intercellular communication in a variety of physiological and pathological processes. Notably, MSC-derived exosomes support or inhibit tumour progression in different cancers through the delivery of proteins, RNA, DNA, and bioactive lipids. Herein, we summarise current advances in MSC-derived exosomes in cancer research, with particular reference to their role in gastrointestinal tumour development. MSC-derived exosomes are expected to be a novel potential strategy for the treatment of gastrointestinal cancers.

Roles of ferroptosis in urologic malignancies

Ferroptosis, an iron-dependent form of non-apoptotic cell death, is believed to strongly contribute to the pathogenesis of multiple cancers. Recently, the positive association between ferroptosis and urologic malignancies has drawn considerable attention, while a comprehensive review focused on this issue is absent. Based on this review, ferroptosis has been implicated in the development and therapeutic responses of prostate cancer, kidney cancer, and bladder cancer. Mechanistically, a large number of biomolecules and tumor-associated signaling pathways, including DECR1, PANX2, HSPB1, ACOT8, SUV39H1, NCOA4, PI3K-AKT-mTOR signaling, VHL/HIF-2α pathway, and Hippo/TAZ signaling pathway, have been reported to regulate ferroptosis in urologic cancers. Ferroptosis inducers, such as erastin, ART, CPNPs, and quinazolinyl-arylurea derivatives, exert potential therapeutic effects per se and/or enhance the anticancer response of other anticancer drugs in urologic oncology. A better understanding of ferroptosis may provide a promising way to treat therapy-resistant urologic cancers.

Assessment of Glutathione Peroxidase-1 (GPX1) Gene Expression as a Specific Diagnostic and Prognostic Biomarker in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a malignant tumor of the mesothelial lining of the thorax. It has been related to frequent exposure to asbestos. Diagnosis of malignant pleural mesothelioma is considered a criticizing problem for clinicians. Early diagnosis and sufficient surgical excision of MPM are considered the cornerstone success factors for the management of early MPM. Glutathione peroxidase-1 (GPX1) is an intracellular protein found to be extensively distributed in all cells, and it belongs to the GPX group. In the current study, we included ninety-eight patients with MPM that underwent surgery at the Zagazig University Hospital in Egypt. We assessed GPX1 gene expression level as it was thought to be related to pathogenicity of cancer in a variety of malignant tumors. We observed a significant elevation in GPX1-mRNA levels in MPM relative to the nearby normal pleural tissues. It was found to be of important diagnostic specificity in the differentiation of MPM from normal tissues. Moreover, we studied the survival of patients in correlation to the GPX1 expression levels and we reported that median overall survival was about 16 months in patients with high GPX1 expression levels, while it was found to be about 40 months in low GPX1 levels.

NADPH debt drives redox bankruptcy: SLC7A11/xCT-mediated cystine uptake as a double-edged sword in cellular redox regulation

Cystine/glutamate antiporter solute carrier family 7 member 11 (SLC7A11; also known as xCT) plays a key role in antioxidant defense by mediating cystine uptake, promoting glutathione synthesis, and maintaining cell survival under oxidative stress conditions. Recent studies showed that, to prevent toxic buildup of highly insoluble cystine inside cells, cancer cells with high expression of SLC7A11 (SLC7A11^high) are forced to quickly reduce cystine to more soluble cysteine, which requires substantial NADPH supply from the glucose-pentose phosphate pathway (PPP) route, thereby inducing glucose- and PPP-dependency in SLC7A11^high cancer cells. Limiting glucose supply to SLC7A11^high cancer cells results in significant NADPH “debt”, redox “bankruptcy”, and subsequent cell death. This review summarizes our current understanding of NADPH-generating and -consuming pathways, discusses the opposing role of SLC7A11 in protecting cells from oxidative stress–induced cell death such as ferroptosis but promoting glucose starvation–induced cell death, and proposes the concept that SLC7A11-mediated cystine uptake acts as a double-edged sword in cellular redox regulation. A detailed understanding of SLC7A11 in redox biology may identify metabolic vulnerabilities in SLC7A11^high cancer for therapeutic targeting.

Redox Pioneer: Professor Regina Brigelius-Flohé

Dr. Regina Brigelius-Flohé (PhD 1978) is recognized here as redox pioneer because she has published an article on redox biology, as first author, that has been cited >1000 times, plus four articles cited >500 times, and a total of 30 articles cited >100 times. She obtained her doctorate in biochemistry at the Institute of Biochemistry of the University of Münster, Germany. She held positions in both, academia (Münster, Munich, Düsseldorf, Hannover, and Potsdam, Germany) and industry (Aachen, Germany). Dr. Brigelius-Flohé is the pioneer who, as head of the department of biochemistry of micronutrients of the German Institute of Human Nutrition (DIfE; Potsdam-Rehbrücke, Germany), worked out the metabolism of tocopherols and tocotrienols ("Key Finding 1"). She was the first to sequence glutathione peroxidase 4 (GPx4) ("Key Finding 2"), and unraveled the role of selenium, in particular of GPxs, in inflammation and carcinogenesis ("Key Finding 3"). Her contributions, thus, focused on serious biomedical problems such as nutrition, inflammation, and carcinogenesis. She has been a member of the scientific advisory board of the German Society of Biochemistry and Molecular Biology for 6 years and was president of SFRR-Europe in 2005-2006. She edited several books and serves on the editorial board of journals in the fields of nutrition, free radicals, and redox regulation. Antioxid. Redox Signal. 35, 595-601.

MicroRNAs mediated regulation of glutathione peroxidase 7 expression and its changes during adipogenesis

Glutathione peroxidase 7 (GPx7) acts as an intracellular stress sensor/transmitter and plays an important role in adipocyte differentiation and the prevention of obesity related pathologies. For this reason, finding the regulatory mechanisms that control GPx7 expression is of great importance. As microRNAs (miRNAs) could participate in the regulation of GPx7 expression, we studied the inhibition of GPx7 expression by four selected miRNAs with relation to obesity and adipogenesis. The effect of the transfection of selected miRNAs mimics on GPx7 expression was tested in three cell models (HEK293, SW480, AT-MSC). The interaction of selected miRNAs with the 3'UTR of GPx7 was followed up on using a luciferase gene reporter assay. In addition, the levels of GPx7 and selected miRNAs in adipose tissue mesenchymal stem cells (AT-MSC) and mature adipocytes from four human donors were compared, with the changes in these levels during adipogenesis analyzed. Our results show for the first time that miR-137 and miR-29b bind to the 3'UTR region of GPx7 and inhibit the expression of this enzyme at the mRNA and protein level in all the human cells tested. However, no negative correlation between miR-137 nor miR-29b level and GPx7 was observed during adipogenesis. Despite the confirmed inhibition of GPx7 expression by miR-137 and miR-29b, the action of these two molecules in adipogenesis and mature adipocytes must be accompanied by other regulators.

Reduced Expression Level of GPX2 in T1 Bladder Cancer and its Role in Early-phase Invasion of Bladder Cancer

BACKGROUND/AIM

The role of glutathione peroxidase 2 (GPX2) expression in urothelial carcinoma (UC) is rarely reported. The aim of this study was to assess the expression status of GPX2 in UC of the bladder.

MATERIALS AND METHODS

We collected samples from 112 patients treated with radical cystectomy for immunohistochemical study.

RESULTS

Following immunohistochemical analysis of the specimens, 86 (76.8%) had weak GPX2 expression. In cases with consistent GPX2 expression within the same lesion, the levels of GPX2 showed significant decreases from pTa to pT1 (47.1%) compared to those from pT1 to pT2 (5.9%) (p=0.017). Specimens obtained with transurethral resection before cancer progressed to muscle invasive bladder cancer showed that pT1 had a lower expression for GPX2 than that of pTa (63.3% vs. 93.3%; p=0.009).

CONCLUSION

The decrease in GPX2 expression among those with UC of the bladder may be involved in the early step of cancer invasion.

Polyphyllin Ⅲ-Induced Ferroptosis in MDA-MB-231 Triple-Negative Breast Cancer Cells can Be Protected Against by KLF4-Mediated Upregulation of xCT

Ferroptosis, which is characterized by the accumulation of intracellular iron and subsequent lipid peroxidation, is a newly discovered form of regulated cell death and plays an important role in tumor suppression. Herein, we showed that Polyphyllin III, which is a major saponin extracted from Paris polyphylla rhizomes, exerted its proliferation-inhibitory effect on MDA-MB-231 triple-negative breast cancer cells mainly through ACSL4-mediated lipid peroxidation elevation and ferroptosis induction. ACSL4 deletion partly attenuated Polyphyllin III-induced ferroptosis. Polyphyllin III treatment also induced KLF4-mediated protective upregulation of xCT, which is the negative regulator of ferroptosis. Interestingly, combination with the xCT inhibitor sulfasalazine (SAS) or downregulation of KLF4 sensitized MDA-MB-231 cells to Polyphyllin III. Furthermore, in vivo xenograft models, SAS significantly sensitized MDA-MB-231 breast cancer cells to Polyphyllin III, likely by enhancing intracellular lipid peroxidation and ferroptosis. The results of this study collectively demonstrated that Polyphyllin III exerts its anticancer effect by inducing ferroptosis via ACSL4 in MDA-MB-231 breast cancer cells. More importantly, we observed for the first time that KLF4-mediated xCT upregulation serves as negative feedback during ferroptosis progression, which might contribute to drug resistance in cancer treatment.

Apatinib induced ferroptosis by lipid peroxidation in gastric cancer

BACKGROUND

Apatinib, a competitive inhibitor of VEGFR2, has anti-angiogenesis and anticancer activities through different mechanisms, but it still cannot fully explain the drug efficacy of apatinib. Ferroptosis, associated with lethal lipid peroxidation, has emerged to play an important role in cancer biology, however, the exact role of ferroptosis in apatinib-mediating anticancer treatment are still not clear.

METHODS

The effects of (1S, 3R)-RSL3 and apatinib were evaluated in different GC cell lines and in normal human gastric epithelial cells. Further, the effects of apatinib and inhibition of antioxidant defense enzyme glutathione peroxidase (GPX4) on cell viability, cell death, glutathione (GSH) levels, lipid ROS production, cellular malondialdehyde (MDA) levels and protein expression were evaluated in vitro as well as in a mouse tumor xenograft model. The expression level of GPX4 in GC tissues and paracancerous tissues was measured by immunohistochemistry.

RESULTS

(1S, 3R)-RSL3 selectively killed GC cells, but not normal cells. Apatinib induced ferroptosis in GC cells by decreasing cellular GSH levels and increasing lipid peroxidation levels. This effect was blocked by co-incubation with ferrostatin-1, liproxstatin-1, GSH, or vitamin E. Further investigation revealed that apatinib down-regulated GPX4 expression via inhibition of the transcription factors Sterol regulatory element-binding protein-1a (SREBP-1a). Besides, we found that multi-drug resistant GC cells were vulnerable to apatinib-induced GPX4 inhibition.

CONCLUSIONS

In summary, we show that apatinib could induce the lipid peroxidation through GPX4 mediated by SREBP-1a, then negatively regulate the GC cell, even the multi-drug-resistant GC cell, ferroptosis.

The Association of Polymorphisms in Nrf2 and Genes Involved in Redox Homeostasis in the Development and Progression of Clear Cell Renal Cell Carcinoma

Deleterious effects of SNPs found in genes encoding transcriptional factors, as well as antioxidant and detoxification enzymes, are disputable; however, their functional significance seems to modify the risk for clear cell renal cell carcinoma (ccRCC) development and progression. We investigated the effect of specific Nrf2, SOD2, GPX1 gene variants and GSTP1ABCD haplotype on ccRCC risk and prognosis and evaluated the association between GSTP1 and regulatory (JNK1/2) and executor (caspase-3) apoptotic molecule expression in ccRCC tissue samples and the presence of GSTP1 : JNK1/2 protein : protein interactions. Genotyping was performed in 223 ccRCC patients and 336 matched controls by PCR-CTTP and qPCR. Protein expression was analyzed using immunoblot, while the existence of GSTP1 : JNK1 protein : protein interactions was investigated by immunoprecipitation experiments. An increased risk of ccRCC development was found among carriers of variant genotypes of both SOD2 rs4880 and GSTP1 rs1695 polymorphisms. Nrf2 rs6721961 genetic polymorphism in combination with both rs4880 and rs1695 showed higher ccRCC risk as well. Haplotype analysis revealed significant risk of ccRCC development in carriers of the GSTP1C haplotype. Furthermore, GSTP1 variant forms seem to affect the overall survival in ccRCC patients, and the proposed molecular mechanism underlying the GSTP1 prognostic role might be the presence of GSTP1 : JNK1/2 protein : protein interactions.

Vitamin C and Cell Death

Significance: Persistent oxidative stress is a common feature of cancer cells, giving a specific weapon to selectively eliminate them. Ascorbate in pharmacological concentration can contribute to the suspended formation of hydroxyl radical via the Fenton reaction; thus, it can be an important element of the oxidative stress therapy against cancer cells. Recent Advances: The main components of ascorbate-induced cell death are DNA double-strand breaks via the production of hydroxyl radical and ATP depletion due to the activation of poly (ADP-ribose) polymerase 1. Presumably, DNA damage can be the primary contributor to the anticancer activity of pharmacological ascorbate, as opposed to the rupture of bioenergetics. The caspase independency of high-dose ascorbate-induced cell death proposed the possible involvement of several types of cell death, such as ferroptosis, necroptosis, and autophagy. Critical Issues: Ascorbate can target at least two key molecular features of cancer cells as a part of the anticancer therapy: the intrinsic or acquired resistance to cell death and the dysregulated metabolism of cancer cells. It seems probable that different concentrations of ascorbate alter the nature of induced cell death. Autophagy and necroptosis may play a role at intermediate concentrations, but caspase-independent apoptosis may dominate at higher concentrations. However, ascorbate behaves as an effective inhibitor of ferroptosis that may have crucial importance in its possible clinical application. Future Directions: The elucidation of the details and the links between high-dose ascorbate-induced cancer selective cell death mechanisms may give us a tool to form and apply synergistic cancer therapies. Antioxid. Redox Signal. 34, 831-844.

A pan-cancer study of selenoprotein genes as promising targets for cancer therapy

Background

The most important health benefit of selenium (Se) is in the prevention and control of cancer. Glutathione peroxidases (GPXs) and thioredoxin reductases (TXNRDs) are selenoenzymes that are thought to play a role in oxidative stress. The differential expression of genes of the TXNRD and GPX families is closely related to carcinogenesis and the occurrence of cancer. This study comprehensively analyzed the expression profiles of seven genes in the TXNRD and GPX families, in terms of their correlations with patient survival and immune-cell subtypes, tumor microenvironment, and drug sensitivity.

Results

The expression profiles of genes in the TXNRD and GPX families differ between different types of cancer, and also between and within individual cancer cases. The expression levels of the seven analyzed genes are related to the overall survival of patients. The TXNRD1 and TXNRD3 genes are mainly related to poor prognoses, while other genes are related to good or poor prognoses depending on the type of cancer. All of the genes were found to be correlated to varying degrees with immune-cell subtypes, level of mechanistic cell infiltration, and tumor cell stemness. The TXNRD1, GPX1, and GPX2 genes may exert dual effects in tumor mutagenesis and development, while the TXNRD1, GPX1, GPX2, and GPX3 genes were found to be related to drug sensitivity or the formation of drug resistance.

Conclusions

The results will greatly help in identifying the association between genes and tumorigenesis, especially in the immune response, tumor microenvironment, and drug resistance, and very important when attempting to identify new therapeutic targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-00930-1.

Changes in Glutathione Content in Liver Diseases: An Update

Glutathione (GSH), a tripeptide particularly concentrated in the liver, is the most important thiol reducing agent involved in the modulation of redox processes. It has also been demonstrated that GSH cannot be considered only as a mere free radical scavenger but that it takes part in the network governing the choice between survival, necrosis and apoptosis as well as in altering the function of signal transduction and transcription factor molecules. The purpose of the present review is to provide an overview on the molecular biology of the GSH system; therefore, GSH synthesis, metabolism and regulation will be reviewed. The multiple GSH functions will be described, as well as the importance of GSH compartmentalization into distinct subcellular pools and inter-organ transfer. Furthermore, we will highlight the close relationship existing between GSH content and the pathogenesis of liver disease, such as non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease (ALD), chronic cholestatic injury, ischemia/reperfusion damage, hepatitis C virus (HCV), hepatitis B virus (HBV) and hepatocellular carcinoma. Finally, the potential therapeutic benefits of GSH and GSH-related medications, will be described for each liver disorder taken into account.

Glutathione Peroxidase 3 as a Biomarker of Recurrence after Lung Cancer Surgery

We aimed to examine the usefulness of serum glutathione peroxidase 3 (GPx3) as a biomarker of lung cancer recurrence after complete resection. We prospectively collected serial serum samples at the baseline, as well as 3, 6 and 12 months after surgery from complete resection cases in 2013. GPx3 levels were measured by enzyme-linked immunosorbent assay. Statistical tests including t-tests and Cox proportional hazard regression analyses were performed. Totally, 135 patients were enrolled, and 39 (28.9%) showed relapse during the median follow-up period (63.60 months; range, 0.167–81.867). The mean GPx3 change was significantly higher in the recurrence group at 6 months (0.32 ± 0.38 vs. 0.15 ± 0.29, p = 0.016) and 12 months (0.40 ± 0.37 vs. 0.13 ± 0.28, p = 0.001). The high GPx3 change group showed significantly higher 60-months recurrence rates than the low group (48.1% vs. 25.2% at 3 months, p = 0.005; 54.5% vs. 28.9% at 6 months, p = 0.018; 38.3% vs. 18.3% at 12 months, p = 0.035). High GPx3 change at 3 months were independent risk factors of recurrence (hazard ratio (HR) 3.318, 95% confidence interval (CI), 1.582–6.960, p = 0.002) and survival (HR 3.150, 95% CI, 1.301–7.628, p = 0.011). Therefore, serum GPx3 changes after surgery may be useful predictive biomarkers for recurrence in lung cancer. Larger-scale validation studies are warranted to confirm these findings.

Emerging roles for non-selenium containing ER-resident glutathione peroxidases in cell signaling and disease

Maintenance of cellular redox control is pivotal for normal cellular functions and cell fate decisions including cell death. Among the key cellular redox systems in mammals, the glutathione peroxidase (GPX) family of proteins is the largest conferring multifaceted functions and affecting virtually all cellular processes. The endoplasmic reticulum (ER)-resident GPXs, designated as GPX7 and GPX8, are the most recently added members of this family of enzymes. Recent studies have provided exciting insights how both enzymes support critical processes of the ER including oxidative protein folding, maintenance of ER redox control by eliminating H₂O₂, and preventing palmitic acid-induced lipotoxicity. Consequently, numerous pathological conditions, such as neurodegeneration, cancer and metabolic diseases have been linked with altered GPX7 and GPX8 expression. Studies in mice have demonstrated that loss of GPX7 leads to increased differentiation of preadipocytes, increased tumorigenesis and shortened lifespan. By contrast, GPX8 deficiency in mice results in enhanced caspase-4/11 activation and increased endotoxic shock in colitis model. With the increasing recognition that both types of enzymes are dysregulated in various tumor entities in man, we deem a review of the emerging roles played by GPX7 and GPX8 in health and disease development timely and appropriate.