The role of peroxiredoxins in cancer

Peroxiredoxin 2 as a potential prognostic biomarker associated with angiogenesis in cervical squamous cell cancer

Peroxiredoxins (Prxs) are a ubiquitously expressed family of antioxidant enzymes that either facilitate or inhibit tumorigenesis, depending on the cancer type and Prx isoform. Prx2 is a typical Prx that has a dual role in tumorigenesis and tumor progression. However, the expression of Prx2 and its precise role in cervical cancer remains to be elucidated. Therefore, the present study aimed to investigate the expression of Prx2 and its association with the progression and prognosis of cervical squamous cell cancer (CSCC). In the present study, the clinicopathological data of 105 patients diagnosed with CSCC were collected from the medical record system at Jingzhou Central Hospital, Tongji Medical College of Huazhong University of Science and Technology (Jingzhou, China). Prx2 protein was also detected in 105 CSCC tissues and 40 adjacent peri-tumoral tissues by immunohistochemical staining. The relationships between Prx2 expression and clinicopathological features, vascular endothelial growth factor A (VEGF-A) expression and micro-vessel density (MVD) in CSCC were then analyzed. Progression-free survival (PFS) was also assessed using both univariate and multivariate analyses. The results of the present study demonstrated that the expression of Prx2 was upregulated in CSCC tissues compared with the adjacent peri-tumoral tissues (P<0.001). In addition, higher Prx2 expression was associated with greater depth of stromal invasion (P=0.023) and positive lymph vascular space invasion (P=0.044), while the Prx2 expression level was not associated with age, tumor size, histological grade, lymph node (LN) metastasis or International Federation of Gynecology and Obstetrics (FIGO) stage (all P>0.05). Furthermore, increased Prx2 expression was associated with high MVD (P=0.016), while expression of VEGF-A was not associated with Prx2 expression (P>0.05). Kaplan-Meier analysis showed that patients with high Prx2 expression (log-rank test, P=0.039), high MVD (log-rank test, P=0.015), a higher FIGO stage (log-rank test, P=0.021) and LN metastasis (log-rank test, P=0.022) had a shorter PFS time than patients with low Prx2 expression, low MVD, a lower FIGO stage and without LN metastasis, respectively. Cox proportional hazard regression analysis revealed that expression of Prx2 [hazard ratio (HR), 2.551; 95% confidence interval (CI), 1.056-6.162; P=0.037], MVD (HR, 2.436; CI, 1.034-5.735; P=0.042) and FIGO stage (HR, 1.543; CI, 1.027-2.319; P=0.037) were independent factors for PFS time. In conclusion, the results of the present study suggested that Prx2 could act as a potential biomarker for predicting CSCC progression and prognosis and could be a novel target for antiangiogenic therapy of CSCC.

SOX11/PRDX2 axis modulates redox homeostasis and chemoresistance in aggressive mantle cell lymphoma

Mantle cell lymphoma (MCL) is an incurable B-cell neoplasm characterized by an aggressive behavior, short responses to conventional therapies and SOX11 overexpression, which is associated with aggressive disease features and inferior clinical outcome of patients. Oxidative stress is known to induce tumorigenesis and tumor progression, whereas high expression levels of antioxidant genes have been associated with chemoresistance in different cancers. However, the role of oxidative stress in MCL pathogenesis and the involvement of SOX11 regulating redox homeostasis in MCL cells are largely unknown. Here, by integrating gene set enrichment analysis of two independent series of MCL, we observed that SOX11+ MCL had higher reactive oxygen species (ROS) levels compared to SOX11- MCL primary tumors and increased expression of Peredoxine2 (PRDX2), which upregulation significantly correlated with SOX11 overexpression, higher ROS production and worse overall survival of patients. SOX11 knockout (SOX11KO) significantly reduced PRDX2 expression, and SOX11KO and PRDX2 knockdown (PRDX2KD) had increased ROS levels and ROS-mediated tumor cell death upon treatment with drugs, compared to control MCL cell lines. Our results suggest an aberrant redox homeostasis associated with chemoresistance in aggressive MCL through SOX11-mediated PRDX2 upregulation, highlighting PRDX2 as promising target for new therapeutic strategies to overcome chemoresistance in aggressive MCLs.

MiR-92a-2-5p suppresses esophageal squamous cell carcinoma cell proliferation and invasion by targeting PRDX2

MicroRNAs (miRNAs) can function as negative regulators of gene expression by binding to the 3'-untranslated region (3'-UTR) of target genes. The aberrant expression of miRNAs in neoplasm is extensively associated with tumorigenesis and cancer progression, including esophageal squamous cell carcinoma (ESCC). Our previous investigation has identified the oncogenic roles of Peroxiredoxin2 (PRDX2) in ESCC progression; however, its upstream regulatory mechanism remains to be elucidated. By merging the prediction results from miRWalk2.0 and miRNA differential expression analysis results based on The Cancer Genome Atlas Esophageal Carcinoma (TCGA-ESCA) database, eight miRNA candidates were predicted to be the potential regulatory miRNAs of PRDX2, followed by further identification of miR-92a-2-5p as the putative miRNA of PRDX2. Subsequent functional studies demonstrated that miR-92a-2-5p can suppress ESCC cell proliferation and migration, as well as tumor growth in subcutaneous tumor xenograft models, which might be mediated by the suppression of AKT/mTOR and Wnt3a/β-catenin signaling pathways upon miR-92a-2-5p mimic transfection condition. These data revealed the tumor suppressive functions of miR-92a-2-5p in ESCC by targeting PRDX2.

The Tumor Suppressor SOCS1 Diminishes Tolerance to Oxidative Stress in Hepatocellular Carcinoma

SOCS1 is a tumor suppressor in hepatocellular carcinoma (HCC). Recently, we showed that a loss of SOCS1 in hepatocytes promotes NRF2 activation. Here, we investigated how SOCS1 expression in HCC cells affected oxidative stress response and modulated the cellular proteome. Murine Hepa1-6 cells expressing SOCS1 (Hepa-SOCS1) or control vector (Hepa-Vector) were treated with cisplatin or tert-butyl hydroperoxide (t-BHP). The induction of NRF2 and its target genes, oxidative stress, lipid peroxidation, cell survival and cellular proteome profiles were evaluated. NRF2 induction was significantly reduced in Hepa-SOCS1 cells. The gene and protein expression of NRF2 targets were differentially induced in Hepa-Vector cells but markedly suppressed in Hepa-SOCS1 cells. Hepa-SOCS1 cells displayed an increased induction of reactive oxygen species but reduced lipid peroxidation. Nonetheless, Hepa-SOCS1 cells treated with cisplatin or t-BHP showed reduced survival. GCLC, poorly induced in Hepa-SOCS1 cells, showed a strong positive correlation with NFE2L2 and an inverse correlation with SOCS1 in the TCGA-LIHC transcriptomic data. A proteomic analysis of Hepa-Vector and Hepa-SOCS1 cells revealed that SOCS1 differentially modulated many proteins involved in diverse molecular pathways, including mitochondrial ROS generation and ROS detoxification, through peroxiredoxin and thioredoxin systems. Our findings indicate that maintaining sensitivity to oxidative stress is an important tumor suppression mechanism of SOCS1 in HCC.

Dual role of PRDX1 in redox-regulation and tumorigenesis: Past and future

Tumour cells often display an active metabolic profile, leading to the intracellular accumulation of reactive oxygen species. As a member of the peroxidase family, peroxiredoxin 1 (PRDX1) functions generally in protecting against cell damage caused by H2O2. Additionally, PRDX1 plays a role as a molecular chaperone in various malignant tumours, exhibiting either tumour-promoting or tumour-suppressing effects. Currently, PRDX1-targeting drugs have demonstrated in vitro anticancer effects, indicating the potential of PRDX1 as a molecular target. Here we discussed the diverse functions of PRDX1 in tumour biology and provided a comprehensive analysis of the therapeutic potential of targeting PRDX1 signalling across various types of cancer.

Inflammation-Associated Cytotoxic Agents in Tumorigenesis

Chronic inflammatory processes are related to all stages of tumorigenesis. As inflammation is closely associated with the activation and release of different cytotoxic agents, the interplay between cytotoxic agents and antagonizing principles is highlighted in this review to address the question of how tumor cells overcome the enhanced values of cytotoxic agents in tumors. In tumor cells, the enhanced formation of mitochondrial-derived reactive species and elevated values of iron ions and free heme are antagonized by an overexpression of enzymes and proteins, contributing to the antioxidative defense and maintenance of redox homeostasis. Through these mechanisms, tumor cells can even survive additional stress caused by radio- and chemotherapy. Through the secretion of active agents from tumor cells, immune cells are suppressed in the tumor microenvironment and an enhanced formation of extracellular matrix components is induced. Different oxidant- and protease-based cytotoxic agents are involved in tumor-mediated immunosuppression, tumor growth, tumor cell invasion, and metastasis. Considering the special metabolic conditions in tumors, the main focus here was directed on the disturbed balance between the cytotoxic agents and protective mechanisms in late-stage tumors. This knowledge is mandatory for the implementation of novel anti-cancerous therapeutic approaches.

The categorizations of vasculogenic mimicry in clear cell renal cell carcinoma unveil inherent connections with clinical and immune features

Background: Clear cell renal cell carcinoma (ccRCC) stands as the prevailing variant kidney cancer in humans. Unfortunately, patients with disseminated RCC at diagnosis often have a diminished prognosis. Rapid tumor growth necessitates efficient blood supply for oxygen and nutrients, involving the circulation of blood from vessels to tumor tissues, facilitating tumor cell entry into the extracellular matrix. Vasculogenic mimicry (VM) significantly contributes to tumor growth and metastasis. Within this investigation, we identified vasculogenic mimicry-related genes (VMRGs) by analyzing data from 607 cases of kidney renal clear cell carcinoma (KIRC) in The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) database (https://www.ncbi.nlm.nih.gov/geo/). These findings offer insights into ccRCC progression and metastasis. Method: We identified VMRGs-related subtypes using consistent clustering methods. The signature of the VMRGs was created using univariate Cox regression and LASSO Cox regression analyses. To evaluate differences in immune cell infiltration, we employed ssGSEA. Afterwards, we created an innovative risk assessment model, known as the VM index, along with a nomogram to forecast the prognosis of ccRCC. Additionally, we verified the expression of an important gene related to VM, peroxiredoxin 2 (PRDX2), in tissue samples. Furthermore, we assessed the sensitivity to drugs in various groups by utilizing the pRRophetic R package. Results: Significant predictors of survival rates in both high- and low-risk groups of KIRC patients were identified as VMRGs. The independent prognostic factors for RCC were confirmed by both univariate and multivariate Cox regression analyses, validating VMRG risk signatures. Differences were observed in drug sensitivity, immune checkpoint expression, and responses to immune therapy between patients classified into high- and low-VMRG-risk groups. Our nomograms consistently demonstrated precise predictive capabilities. Finally, we experimentally verified PRDX2 expression levels and their impact on prognosis. Conclusion: The signature predicts patient prognosis and therapy response, laying the groundwork for future clinical strategies in treating ccRCC patients.

Silencing of peroxiredoxin III inhibits formaldehyde-induced oxidative damage of bone marrow cells in BALB/c mice

BACKGROUND

Formaldehyde (FA) is associated with the occurrence of leukemia, and oxidative stress is considered to be a major reason. As an endogenous biomarker of oxidative stress, few studies focus on the relationship between peroxiredoxin III (PrxIII) and FA toxicity. Our previous research observed high expression of PrxIII occurred in the process of apoptosis of bone marrow cells (BMCs) induced by FA, however the exact mechanism is unclear. Therefore, this paper aimed to explore the possible association between FA toxicity and PrxIII gene.

METHODS

We first, used a Cell Counting Kit-8 (CCK-8) to detect the viability of BMCs after they were exposed to different doses of FA (50, 100, 200 μmol/L) for different exposure time (12, 24, 48 h), then chose 24 h as an exposure time to detect the expression of PrxIII for exposing different doses of FA by Quantitative reverse transcription-PCR (qRT-PCR) and Western blot analysis. Based on our preliminary experimental results, we chose 100 μmol/L FA as an exposure dose to expose for 24 h, and used a small interfering RNA (siRNA) to silenced PrxIII to examine the cell viability by CCK-8, reactive oxygen species (ROS) level by DCFH-DA, apoptosis by Annexin V/PI double staining and cell cycle by flow cytometry (FCM) so as to explore the possible regulatory effect of PrxIII silencing on FA-induced bone marrow toxicity.

RESULTS

High expression of PrxIII occurred in the process of FA-induced oxidative stress. Silencing of PrxIII prevented FA from inducing oxidative stress, thus increasing cell viability, decreasing ROS level, rescuing G0 -G1 and G2 -M arrest, and reducing cell apoptosis.

CONCLUSION

PrxIII silencing might be a potential target for alleviating FA-induced oxidative damage.

Two-Dimensional-PAGE Coupled with nLC-MS/MS-Based Identification of Differentially Expressed Proteins and Tumorigenic Pathways in MCF7 Breast Cancer Cells Transfected for JTB Protein Silencing

The identification of new cancer-associated genes/proteins, the characterization of their expression variation, the interactomics-based assessment of differentially expressed genes/proteins (DEGs/DEPs), and understanding the tumorigenic pathways and biological processes involved in BC genesis and progression are necessary and possible by the rapid and recent advances in bioinformatics and molecular profiling strategies. Taking into account the opinion of other authors, as well as based on our own team's in vitro studies, we suggest that the human jumping translocation breakpoint (hJTB) protein might be considered as a tumor biomarker for BC and should be studied as a target for BC therapy. In this study, we identify DEPs, carcinogenic pathways, and biological processes associated with JTB silencing, using 2D-PAGE coupled with nano-liquid chromatography tandem mass spectrometry (nLC-MS/MS) proteomics applied to a MCF7 breast cancer cell line, for complementing and completing our previous results based on SDS-PAGE, as well as in-solution proteomics of MCF7 cells transfected for JTB downregulation. The functions of significant DEPs are analyzed using GSEA and KEGG analyses. Almost all DEPs exert pro-tumorigenic effects in the JTBlow condition, sustaining the tumor suppressive function of JTB. Thus, the identified DEPs are involved in several signaling and metabolic pathways that play pro-tumorigenic roles: EMT, ERK/MAPK, PI3K/AKT, Wnt/β-catenin, mTOR, C-MYC, NF-κB, IFN-γ and IFN-α responses, UPR, and glycolysis/gluconeogenesis. These pathways sustain cancer cell growth, adhesion, survival, proliferation, invasion, metastasis, resistance to apoptosis, tight junctions and cytoskeleton reorganization, the maintenance of stemness, metabolic reprogramming, survival in a hostile environment, and sustain a poor clinical outcome. In conclusion, JTB silencing might increase the neoplastic phenotype and behavior of the MCF7 BC cell line. The data is available via ProteomeXchange with the identifier PXD046265.

Single-cell RNA sequencing of a poorly metastatic melanoma cell line and its subclones with high lung and brain metastasis potential reveals gene expression signature of metastasis with prognostic implication

The molecular mechanisms underlying melanoma metastasis remain poorly understood. In this study, we aimed to delineate the mechanisms underlying gene expression alterations during metastatic potential acquisition and characterize the metastatic subclones within primary cell lines. We performed single-cell RNA sequencing of a poorly metastatic melanoma cell line (WM239A) and its subclones with high metastatic potential to the lung (113/6-4L) and the brain (131/4-5B1 and 131/4-5B2). Unsupervised clustering of 8173 melanoma cells identified three distinct clusters according to cell type ('Primary', 'Lung' and 'Brain' clusters) with differential expression of MITF and AXL pathways and putative cancer and cell cycle drivers, with the lung cluster expressing intermediate but distinct gene profiles between primary and brain clusters. Principal component (PC) analysis revealed that PC2 (the second PC), which was positively associated with MITF expression and negatively with AXL pathways, primarily segregated cell types, in addition to PC1 of the cell cycle pathway. Pseudotime trajectory and RNA velocity analyses suggested the existence of cellular subsets with metastatic potential in the Primary cluster and an association between PC2 signature alteration and metastasis potential acquisition. Analysis of The Cancer Genome Atlas melanoma samples by clustering into PC2-high and -low clusters by quartiles of PC2 signature expression revealed that the PC2-high cluster was an independent significant factor for poor prognosis (p-value = 0.003) with distinct genomic and transcriptomic characteristics, compared to the PC2-low cluster. In conclusion, we identified signatures of melanoma metastasis with prognostic significance and putative pro-metastatic subclones within a primary cell line.

Kinetic Effects of Transferrin-Conjugated Gold Nanoparticles on the Antioxidant Glutathione-Thioredoxin Pathway

Nanoparticle-based therapeutics are being clinically translated for treating cancer. Even when thought to be biocompatible, nanoparticles are being increasingly identified as altering cell regulation and homeostasis. Antioxidant pathways are important for maintaining cell redox homeostasis and play important roles by maintaining ROS levels within tolerable ranges. Here, we sought to understand how a model of a relatively inert nanoparticle without any therapeutic agent itself could antagonize a cancer cell lines' antioxidant mechanism. A label-free protein expression approach was used to assess the glutathione-thioredoxin antioxidative pathway in a prostate cancer cell line (PC-3) after exposure to gold nanoparticles conjugated with a targeting moiety (transferrin). The impact of the nanoparticles was also corroborated through morphological analysis with TEM and classification of pro-apoptotic cells by way of the sub-G0/G1 population via the cell cycle and annexin V apoptosis assay. After a two-hour exposure to nanoparticles, major proteins associated with the glutathione-thioredoxin antioxidant pathway were downregulated. However, this response was acute, and in terms of protein expression, cells quickly recovered within 24 h once nanoparticle exposure ceased. The impact on PRDX-family proteins appears as the most influential factor in how these nanoparticles induced an oxidative stress response in the PC-3 cells. An apparent adaptive response was observed if exposure to nanoparticles continued. Acute exposure was observed to have a detrimental effect on cell viability compared to continuously exposed cells. Nanoparticle effects on cell regulation likely provide a compounding therapeutic advantage under some circumstances, in addition to the action of any cytotoxic agents; however, any therapeutic advantage offered by nanoparticles themselves with regard to vulnerabilities specific to the glutathione-thioredoxin antioxidative pathway is highly temporal.

Comparative proteomics analysis in different stages of urothelial bladder cancer for identification of potential biomarkers: highlighted role for antioxidant activity

BACKGROUND

Non-muscle-invasive bladder cancer (NMIBC) has a high recurrence rate and muscle-invasive bladder cancer (MIBC) has unfavorable outcomes in urothelial bladder cancer (UBC) patients. Complex UBC-related protein biomarkers for outcome prediction may provide a more efficient management approach with an improved clinical outcome. The aim of this study is to recognize tumor-associated proteins, which are differentially expressed in different stages of UBC patients compared non-cancerous tissues.

METHODS

The proteome of tissue samples of 42 UBC patients (NMIBC n = 25 and MIBC n = 17) was subjected to two-dimensional electrophoresis (2-DE) combined with Liquid chromatography-mass spectrometry (LC-MS) system to identify differentially expressed proteins. The intensity of protein spots was quantified and compared with Prodigy SameSpots software. Functional, pathway, and interaction analyses of identified proteins were performed using geneontology (GO), PANTHER, Reactome, Gene MANIA, and STRING databases.

RESULTS

Twelve proteins identified by LC-MS showed differential expression (over 1.5-fold, p < 0.05) by LC-MS, including 9 up-regulated in NMIBC and 3 up-regulated in MIBC patients. Proteins involved in the detoxification of reactive oxygen species and cellular responses to oxidative stress showed the most significant changes in UBC patients. Additionally, the most potential functions related to these detected proteins were associated with peroxidase, oxidoreductase, and antioxidant activity.

CONCLUSION

We identified several alterations in protein expression involved in canonical pathways which were correlated with the clinical outcomes suggested might be useful as promising biomarkers for early detection, monitoring, and prognosis of UBC.

Prdx5 in the Regulation of Tuberous Sclerosis Complex Mutation-Induced Signaling Mechanisms

(1) Background: Tuberous sclerosis complex (TSC) mutations directly affect mTORC activity and, as a result, protein synthesis. In several cancer types, TSC mutation is part of the driver mutation panel. TSC mutations have been associated with mitochondrial dysfunction, tolerance to reactive oxygen species due to increased thioredoxin reductase (TrxR) enzyme activity, tolerance to endoplasmic reticulum (ER) stress, and apoptosis. The FDA-approved drug rapamycin is frequently used in clinical applications to inhibit protein synthesis in cancers. Recently, TrxR inhibitor auranofin has also been involved in clinical trials to investigate the anticancer efficacy of the combination treatment with rapamycin. We aimed to investigate the molecular background of the efficacy of such drug combinations in treating neoplasia modulated by TSC mutations. (2) Methods: TSC2 mutant and TSC2 wild-type (WT) cell lines were exposed to rapamycin and auranofin in either mono- or combination treatment. Mitochondrial membrane potential, TrxR enzyme activity, stress protein array, mRNA and protein levels were investigated via cell proliferation assay, electron microscopy, etc. (3) Results: Auranofin and rapamycin normalized mitochondrial membrane potential and reduced proliferation capacity of TSC2 mutant cells. Database analysis identified peroxiredoxin 5 (Prdx5) as the joint target of auranofin and rapamycin. The auranofin and the combination of the two drugs reduced Prdx5 levels. The combination treatment increased the expression of heat shock protein 70, a cellular ER stress marker. (4) Conclusions: After extensive analyses, Prdx5 was identified as a shared target of the two drugs. The decreased Prdx5 protein level and the inhibition of both TrxR and mTOR by rapamycin and auranofin in the combination treatment made ER stress-induced cell death possible in TSC2 mutant cells.

Molecular cloning and functional characterization of peroxiredoxin 4 (prx 4) in freshwater crayfish, Procambarus clarkii

Peroxiredoxin (Prx), which is a newly discovered member of the antioxidant protein family, performs important biological functions in intracellular signal transduction. In the present study, a peroxiredoxin 4 gene was cloned from crayfish for the first time and named Pc-prx 4. According to the amino acid sequence signature, Pc-Prx 4 was identified as the typical 2-Cys Prx molecule, which possessed two conserved cysteines (Cys98 and Cys219). Time-course expression patterns post V. harveyi infection revealed that Pc-prx 4 was likely related to crayfish innate immune defense responses. In particular, the highest fold upregulation of the Pc-prx 4 mRNA transcript reached approximately 170 post V. harveyi infection in the crayfish hepatopancreas. The results of the mixed functional oxidase assay showed that rPc-Prx 4^△ could resist the damaging effect of reactive oxygen species generated from the thiol/Fe³⁺/O₂^- reaction system to some extent. In addition, the results of the RNAi assay revealed that the crayfish survival rate was obviously increased post injection of V. harveyi when Pc-prx 4 was knocked down. Further study revealed that both hemolymph melanization and PO activity were strengthened to different degrees in the RNAi assay. Therefore, we speculated that the increase in the crayfish survival rate was likely due to the increase in hemolymph melanization. The obviously reinforced hemolymph melanization was directly caused by the upregulation of hemolymph PO activity, which was induced by the knockdown of Pc-prx 4. However, further studies are still indispensable for illuminating the molecular mechanism of Pc-prx 4 in the crayfish innate immune defense system.

Target proteins profiling of irreversible kinase inhibitor pelitinib and discovery of degradation of PRDX4 by label free chemoproteomics

Cell-based methods for profiling the kinase inhibitor selectivity are badly needed, especially for the irreversible kinase inhibitors. Here we reported a chemoproteomics approach for profiling the target proteins of irreversible kinase inhibitor with label free quantitative proteomics by using iodoacetamide alkyne as a chemical probe. In total 41 proteins were identified in high confidence (fold change 3.5, p value < 0.05) including PRDX4, STAT3, E2 conjugating enzymes UBE2L3, UBE2K, UBE2N, UBE2V1 and UBE2Z as well as E3 ligase TRIM 25. We validated the interaction between pelitinib and PRDX4 with a cell-based assay, and discovered that pelitinib can induce the degradation of PRDX4. The discovery was confirmed by biochemical assay, cellular thermal shift assay and miRNA knockdown experiment. Our data suggested that pelitinib can be a covalent molecular glue inducing the degradation of PRDX4. In addition, our work demonstrated that identification of the interactions between ligand and ubiquitylation associated proteins by chemoproteomics profiling can be used as a new strategy for identifying molecular glue degraders.

The molecular mechanisms of apoptosis accompanied with the epigenetic regulation of the NY-ESO-1 antigen in non-small lung cancer cells treated with decitabine (5-aza-CdR)

Dysregulated epigenetic modifications are common in lung cancer but have been reversed using demethylating agent like 5-Aza-CdR. 5-Aza-CdR induces/upregulates the NY-ESO-1 antigen in lung cancer. Therefore, we investigated the molecular mechanisms accompanied with the epigenetic regulation of NY-ESO-1 in 5-Aza-CdR-treated NCI-H1975 cell line. We showed significant induction of the NY-ESO-1 protein (**p < 0.0097) using Cellular ELISA. Bisulfite-sequencing demonstrated 45.6% demethylation efficiency at the NY-ESO-1 gene promoter region and RT-qPCR analysis confirmed the significant induction of NY-ESO-1 at mRNA level (128-fold increase, *p < 0.050). We then investigated the mechanism by which 5-Aza-CdR inhibits cell proliferation in the NCI-H1975 cell line. Upregulation of the death receptors TRAIL (2.04-fold *p < 0.011) and FAS (2.1-fold *p < 0.011) indicate activation of the extrinsic apoptotic pathway. The upregulation of Voltage-dependent anion-selective channel protein 1 (1.9-fold), Major vault protein (1.8-fold), Bax (1.16-fold), and Cytochrome C (1.39-fold) indicate the activation of the intrinsic pathway. We also observed the differential expression of protein Complement C3 (3.3-fold), Destrin (-5.1-fold), Vimentin (-1.7-fold), Peroxiredoxin 4 (-1.6-fold), Fascin (-1.8-fold), Heme oxygenase-2 (-0.67-fold**p < 0.0055), Hsp27 (-0.57-fold**p < 0.004), and Hsp70 (-0.39-fold **p < 0.001), indicating reduced cell growth, cell migration, and metastasis. The upregulation of 40S ribosomal protein S9 (3-fold), 40S ribosomal protein S15 (4.2-fold), 40S ribosomal protein S18 (2.5-fold), and 60S ribosomal protein L22 (4.4-fold) implied the induction of translation machinery. These results reiterate the decisive role of 5-Aza-CdR in lung cancer treatment since it induces the epigenetic regulation of NY-ESO-1 antigen, inhibits cell proliferation, increases apoptosis, and decreases invasiveness.

Oxidative Stress, Inflammation and Colorectal Cancer: An Overview

Colorectal cancer (CRC) represents the second leading cause of cancer-related deaths worldwide. The pathogenesis of CRC is a complex multistep process. Among other factors, inflammation and oxidative stress (OS) have been reported to be involved in the initiation and development of CRC. Although OS plays a vital part in the life of all organisms, its long-term effects on the human body may be involved in the development of different chronic diseases, including cancer diseases. Chronic OS can lead to the oxidation of biomolecules (nucleic acids, lipids and proteins) or the activation of inflammatory signaling pathways, resulting in the activation of several transcription factors or the dysregulation of gene and protein expression followed by tumor initiation or cancer cell survival. In addition, it is well known that chronic intestinal diseases such as inflammatory bowel disease (IBD) are associated with an increased risk of cancer, and a link between OS and IBD initiation and progression has been reported. This review focuses on the role of oxidative stress as a causative agent of inflammation in colorectal cancer.

Peroxiredoxin 5 is involved in cancer cell invasion and tumor growth of oral squamous cell carcinoma

OBJECTIVES

Peroxiredoxins (Prxs) are antioxidant enzymes that can coordinate cell signal transduction via reactive species scavenging or by acting as redox sensors. The mechanism by which Prxs promote cancer invasion and progression is not yet fully understood. This study aims to elucidate the precise mechanism through which Prx type 5 (Prx5) promotes cancer invasion and tumor growth.

MATERIALS AND METHODS

We analyzed the Prx5 expression in oral squamous cell carcinoma (OSCC) by using microarray analysis for gene expression profiling. To identify Prx5 function in cancer, lentiviral short hairpin RNA was used for Prx5 depletion, and invasion assay and mouse xenograft were performed.

RESULTS

In microarray data obtained from OSCC patients, Prx5 showed higher expression at the tumor margin (TM) compared to the tumor center (TC) of the collective invasion. The depletion of Prx5 in OSCC cells (Prx5^dep ) led to decreased invasion activity. In orthotopic xenograft models, Prx5^dep cells harbored delimited tumorigenicity compared to wild-type cells as well as the suppression of lymph node metastasis. Prx5^dep cells showed growth retardation and increased cellular reactive oxygen species (ROS) levels. The growth retardation of Prx5^dep cells resulted in G1 phase arrest.

CONCLUSIONS

This study provides evidence that Prx5 removes excess ROS, especially in the TM, contributing to cancer invasion and tumor progression.

Protein persulfidation: Rewiring the hydrogen sulfide signaling in cell stress response

The past few decades have witnessed significant progress in the discovery of hydrogen sulfide (H₂S) as a ubiquitous gaseous signaling molecule in mammalian physiology, akin to nitric oxide and carbon monoxide. As the third gasotransmitter, H₂S is now known to exert a wide range of physiological and cytoprotective functions in the biological systems. However, endogenous H₂S concentrations are usually low, and its potential biologic mechanisms responsible have not yet been fully clarified. Recently, a growing body of evidence has demonstrated that protein persulfidation, a posttranslational modification of cysteine residues (RSH) to persulfides (RSSH) elicited by H₂S, is a fundamental mechanism of H₂S-mediated signaling pathways. Persulfidation, as a biological switch for protein function, plays an important role in the maintenance of cell homeostasis in response to various internal and external stress stimuli and is also implicated in numerous diseases, such as cardiovascular and neurodegenerative diseases and cancer. In this review, the biological significance of protein persulfidation by H₂S in cell stress response is reviewed providing a framework for understanding the multifaceted roles of H₂S. A mechanism-guided perspective can help open novel avenues for the exploitation of therapeutics based on H₂S-induced persulfidation in the context of diseases.

Selenium, selenoproteins and cancer of the thyroid

Selenium is an essential mineral element with important biological functions for the whole body through incorporation into selenoproteins. This element is highly concentrated in the thyroid gland. Selenoproteins provide antioxidant protection for this tissue against the oxidative stress caused by free radicals and contribute, via iodothyronine deiodinases, to the metabolism of thyroid hormones. It is known that oxidative stress plays a major role in carcinogenesis and that in recent decades there has been an increase in the incidence of thyroid cancer. The anti-carcinogenic action of selenium, although not fully understood, is mainly attributable to selenoproteins antioxidant properties, and to the ability to modulate cell proliferation (cell cycle and apoptosis), energy metabolism, and cellular immune response, significantly altered during tumorigenesis. Researchers have suggested that different forms of selenium supplementation may be beneficial in the prevention and treatment of thyroid cancer; however, the studies have several methodological limitations. This review is a summary of the current knowledge on how selenium and selenoproteins related to thyroid cancer.

Peroxiredoxins and Hypoxia-Inducible Factor-1α in Duodenal Tissue: Emerging Factors in the Pathophysiology of Pediatric Celiac Disease Patients

Celiac disease (CD) is an autoimmune enteropathy. Peroxiredoxins (PRDXs) are powerful antioxidant enzymes having an important role in significant cellular pathways including cell survival, apoptosis, and inflammation. This study aimed at investigating the expression levels of all PRDX isoforms (1-6) and their possible relationships with a transcription factor, HIF-1α, in the small intestinal tissue samples of pediatric CD patients. The study groups consisted of first-diagnosed CD patients (n = 7) and non-CD patients with functional gastrointestinal tract disorders as the controls (n = 7). The PRDXs and HIF-1α expression levels were determined by using real-time PCR and Western blotting in duodenal biopsy samples. It was observed that the mRNA and protein expression levels of PRDX 5 were significantly higher in the CD patients, whereas the PRDX 1, -2, and -4 expressions were decreased in each case compared to the control group. No significant differences were detected in the PRDX 3 and PRDX 6 expressions. The expression of HIF-1α was also significantly elevated in CD patients. These findings indicate, for the first time, that PRDXs, particularly PRDX 5, may play a significant role in the pathogenesis of CD. Furthermore, our results suggest that HIF-1α may upregulate PRDX-5 transcription in the duodenal tissue of CD.

Thioredoxin Signaling Pathways in Cancer

Significance: Thioredoxin (Trx) is a powerful antioxidant that reduces protein disulfides to maintain redox stability in cells and is involved in regulating multiple redox-dependent signaling pathways. Recent Advance: The current accumulation of findings suggests that Trx participates in signaling pathways that interact with various proteins to manipulate their dynamic regulation of structure and function. These network pathways are critical for cancer pathogenesis and therapy. Promising clinical advances have been presented by most anticancer agents targeting such signaling pathways. Critical Issues: We herein link the signaling pathways regulated by the Trx system to potential cancer therapeutic opportunities, focusing on the coordination and strengths of the Trx signaling pathways in apoptosis, ferroptosis, immunomodulation, and drug resistance. We also provide a mechanistic network for the exploitation of therapeutic small molecules targeting the Trx signaling pathways. Future Directions: As research data accumulate, future complex networks of Trx-related signaling pathways will gain in detail. In-depth exploration and establishment of these signaling pathways, including Trx upstream and downstream regulatory proteins, will be critical to advancing novel cancer therapeutics. Antioxid. Redox Signal. 38, 403-424.

Prdx5 regulates DNA damage response through autophagy-dependent Sirt2-p53 axis

DNA damage response (DDR) is an important signaling-transduction network that promotes the repair of DNA lesions which can induce and/or support diseases. However, the mechanisms involved in its regulation are not fully understood. Recent studies suggest that the peroxiredoxin 5 (Prdx5) enzyme, which detoxifies reactive oxygen species, is associated to genomic instability and signal transduction. Its role in the regulation of DDR, however, is not well characterized. In this study, we demonstrate a role of Prdx5 in the regulation of the DDR signaling pathway. Knockdown of Prdx5 resulted in DNA damage manifested by the induction of phosphorylated histone H2AX (γ-H2AX) and p53-binding protein 1 (53BP1). We show that Prdx5 regulates DDR through (1) polo-like kinase 1 (Plk1) mediated phosphorylation of ataxia telangiectasia mutated (ATM) kinase to further trigger downstream mediators Chek1 and Chek2; (2) the increase of the acetylation of p53 at lysine 382, stabilizing p53 in the nucleus and enhancing transcription and (3) the induction of autophagy, which regulates the recycling of molecules involved in DDR. We identified Sirt2 as a novel deacetylase of p53 at lysine 382, and Sirt2 regulated the acetylation status of p53 at lysine 382 in a Prdx5-dependent manner. Furthermore, we found that exogenous expression of Prdx5 decreased DNA damage and the activation of ATM in Pkd1 mutant renal epithelial cells, suggesting that Prdx5 may play a protective role from DNA damage in cystic renal epithelial cells. This study identified a novel mechanism of Prdx5 in the regulation of DDR through the ATM/p53/Sirt2 signaling cascade.

NADPH oxidase 1 in chronic pancreatitis-activated pancreatic stellate cells facilitates the progression of pancreatic cancer

Patients suffering from chronic pancreatitis (CP) have a higher risk of pancreatic ductal adenocarcinoma (PDAC) compared to the general population. For instance, the presence of an activated pancreatic stellate cell (PaSC)-rich stroma in CP has facilitated the progression of non-invasive pancreatic intraepithelial neoplasia (PanIN) lesions to invasive PDAC. We have previously found that in a mouse model of CP, NADPH oxidase 1 (Nox1) in activated PaSCs forms fibrotic tissue and up-regulates both matrix metalloproteinase (MMP) 9 and the transcription factor Twist1. Yet, the role and mechanism of Nox1 in activated PaSCs from mice with CP (CP-activated PaSCs) in the progression of PDAC is unknown. For that, we tested the ability of Nox1 in CP-activated PaSCs to facilitate the growth of pancreatic cancer cells, and the mechanisms involved in these effects by identifying proteins in the secretome of CP-activated PaSCs whose production were Nox1-dependent. We found that, in vitro, Nox1 evoked a pro-invasive and cancer-promoting phenotype in CP-activated PaSCs via Twist1/MMP-9 expression, causing changes in the extracellular matrix composition. In vivo, Nox1 in CP-activated PaSCs facilitated tumor growth and stromal expansion. Using mass spectrometry, we identified proteins protecting from endoplasmic reticulum, oxidative and metabolic stresses in the secretome of CP-activated PaSCs whose production was Nox1-dependent, including peroxiredoxins (Prdx1 and Prdx4), and thioredoxin reductase 1. In conclusion, inhibiting the Nox1 signaling in activated PaSCs from patients with CP at early stages can reduce the reorganization of extracellular matrix, and the protection of neoplastic cells from cellular stresses, ameliorating the progression of PDAC.

NEK6 Regulates Redox Balance and DNA Damage Response in DU-145 Prostate Cancer Cells

NEK6 is a central kinase in developing castration-resistant prostate cancer (CRPC). However, the pathways regulated by NEK6 in CRPC are still unclear. Cancer cells have high reactive oxygen species (ROS) levels and easily adapt to this circumstance and avoid cell death by increasing antioxidant defenses. We knocked out the NEK6 gene and evaluated the redox state and DNA damage response in DU-145 cells. The knockout of NEK6 decreases the clonogenic capacity, proliferation, cell viability, and mitochondrial activity. Targeting the NEK6 gene increases the level of intracellular ROS; decreases the expression of antioxidant defenses (SOD1, SOD2, and PRDX3); increases JNK phosphorylation, a stress-responsive kinase; and increases DNA damage markers (p-ATM and γH2AX). The exogenous overexpression of NEK6 also increases the expression of these same antioxidant defenses and decreases γH2AX. The depletion of NEK6 also induces cell death by apoptosis and reduces the antiapoptotic Bcl-2 protein. NEK6-lacking cells have more sensitivity to cisplatin. Additionally, NEK6 regulates the nuclear localization of NF-κB2, suggesting NEK6 may regulate NF-κB2 activity. Therefore, NEK6 alters the redox balance, regulates the expression of antioxidant proteins and DNA damage, and its absence induces the death of DU-145 cells. NEK6 inhibition may be a new strategy for CRPC therapy.

Coordinated reprogramming of renal cancer transcriptome, metabolome and secretome associates with immune tumor infiltration

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cancer. The molecules (proteins, metabolites) secreted by tumors affect their extracellular milieu to support cancer progression. If secreted in amounts detectable in plasma, these molecules can also serve as useful, minimal invasive biomarkers. The knowledge of ccRCC tumor microenvironment is fragmentary. In particular, the links between ccRCC transcriptome and the composition of extracellular milieu are weakly understood. In this study, we hypothesized that ccRCC transcriptome is reprogrammed to support alterations in tumor microenvironment. Therefore, we comprehensively analyzed ccRCC extracellular proteomes and metabolomes as well as transcriptomes of ccRCC cells to find molecules contributing to renal tumor microenvironment.

METHODS

Proteomic and metabolomics analysis of conditioned media isolated from normal kidney cells as well as five ccRCC cell lines was performed using mass spectrometry, with the following ELISA validation. Transcriptomic analysis was done using microarray analysis and validated using real-time PCR. Independent transcriptomic and proteomic datasets of ccRCC tumors were used for the analysis of gene and protein expression as well as the level of the immune infiltration.

RESULTS

Renal cancer secretome contained 85 proteins detectable in human plasma, consistently altered in all five tested ccRCC cell lines. The top upregulated extracellular proteins included SPARC, STC2, SERPINE1, TGFBI, while downregulated included transferrin and DPP7. The most affected extracellular metabolites were increased 4-hydroxy-proline, succinic acid, cysteine, lactic acid and downregulated glutamine. These changes were associated with altered expression of genes encoding the secreted proteins (SPARC, SERPINE1, STC2, DPP7), membrane transporters (SLC16A4, SLC6A20, ABCA12), and genes involved in protein trafficking and secretion (KIF20A, ANXA3, MIA2, PCSK5, SLC9A3R1, SYTL3, and WNTA7). Analogous expression changes were found in ccRCC tumors. The expression of SPARC predicted the infiltration of ccRCC tumors with endothelial cells. Analysis of the expression of the 85 secretome genes in > 12,000 tumors revealed that SPARC is a PanCancer indicator of cancer-associated fibroblasts' infiltration.

CONCLUSIONS

Transcriptomic reprogramming of ccRCC supports the changes in an extracellular milieu which are associated with immune infiltration. The proteins identified in our study represent valuable cancer biomarkers detectable in plasma.

Phosphatase of Regenerating Liver-1 (PRL-1)-Overexpressing Placenta-Derived Mesenchymal Stem Cells Enhance Antioxidant Effects via Peroxiredoxin 3 in TAA-Injured Rat Livers

DNA damage repair is induced by several factors and is critical for cell survival, and many cellular DNA damage repair mechanisms are closely linked. Antioxidant enzymes that control cytokine-induced peroxide levels, such as peroxiredoxins (Prxs) and catalase (CAT), are involved in DNA repair systems. We previously demonstrated that placenta-derived mesenchymal stem cells (PD-MSCs) that overexpress PRL-1 (PRL-1(+)) promote liver regeneration via antioxidant effects in TAA-injured livers. However, the efficacy of these cells in regeneration and the role of Prxs in their DNA repair system have not been reported. Therefore, our objective was to analyze the Prx-based DNA repair mechanism in naïve or PRL-1(+)-transplanted TAA-injured rat livers. Apoptotic cell numbers were significantly decreased in the PRL-1(+) transplantation group versus the nontransplantation (NTx) group (p < 0.05). The expression of antioxidant markers was significantly increased in PRL-1(+) cells compared to NTx cells (p < 0.05). MitoSOX and Prx3 demonstrated a significant negative correlation coefficient (R2 = −0.8123). Furthermore, DNA damage marker levels were significantly decreased in PRL-1(+) cells compared to NTx cells (p < 0.05). In conclusion, increased Prx3 levels in PRL-1(+) cells result in an effective antioxidant effect in TAA-injured liver disease, and Prx3 is also involved in repairing damaged DNA.

Prx4 acts as DAMP in shrimp, enhancing bacterial resistance via the toll pathway and prophenoloxidase activation

Peroxiredoxin (Prx), an antioxidant enzyme family, has been identified as immune modulating damage-associated molecular patterns (DAMPs) in mammals but not in shrimp. Acute non-lethal heat shock (NLHS) that enhances shrimp Penaeus vannamei resistance to Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease (VP_AHPND). Among the five P. vannamei Prxs (LvPrx) isoforms, LvPrx4, the most abundant in unchallenged shrimp hemocytes that was upregulated in hemocytes following NLHS treatment, is of great interest. The escalation of the LvPrx4 monomer in hemolymph of NLHS treated shrimp indicates that it probably acts as DAMP. This study revealed that pre-challenge with rLvPrx4 could prolong VP_AHPND-infected shrimp survival, increase prophenoloxidase (proPO) activity and promote Toll pathway-related genes expression mediated by Toll-like receptor (TLR) 1 and 2. The presented findings elucidated the molecular mechanism of LvPrx4 monomer as DAMP in NLHS-induced VP_AHPND resistance by inducing the TLR1/2 signaling pathway and the proPO activating system.

Investigating the Function of Human Jumping Translocation Breakpoint Protein (hJTB) and Its Interacting Partners through In-Solution Proteomics of MCF7 Cells

Human jumping translocation breakpoint (hJTB) gene is located on chromosome 1q21 and is involved in unbalanced translocation in many types of cancer. JTB protein is ubiquitously present in normal cells but it is found to be overexpressed or downregulated in various types of cancer cells, where this protein and its isoforms promote mitochondrial dysfunction, resistance to apoptosis, genomic instability, proliferation, invasion and metastasis. Hence, JTB could be a tumor biomarker for different types of cancer, such as breast cancer (BC), and could be used as a drug target for therapy. However, the functions of the protein or the pathways through which it increases cell proliferation and invasiveness of cancer cells are not well-known. Therefore, we aim to investigate the functions of JTB by using in-solution digestion-based cellular proteomics of control and upregulated and downregulated JTB protein in MCF7 breast cancer cell line, taking account that in-solution digestion-based proteomics experiments are complementary to the initial in-gel based ones. Proteomics analysis allows investigation of protein dysregulation patterns that indicate the function of the protein and its interacting partners, as well as the pathways and biological processes through which it functions. We concluded that JTB dysregulation increases the epithelial-mesenchymal transition (EMT) potential and cell proliferation, harnessing cytoskeleton organization, apical junctional complex, metabolic reprogramming, and cellular proteostasis. Deregulated JTB expression was found to be associated with several proteins involved in mitochondrial organization and function, oxidative stress (OS), apoptosis, and interferon alpha and gamma signaling. Consistent and complementary to our previous results emerged by using in-gel based proteomics of transfected MCF7 cells, JTB-related proteins that are overexpressed in this experiment suggest the development of a more aggressive phenotype and behavior for this luminal type A non-invasive/poor-invasive human BC cell line that does not usually migrate or invade compared with the highly metastatic MDA-MB-231 cells. This more aggressive phenotype of MCF7 cells related to JTB dysregulation and detected by both in-gel and in-solution proteomics could be promoted by synergistic upregulation of EMT, Mitotic spindle and Fatty acid metabolism pathways. However, in both JTB dysregulated conditions, several downregulated JTB-interacting proteins predominantly sustain antitumor activities, attenuating some of the aggressive phenotypical and behavioral traits promoted by the overexpressed JTB-related partners.

Oxidative Stress Correlates with More Aggressive Features in Thyroid Cancer

Oxidative stress (OS) can have an impact in the pathogenesis and in the progression of thyroid cancer. We investigated the levels of reactive oxygen species (ROS) in 50 malignant and benign thyroid lesions and 41 normal tissues, and correlated them with the thyroid differentiation score-TDS and the clinico-pathologic features. NOX4 expression, GPx activity and the genetic pattern of tumors were evaluated. In malignant and benign lesions, ROS generation and NOX4 protein expression were higher than in normal tissues. Follicular (FTCs) and anaplastic/poorly differentiated cancers had increased OS relative to papillary tumors (PTCs). Moreover, OS in FTCs was higher than in follicular adenomas. Mutated PTCs showed increased OS compared with non-mutated PTCs. In malignant tumors, OS was inversely correlated with TDS, and directly correlated with tumor stage and ATA risk. GPx activity was increased in tumors compared with normal tissues, and inversely correlated to OS. In conclusion, our data indicate that thyroid tumors are exposed to higher OS compared with normal tissues, while showing a compensative increased GPx activity. OS correlates with tumor aggressiveness and mutations in the MEK-ERK pathway in PTC. The inverse correlation between OS and TDS suggests that ROS may repress genes involved in thyroid differentiation.

Thioredoxin System and miR-21, miR-23a/b and let-7a as Potential Biomarkers for Brain Tumor Progression: Preliminary Case Data

BACKGROUND

The thioredoxin system and microRNAs (miRNAs) are potential targets for both cancer progression and treatment. However, the role of miRNAs and their relation with the expression profile of thioredoxin system in brain tumor progression remains unclear.

METHODS

In this study, we aimed to determine the expression profiles of redox components Trx-1, TrxR-1 and PRDX-1, and oncogenic miR-21, miR-23a/b and let-7a and oncosuppressor miR-125 in different brain tumor tissues and their association with increasing tumor grade. We studied Trx-1, TrxR-1, and PRDX-1 messenger RNA expression levels by quantitative real-time polymerase chain reaction and protein levels by Western blot and miR-23a, miR-23b, miR-125a, miR-21, and let-7a miRNA expression levels by quantitative real-time polymerase chain reaction in 16 glioma, 15 meningioma, 5 metastatic, and 2 benign tumor samples. We also examined Trx-1, TrxR-1, and PRDX-1 protein levels in serum samples of 36 patients with brain tumor and 37 healthy volunteers by enzyme-linked immunosorbent assay.

RESULTS

We found that Trx-1, TrxR-1, and PRDX-1 presented high messenger RNA expression but low protein expression in low-grade brain tumor tissues, whereas they showed higher protein expression in sera of patients with low-grade brain tumors. miR-23b, miR-21, miR-23a, and let-7a were highly expressed in low-grade brain tumor tissues and positively correlated with the increase in thioredoxin system activity.

CONCLUSIONS

Our findings showed that Trx-1, TrxR-1, miR-21, miR-23a/b, and let-7a might be used for brain tumor diagnosis in the clinic. Further prospective studies including molecular pathway analyses are required to validate the miRNA/Trx system regulatory axis in brain tumor progression.

The Development and Clinical Applications of Oral Arsenic Trioxide for Acute Promyelocytic Leukaemia and Other Diseases

Appreciation of the properties of arsenic trioxide (ATO) has redefined the treatment landscape for acute promyelocytic leukaemia (APL) and offers promise as a treatment for numerous other diseases. The benefits of ATO in patients with APL is related to its ability to counteract the effects of PML::RARA, an oncoprotein that is invariably detected in the blood or bone marrow of affected individuals. The PML::RARA oncoprotein is degraded specifically by binding to ATO. Thus ATO, in combination with all-trans retinoic acid, has become the curative treatment for ATO. The multiple mechanisms of action of ATO has also paved the way for application in various condition encompassing autoimmune or inflammatory disorders, solid organ tumours, lymphomas and other subtypes of AML. The development of oral formulation of ATO (oral ATO) has reduced costs of treatment and improved treatment convenience allowing widespread applicability. In this review, we discuss the mechanisms of action of ATO, the development of oral ATO, and the applications of oral ATO in APL and other diseases.

The immunohistochemical detection of peroxiredoxin 1 and 2 in canine spontaneous vascular endothelial tumors

Peroxiredoxin (PRDX) is an antioxidant enzyme family with six isoforms (PRDX1-6). The main function of PRDXs is to decrease cellular oxidative stress by reducing reactive oxygen species, such as hydrogen peroxide, to H2O. Recently, it has been reported that PRDXs are overexpressed in various malignant tumors in humans, and are involved in the development, proliferation, and metastasis of tumors. However, studies on the expression of PRDXs in tumors of animals are limited. Therefore, in the present study, we immunohistochemically investigated the expression of PRDX1 and 2 in spontaneous canine hemangiosarcoma (HSA) and hemangioma (HA), as well as in selected normal tissue and granulation tissue, including newly formed blood vessels. Although there were some exceptions, immunolocalization of PRDX1 and 2 in normal canine tissues was similar to those in humans, rats, or mice. In granulation tissue, angiogenic endothelial cells were strongly positive for PRDX1 and 2, whereas quiescent endothelial cells in mature vessels were negative. Both PRDX1 and 2 were significantly highly expressed in HSA compared to HA. There were no significant differences in the expression of PRDX1 and 2 among the subtypes and primary sites of HSA. These results suggest that PRDX1 and 2 may be involved in the angiogenic phenotypes of endothelial cells in granulation tissue as well as in the behavior in the malignant endothelial tumors.

Bioinformatics-Driven Identification of p62 as A Crucial Oncogene in Liver Cancer

Liver hepatocellular carcinoma (LIHC) is the major form of liver cancer that is the fourth most common cause of cancer death worldwide. It has been reported that the multifunctional protein p62 (also known as SQSTM1) plays a cancer-promoting role in LIHC, but the detailed mechanisms underlying p62 interaction with LIHC remains unclear. To gain a comprehensive understanding of p62 interaction with LIHC in clinical settings, we performed bioinformatic analyses using various online algorithms derived from high throughput profiling. Our results indicate that p62 expression is significantly upregulated, partially due to its promoter demethylation, rather than p62 gene mutation, in LIHC. Mutation of TP53, CTNNB1, or ALB significantly correlates with, and mutation of AXIN1 reversely correlates with, the p62 expression level. Its upregulation occurs as early as liver cirrhosis, and go through all stages of the carcinogenesis. HCV infection makes a significant contribution to p62 upregulation in LIHC. We further identified p62-associated molecular signatures in LIHC, including many genes that are involved in antioxidant stress and metabolism, such as SRX1 and TXNRD1. Regarding to the clinical outcome, p62 expression level reversely correlates with the survival of LIHC patients (p<0.01). Importantly, we experimentally validated that p62 depletion in liver cancer cell lines downregulates the expression of SRX1 and TXNRD1 at both transcriptional and translational levels, and reduces cell proliferation. As the potential mechanisms underlying the tumor-promoting role of p62, we show that p62 upregulation is remarkably associated with reprogramming of pathways mediated by p53, Wnt/β-catenin, and Keap1-NRF2, which are crucial for oncogenesis in many contexts. Our findings provide a comprehensive insight into the interaction between p62 and LIHC, offering valuable information for understanding of LIHC pathogenesis.

High-Dose Vitamin C for Cancer Therapy

In recent years, the idea that Vitamin C (Vit-C) could be utilized as a form of anti-cancer therapy has generated many contradictory arguments. Recent insights into the physiological characteristics of Vit-C, its pharmacokinetics, and results from preclinical reports, however, suggest that high-dose Vit-C could be effectively utilized in the management of various tumor types. Studies have shown that the pharmacological action of Vit-C can attack various processes that cancerous cells use for their growth and development. Here, we discuss the anti-cancer functions of Vit-C, but also the potential for the use of Vit-C as an epigenetic regulator and immunotherapy enhancer. We also provide a short overview of the current state of systems for scavenging reactive oxygen species (ROS), especially in the context of their influencing high-dose Vit-C toxicity for the inhibition of cancer growth. Even though the mechanisms of Vit-C action are promising, they need to be supported with robust randomized and controlled clinical trials. Moreover, upcoming studies should focus on how to define the most suitable cancer patient populations for high-dose Vit-C treatments and develop effective strategies that combine Vit-C with various concurrent cancer treatment regimens.

Peroxiredoxin, Senescence, and Cancer

Peroxiredoxins are multifunctional enzymes that play a key role in protecting cells from stresses and maintaining the homeostasis of many cellular processes. Peroxiredoxins were firstly identified as antioxidant enzymes that can be found in all living organisms. Later studies demonstrated that peroxiredoxins also act as redox signaling regulators, chaperones, and proinflammatory factors and play important roles in oxidative defense, redox signaling, protein folding, cycle cell progression, DNA integrity, inflammation, and carcinogenesis. The versatility of peroxiredoxins is mainly based on their unique active center cysteine with a wide range of redox states and the ability to switch between low- and high-molecular-weight species for regulating their peroxidase and chaperone activities. Understanding the molecular mechanisms of peroxiredoxin in these processes will allow the development of new approaches to enhance longevity and to treat various cancers. In this article, we briefly review the history of peroxiredoxins, summarize recent advances in our understanding of peroxiredoxins in aging- and cancer-related biological processes, and discuss the future perspectives of using peroxiredoxins in disease diagnostics and treatments.

The Role of the Thioredoxin Detoxification System in Cancer Progression and Resistance

The intracellular redox homeostasis is a dynamic balancing system between the levels of free radical species and antioxidant enzymes and small molecules at the core of cellular defense mechanisms. The thioredoxin (Trx) system is an important detoxification system regulating the redox milieu. This system is one of the key regulators of cells’ proliferative potential as well, through the reduction of key proteins. Increased oxidative stress characterizes highly proliferative, metabolically hyperactive cancer cells, which are forced to mobilize antioxidant enzymes to balance the increase in free radical concentration and prevent irreversible damage and cell death. Components of the Trx system are involved in high-rate proliferation and activation of pro-survival mechanisms in cancer cells, particularly those facing increased oxidative stress. This review addresses the importance of the targetable redox-regulating Trx system in tumor progression, as well as in detoxification and protection of cancer cells from oxidative stress and drug-induced cytotoxicity. It also discusses the cancer cells’ counteracting mechanisms to the Trx system inhibition and presents several inhibitors of the Trx system as prospective candidates for cytostatics’ adjuvants. This manuscript further emphasizes the importance of developing novel multitarget therapies encompassing the Trx system inhibition to overcome cancer treatment limitations.

Elevation of fatty acid desaturase 2 in esophageal adenocarcinoma increases polyunsaturated lipids and may exacerbate bile acid-induced DNA damage

Background

The risk of esophageal adenocarcinoma (EAC) is associated with gastro‐esophageal reflux disease (GERD) and obesity. Lipid metabolism‐targeted therapies decrease the risk of progressing from Barrett's esophagus (BE) to EAC, but the precise lipid metabolic changes and their roles in genotoxicity during EAC development are yet to be established.

Methods

Esophageal biopsies from the normal epithelium (NE), BE, and EAC, were analyzed using concurrent lipidomics and proteomics (n = 30) followed by orthogonal validation on independent samples using RNAseq transcriptomics (n = 22) and immunohistochemistry (IHC, n = 80). The EAC cell line FLO‐1 was treated with FADS2 selective inhibitor SC26196, and/or bile acid cocktail, followed by immunofluorescence staining for γH2AX.

Results

Metabolism‐focused Reactome analysis of the proteomics data revealed enrichment of fatty acid metabolism, ketone body metabolism, and biosynthesis of specialized pro‐resolving mediators in EAC pathogenesis. Lipidomics revealed progressive alterations (NE‐BE‐EAC) in glycerophospholipid synthesis with decreasing triglycerides and increasing phosphatidylcholine and phosphatidylethanolamine, and sphingolipid synthesis with decreasing dihydroceramide and increasing ceramides. Furthermore, a progressive increase in lipids with C20 fatty acids and polyunsaturated lipids with ≥4 double bonds were also observed. Integration with transcriptome data identified candidate enzymes for IHC validation: Δ4‐Desaturase, Sphingolipid 1 (DEGS1) which desaturates dihydroceramide to ceramide, and Δ5 and Δ6‐Desaturases (fatty acid desaturases, FADS1 and FADS2), responsible for polyunsaturation. All three enzymes showed significant increases from BE through dysplasia to EAC, but transcript levels of DEGS1 were decreased suggesting post‐translational regulation. Finally, the FADS2 selective inhibitor SC26196 significantly reduced polyunsaturated lipids with three and four double bonds and reduced bile acid‐induced DNA double‐strand breaks in FLO‐1 cells in vitro.

Conclusions

Integrated multiomics revealed sphingolipid and phospholipid metabolism rewiring during EAC development. FADS2 inhibition and reduction of the high polyunsaturated lipids effectively protected EAC cells from bile acid‐induced DNA damage in vitro, potentially through reduced lipid peroxidation.

ROS-Influenced Regulatory Cross-Talk With Wnt Signaling Pathway During Perinatal Development

Over a century ago, it was found that a rapid burst of oxygen is needed and produced by the sea urchin oocyte to activate fertilization and block polyspermy. Since then, scientific research has taken strides to establish that Reactive Oxygen Species (ROS), besides being toxic effectors of cellular damage and death, also act as molecular messengers in important developmental signaling cascades, thereby modulating them. Wnt signaling pathway is one such developmental pathway, which has significant effects on growth, proliferation, and differentiation of cells at the earliest embryonic stages of an organism, apart from being significant role-players in the instances of cellular transformation and cancer when this tightly-regulated system encounters aberrations. In this review, we discuss more about the Wnt and ROS signaling pathways, how they function, what roles they play overall in animals, and mostly about how these two major signaling systems cross paths and interplay in mediating major cellular signals and executing the predestined changes during the perinatal condition, in a systematic manner.

Characterization of a cytoplasmic 2-Cys peroxiredoxin from Citrus sinensis and its potential role in protection from oxidative damage and wound healing

In present work, the recombinant cytoplasmic 2-Cys peroxiredoxin from Citrus sinensis (CsPrx) was purified and characterized. The peroxidase activity was examined with different substrates using DTT, a non-physiological electron donor. The conformational studies, in oxidized and reduced states, were performed using circular dichroism (CD) and fluorescence measurement. The CD analysis showed higher α-helical content for reduced state of the protein. The thermal stability studies of CsPrx by Differential Scanning Calorimetry (DSC) showed that oxidized state is more stable as compared to the reduced state of CsPrx. In vitro studies showed that the CsPrx provides a protective shield against ROS and free radicals that participate in the degradation of plasmid DNA. The pre-treatment of 10 μM CsPrx provide almost 100% protection against peroxide-mediated cell killing in the Vero cells. CsPrx showed significant cell proliferation and wound healing properties. The superior morphology of viable cells and wound closure was found at 20 μM CsPrx treated for 12 h. The results demonstrated that CsPrx is a multifaceted protein with a significant role in cell proliferation, wound healing and protection against hydrogen peroxide-induced cellular damage. This could be the first report of a plant peroxiredoxin being characterized for biomedical applications.

Dihydroartemisinin enhances the anti-tumor activity of oxaliplatin in colorectal cancer cells by altering PRDX2-reactive oxygen species-mediated multiple signaling pathways

BACKGROUND

Globally, colorectal cancer (CRC) is one of the leading causes of cancer-related deaths. Oxaliplatin based treatments are frequently used as chemotherapeutic methods for CRC, however, associated side effects and drug resistance often limit their clinical application. Dihydroartemisinin (DHA) induces apoptosis in various cancer cells by increasing reactive oxygen species (ROS) production. However, the direct target of DHA and underlying molecular mechanisms in oxaliplatin-mediated anti-tumor activities against CRC are unclear.

METHODS

We used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), flow cytometry, and colony formation assays to investigate cell phenotype alterations and ROS generation. We also used quantitative Real-Time PCR (qRT-PCR) and western blotting to measure relative gene and protein expression. Finally, an in vivo mouse xenograft model was used to assess the anti-tumor activity of oxaliplatin and DHA alone, and combinations.

RESULTS

DHA synergistically enhanced the anti-tumor activity of oxaliplatin in colon cancer cells by regulating ROS-mediated ER stress, signal transducer and activator of transcription 3 (STAT3), C-Jun-amino-terminal kinase (JNK), and p38 signaling pathways. Mechanistically, DHA increased ROS levels by inhibiting peroxiredoxin 2 (PRDX2) expression, and PRDX2 knockdown sensitized DHA-mediated cell growth inhibition and ROS production in CRC cells. A mouse xenograft model showed strong anti-tumor effects from combination treatments when compared with single agents.

CONCLUSIONS

We demonstrated an improved therapeutic strategy for CRC patients by combining DHA and oxaliplatin treatments.

PRDX4 Potentially Predicts the Postoperative Outcome in Advanced Papillary Thyroid Carcinoma

Background: Peroxiredoxin 4 (PRDX4), a secreted antioxidant enzyme, can protect against hepatocellular carcinoma and lung adenocarcinoma, but its role in papillary thyroid carcinoma (PTC) is still unclear. In this study, we investigated the association of the PRDX4 expression with the prognosis of patients with advanced PTC. Methods: We conducted a retrospective case-control study at Kanazawa Medical University Hospital. We selected PTC patients over 55 years of age who received surgery from 2006 to 2014. The PRDX4 expression was immunohistochemically analyzed in paraffin-embedded tumor specimens of 70 patients with stages Ⅱ–Ⅳ advanced PTC. We also investigated the key roles of PRDX4 in a human PTC cell line (K-1) in vitro. Result: The weak expression of PRDX4 was found to be significantly associated with recurrence. In a multivariate analysis, the weak expression of PRDX4—rather than other pathological features of high invasiveness—predicted a poor prognosis. In vitro, the viability of human PTC cells was significantly suppressed after PRXD4 plasmid transfection. Conclusion: The weak expression of PRDX4 can predict recurrence with a potential poor prognosis in advanced PTC.

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.

Helicobacter pylori-Mediated Oxidative Stress and Gastric Diseases: A Review

Gastric cancer is considered to be a type of gastrointestinal tumor and is mostly accompanied by Helicobacter pylori (HP) infection at the early stage. Hence, the long-term colonization of the gastric mucosa by HP as a causative factor for gastrointestinal diseases cannot be ignored. The virulence factors secreted by the bacterium activate the signaling pathway of oxidative stress and mediate chronic inflammatory response in the host cells. The virulence factors also thwart the antibacterial effect of neutrophils. Subsequently, DNA methylation is induced, which causes continuous cell proliferation and evolution toward low-grade-differentiated gastric cells. This process provides the pathological basis for the occurrence of progressive gastric cancer. Therefore, this review aims to summarize the oxidative stress response triggered by HP in the gastric mucosa and the subsequent signaling pathways. The findings are expected to help in the formulation of new targeted drugs for preventing the occurrence of early gastric cancer and its progression to middle and advanced cancer.

Epithelial-mesenchymal transition and H2O2 signaling - a driver of disease progression and a vulnerability in cancers

Mutation-selective drugs constitute a great advancement in personalized anticancer treatment with increased quality of life and overall survival in cancers. However, the high adaptability and evasiveness of cancers can lead to disease progression and the development of drug resistance, which cause recurrence and metastasis. A common characteristic in advanced neoplastic cancers is the epithelial-mesenchymal transition (EMT) which is strongly interconnected with H₂O₂ signaling, increased motility and invasiveness. H₂O₂ relays its signal through the installation of oxidative posttranslational modifications on cysteines. The increased H₂O₂ levels that are associated with an EMT confer a heightened sensitivity towards the induction of ferroptosis as a recently discovered vulnerability.

The Potential Role of Curcumin in Modulating the Master Antioxidant Pathway in Diabetic Hypoxia-Induced Complications

Oxidative stress is the leading player in the onset and development of various diseases. The Keap1-Nrf2 pathway is a pivotal antioxidant system that preserves the cells' redox balance. It decreases inflammation in which the nuclear trans-localization of Nrf2 as a transcription factor promotes various antioxidant responses in cells. Through some other directions and regulatory proteins, this pathway plays a fundamental role in preventing several diseases and reducing their complications. Regulation of the Nrf2 pathway occurs on transcriptional and post-transcriptional levels, and these regulations play a significant role in its activity. There is a subtle correlation between the Nrf2 pathway and the pivotal signaling pathways, including PI3 kinase/AKT/mTOR, NF-κB and HIF-1 factors. This demonstrates its role in the development of various diseases. Curcumin is a yellow polyphenolic compound from Curcuma longa with multiple bioactivities, including antioxidant, anti-inflammatory, anti-tumor, and anti-viral activities. Since hyperglycemia and increased reactive oxygen species (ROS) are the leading causes of common diabetic complications, reducing the generation of ROS can be a fundamental approach to dealing with these complications. Curcumin can be considered a potential treatment option by creating an efficient therapeutic to counteract ROS and reduce its detrimental effects. This review discusses Nrf2 pathway regulation at different levels and its correlation with other important pathways and proteins in the cell involved in the progression of diabetic complications and targeting these pathways by curcumin.

Peroxiredoxin-6 regulates p38-mediated epithelial-mesenchymal transition in HCT116 colon cancer cells

Background

Peroxiredoxins (Prxs) are antioxidant enzymes that protect cells from oxidative stress induced by several factors. They regulate several signaling pathways, such as metabolism, immune response, and intracellular reactive oxygen species (ROS) homeostasis. Epithelial–mesenchymal transition (EMT) is a transforming process that induces the loss of epithelial features of cancer cells and the gain of the mesenchymal phenotype. The EMT promotes metastasis and cancer cell progression mediated by several pathways, such as mitogen-activated protein kinases (MAPKs) and epigenetic regulators.

Methods

We used Prx6 overexpressed and downregulated HCT116 cells to study the mechanism between Prx6 and colon cancer. The expression of Prx6, GAPDH, Snail, Twist1, E-cadherin, Vimentin, N-cadherin, ERK, p-ERK, p38, p-p38, JNK, and p-JNK were detected by Western blotting. Additionally, an animal study for xenograft assay was conducted to explore the function of Prx6 on tumorigenesis. Cell proliferation and migration were determined by IncuCyte Cell Proliferation and colony formation assays.

Results

We confirmed that the expression of Prx6 and EMT signaling highly occurs in HCT116 compared with that in other colon cancer cell lines. Prx6 regulates the EMT signaling pathway by modulating EMT-related transcriptional repressors and mesenchymal genes in HCT116 colon cancer cells. Under the Prx6-overexpressed condition, HCT116 cells proliferation increased significantly. Moreover, the HCT116 cells proliferation decreased in the siPrx6-treated cells. Eleven days after HCT116 cell injection, Prx6 was overexpressed in the HCT116-injected mice, and the tumor volume increased significantly compared with that of the control mice. Furthermore, Prx6 regulates EMT signaling through p38 phosphorylation in colon cancer cells.

Conclusion

We suggested that Prx6 regulates EMT signaling pathway through p38 phosphorylation modulation in HCT116 colon cancer cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40709-021-00153-6.

Redox regulation of DUBs and its therapeutic implications in cancer

Reactive oxygen species (ROS) act as a double-edged sword in cancer, where low levels of ROS are beneficial but excessive accumulation leads to cancer progression. Elevated levels of ROS in cancer are counteracted by the antioxidant defense system. An imbalance between ROS generation and the antioxidant system alters gene expression and cellular signaling, leading to cancer progression or death. Post-translational modifications, such as ubiquitination, phosphorylation, and SUMOylation, play a critical role in the maintenance of ROS homeostasis by controlling ROS production and clearance. Recent evidence suggests that deubiquitinating enzymes (DUBs)-mediated ubiquitin removal from substrates is regulated by ROS. ROS-mediated oxidation of the catalytic cysteine (Cys) of DUBs, leading to their reversible inactivation, has emerged as a key mechanism regulating DUB-controlled cellular events. A better understanding of the mechanism by which DUBs are susceptible to ROS and exploring the ways to utilize ROS to pharmacologically modulate DUB-mediated signaling pathways might provide new insight for anticancer therapeutics. This review assesses the recent findings regarding ROS-mediated signaling in cancers, emphasizes DUB regulation by oxidation, highlights the relevant recent findings, and proposes directions of future research based on the ROS-induced modifications of DUB activity.

Macrophage peroxiredoxin 5 deficiency promotes lung cancer progression via ROS-dependent M2-like polarization

Strategies for cancer treatment have traditionally focused on suppressing cancer cell behavior, but many recent studies have demonstrated that regulating the tumor microenvironment (TME) can also inhibit disease progression. Macrophages are major TME components, and the direction of phenotype polarization is known to regulate tumor behavior, with M2-like polarization promoting progression. It is also known that reactive oxygen species (ROS) in macrophages drive M2 polarization, and M2 polarization promote lung cancer progression. Lung cancer patients with lower expression of the antioxidant enzyme peroxiredoxin 5 (Prx5) demonstrate poorer survival. This study revealed that Prx5 deficiency in macrophages induced M2 macrophage polarization by lung cancer. We report that injection of lung cancer cells produced larger tumors in Prx5-deficit mice than wild-type mice independent of cancer cell Prx5 expression. Through co-culture with lung cancer cell lines, Prx5-deficient macrophages exhibited M2 polarization, and reduced expression levels of the M1-associated inflammatory factors iNOS, TNFα, and Il-1β. Moreover, these Prx5-deficient macrophages promoted the proliferation and migration of co-cultured lung cancer cells. Conversely, suppression of ROS generation by N-acetyl cysteine (NAC) inhibited the M2-like polarization of Prx5-deficient macrophages, increased expression levels of inflammatory factors, inhibited the proliferation and migration of co-cultured lung cancer cells, and suppressed tumor growth in mice. These findings suggest that blocking the M2 polarization of macrophages may promote lung cancer regression.

The sulfiredoxin-peroxiredoxin redox system regulates the stemness and survival of colon cancer stem cells

Cancer stem cells (CSCs) initiate tumor formation and are known to be resistant to chemotherapy. A metabolic alteration in CSCs plays a critical role in stemness and survival. However, the association between mitochondrial energy metabolism and the redox system remains undefined in colon CSCs. In this study, we assessed the role of the Sulfiredoxin-Peroxiredoxin (Srx-Prx) redox system and mitochondrial oxidative phosphorylation (OXPHOS) in maintaining the stemness and survival of colon CSCs. Notably, Srx contributed to the stability of PrxI, PrxII, and PrxIII proteins in colon CSCs. Increased Srx expression promoted the stemness and survival of CSCs and was important for the maintenance of the mitochondrial OXPHOS system. Furthermore, Nrf2 and FoxM1 led to OXPHOS activation and upregulated expression of Srx-Prx redox system-related genes. Therefore, the Nrf2/FoxM1-induced Srx-Prx redox system is a potential therapeutic target for eliminating CSCs in colon cancer.