Are peroxiredoxins tumor suppressors?

Comparative Analysis of Inhibitor Binding to Peroxiredoxins from Candidatus Liberibacter asiaticus and Its Host Citrus sinensis

The peroxiredoxins (Prxs), potential drug targets, constitute an important class of antioxidant enzymes present in both pathogen and their host. The comparative binding potential of inhibitors to Prxs from pathogen and host could be an important step in drug development against pathogens. Huanglongbing (HLB) is a most devastating disease of citrus caused by Candidatus Liberibacter asiaticus (CLa). In this study, the binding of conoidin-A (conoidin) and celastrol inhibitor molecules to peroxiredoxin of bacterioferritin comigratory protein family from CLa (CLaBCP) and its host plant peroxiredoxin from Citrus sinensis (CsPrx) was assessed. The CLaBCP has a lower specific activity than CsPrx and is efficiently inhibited by conoidin and celastrol molecules. The biophysical studies showed conformational changes and significant thermal stability of CLaBCP in the presence of inhibitor molecules as compared to CsPrx. The surface plasmon resonance (SPR) studies revealed that the conoidin and celastrol inhibitor molecules have a strong binding affinity (KD) with CLaBCP at 33.0 µM, and 18.5 µM as compared to CsPrx at 52.0 µM and 61.6 µM, respectively. The docked complexes of inhibitor molecules showed more structural stability of CLaBCP as compared to CsPrx during the run of molecular dynamics-based simulations for 100 ns. The present study suggests that the conoidin and celastrol molecules can be exploited as potential inhibitor molecules against the CLa to manage the HLB disease.

Reactive Oxygen Species Modulation in the Current Landscape of Anticancer Therapies

Significance: Reactive oxygen species (ROS) are generated during mitochondrial oxidative metabolism, and are tightly controlled through homeostatic mechanisms to maintain intracellular redox, regulating growth and proliferation in healthy cells. However, ROS production is perturbed in cancers where abnormal accumulation of ROS leads to oxidative stress and genomic instability, triggering oncogenic signaling pathways on one hand, while increasing oxidative damage and triggering ROS-dependent death signaling on the other. Recent Advances: Our review illuminates how critical interactions between ROS and oncogenic signaling, the tumor microenvironment, and DNA damage response (DDR) pathways have led to interest in ROS modulation as a means of enhancing existing anticancer strategies and developing new therapeutic opportunities. Critical Issues: ROS equilibrium exists via a delicate balance of pro-oxidant and antioxidant species within cells. "Antioxidant" approaches have been explored mainly in the form of chemoprevention, but there is insufficient evidence to advocate its routine application. More progress has been made via the "pro-oxidant" approach of targeting cancer vulnerabilities and inducing oxidative stress. Various therapeutic modalities have employed this approach, including direct ROS-inducing agents, chemotherapy, targeted therapies, DDR therapies, radiotherapy, and immunotherapy. Finally, emerging delivery systems such as "nanosensitizers" as radiotherapy enhancers are currently in development. Future Directions: While approaches designed to induce ROS have shown considerable promise in selectively targeting cancer cells and dealing with resistance to conventional therapies, most are still in early phases of development and challenges remain. Further research should endeavor to refine treatment strategies, optimize drug combinations, and identify predictive biomarkers of ROS-based cancer therapies.

Disarib, a Specific BCL2 Inhibitor, Induces Apoptosis in Triple-Negative Breast Cancer Cells and Impedes Tumour Progression in Xenografts by Altering Mitochondria-Associated Processes

Targeted cancer therapy aims to disrupt the functions of proteins that regulate cancer progression, mainly by using small molecule inhibitors (SMIs). SMIs exert their effect by modulating signalling pathways, organelle integrity, chromatin components, and several biosynthetic processes essential for cell division and survival. Antiapoptotic protein BCL2 is highly upregulated in many cancers compared with normal cells, making it an ideal target for cancer therapy. Around 75% of primary breast cancers overexpress BCL2, providing an opportunity to explore BCL2 inhibitors as a therapeutic option. Disarib is an SMI that has been developed as a selective BCL2 inhibitor. Disarib works by disrupting BCL2-BAK interaction and activating intrinsic apoptotic pathways in leukemic cells while sparing normal cells. We investigated the effects of Disarib, a BCL2 specific inhibitor, on breast cancer cells and xenografts. Cytotoxicity and fluorometric assays revealed that Disarib induced cell death by increasing reactive oxygen species and activating intrinsic apoptotic pathways in Triple-Negative Breast Cancer cells (MDA-MB-231 and MDA-MB-468). Disarib also affected the colony-forming properties of these cells. MDA-MB-231- and MDA-MB-468-derived xenografts showed a significant reduction in tumours upon Disarib treatment. Through the transcriptomics approach, we also explored the influence of BCL2 inhibitors on energy metabolism, mitochondrial dynamics, and epithelial-to-mesenchymal transition (EMT). Mitochondrial dynamics and glucose metabolism mainly regulate energy metabolism. The change in energetics regulates tumour growth through epithelial-mesenchymal transition, and angiogenesis. RNA sequencing (RNAseq) analysis revealed that BCL2 inhibitors ABT-199 and Disarib maintain Oxphos levels in MDA-MB-231. However, key glycolytic genes were significantly downregulated. Mitochondrial fission genes were seen to be downregulated both in RNAseq data and semi quantitative real time polymerase chain reaction (qRTPCR) in Disarib-treated TNBC cells and xenografts. Lastly, Disarib inhibited wound healing and epithelial-to-mesenchymal transition. This study showed that Disarib disrupts mitochondrial function, activates the intrinsic apoptotic pathway in breast cancer, and inhibits epithelial-to-mesenchymal transition both in vitro and in vivo. These findings highlight Disarib's potential as a multifaceted therapeutic strategy for patients with Triple-Negative Breast Cancer.

Modeling Melanoma Heterogeneity In Vitro: Redox, Resistance and Pigmentation Profiles

Microenvironment and transcriptional plasticity generate subpopulations within the tumor, and the use of BRAF inhibitors (BRAFis) contributes to the rise and selection of resistant clones. We stochastically isolated subpopulations (C1, C2, and C3) from naïve melanoma and found that the clones demonstrated distinct morphology, phenotypic, and functional profiles: C1 was less proliferative, more migratory and invasive, less sensitive to BRAFis, less dependent on OXPHOS, more sensitive to oxidative stress, and less pigmented; C2 was more proliferative, less migratory and invasive, more sensitive to BRAFis, less sensitive to oxidative stress, and more pigmented; and C3 was less proliferative, more migratory and invasive, less sensitive to BRAFis, more dependent on OXPHOS, more sensitive to oxidative stress, and more pigmented. Hydrogen peroxide plays a central role in oxidative stress and cell signaling, and PRDXs are one of its main consumers. The intrinsically resistant C1 and C3 clones had lower MITF, PGC-1α, and PRDX1 expression, while C1 had higher AXL and decreased pigmentation markers, linking PRDX1 to clonal heterogeneity and resistance. PRDX2 is depleted in acquired BRAFi-resistant cells and acts as a redox sensor. Our results illustrate that decreased pigmentation markers are related to therapy resistance and decreased antioxidant defense.

ACA-28, an ERK MAPK Signaling Modulator, Exerts Anticancer Activity through ROS Induction in Melanoma and Pancreatic Cancer Cells

The extracellular signal-regulated kinase (ERK) MAPK pathway is dysregulated in various human cancers and is considered an attractive therapeutic target for cancer. Therefore, several inhibitors of this pathway are being developed, and some are already used in the clinic. We have previously identified an anticancer compound, ACA-28, with a unique property to preferentially induce ERK-dependent apoptosis in melanoma cells. To comprehensively understand the biological cellular impact induced by ACA-28, we performed a global gene expression analysis of human melanoma SK-MEL-28 cells exposed to ACA-28 using a DNA microarray. The transcriptome analysis identified nuclear factor erythroid 2-related factor 2 (Nrf2), a master transcription factor that combats oxidative stress, as the most upregulated genetic pathway after ACA-28 treatment. Consistently, ACA-28 showed properties to increase the levels of reactive oxygen species (ROS) as well as Nrf2 protein, which is normally repressed by proteasomal degradation and activated in response to oxidative stresses. Furthermore, the ROS scavenger N-acetyl cysteine significantly attenuated the anticancer activity of ACA-28. Thus, ACA-28 activates Nrf2 signaling and exerts anticancer activity partly via its ROS-stimulating property. Interestingly, human A549 cancer cells with constitutively high levels of Nrf2 protein showed resistance to ACA-28, as compared with SK-MEL-28. Transient overexpression of Nrf2 also increased the resistance of cells to ACA-28, while knockdown of Nrf2 exerted the opposite effect. Thus, upregulation of Nrf2 signaling protects cancer cells from ACA-28-mediated cell death. Notably, the Nrf2 inhibitor ML385 substantially enhanced the cell death-inducing property of ACA-28 in pancreatic cancer cells, T3M4 and PANC-1. Our data suggest that Nrf2 plays a key role in determining cancer cell susceptibility to ACA-28 and provides a novel strategy for cancer therapy to combine the Nrf2 inhibitor and ACA-28.

Marine Natural Compound (Neviotin A) Displays Anticancer Efficacy by Triggering Transcriptomic Alterations and Cell Death in MCF-7 Cells

We investigated the anticancer mechanism of a chloroform extract of marine sponge (Haliclona fascigera) (sample C) in human breast adenocarcinoma (MCF-7) cells. Viability analysis using MTT and neutral red uptake (NRU) assays showed that sample C exposure decreased the proliferation of cells. Flow cytometric data exhibited reactive oxygen species (ROS), nitric oxide (NO), dysfunction of mitochondrial potential, and apoptosis in sample C-treated MCF-7 cells. A qPCR array of sample C-treated MCF-7 cells showed crosstalk between different pathways of apoptosis, especially BIRC5, BCL2L2, and TNFRSF1A genes. Immunofluorescence analysis affirmed the localization of p53, bax, bcl2, MAPKPK2, PARP-1, and caspase-3 proteins in exposed cells. Bioassay-guided fractionation of sample C revealed Neviotin A as the most active compound triggering maximum cell death in MCF-7, indicating its pharmacological potency for the development of a drug for the treatment of human breast cancer.

Effectiveness of Nonfunctionalized Graphene Oxide Nanolayers as Nanomedicine against Colon, Cervical, and Breast Cancer Cells

Recent studies in nanomedicine have intensively explored the prospective applications of surface-tailored graphene oxide (GO) as anticancer entity. However, the efficacy of nonfunctionalized graphene oxide nanolayers (GRO-NLs) as an anticancer agent is less explored. In this study, we report the synthesis of GRO-NLs and their in vitro anticancer potential in breast (MCF-7), colon (HT-29), and cervical (HeLa) cancer cells. GRO-NLs-treated HT-29, HeLa, and MCF-7 cells showed cytotoxicity in the MTT and NRU assays via defects in mitochondrial functions and lysosomal activity. HT-29, HeLa, and MCF-7 cells treated with GRO-NLs exhibited substantial elevations in ROS, disturbances of the mitochondrial membrane potential, an influx of Ca2+, and apoptosis. The qPCR quantification showed the upregulation of caspase 3, caspase 9, bax, and SOD1 genes in GRO-NLs-treated cells. Western blotting showed the depletion of P21, P53, and CDC25C proteins in the above cancer cell lines after GRO-NLs treatment, indicating its function as a mutagen to induce mutation in the P53 gene, thereby affecting P53 protein and downstream effectors P21 and CDC25C. In addition, there may be a mechanism other than P53 mutation that controls P53 dysfunction. We conclude that nonfunctionalized GRO-NLs exhibit prospective biomedical application as a putative anticancer entity against colon, cervical, and breast cancers.

p66Shc in Cardiovascular Pathology

p66Shc is a widely expressed protein that governs a variety of cardiovascular pathologies by generating, and exacerbating, pro-apoptotic ROS signals. Here, we review p66Shc’s connections to reactive oxygen species, expression, localization, and discuss p66Shc signaling and mitochondrial functions. Emphasis is placed on recent p66Shc mitochondrial function discoveries including structure/function relationships, ROS identity and regulation, mechanistic insights, and how p66Shc-cyt c interactions can influence p66Shc mitochondrial function. Based on recent findings, a new p66Shc mitochondrial function model is also put forth wherein p66Shc acts as a rheostat that can promote or antagonize apoptosis. A discussion of how the revised p66Shc model fits previous findings in p66Shc-mediated cardiovascular pathology follows.

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.

Eriocitrin, a dietary flavonoid suppressed cell proliferation, induced apoptosis through modulation of JAK2/STAT3 and JNK/p38 MAPKs signaling pathway in MCF-7 cells

Eriocitrin, a lemons flavanone, exhibits several biological properties, antiproliferative, and proapoptotic effects. However, its molecular mechanical action is not entirely clarified. Oxidative stress causes abnormal stimulation of signal transducer and activator of transcription 3 (STAT3) and c-Jun NH2-terminal kinase (JNK), p38 mitogen-activated protein kinases (MAPKs) signaling has been strongly connected with the ruling of cell survival and apoptosis of cancer cells. Herein, we investigated an antiproliferative and proapoptotic effect that Eriocitrin modulates STAT3/MAPKs signaling activation in MCF-7 cells. We noticed that Eriocitrin strongly enhances reactive oxygen species (ROS) generation, alteration of mitochondrial outer membrane potential, and enhances apoptotic morphological changes. Furthermore, Eriocitrin suppressed STAT3 phosphorylation via inhibiting an upstream molecule of JAK2 and Src kinase activation, thereby blocking STAT3 nuclear translocation. Similarly, Eriocitrin causes oxidative stress-mediated JNK/p38 MAPK signaling activation. We confirmed that Eriocitrin induced ROS-mediated apoptosis inhibited by the antioxidant substance of N-acetylcysteine. Eriocitrin induced apoptosis via suppression of STAT3 signaling regulated proteins, activating proapoptotic factors Bax, caspase 7, 8, 9 and suppressing Bcl-2, Bcl-x expression in MCF-7 cells. Overall, these results evidenced that Eriocitrin can affect multiple signaling events associated with tumorigenesis. From this evidence, Eriocitrin, a novel chemotherapeutic agent, can be used to treat breast cancer.

Integrative analysis the characterization of peroxiredoxins in pan-cancer

Background

Peroxiredoxins (PRDXs) are an antioxidant enzymes protein family involved in several biological functions such as differentiation, cell growth. In addition, previous studies report that PRDXs play critical roles in the occurrence and development of carcinomas. However, few studies have conducted systematic analysis of PRDXs in cancers. Therefore, the present study sought to explore the molecular characteristics and potential clinical significance of PRDX family members in pan cancer and further validate the function of PRDX6 in bladder urothelial carcinoma (BLCA).

Methods

A comprehensive analysis of PRDXs in 33 types of cancer was performed based on the TCGA database. This involved an analysis of mRNA expression profiles, genetic alterations, methylation, prognostic values, potential biological pathways and target drugs. Moreover, both the gain and loss of function strategies were used to assess the importance and mechanism of PRDX6 in the cell cycle of BLCA.

Result

Analysis showed abnormal expression of PRDX1-6 in several types of cancer compared to normal tissues. Univariate Cox proportional hazard regression analysis showed that expression levels of PRDX1, PRDX4 and PRDX6 were mostly associated with poor survival of OS, DSS and PFI, and PRDX2 and PRDX3 with favorable survival. In addition, the expression of PRDX genes were positively correlated with CNV and negatively with methylation. Moreover, analysis based on PharmacoDB dataset showed that the augmented levels of PRDX1, PRDX3 and PRDX6 were significantly correlated with EGFR/VEGFR inhibitor drugs. Furthermore, knocking down of PRDX6 inhibited growth of cancer cells through the JAK2-STAT3 in bladder cell lines.

Conclusions

PRDXs are potential biomarkers and therapeutic targets for several carcinomas, especially for BLCA. In addition, PRDX6 could regulate proliferation of cancer cell via JAK2-STAT3 pathway and involve into the process of cell cycle in BLCA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02064-x.

Pink1/PARK2/mROS-Dependent Mitophagy Initiates the Sensitization of Cancer Cells to Radiation

Autophagy plays a double-edged sword for cancer; particularly, mitophagy plays important roles in the selective degradation of damaged mitochondria. However, whether mitophagy is involved in killing effects of tumor cells by ionizing radiation (IR) and its underlying mechanism remain elusive. The purpose is to evaluate the effects of mitochondrial ROS (mROS) on autophagy after IR; furthermore, we hypothesized that KillerRed (KR) targeting mitochondria could induce mROS generation, subsequent mitochondrial depolarization, accumulation of Pink1, and recruitment of PARK2 to promote the mitophagy. Thereby, we would achieve a new strategy to enhance mROS accumulation and clarify the roles and mechanisms of radiosensitization by KR and IR. Our data demonstrated that IR might cause autophagy of both MCF-7 and HeLa cells, which is related to mitochondria and mROS, and the ROS scavenger N-acetylcysteine (NAC) could reduce the effects. Based on the theory, mitochondrial targeting vector sterile α- and HEAT/armadillo motif-containing protein 1- (Sarm1-) mtKR has been successfully constructed, and we found that ROS levels have significantly increased after light exposure. Furthermore, mitochondrial depolarization of HeLa cells was triggered, such as the decrease of Na⁺K⁺ ATPase, Ca²⁺Mg²⁺ ATPase, and mitochondrial respiratory complex I and III activities, and mitochondrial membrane potential (MMP) has significantly decreased, and voltage-dependent anion channel 1 (VDAC1) protein has significantly increased in the mitochondria. Additionally, HeLa cell proliferation was obviously inhibited, and the cell autophagic rates dramatically increased, which referred to the regulation of the Pink1/PARK2 pathway. These results indicated that mitophagy induced by mROS can initiate the sensitization of cancer cells to IR and might be regulated by the Pink1/PARK2 pathway.

Suppression of mitochondrial ROS by prohibitin drives glioblastoma progression and therapeutic resistance

Low levels of reactive oxygen species (ROS) are crucial for maintaining cancer stem cells (CSCs) and their ability to resist therapy, but the ROS regulatory mechanisms in CSCs remains to be explored. Here, we discover that prohibitin (PHB) specifically regulates mitochondrial ROS production in glioma stem-like cells (GSCs) and facilitates GSC radiotherapeutic resistance. We find that PHB is upregulated in GSCs and is associated with malignant gliomas progression and poor prognosis. PHB binds to peroxiredoxin3 (PRDX3), a mitochondrion-specific peroxidase, and stabilizes PRDX3 protein through the ubiquitin-proteasome pathway. Knockout of PHB dramatically elevates ROS levels, thereby inhibiting GSC self-renewal. Importantly, deletion or pharmacological inhibition of PHB potently slows tumor growth and sensitizes tumors to radiotherapy, thus providing significant survival benefits in GSC-derived orthotopic tumors and glioblastoma patient-derived xenografts. These results reveal a selective role of PHB in mitochondrial ROS regulation in GSCs and suggest that targeting PHB improves radiotherapeutic efficacy in glioblastoma.

How ROS levels are regulated in cancer stem cells and their contribution to cancer resistance is currently not clear. Here, the authors show that prohibitin regulates mitochondrial ROS production stabilizing the peroxidase PRDX3 and this accounts for radiotherapy resistance in glioma stem-like cells.

Regulatory function of peroxiredoxin I on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung cancer development

Smoking is a major cause of lung cancer, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is one of the most important carcinogens in cigarette smoke. NNK modulates the expression of peroxiredoxin (Prdx) I in lung cancer. Prdx1 is upregulated in lung squamous cell carcinoma and lung adenocarcinoma, and considered a potential biomarker for lung cancer. The current article reviewed the role and regulatory mechanisms of Prdx1 in NNK-induced lung cancer cells. Prdx1 protects erythrocytes and DNA from NNK-induced oxidative damage, prevents malignant transformation of cells and promotes cytotoxicity of natural killer cells, hence suppressing tumor formation. In addition, Prdx1 has the ability to prevent NNK-induced lung tumor metabolic activity and generation of large amount of reactive oxygen species (ROS) and ROS-induced apoptosis, thus promoting tumor cell survival. In contrast to this, Prdx1, together with NNK, can promote the epithelial-mesenchymal transition and migration of lung tumor cells. The signaling pathways associated with NNK and Prdx1 in lung cancer cells have been discussed in present review; however, numerous potential pathways are yet to be studied. To develop novel methods for treating NNK-induced lung cancer, and improve the survival rate of patients with lung cancer, further research is needed to understand the complete mechanism associated with NNK.

Free Radicals as a Double-Edged Sword: The Cancer Preventive and Therapeutic Roles of Curcumin

Free radicals, generally composed of reactive oxygen species (ROS) and reactive nitrogen species (RNS), are generated in the body by various endogenous and exogenous systems. The overproduction of free radicals is known to cause several chronic diseases including cancer. However, increased production of free radicals by chemotherapeutic drugs is also associated with apoptosis in cancer cells, indicating the dual nature of free radicals. Among various natural compounds, curcumin manifests as an antioxidant in normal cells that helps in the prevention of carcinogenesis. It also acts as a prooxidant in cancer cells and is associated with inducing apoptosis. Curcumin quenches free radicals, induces antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase), and upregulates antioxidative protein markers-Nrf2 and HO-1 that lead to the suppression of cellular oxidative stress. In cancer cells, curcumin aggressively increases ROS that results in DNA damage and subsequently cancer cell death. It also sensitizes drug-resistant cancer cells and increases the anticancer effects of chemotherapeutic drugs. Thus, curcumin shows beneficial effects in prevention, treatment and chemosensitization of cancer cells. In this review, we will discuss the dual role of free radicals as well as the chemopreventive and chemotherapeutic effects of curcumin and its analogues against cancer.

Overexpression and biological function of PRDX6 in human cervical cancer

Background: Our previous study demonstrated that the peroxiredoxin 6 (PRDX6) protein was downregulated in squamous cervical cancer samples after neoadjuvant chemotherapy compared with the expression level before chemotherapy. However, the effect of PRDX6 on the biological behavior of cervical cancer is still uncertain. Thus, the purpose of this study was to explore the functional impacts of PRDX6 gene on the biological behavior of cervical squamous cancer cells.

Methods: An immunofluorescence assay was applied to evaluate the expression difference of PRDX6 between cervical cancer tissue and normal cervical tissue samples. A lentivirus was used to upregulate and downregulate PRDX6 expression in SiHa cells. Furthermore, the role of PRDX6 on cell proliferation, apoptosis, migration and invasion was evaluated. Additionally, the effect of PRDX6 on the progression of the cervical cancer was investigated via a xenograft model in BALB/c nude mice that either overexpressed or underexpressed PRDX6.

Results: The expression of PRDX6 was generally increased in cervical cancer tissues. Furthermore, the overexpression of PRDX6 stimulated the proliferation, migration and invasion of cervical squamous cancer cells, and suppressed cell apoptosis. The opposite results were also obtained after successful knockdown of PRDX6. In addition, the overexpression of PRDX6 significantly promoted the growth of cervical carcinoma in vivo.

Conclusions: PRDX6 promoted the proliferation, migration and invasion, and inhibited apoptosis in cervical cancer cells, indicating that PRDX6 is an important promoter of cervical cancer tumorigenicity.

Up-regulation of peroxiredoxin-1 promotes cell proliferation and metastasis and inhibits apoptosis in cervical cancer

Objective: To investigate the effect of peroxiredoxin 1 (PRDX1) on the biological behavior of cervical cancer cells and the possible mechanism.

Materials and methods: The expression of PRDX1 in human cervical cancer tissues and adjacent non-tumor tissues were detected by immunohistochemistry (IHC). Lentivirus containing PRDX1-cDNA or shRNA against PRDX1 was constructed to overexpress or knockdown PRDX1 in SiHa cervical cancer cells. Cell proliferation was tested by CCK-8 and BrdU incorporation assay and cell apoptosis was evaluated by AnnexinV-PE /7AAD assay. Scratch wound and transwell invasion assay were used to test migration and invasion activity after PRDX1 was overexpressed or suppressed. Furthermore, the effect of PRDX1 on cell proliferation and apoptosis was also studied using a xenograft model of nude mice.

Results: The expression of PRDX1 protein was significantly up-regulated in the tumor tissues compared with the paired adjacent non-tumor tissues. Meanwhile, PRDX1 overexpression was associated with tumor stage, lymphatic metastasis and differentiation. Overexpression of PRDX1 significantly promoted proliferation and inhibited apoptosis by increasing the expression of Nanog, proliferating cell nuclear antigen (PCNA), B-cell lymphoma-2 (Bcl-2) and downregulating the expression of Bcl2-associated X protein (BAX) in SiHa cervical cancer cells. Moreover, PRDX1 overexpression increased invasion and migration of SiHa cervical cancer cells via up-regulating the expression of Snail and matrix metalloprotein 9 (MMP-9) and down-regulating the expression of E-cadherin. Knockdown of PRDX1 resulted in the opposite results. The role of PRDX1 in promoting SiHa cervical cancer cell proliferation and inhibiting apoptosis has also been confirmed in vivo in a mouse xenograft model.

Conclusions: PRDX1 promoted cell proliferation, migration, and invasion and suppressed apoptosis of cervical cancer possibly via regulating the expression of related protein.

Understanding of ROS-Inducing Strategy in Anticancer Therapy

Redox homeostasis is essential for the maintenance of diverse cellular processes. Cancer cells have higher levels of reactive oxygen species (ROS) than normal cells as a result of hypermetabolism, but the redox balance is maintained in cancer cells due to their marked antioxidant capacity. Recently, anticancer therapies that induce oxidative stress by increasing ROS and/or inhibiting antioxidant processes have received significant attention. The acceleration of accumulative ROS disrupts redox homeostasis and causes severe damage in cancer cells. In this review, we describe ROS-inducing cancer therapy and the anticancer mechanism employed by prooxidative agents. To understand the comprehensive biological response to certain prooxidative anticancer drugs such as 2-methoxyestradiol, buthionine sulfoximine, cisplatin, doxorubicin, imexon, and motexafin gadolinium, we propose and visualize the drug-gene, drug-cell process, and drug-disease interactions involved in oxidative stress induction and antioxidant process inhibition as well as specific side effects of these drugs using pathway analysis with a big data-based text-mining approach. Our review will be helpful to improve the therapeutic effects of anticancer drugs by providing information about biological changes that occur in response to prooxidants. For future directions, there is still a need for pharmacogenomic studies on prooxidative agents as well as the molecular mechanisms underlying the effects of the prooxidants and/or antioxidant-inhibitor agents for effective anticancer therapy through selective killing of cancer cells.

Prdx2 Upregulation Promotes the Growth and Survival of Gastric Cancer Cells

Peroxiredoxins (Prdxs) play important roles in cell proliferation, differentiation, and the mediation of intracellular signalling pathways. Prdx2 is an important member of the peroxiredoxin family and is upregulated in many cancers. Until now, the biological functions of Prdx2 in gastric cancer have not been completely understood, and the underlying mechanisms remain elusive. The aim of this study was to identify the role of Prdx2 on the growth of gastric cancer cells and the underlying mechanisms. We demonstrated that Prdx2 was highly expressed in gastric cancer tissues and cell lines and that the over-expression of Prdx2 correlated with the progression of gastric cancer. Further, Prdx2 was silenced with a specific, lentiviral vector-mediated shRNA, and this suppressed the proliferation of gastric cancer cells and promoted the apoptosis of gastric cancer cells. Finally, the knockdown of Prdx2 contributed to the attenuated gastric cancer growth in BALB/c nude mice. In conclusion, these findings demonstrate that Prdx2 may participate in the carcinogenesis and development of gastric cancer.

Role of Reactive Oxygen Species in Cancer Progression: Molecular Mechanisms and Recent Advancements

Reactive oxygen species (ROS) play a pivotal role in biological processes and continuous ROS production in normal cells is controlled by the appropriate regulation between the silver lining of low and high ROS concentration mediated effects. Interestingly, ROS also dynamically influences the tumor microenvironment and is known to initiate cancer angiogenesis, metastasis, and survival at different concentrations. At moderate concentration, ROS activates the cancer cell survival signaling cascade involving mitogen-activated protein kinase/extracellular signal-regulated protein kinases 1/2 (MAPK/ERK1/2), p38, c-Jun N-terminal kinase (JNK), and phosphoinositide-3-kinase/ protein kinase B (PI3K/Akt), which in turn activate the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), matrix metalloproteinases (MMPs), and vascular endothelial growth factor (VEGF). At high concentrations, ROS can cause cancer cell apoptosis. Hence, it critically depends upon the ROS levels, to either augment tumorigenesis or lead to apoptosis. The major issue is targeting the dual actions of ROS effectively with respect to the concentration bias, which needs to be monitored carefully to impede tumor angiogenesis and metastasis for ROS to serve as potential therapeutic targets exogenously/endogenously. Overall, additional research is required to comprehend the potential of ROS as an effective anti-tumor modality and therapeutic target for treating malignancies.

Catalysis of Peroxide Reduction by Fast Reacting Protein Thiols

Life on Earth evolved in the presence of hydrogen peroxide, and other peroxides also emerged before and with the rise of aerobic metabolism. They were considered only as toxic byproducts for many years. Nowadays, peroxides are also regarded as metabolic products that play essential physiological cellular roles. Organisms have developed efficient mechanisms to metabolize peroxides, mostly based on two kinds of redox chemistry, catalases/peroxidases that depend on the heme prosthetic group to afford peroxide reduction and thiol-based peroxidases that support their redox activities on specialized fast reacting cysteine/selenocysteine (Cys/Sec) residues. Among the last group, glutathione peroxidases (GPxs) and peroxiredoxins (Prxs) are the most widespread and abundant families, and they are the leitmotif of this review. After presenting the properties and roles of different peroxides in biology, we discuss the chemical mechanisms of peroxide reduction by low molecular weight thiols, Prxs, GPxs, and other thiol-based peroxidases. Special attention is paid to the catalytic properties of Prxs and also to the importance and comparative outlook of the properties of Sec and its role in GPxs. To finish, we describe and discuss the current views on the activities of thiol-based peroxidases in peroxide-mediated redox signaling processes.

The Association of Peroxiredoxin 4 with the Initiation and Progression of Hepatocellular Carcinoma

AIMS

Peroxiredoxin 4 (PRDX4) is a member of the peroxiredoxin family of antioxidant enzymes. Previously, we reported that PRDX4 can restrain the initiation and progression of nonalcoholic steatohepatitis by reducing local and systemic reactive oxygen species (ROS) levels. Oxidative stress is recognized as a key factor in hepatocarcinogenesis, and a high ROS level has also been found in hepatocellular carcinoma (HCC). Here, our aim is to investigate roles of PRDX4 in the initiation and progression of HCC.

RESULTS

In this study, for hepatocarcinogenesis, wild-type (WT), PRDX4 knockout (PRDX4^-/y), and human PRDX4 transgenic (hPRDX4^+/+) mice were given a weekly intraperitoneal injection of diethylnitrosamine for 25 weeks. The HCC incidence was higher in PRDX4^-/y mice than in WT or hPRDX4^+/+ mice. Intrahepatic and circulating oxidative stress and inflammatory cell infiltration in the liver were obviously decreased in hPRDX4^+/+ mice, compared with WT mice. Furthermore, in our cohort study, human HCC specimens with low expression of PRDX4 had higher ROS levels and a highly malignant phenotype, which was associated with a reduced overall survival, compared with those with high PRDX4 expression. However, in human HCC cell lines, PRDX4 knockdown led to a rapidly increased intracellular ROS level and suppressed cell proliferation, inducing cell death. Innovation and Conclusion: Our results clearly indicate that PRDX4 has an inhibitory effect in the initiation of HCC, but a dual (inhibitory or promoting) role in the progression of HCC, suggesting the potential utility of PRDX4 activators or inhibitors as therapy for different stages and phenotypes of HCC.

Peroxiredoxin2 downregulation enhances hepatocellular carcinoma proliferation and migration, and is associated with unfavorable prognosis in patients

It has been revealed by our previous proteomic study that the expression profile is different between well-differentiated and poorly differentiated hepatocellular carcinoma (HCC). Among those differently expressed proteins, peroxiredoxin2 (PRDX2) was our protein of interest. The present study aimed to further investigate the value of PRDX2 as a prognostic factor in HCC. Tissue microarrays were used to investigate the expression difference between HCC tissues and their adjacent normal liver tissues. The expression of PRDX2 at both mRNA and protein levels was examined by q-RT-PCR, western blotting and immunohistochemical assessment in HCC tissues and cell line HCCLM3. Silencing of PRDX2 in HCCLM3 was achieved usingpGMLV-SC1 lentiviral vectors. Cell Counting Kit-8 (CCK-8) and Transwell migration assays were used to assess cell proliferation and migration, respectively. Categorical variables were assessed using the Chi-square test, and ordinal variables were examined using the Mann-Whitney U test. The difference of continuous variables between groups were compared with t-tests. The Kaplan-Meier method was used to calculate the overall survival (OS) and disease-free survival (DFS) of patients, and the log-rank test was used to analyze the differences between groups. The results revealed that the expression of PRDX2 was decreased at both the mRNA and protein levels in an HCC cell line compared to that of a normal human liver cell line. PRDX2 protein expression levels were significantly downregulated in HCC tissues and were positively linked to overall survival (OS) and disease-free survival (DFS) of HCC patients. Patients with high PRDX2 expression levels had longer OS and DFS times than those with lower PRDX2 expression. Silencing of PRDX2 in the HCC cell line HCCLM3 promoted cancer cell proliferation and migration. Our findings indicated that PRDX2 may play an important role in HCC development; PRDX2 may serve as a useful prognostic factor and a therapeutic target.

Global analysis of erythroid cells redox status reveals the involvement of Prdx1 and Prdx2 in the severity of beta thalassemia

β-thalassemia is a worldwide distributed monogenic red cell disorder, characterized by an absent or reduced beta globin chain synthesis. The unbalance of alpha-gamma chain and the presence of pathological free iron promote severe oxidative damage, playing crucial a role in erythrocyte hemolysis, exacerbating ineffective erythropoiesis and decreasing the lifespan of red blood cells (RBC). Catalase, glutathione peroxidase and peroxiredoxins act together to protect RBCs from hydrogen peroxide insult. Among them, peroxiredoxins stand out for their overall abundance and reactivity. In RBCs, Prdx2 is the third most abundant protein, although Prdxs 1 and 6 isoforms are also found in lower amounts. Despite the importance of these enzymes, Prdx1 and Prdx2 may have their peroxidase activity inactivated by hyperoxidation at high hydroperoxide concentrations, which also promotes the molecular chaperone activity of these proteins. Some studies have demonstrated the importance of Prdx1 and Prdx2 for the development and maintenance of erythrocytes in hemolytic anemia. Now, we performed a global analysis comparatively evaluating the expression profile of several antioxidant enzymes and their physiological reducing agents in patients with beta thalassemia intermedia (BTI) and healthy individuals. Furthermore, increased levels of ROS were observed not only in RBC, but also in neutrophils and mononuclear cells of BTI patients. The level of transcripts and the protein content of Prx1 were increased in reticulocyte and RBCs of BTI patients and the protein content was also found to be higher when compared to beta thalassemia major (BTM), suggesting that this peroxidase could cooperate with Prx2 in the removal of H₂O₂. Furthermore, Prdx2 production is highly increased in RBCs of BTM patients that present high amounts of hyperoxidized species. A significant increase in the content of Trx1, Srx1 and Sod1 in RBCs of BTI patients suggested protective roles for these enzymes in BTI patients. Finally, the upregulation of Nrf2 and Keap1 transcription factors found in BTI patients may be involved in the regulation of the antioxidant enzymes analyzed in this work.

Piecing Together How Peroxiredoxins Maintain Genomic Stability

Peroxiredoxins, a highly conserved family of thiol oxidoreductases, play a key role in oxidant detoxification by partnering with the thioredoxin system to protect against oxidative stress. In addition to their peroxidase activity, certain types of peroxiredoxins possess other biochemical activities, including assistance in preventing protein aggregation upon exposure to high levels of oxidants (molecular chaperone activity), and the transduction of redox signals to downstream proteins (redox switch activity). Mice lacking the peroxiredoxin Prdx1 exhibit an increased incidence of tumor formation, whereas baker's yeast (Saccharomyces cerevisiae) lacking the orthologous peroxiredoxin Tsa1 exhibit a mutator phenotype. Collectively, these findings suggest a potential link between peroxiredoxins, control of genomic stability, and cancer etiology. Here, we examine the potential mechanisms through which Tsa1 lowers mutation rates, taking into account its diverse biochemical roles in oxidant defense, protein homeostasis, and redox signaling as well as its interplay with thioredoxin and thioredoxin substrates, including ribonucleotide reductase. More work is needed to clarify the nuanced mechanism(s) through which this highly conserved peroxidase influences genome stability, and to determine if this mechanism is similar across a range of species.

The Multifaceted Impact of Peroxiredoxins on Aging and Disease

SIGNIFICANCE

Peroxiredoxins (Prxs), a family of thiol-associated peroxidases, are purported to play a major role in sensing and managing hydrogen peroxide concentrations and transducing peroxide-derived signals. Recent Advances: Prxs can act as detoxifying factors and impart effects to cells that can be either sparing or suicidal. Advances have been made to address the qualitative changes in Prx function in response to quantitative changes in the signal level and to understand how Prx activity could be affected by their own substrates. Here we rationalize the basis for both positive and negative effects on signaling pathways and cell physiology, summarizing data from model organisms, including invertebrates.

CRITICAL ISSUES

Resolving the relationship between the promiscuous behavior of reactive oxygen species and the specificity of Prxs toward different targets in redox-sensitive signaling pathways is a key area of research. Attempts to understand Prx function and underlying mechanisms were conducted in vitro or in vivo under nonphysiological conditions, leaving the physiological relevance yet to be defined. Other issues: Why despite the high degree of homology and similarities in subcellular and tissue distribution between Prxs do they display differential effects on signaling? How is the specificity of post-translational protein modifications determined? Other than chaperone-like activity, how do hyperoxidized Prxs function?

FUTURE DIRECTIONS

Genetic models with mutated catalytic and resolving cysteines should be further exploited to dissect the functional significance of individual Prxs in their different states together with their alternative reducing partners. Such an analysis may then be extended to help identify Prx-specific targets.

Dual Roles of Oxidative Stress in Metal Carcinogenesis

It has been well established that environmental and occupational exposure to heavy metal causes cancer in several organs. Although the exact mechanism of heavy metal carcinogenesis remains elusive, metal-generated reactive oxygen species (ROS) are essential. ROS can play two roles in metal carcinogenesis; two stages in the process of metal carcinogenesis differ in the amounts of ROS activating a dual redox-mediated mechanism. In the early stage of metal carcinogenesis, ROS acts in an oncogenic role. However, in the late stage of metal carcinogenesis, ROS plays an antioncogenic role. Similarly, NF-E2-related factor 2 (Nrf2) also has two different roles, which makes it a key molecule for separating metal carcinogenesis into two different stages. In the early stage, inducible Nrf2 fights against elevated ROS to decrease cell transformation by its antioxidant protection property. In the late stage, constitutively activated Nrf2 manipulates reduced ROS to perform a comfortable environment for apoptosis resistance through an oncogenic role. Interestingly, a cunning carcinogenic mechanism takes advantage of the dual role of Nrf2 to implement the dual role of ROS through a series of redox adaption mechanisms. In this review, we discuss the paradox in the rationales behind the two opposite ROS roles and focus on their potential pharmacological application. The dual role of ROS represents a 'double-edged sword' with many possible novel ROS-mediated strategies in cancer therapy in metal carcinogenesis.

A Peroxidase Peroxiredoxin 1-Specific Redox Regulation of the Novel FOXO3 microRNA Target let-7

Precision in redox signaling is attained through posttranslational protein modifications such as oxidation of protein thiols. The peroxidase peroxiredoxin 1 (PRDX1) regulates signal transduction through changes in thiol oxidation of its cysteines. We demonstrate here that PRDX1 is a binding partner for the tumor suppressive transcription factor FOXO3 that directly regulates the FOXO3 stress response. Heightened oxidative stress evokes formation of disulfide-bound heterotrimers linking dimeric PRDX1 to monomeric FOXO3. Absence of PRDX1 enhances FOXO3 nuclear localization and transcription that are dependent on the presence of Cys31 or Cys150 within FOXO3. Notably, FOXO3-T32 phosphorylation is constitutively enhanced in these mutants, but nuclear translocation of mutant FOXO3 is restored with PI3K inhibition. Here we show that on H₂O₂ exposure, transcription of tumor suppressive miRNAs let-7b and let-7c is regulated by FOXO3 or PRDX1 expression levels and that let-7c is a novel target for FOXO3. Conjointly, inhibition of let-7 microRNAs increases let-7-phenotypes in PRDX1-deficient breast cancer cells. Altogether, these data ascertain the existence of an H₂O₂-sensitive PRDX1-FOXO3 signaling axis that fine tunes FOXO3 activity toward the transcription of gene targets in response to oxidative stress. Antioxid. Redox Signal. 28, 62-77.

New Challenges to Study Heterogeneity in Cancer Redox Metabolism

Reactive oxygen species (ROS) are important pathophysiological molecules involved in vital cellular processes. They are extremely harmful at high concentrations because they promote the generation of radicals and the oxidation of lipids, proteins, and nucleic acids, which can result in apoptosis. An imbalance of ROS and a disturbance of redox homeostasis are now recognized as a hallmark of complex diseases. Considering that ROS levels are significantly increased in cancer cells due to mitochondrial dysfunction, ROS metabolism has been targeted for the development of efficient treatment strategies, and antioxidants are used as potential chemotherapeutic drugs. However, initial ROS-focused clinical trials in which antioxidants were supplemented to patients provided inconsistent results, i.e., improved treatment or increased malignancy. These different outcomes may result from the highly heterogeneous redox responses of tumors in different patients. Hence, population-based treatment strategies are unsuitable and patient-tailored therapeutic approaches are required for the effective treatment of patients. Moreover, due to the crosstalk between ROS, reducing equivalents [e.g., NAD(P)H] and central metabolism, which is heterogeneous in cancer, finding the best therapeutic target requires the consideration of system-wide approaches that are capable of capturing the complex alterations observed in all of the associated pathways. Systems biology and engineering approaches may be employed to overcome these challenges, together with tools developed in personalized medicine. However, ROS- and redox-based therapies have yet to be addressed by these methodologies in the context of disease treatment. Here, we review the role of ROS and their coupled redox partners in tumorigenesis. Specifically, we highlight some of the challenges in understanding the role of hydrogen peroxide (H₂O₂), one of the most important ROS in pathophysiology in the progression of cancer. We also discuss its interplay with antioxidant defenses, such as the coupled peroxiredoxin/thioredoxin and glutathione/glutathione peroxidase systems, and its reducing equivalent metabolism. Finally, we highlight the need for system-level and patient-tailored approaches to clarify the roles of these systems and identify therapeutic targets through the use of the tools developed in personalized medicine.

ROS-modulated therapeutic approaches in cancer treatment

PURPOSE

Reactive oxygen species (ROS) are produced in cancer cells as a result of increased metabolic rate, dysfunction of mitochondria, elevated cell signaling, expression of oncogenes and increased peroxisome activities. Certain level of ROS is required by cancer cells, above or below which lead to cytotoxicity in cancer cells. This biochemical aspect can be exploited to develop novel therapeutic agents to preferentially and selectively target cancer cells.

METHODS

We searched various electronic databases including PubMed, Web of Science, and Google Scholar for peer-reviewed english-language articles. Selected articles ranging from research papers, clinical studies, and review articles on the ROS production in living systems, its role in cancer development and cancer treatment, and the role of microbiota in ROS-dependent cancer therapy were analyzed.

RESULTS

This review highlights oxidative stress in tumors, underlying mechanisms of different relationships of ROS and cancer cells, different ROS-mediated therapeutic strategies and the emerging role of microbiota in cancer therapy.

CONCLUSION

Cancer cells exhibit increased ROS stress and disturbed redox homeostasis which lead to ROS adaptations. ROS-dependent anticancer therapies including ROS scavenging anticancer therapy and ROS boosting anticancer therapy have shown promising results in vitro as well as in vivo. In addition, response to cancer therapy is modulated by the human microbiota which plays a critical role in systemic body functions.

The role of peroxiredoxins in cancer

Peroxiredoxins (PRDXs) are a ubiquitously expressed family of small (22–27 kDa) non-seleno peroxidases that catalyze the peroxide reduction of H₂O₂, organic hydroperoxides and peroxynitrite. They are highly involved in the control of various physiological functions, including cell growth, differentiation, apoptosis, embryonic development, lipid metabolism, the immune response, as well as cellular homeostasis. Although the protective role of PRDXs in cardiovascular and neurological diseases is well established, their role in cancer remains controversial. Increasing evidence suggests the involvement of PRDXs in carcinogenesis and in the development of drug resistance. Numerous types of cancer cells, in fact, are characterized by an increase in reactive oxygen species (ROS) production, and often exhibit an altered redox environment compared with normal cells. The present review focuses on the complex association between oxidant balance and cancer, and it provides a brief account of the involvement of PRDXs in tumorigenesis and in the development of chemoresistance.

Peroxiredoxin 1 - an antioxidant enzyme in cancer

Peroxiredoxins (PRDXs), a ubiquitous family of redox‐regulating proteins, are reported of potential to eliminate various reactive oxygen species (ROS). As a major member of the antioxidant enzymes, PRDX1 can become easily over‐oxidized on its catalytically active cysteine induced by a variety of stimuli in vitro and in vivo. In nucleus, oligomeric PRDX1 directly associates with p53 or transcription factors such as c‐Myc, NF‐κB and AR, and thus affects their bioactivities upon gene regulation, which in turn induces or suppresses cell death. Additionally, PRDX1 in cytoplasm has anti‐apoptotic potential through direct or indirect interactions with several ROS‐dependent (redox regulation) effectors, including ASK1, p66^Shc, GSTpi/JNK and c‐Abl kinase. PRDX1 is proven to be a versatile molecule regulating cell growth, differentiation and apoptosis. Recent studies have found that PRDX1 and/or PRDX1‐regulated ROS‐dependent signalling pathways play an important role in the progression and metastasis of human tumours, particularly in breast, oesophageal and lung cancers. In this paper, we review the structure, effector functions of PRDX1, its role in cancer and the pivotal role of ROS in anticancer treatment.

S-nitrosylation of peroxiredoxin 1 contributes to viability of lung epithelial cells during Bacillus anthracis infection

BACKGROUND

Using Bacillus anthracis as a model gram-positive bacterium, we investigated the effects of host protein S-nitrosylation during bacterial infection. B. anthracis possesses a bacterial nitric oxide synthase (bNOS) that is important for its virulence and survival. However, the role of S-nitrosylation of host cell proteins during B. anthracis infection has not been determined.

METHODS

Nitrosoproteomic analysis of human small airway epithelial cells (HSAECs) infected with toxigenic B. anthracis Sterne was performed, identifying peroxiredoxin 1 (Prx1) as one predominant target. Peroxidase activity of Prx during infection was measured using 2-Cys-Peroxiredoxin activity assay. Chaperone activity of S-nitrosylated Prx1 was measured by insulin aggregation assay, and analysis of formation of multimeric species using Native PAGE. Griess assay and DAF-2DA fluorescence assay were used to measure NO production. Cell viability was measured using the Alamar Blue assay and the ATPlite assay (Perkin Elmer).

RESULTS

S-nitrosylation of Prx1 in Sterne-infected HSAECs leads to a decrease in its peroxidase activity while enhancing its chaperone function. Treatment with bNOS inhibitor, or infection with bNOS deletion strain, reduces S-nitrosylation of Prx1 and decreases host cell survival. Consistent with this, siRNA knockdown of Prx1 lowers bNOS-dependent protection of HSAEC viability.

CONCLUSIONS

Anthrax infection results in S-nitrosylation of multiple host proteins, including Prx1. The nitrosylation-dependent decrease in peroxidase activity of Prx1 and increase in its chaperone activity is one factor contributing to enhancing infected cell viability.

GENERAL SIGNIFICANCE

These results provide a new venue of mechanistic investigation for inhalational anthrax that could lead to novel and potentially effective countermeasures.

Differential proteins among normal cervix cells and cervical cancer cells with HPV-16 infection, through mass spectrometry-based Proteomics (2D-DIGE) in women from Southern México

Background

Cervical cancer (CC) is the fourth most common cancer in women worldwide with an estimated 528,000 new cases in 2012. The same year México had an incidence of 13,960 and a mortality of 4769 cases. There are several diagnosis methods of CC; among the most frequents are the conventional Pap cytology (Pap), colposcopy, and visual inspection with acetic acid (VIA), histopathological examination, tests of imaging and detection of high-risk papilloma virus (HR-HPV) with molecular tests (PCR, hybridization, sequencing). Proteomics is a tool for the detection of new biomarkers that can be associated with clinical stage, histological type, prognosis, and/or response to treatment. In this study we performed a comparative analysis of CC cells with normal cervical cells. The proteomic analysis was carried out with the fluorescent two-dimensional electrophoresis (2D-DIGE) technique to subsequently identify differential protein profiles using Decyder Software, and the selected proteins were identified by Mass Spectrometry (MALDI-TOF).

Results

The proteins that showed an increased expression in cervical cancer in comparison with normal cervix cells were: Mimecan, Actin from aortic smooth muscle and Lumican. While Keratin, type II cytoskeletal 5, Peroxiredoxin-1 and 14-3-3 protein sigma showed a decrease in their protein expression level in cervical cancer in comparison with normal cervix cells.

Conclusions

Thus, this study was successful in identifying biomarker signatures for cervical cancer, and might provide new insights into the mechanism of CC progression.

SIRT2 Deacetylates and Inhibits the Peroxidase Activity of Peroxiredoxin-1 to Sensitize Breast Cancer Cells to Oxidant Stress-Inducing Agents

SIRT2 is a protein deacetylase with tumor suppressor activity in breast and liver tumors where it is mutated; however, the critical substrates mediating its antitumor activity are not fully defined. Here we demonstrate that SIRT2 binds, deacetylates, and inhibits the peroxidase activity of the antioxidant protein peroxiredoxin (Prdx-1) in breast cancer cells. Ectopic overexpression of SIRT2, but not its catalytically dead mutant, increased intracellular levels of reactive oxygen species (ROS) induced by hydrogen peroxide, which led to increased levels of an overoxidized and multimeric form of Prdx-1 with activity as a molecular chaperone. Elevated levels of SIRT2 sensitized breast cancer cells to intracellular DNA damage and cell death induced by oxidative stress, as associated with increased levels of nuclear FOXO3A and the proapoptotic BIM protein. In addition, elevated levels of SIRT2 sensitized breast cancer cells to arsenic trioxide, an approved therapeutic agent, along with other intracellular ROS-inducing agents. Conversely, antisense RNA-mediated attenuation of SIRT2 reversed ROS-induced toxicity as demonstrated in a zebrafish embryo model system. Collectively, our findings suggest that the tumor suppressor activity of SIRT2 requires its ability to restrict the antioxidant activity of Prdx-1, thereby sensitizing breast cancer cells to ROS-induced DNA damage and cell cytotoxicity. Cancer Res; 76(18); 5467-78. ©2016 AACR.

Silencing PRDX3 Inhibits Growth and Promotes Invasion and Extracellular Matrix Degradation in Hepatocellular Carcinoma Cells

PRDX3 is a mitochondrial peroxide reductase that regulates cellular redox state. It has been reported that PRDX3 is overexpressed in liver cancer, but how PRDX3 is involved in hepatocellular carcinoma (HCC) tumorigenesis and progression has not been well-characterized. In the present study, we established two stable cell lines by overexpressing or knocking down PRDX3 in HepG2 cells. We found that PRDX3 silencing decreased the growth rate of HepG2 cells and increased mtDNA oxidation. Quantitative proteomics identified 475 differentially expressed proteins between the PRDX3 knockdown and the control cells. These proteins were involved in antioxidant activity, angiogenesis, cell adhesion, cell growth, ATP synthesis, nucleic acid binding, redox, and chaperones. PRDX3 knockdown led to the down-regulation of ATP synthases and the decreased cellular ATP level, contributing to the slow-down of cell growth. Furthermore, silencing PRDX3 enhanced invasive properties of HepG2 cells via TIMP-1 down-regulation and the increased ECM degradation. Taken together, our results indicate that PRDX3 promotes HCC growth and mediates cell migration and invasiveness and is a potential therapeutic target for HCC treatment.

Effective Killing of Cancer Cells Through ROS-Mediated Mechanisms by AMRI-59 Targeting Peroxiredoxin I

AIMS

The intrinsic increase of reactive oxygen species (ROS) production in cancer cells after malignant transformation frequently induces redox adaptation, leading to enhanced antioxidant capacity. Peroxiredoxin I (PrxI), an enzyme responsible for eliminating hydrogen peroxide, has been found to be elevated in many types of cancer cells. Since overexpression of PrxI promoted cancer cells' survival and resistance to chemotherapy and radiotherapy, PrxI has been proposed as a therapeutic target for anticancer drugs. In this study, we aimed to investigate the anticancer efficacy of a small molecule inhibitor of PrxI.

RESULTS

By a high-throughput screening approach, we identified AMRI-59 as a potent inhibitor of PrxI. AMRI-59 increased cellular ROS, leading to the activation of both mitochondria- and apoptosis signal-regulated kinase-1-mediated signaling pathways, resulting in apoptosis of A549 human lung adenocarcinoma. AMRI-59 caused no significant changes in ROS level, proliferation, and apoptosis of PrxI-knockdown A549 cells by RNA interference. PrxI overexpression or N-acetylcysteine pretreatment abrogated AMRI-59-induced cytotoxicity in A549 cells. AMRI-59 rendered tumorigenic ovarian cells more susceptible to ROS-mediated death compared with nontumorigenic cells. Moreover, significant antitumor activity of AMRI-59 was observed in mouse tumor xenograft model implanted with A549 cells with no apparent acute toxicity.

INNOVATION

This study offers preclinical proof-of-concept for AMRI-59, a lead small molecule inhibitor of PrxI, as an anticancer agent.

CONCLUSIONS

Our results highlight a promising strategy for cancer therapy that preferentially eradicates cancer cells by targeting the PrxI-mediated redox-dependent survival pathways.

Gypenosides Synergistically Enhances the Anti-Tumor Effect of 5-Fluorouracil on Colorectal Cancer In Vitro and In Vivo: A Role for Oxidative Stress-Mediated DNA Damage and p53 Activation

Objective

5-Fluorouracil (5-Fu) has been widely used as a first-line drug for colorectal cancer (CRC) treatment but limited by drug resistance and severe toxicity. The chemo-sensitizers that augment its efficiency and overcome its limitation are urgently needed. Gypenosides (Gyp), the main components from Gynostemma pentaphyllum (Thunb.) Makino, has shown potential anti-tumor property with little side-effect. Here, we carefully explored the chemo-sensitization of Gyp to potentiate the anti-tumor effect of 5-Fu in vitro and in vivo.

Methodology / Principal Findings

3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltertrazolium bromide tetrazolium assay and colony formation test reveal that Gyp could significantly enhance the 5-Fu-caused SW-480,SW-620 and Caco2 cells viability loss. Calcusyn analysis shows that Gyp acts synergistically with 5-Fu. Annexin V-PE/7-AAD staining indicates 5-Fu + Gyp could induce SW-480 cell apoptosis. The activations of caspase 3, caspase 9 and poly (ADP-ribose) polymerase (PARP) were involved in the process. Gyp was also found to up-regulate 5-Fu-caused phospho-p53 expression and thus augment 5-Fu-induced G0/G1 phase arrest. Gyp elevated intracellular ROS level, significantly enhanced 5-Fu-triggered DNA damage response as evidenced by flow cytometry, comet assay and the expression of Ser139-Histone H2A.X. Inhibition of ROS and p53 respectively reversed the cell death induced by 5-Fu + Gyp, suggesting the key roles of ROS and p53 in the process. Moreover, 5-Fu and Gyp in combination exhibits much superior tumor volume and weight inhibition on CT-26 xenograft mouse model in comparison to 5-Fu or Gyp alone. Immunohistochemistry analysis suggests the combinations greatly suppressed tumor proliferation. Preliminary toxicological results show that 5-Fu + Gyp treatment is relatively safe.

Conclusions

As a potential chemo-sensitizer, Gyp displays a splendid synergistic effect with 5-Fu to inhibit cancer cell proliferation and tumor growth. By using 5-Fu and Gyp in combination would be a promising therapeutic strategy for CRC treatment.

Dysregulation of redox-state-regulating enzymes in melanocytic skin tumours and the surrounding microenvironment

AIMS

To investigate redox-regulating enzymes that may have a special role in melanoma pathogenesis due to continuous exposure to microenvironment-produced and ultraviolet radiation-induced oxidative stress.

METHODS AND RESULTS

We assessed immunohistochemically the expression of antioxidant enzymes peroxiredoxins (Prxs) I-IV, sulfiredoxin (Srx) and redox-regulated proto-oncogene DJ-1 in material consisting of 30 benign naevi, 14 lentigo malignas and 67 malignant melanomas. Evaluation of immunostaining was performed with special attention paid to protein expression in different tumour compartments. In particular, the expression patterns of nuclear Prx I and Prx II and cytoplasmic DJ-1 were decreased significantly in melanomas compared with dysplastic and benign naevi. In multivariate analysis, several prognostic factors were identified: Prx III expression in the cytoplasm of stromal fibroblasts was associated with shortened melanoma-specific survival [hazard ratio (HR) 6.730; 95% confidence interval (CI) 1.579-28.689], while cytoplasmic Prx IV expression in endothelial cells (HR 6.563; 95% CI 1.750-24.620) and Srx expression in the cytoplasm of keratinocytes (HR 6.988; 95% CI 1.559-31.324) were associated with better prognosis independently of ulceration, thickness of melanoma or its diagnostic type.

CONCLUSIONS

Redox-regulating enzymes have the potential to serve as novel prognostic factors and targeting them may offer new therapeutic options in malignant melanoma.

High intensity of cytoplasmic peroxiredoxin VI expression is associated with adverse outcome in diffuse large B-cell lymphoma independently of International Prognostic Index

AIMS

Diffuse large B-cell lymphoma (DLBCL) is an aggressive and potentially fatal disease. Prediction of risk of relapse is based on clinical markers. There is a need for more accurate biomarkers to select patients for more aggressive first-line treatments. Peroxiredoxins (Prxs) are a family of potent antioxidant proteins. Their prognostic role in DLBCL is unknown.

METHODS

Altogether, 103 diagnostic biopsy samples from patients with DLBCL were immunohistochemically stained for Prxs I, II, III, V and VI.

RESULTS

Strong Prx VI expression was associated with the presence of B-symptoms. There were no other significant associations with traditional risk factors. Five-year disease-specific survival was 68.6% in patients with high cytoplasmic Prx VI intensity vs 97.0% in those with low intensity. In multivariate analysis, high Prx VI expression (HR 12.846, 95% CI 1.722 to 95.807, p=0.013) was an independent risk factor of lymphoma-associated death not related to International Prognostic Index score (HR 2.514, 95% CI 1.040 to 6.073, p=0.041).

CONCLUSIONS

High intensity of cytoplasmic Prx VI expression in pretreatment DLBCL samples predicts worse outcome in patients with DLBCL. Whether Prx VI is associated with chemoresistance, and therefore a poorer outcome, needs to be evaluated. If Prx VI is a predictive marker and it proves causality, it would be crucial to study Prx VI ability to become a target enzyme for treatment.

Forced extinction of CD24 stem-like breast cancer marker alone promotes radiation resistance through the control of oxidative stress

Along with CD44, CD24 is a key marker of breast cancer stem cells (CSCs), frequently defined by CD24(-)/CD44(+) labeling. Among all phenotypes classically attributed to breast CD24(-)/CD44(+) cancer cells, radiation resistance has been extensively described and seen as being implicated in radiotherapy failure. Our previous data indicated that CD24(-) cells constitute a radiation-resistant subpopulation transitory selected by high doses of ionizing radiation. However, little is known about the biological role of CD24 in breast cancers, and no function has been assigned to CD24 in radiation response. Here, CD24 expression was induced in CD24(-) cells or knocked-down in CD24(+) cells. We show that forced extinction of CD24 expression is associated with decreased proliferation rate, lower levels of reactive oxygen species (ROS) and decreased genomic instability. On the opposite when CD24 is artificially expressed in CD24(-) cells, proliferation rates in vitro and in vivo, ROS levels and genomic instability are enhanced. Moreover, we observe that loss of CD24 expression leads to radiation resistance, by preventing radiation-induced cell death and promoting generation of progeny in relation to lower G2/M blockade and a smaller proportion of polyploid cells. Finally, control of ROS levels appears to be the key event in the CD24-mediated radiation response. For the first time, CD24 is proposed as a direct actor in radiation response of breast cancer cells, independently of CD44 expression. These findings could have interesting applications in evaluating the intrinsic radiation response of primary tumors.

Quantitative iTRAQ LC-MS/MS proteomics reveals the proteome profiles of DF-1 cells after infection with subgroup J Avian leukosis virus

Avian leukosis virus subgroup J (ALV-J) is an avian oncogenic retrovirus that can induce various clinical tumors and has caused severe economic losses in China. To improve our understanding of the host cellular responses to virus infection and the pathogenesis of ALV-J infection, we applied isobaric tags for relative and absolute quantification (iTRAQ) labeling coupled with multidimensional liquid chromatography-tandem mass spectrometry to detect the protein changes in DF-1 cells infected and mock-infected with ALV-J. A total of 75 cellular proteins were significantly changed, including 33 upregulated proteins and 42 downregulated proteins. The reliability of iTRAQ-LC MS/MS was confirmed via real-time PCR. Most of these proteins were related to the physiological functions of metabolic processes, biosynthetic processes, responses to stimuli, protein binding, signal transduction, cell cytoskeleton, and so forth. We also found some proteins that play important roles in apoptosis and oncogenicity. The differentially expressed proteins identified may provide valuable information to elucidate the pathogenesis of virus infection and virus-host interactions.

Lung Cancer Biomarkers

Lung cancer is the most frequently occurring cancer in the world and continually leads in mortality among cancers. The overall 5-year survival rate for lung cancer has risen only 4% (from 12% to 16%) over the past 4 decades, and late diagnosis is a major obstacle in improving lung cancer prognosis. Survival of patients undergoing lung resection is greater than 80%, suggesting that early detection and diagnosis of cancers before they become inoperable and lethal will greatly improve mortality. Lung cancer biomarkers can be used for screening, detection, diagnosis, prognosis, prediction, stratification, therapy response monitoring, and so on. This review focuses on noninvasive diagnostic and prognostic biomarkers. For that purpose, our discussion in this review will focus on biological fluid-based biomarkers. The body fluids include blood (serum or plasma), sputum, saliva, BAL, pleural effusion, and VOC. Since it is rich in different cellular and molecular elements and is one of the most convenient and routine clinical procedures, serum or plasma is the main source for the development and validation of many noninvasive biomarkers. In terms of molecular aspects, the most widely validated ones are proteins, some of which are used in the clinical sector, though in limited accessory purposes. We will also discuss the lung cancer (protein) biomarkers in clinical trials and currently in the validation phase with hundreds of samples. After proteins, we will discuss microRNAs, methylated DNA, and circulating tumor cells, which are being vigorously developed and validated as potential lung cancer biomarkers. The main aim of this review is to provide researchers and clinicians with an understanding of the potential noninvasive lung cancer biomarkers in biological fluids that have recently been discovered.

Induced nitric oxide synthetase and peroxiredoxin expression in intramucosal poorly differentiated gastric cancer of young patients

To investigate the relationship between oxidative stress and gastric carcinogenesis of poorly differentiated adenocarcinoma in young patients, we analyzed the surgically resected specimens of 22 young patients (21-30 years) and 29 older patients (41-72 years) with intramucosal gastric cancer of the poorly differentiated type. We used immunohistochemical staining to evaluate the expression of 8-hydroxydeoxyguanosine (8OHdG), induced nitric oxide synthetase (iNOS), and antioxidant enzymes (thioredoxin [TRX] and peroxiredoxin [PRDX1, 2 and 3]). We assessed these proteins in the cancer, noncancerous gastric foveolar epithelium and noncancerous mucosal neck. In both the young and older patient groups, the 8OHdG and TRX expressions were gradually increased in cancer cells compared with the noncancerous foveolar epithelial cells and the noncancerous mucosal neck cells (P < 0.001). Although the iNOS and PRDXs expressions were increased in the noncancerous mucosal neck cells compared with the noncancerous foveolar epithelial cells, regardless of age (P < 0.001), the iNOS and PRDX2 expression in the cancer cells were significantly reduced in the young patients compared with the older patients (P < 0.001, P < 0.05). In conclusion, the reduced expression of iNOS or PRDX2 may play an important role in the carcinogenesis of gastric cancer associated with Helicobacter pylori-induced chronic active gastritis in young patients.

MicroRNA-510 promotes cell and tumor growth by targeting peroxiredoxin1 in breast cancer

Introduction

MicroRNAs are small non-coding RNAs that are involved in the post-transcriptional negative regulation of mRNAs. MicroRNA 510 (miR-510) was initially shown to have a potential oncogenic role in breast cancer by the observation of its elevated levels in human breast tumor samples when compared to matched non-tumor samples. Few targets have been identified for miR-510. However, as microRNAs function through the negative regulation of their direct targets, the identification of those targets is critical for the understanding of their functional role in breast cancer.

Methods

Breast cancer cell lines were transfected with pre-miR-510 or antisense miR-510 and western blotting and quantitative real time PCR were performed. Functional assays performed included cell growth, migration, invasion, colony formation, cytotoxicity and in vivo tumor growth. We performed a PCR assay to identify novel direct targets of miR-510. The study focused on peroxiredoxin 1 (PRDX1) as it was identified through our screen and was bioinformatically predicted to contain a miR-510 seed site in its 3' untranslated region (3'UTR). Luciferase reporter assays and site-directed mutagenesis were performed to confirm PRDX1 as a direct target. The Student's two-sided, paired t-test was used and a P-value less than 0.05 was considered significant.

Results

We show that miR-510 overexpression in non-transformed and breast cancer cells can increase their cell growth, migration, invasion and colony formation in vitro. We also observed increased tumor growth when miR-510 was overexpressed in vivo. We identified PRDX1 through a novel PCR screen and confirmed it as a direct target using luciferase reporter assays. The reintroduction of PRDX1 into breast cancer cell lines without its regulatory 3'UTR confirmed that miR-510 was mediating its migratory phenotype at least in part through the negative regulation of PRDX1. Furthermore, the PI3K/Akt pathway was identified as a positive regulator of miR-510 both in vitro and in vivo.

Conclusions

In this study, we provide evidence to support a role for miR-510 as a novel oncomir. We show that miR-510 directly binds to the 3'UTR of PRDX1 and blocks its protein expression, thereby suppressing migration of human breast cancer cells. Taken together, these data support a pivotal role for miR-510 in breast cancer progression and suggest it as a potential therapeutic target in breast cancer patients.

Phenethyl isothiocyanate induces DNA damage-associated G2/M arrest and subsequent apoptosis in oral cancer cells with varying p53 mutations

Phenethyl isothiocyanate (PEITC) is a naturally occurring cruciferous vegetable-derived compound that inhibits cell growth and induces apoptosis in oral cancer cells. However, the exact mechanism of PEITC action has not been fully elucidated. This study investigated the molecular mechanism and anticancer potential of PEITC in oral squamous cell carcinoma (OSCC) cells with various p53 statuses. PEITC inhibited the growth of OC2, SCC4, and SCC25 cells (functional p53 mutants) in a dose-dependent manner with low toxicity to normal cells. Treatment with PEITC induced reactive oxygen species production, nitric oxide generation, and GSH depletion and triggered DNA damage response as evidenced by flow cytometry, 8-OHdG formation, and comet assay. Furthermore, the subsequent activation of ATM, Chk2, and p53 as well as the increased expression of downstream proteins p21 and Bax resulted in a G2/M phase arrest by inhibiting Cdc25C, Cdc2, and cyclin B1. The PEITC-induced apoptotic cell death, following a diminished mitochondrial transmembrane potential, reduced the expression of Bcl-2 and Mcl-1, released mitochondrial cytochrome c, and activated caspase 3 and PARP cleavage. The p53 inhibitor pifithrin-α and the antioxidants N-acetylcysteine and glutathione (GSH) protected the cells from PEITC-mediated apoptosis. However, mito-TEMPO, catalase, apocynin, and L-NAME did not prevent PEITC-induced cell death, suggesting that PEITC induced G2/M phase arrest and apoptosis in oral cancer cells via a GSH redox stress and oxidative DNA damage-induced ATM-Chk2-p53-related pathway. These results provide new insights into the critical roles of both GSH redox stress and p53 in the regulation of PEITC-induced G2/M cell cycle arrest and apoptosis in OSCCs.

Induction of peroxiredoxin 1 by hypoxia regulates heme oxygenase-1 via NF-κB in oral cancer

Overexpression of peroxiredoxin 1 (Prx1) has been observed in numerous cancers including oral squamous cell carcinoma (OSCC). The precise molecular mechanism of up-regulation of Prx1 in carcinogenesis, however, is still poorly understood. The objective of this study is to investigate the relationship between Prx1 and hypoxia, and potential mechanism(s) of Prx1 in OSCC cell line SCC15 and xenograft model. We treated wild-type and Prx1 knockdown SCC15 cells with transient hypoxia followed by reoxygenation. We detected the condition of hypoxia, production of reactive oxygen species (ROS), and expression and/or activity of Prx1, heme oxygenase 1 (HO-1) and nuclear factor-kappa B (NF-κB). We found that hypoxia induces ROS accumulation, up-regulates Prx1, increases NF-κB translocation and DNA binding activity, and down-regulates HO-1 in vitro. In Prx1 knockdown cells, the expression level of HO-1 was increased, while NFκB translocation and DNA binding activity were decreased after hypoxia or hypoxia/reoxygenation treatment. Moreover, we mimicked the dynamic oxygenation tumor microenvironment in xenograft model and assessed the above indices in tumors with the maximal diameter of 2 mm, 5 mm, 10 mm or 15 mm, respectively. Our data showed that tumor hypoxic condition and expression of Prx1 are significantly associated with tumor growth. The expression of HO-1 and NF-κB, and NF-κB DNA binding activity were significantly elevated in 15 mm tumors, and the level of 8-hydroxydeoxyguanosine was increased in 10 mm and 15 mm tumors, compared to those in size of 2 mm. The results from this study provide experimental evidence that overexpression of Prx1 is associated with hypoxia, and Prx1/NF-κB/HO-1 signaling pathway may be involved in oral carcinogenesis.