Proteomics in HepG2 hepatocarcinoma cells with stably silenced expression of PRDX1

Ferritin light chain as a potential biomarker for the prognosis of liver hepatocellular carcinoma

High expression of the ferritin light chain (FTL) in cancer promotes its onset and progression and is associated with tumour evolution. However, the significance of FTL in pan-cancer progression and prognosis in humans remains unclear. Therefore, we selected various bioinformatics databases to perform a pan-cancer analysis on a public dataset. Our results showed that FTL was differentially expressed in pan-cancer tissues compared to normal tissues. High FTL expression significantly correlated with the clinicopathological characteristics of patients with liver hepatocellular carcinoma (LIHC). The subsequent validation experiments confirmed these observations. Notably, our study found for the first time that FTLs are closely associated with LIHC and that FTLs have important clinical diagnostic and prognostic value for patients with LIHC. We confirmed that FTL expression was closely associated with altered DNA cycles and immune infiltration in LIHC. In conclusion, high levels of FTL expression are associated with poor prognosis in LIHC patients and are expected to be a potential prognostic and immune marker for LIHC.

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

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

Long noncoding RNA LINC01132 enhances immunosuppression and therapy resistance via NRF1/DPP4 axis in hepatocellular carcinoma

Background

Long noncoding RNAs (lncRNAs) are emerging as critical regulators of gene expression and play fundamental roles in various types of cancer. Current developments in transcriptome analyses unveiled the existence of lncRNAs; however, their functional characterization remains a challenge.

Methods

A bioinformatics screen was performed by integration of multiple omics data in hepatocellular carcinoma (HCC) prioritizing a novel oncogenic lncRNA, LINC01132. Expression of LINC01132 in HCC and control tissues was validated by qRT-PCR. Cell viability and migration activity was examined by MTT and transwell assays. Finally, our results were confirmed in vivo mouse model and ex vivo patient derived tumor xenograft experiments to determine the mechanism of action and explore LINC01132-targeted immunotherapy.

Results

Systematic investigation of lncRNAs genome-wide expression patterns revealed LINC01132 as an oncogene in HCC. LINC01132 is significantly overexpressed in tumor and associated with poor overall survival of HCC patients, which is mainly driven by copy number amplification. Functionally, LINC01132 overexpression promoted cell growth, proliferation, invasion and metastasis in vitro and in vivo. Mechanistically, LINC01132 acts as an oncogenic driver by physically interacting with NRF and enhancing the expression of DPP4. Notably, LINC01132 silencing triggers CD8+ T cells infiltration, and LINC01132 knockdown combined with anti-PDL1 treatment improves antitumor immunity, which may prove a new combination therapy in HCC.

Conclusions

LINC01132 functions as an oncogenic driver that induces HCC development via the NRF1/DPP4 axis. Silencing LINC01132 may enhance the efficacy of anti-PDL1 immunotherapy in HCC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02478-z.

Expression and prognostic roles of PRDXs gene family in hepatocellular carcinoma

Background

As the fourth leading cause of cancer-related death in the world, the therapeutic effect and 5-year overall survival of hepatocellular carcinoma (HCC) are not optimistic. Previous researches indicated that the disorder of PRDXs was related to the occurrence and development of cancers.

Methods

In this study, PRDXs were found in various tumor cell lines by CCLE database analysis. The analysis results of UALCAN, HCCDB and Human Protein Atlas databases showed the expression of PRDXs mRNA and protein in HCC tissues was dysregulated. Besides, UALCAN was used to assess the correlations between PRDXs mRNA as well as methylation levels and clinical characterization.

Results

High expression of PRDX1 or low expression of PRDX2/3 suggested poor prognosis for HCC patients which was demonstrated by Kaplan–Meier Plotter. The genetic alterations and biological interaction network of PRDXs in HCC samples were obtained from c-Bioportal. In addition, LinkedOmics was employed to analyze PRDXs related differentially expressed genes, and on this basis, enrichment of KEGG pathway and miRNAs targets of PRDXs were conducted. The results indicated that these genes were involved in several canonical pathways and certain amino acid metabolism, some of which may effect on the progression of HCC.

Conclusions

In conclusion, the disordered expression of some PRDX family members was associated with the prognosis of HCC patients, suggesting that these PRDX family members may become new molecular targets for the treatment and prognosis prediction of HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02792-8.

Molecular Mechanisms Underlying Hepatocellular Carcinoma Induction by Aberrant NRF2 Activation-Mediated Transcription Networks: Interaction of NRF2-KEAP1 Controls the Fate of Hepatocarcinogenesis

NF-E2-related factor 2 (NRF2) is a basic leucine zipper transcription factor, a master regulator of redox homeostasis regulating a variety of genes for antioxidant and detoxification enzymes. NRF2 was, therefore, initially thought to protect the liver from oxidative stress. Recent studies, however, have revealed that mutations in NRF2 cause aberrant accumulation of NRF2 in the nucleus and exert the upregulation of NRF2 target genes. Moreover, among all molecular changes in hepatocellular carcinoma (HCC), NRF2 activation has been revealed as a more prominent pathway contributing to the progression of precancerous lesions to malignancy. Nevertheless, how its activation leads to poor prognosis in HCC patients remains unclear. In this review, we provide an overview of how aberrant activation of NRF2 triggers HCC development. We also summarize the emerging roles of other NRF family members in liver cancer development.

PRDX1 enhances cerebral ischemia-reperfusion injury through activation of TLR4-regulated inflammation and apoptosis

Stroke is still a leading cause of death across the world. Despite various signals or molecules that contribute to the pathophysiological process have been investigated, the exact molecular mechanisms revealing stroke damage still remain to be explored. Peroxiredoxin 1 (PRDX1) has been identified as a stress-induced macrophage redox protein with multiple functions. Although PRDX1 is a critical factor related to the regulation of immunity, inflammation, apoptosis and oxidative stress, its effects on cerebral ischemia-reperfusion (I-R) injury were presently unclear. In the study, by using a mouse model of I-R injury, we found that PRDX1 expression was up-regulated during I-R injury in a time-dependent manner. Additionally, PRDX1-knockout mice showed reduced infarction area and alleviated neuropathological scores with decreased brain water contents. Furthermore, cell death and inflammatory response in mice with cerebral I-R injury were markedly attenuated by PRDX1 knockout, which were associated with the blockage of Caspase-3 and nuclear factor-κB (NF-κB) signaling pathways. Mechanistically, PRDX1-regulated cerebral I-R injury was through the promotion of toll-like receptor-4 (TLR4), as proved by the evidence that TLR4 suppression abrogated the exacerbated effect of TLR4 on inflammatory response and apoptosis in oxygen and glucose deprivation (OGD)-treated primary microglial cells. These data demonstrated that PRDX1 contributed to cerebral stroke by interacting with TLR4, providing an effective therapeutic approach for cerebral I-R injury.

Rapamycin induces the expression of heme oxygenase-1 and peroxyredoxin-1 in normal hepatocytes but not in tumorigenic liver cells

Rapamycin (sirolimus) is employed as an immunosuppressant following liver transplant, to inhibit the re-growth of cancer cells following liver resection for hepatocellular carcinoma (HCC), and for the treatment of advanced HCC. Rapamycin also induces the expression of antioxidant enzymes in the liver, suggesting that pretreatment with the drug could provide a potential strategy to reduce ischemia reperfusion injury following liver surgery. The aim of this study was to further investigate the actions of rapamycin in inducing expression of the antioxidant enzymes heme oxygenase-1 (HO-1) and peroxiredoxin-1 (Prx-1) in normal liver and in tumorigenic liver cells. A rat model of segmental hepatic ischemia and reperfusion, cultured freshly-isolated rat hepatocytes, and tumorigenic H4IIE rat liver cells in culture were employed. Expression of HO-1 and Prx-1 was measured using quantitative PCR and western blot. Rapamycin pre-treatment of normal liver in vivo or normal hepatocytes in vitro led to a substantial induction of mRNA encoding HO-1 and Prx-1. The dose-response curve for the action of rapamycin on mRNA expression was biphasic, showing an increase in expression at 0 - 0.1 μM rapamycin but a decrease from maximum at concentrations greater than 0.1 μM. By contrast, in H4IIE cells, rapamycin inhibited the expression of HO-1 and Prx-1 mRNA. Oltipraz, an established activator of transcription factor Nrf2, caused a large induction of HO-1 and Prx-1 mRNA. The dose response curve for the inhibition by rapamycin of HO-1 and Prx-4 mRNA expression, determined in the presence of oltipraz, was monophasic with half maximal inhibition at about 0.01 μM. It is concluded that, at concentrations comparable to those used clinically, pre-treatment of the liver with rapamycin induces the expression of HO-1 and Prx-1. However, the actions of rapamycin on the expression of these two antioxidant enzymes in normal hepatocytes are complex and, in tumorigenic liver cells, differ from those in normal hepatocytes. Further studies are warranted to evaluate preconditioning the livers of patients subject to liver resection or liver transplant with rapamycin as a viable strategy to reduce IR injury following liver surgery.

The application of gene silencing in proteomics: from laboratory to clinic

INTRODUCTION

Since the completion of genome sequencing, gene silencing technologies have emerged as powerful tools to study gene functions in various biological processes, both in vivo and in vitro. Moreover, they have also been proposed as therapeutic agents to inhibit selected genes in a variety of pathological conditions, such as cancer, neurodegenerative, and cardiovascular diseases. Area covered: This review summarizes the mechanisms of action and applications of genome editing tools, from RNA interference to clustered regularly interspaced short palindromic repeats-based systems, in research and in clinics. We describe their essential role in high-throughput genetic screens and, in particular, in functional proteomics studies, to identify diagnostic markers and therapeutic targets. Indeed, gene silencing and proteomics have been extensively integrated to study global proteome changes, posttranslational modifications, and protein-protein interactions. Expert commentary: Functional proteomics approaches that leverage gene silencing tools have been successfully applied to examine the role of several genes in various contexts, leading to a deeper knowledge of biological pathways and disease mechanisms. Recent developments of gene silencing tools have improved their performance, also in terms of off-targets effects reduction, paving the way for a wider therapeutic application of these systems.

Peroxiredoxin I is important for cancer-cell survival in Ras-induced hepatic tumorigenesis

Peroxiredoxin I (Prx I), an antioxidant enzyme, has multiple functions in human cancer. However, the role of Prx I in hepatic tumorigenesis has not been characterized. Here we investigated the relevance and underlying mechanism of Prx I in hepatic tumorigenesis. Prx I increased in tumors of hepatocellular carcinoma (HCC) patients that aligned with overexpression of oncogenic H-ras. Prx I also increased in H-ras^G12V transfected HCC cells and liver tumors of H-ras^G12V transgenic (Tg) mice, indicating that Prx I may be involved in Ras-induced hepatic tumorigenesis. When Prx I was knocked down or deleted in HCC-H-ras^G12V cells or H-ras^G12V Tg mice, cell colony or tumor formation was significantly reduced that was associated with downregulation of pERK pathway as well as increased intracellular reactive oxygen species (ROS) induced DNA damage and cell death. Overexpressing Prx I markedly increased Ras downstream pERK/FoxM1/Nrf2 signaling pathway and inhibited oxidative damage in HCC cells and H-ras^G12V Tg mice. In this study, we found Nrf2 was transcriptionally activated by FoxM1, and Prx I was activated by the H-ras^G12V/pERK/FoxM1/Nrf2 pathway and suppressed ROS-induced hepatic cancer-cell death along with formation of a positive feedback loop with Ras/ERK/FoxM1/Nrf2 to promote hepatic tumorigenesis.

Pro-Apoptotic Effects of JDA-202, a Novel Natural Diterpenoid, on Esophageal Cancer Through Targeting Peroxiredoxin I

AIMS

Esophageal cancer (EC) is an aggressive malignancy and the most common solid tumor of gastrointestinal tract all over the world, with high incidence in Asia. The current study was designed to investigate the anticancer efficacy and mechanism that is involved in the action of a natural ent-kaurene diterpenoid, JDA-202, targeting EC.

RESULTS

We found that an antioxidant protein peroxiredoxin I (Prx I) was upregulated in human EC tissues as well as in EC cell lines. JDA-202, a novel natural compound isolated from Isodon rubescens (Labiatae), was proved to possess strong anti-proliferative activities on those cell lines. Importantly, JDA-202 does not only bind to Prx I directly and markedly inhibit the activity of Prx I in vitro, but it also significantly induces hydrogen peroxide (H₂O₂)-related cell death. Furthermore, overexpression of Prx I significantly reversed EC109 cell apoptosis caused by JDA-202, whereas short interfering RNA (siRNA)-induced Prx I knockdown resulted in marked cell death even without JDA-202 pretreatment. On the other hand, the increased phosphorylation of mitogen-activated protein kinase (MAPK) proteins (c-Jun N-terminal kinase [JNK], p38, and extracellular signal-regulated kinase [ERK]) by JDA-202 was suppressed by N-acetylcysteine (NAC) or catalase, a known reactive oxygen species (ROS) or H₂O₂ scavenger. JDA-202 also significantly inhibited the growth of EC109 tumor xenograft, without significant body weight loss and multi-organ toxicities. Innovation and Conclusion: Our findings, for the first time, demonstrated that JDA-202 may serve as a lead compound, targeting the overexpressed Prx I in EC cell lines and ROS accumulation as well as inhibiting the activation of their downstream targets in MAPKs. Antioxid. Redox Signal. 27, 73-92.

Effects of the cyclophilin-type peptidylprolyl cis-trans isomerase from Pyropia yezoensis against hydrogen peroxide-induced oxidative stress in HepG2 cells

The present study aimed to describe the expression and purification of cyclophilin-type peptidylprolyl cis-trans isomerase (PPI) from the red alga Pyropia yezoensis. The antioxidant activity of the purified protein was also demonstrated, based on its ability to act against oxidative stress in HepG2 human hepatocellular carcinoma cells. HepG2 cells that were treated with recombinant PPI protein exhibited a reduction in the formation of hydrogen peroxide (H2O2)‑mediated reactive oxygen species (ROS). In HepG2 cells, treatment of recombinant PPI protein expression diminished H2O2‑mediated oxidative stress and restored both the expression and the activity of certain antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and thioredoxin reductase (TRR). CAT, SOD and TRR activities were upregulated by treatment with the purified protein. CAT mRNA expression was significantly increased in HepG2 cells treated with recombinant PPI protein. These enzymes are the first line of antioxidant defense against ROS generated in times of oxidative stress. Accordingly, data from the present study indicate that the recombinant PPI protein is able to regulate the expression of antioxidant enzymes. Recombinant PPI has antioxidant properties that prevent oxidative stress‑induced toxicity, enhance cell viability, decrease ROS production and inhibit oxidative damage and mitochondrial dysfunction in HepG2 cells. Therefore, the present study hypothesizes that the recombinant PPI protein has the potential to protect the liver against oxidative stress‑induced cell damage and should be considered as an antioxidant.

Antioxidant enzymes as redox-based biomarkers: a brief review

The field of redox proteomics focuses to a large extent on analyzing cysteine oxidation in proteins under different experimental conditions and states of diseases. The identification and localization of oxidized cysteines within the cellular milieu is critical for understanding the redox regulation of proteins under physiological and pathophysiological conditions, and it will in turn provide important information that are potentially useful for the development of novel strategies in the treatment and prevention of diseases associated with oxidative stress. Antioxidant enzymes that catalyze oxidation/reduction processes are able to serve as redox biomarkers in various human diseases, and they are key regulators controlling the redox state of functional proteins. Redox regulators with antioxidant properties related to active mediators, cellular organelles, and the surrounding environments are all connected within a network and are involved in diseases related to redox imbalance including cancer, ischemia/reperfusion injury, neurodegenerative diseases, as well as normal aging. In this review, we will briefly look at the selected aspects of oxidative thiol modification in antioxidant enzymes and thiol oxidation in proteins affected by redox control of antioxidant enzymes and their relation to disease. [BMB Reports 2015; 48(4): 200-208]

Redox proteomics: Methods for the identification and enrichment of redox-modified proteins and their applications

PTMs are defined as covalent additions to functional groups of amino acid residues in proteins like phosphorylation, glycosylation, S-nitrosylation, acetylation, methylation, lipidation, SUMOylation as well as oxidation. Oxidation of proteins has been characterized as a double-edged sword. While oxidative modifications, in particular of cysteine residues, are widely involved in the regulation of cellular homeostasis, oxidative stress resulting in the oxidation of biomolecules along with the disruption of their biological functions can be associated with the development of diseases, such as cancer, diabetes, and neurodegenerative diseases, respectively. This is also the case for advanced glycation end products, which result from chemical reactions of keto compounds such as oxidized sugars with proteins. The role of oxidative modifications under physiological and pathophysiological conditions remains largely unknown. Recently, novel technologies have been established that allow the enrichment, identification, and characterization of specific oxidative PTMs (oxPTMs). This is essential to develop strategies to prevent and treat diseases that are associated with oxidative stress. Therefore this review will focus on (i) the methods and technologies, which are currently applied for the detection, identification, and quantification of oxPTMs including the design of high throughput approaches and (ii) the analyses of oxPTMs related to physiological and pathological conditions.

Aberrant expression of peroxiredoxin 1 and its clinical implications in liver cancer

AIM: To investigate the expression characteristics of peroxiredoxin 1 (PRDX1) mRNA and protein in liver cancer cell lines and tissues.

METHODS: The RNA sequencing data from 374 patients with liver cancer were obtained from The Cancer Genome Atlas. The expression and clinical characteristics of PRDX1 mRNA were analyzed in this dataset. The Kaplan-Meier and Cox regression survival analysis was performed to determine the relationship between PRDX1 levels and patient survival. Subcellular fractionation and Western blotting were used to demonstrate the expression of PRDX1 protein in six liver cancer cell lines and 29 paired fresh tissue specimens. After bioinformatics prediction, a putative post-translational modification form of PRDX1 was observed using immunofluorescence under confocal microscopy and immunoprecipitation analysis in liver cancer cells.

RESULTS: The mRNA of PRDX1 gene was upregulated about 1.3-fold in tumor tissue compared with the adjacent non-tumor control (P = 0.005). Its abundance was significantly higher in men than women (P < 0.001). High levels of PRDX1 mRNA were associated with a shorter overall survival time (P = 0.04) but not with recurrence-free survival. The Cox regression analysis demonstrated that patients with high PRDX1 mRNA showed about 1.9-fold increase of risk for death (P = 0.03). In liver cancer cells, PRDX1 protein was strongly expressed with multiple different bands. PRDX1 in the cytosol fraction existed near the theoretical molecular weight, whereas two higher molecular weight bands were present in the membrane/organelle and nuclear fractions. Importantly, the theoretical PRDX1 band was increased, whereas the high molecular weight form was decreased in tumor tissues. Subsequent experiments revealed that the high molecular weight bands of PRDX1 might result from the post-translational modification by small ubiquitin-like modifier-1 (SUMO1).

CONCLUSION: PRDX1 was overexpressed in the tumor tissues of liver cancer and served as an independent poor prognostic factor for overall survival. PRDX1 can be modified by SUMO to play specific roles in hepatocarcinogenesis.

Liver expression of Nrf2-related genes in different liver diseases

BACKGROUND

The KEAP1-Nrf2 antioxidant signaling pathway is important in protecting liver from various insults. However, little is known about the expression of Nrf2-related genes in human liver in different diseases.

METHODS

This study utilized normal donor liver tissues (n=35), samples from patients with hepatocellular carcinoma (HCC, n=24), HBV-related cirrhosis (n=27), alcoholic cirrhosis (n=5) and end-stage liver disease (n=13). All of the liver tissues were from the Oriental Liver Transplant Center, Beijing, China. The expressions of Nrf2 and Nrf2-related genes, including its negative regulator Kelch-like ECH-associated protein 1 (KEAP1), its targeted gene NAD(P)H-quinone oxidoreductase 1 (NQO1), glutamate-cysteine ligase catalytic subunit (GCLC) and modified subunit (GCLM), heme oxygenase 1 (HO-1) and peroxiredoxin-1 (PRDX1) were evaluated.

RESULTS

The expression of Nrf2 was decreased in HCC, increased in alcoholic cirrhosis and end-stage liver disease. The expression of KEAP1 was increased in all of the liver samples. The most notable finding was the increased expression of NQO1 in HCC (18-fold), alcoholic cirrhosis (6-fold), end-stage liver disease (5-fold) and HBV-related cirrhosis (3-fold). Peri-HCC also had 4-fold higher NQO1 mRNA as compared to the normal livers. GCLC mRNA levels were lower only in HCC, as compared to the normal livers and peri-HCC tissues. GCLM mRNA levels were higher in HBV-related cirrhosis and end-stage liver disease. HO-1 mRNA levels were increased in all liver tissues except for HCC. Peri-HCC had higher PRDX1 mRNA levels compared with HCC and normal livers.

CONCLUSION

Nrf2 and Nrf2-related genes are aberrantly expressed in the liver in different diseases and the increase of NQO1 was the most notable finding, especially in HCC.

Peroxiredoxin 1 promotes tumorigenesis through regulating the activity of mTOR/p70S6K pathway in esophageal squamous cell carcinoma

The biological function of Peroxiredoxin 1 (Prdx1) in cancer is still ambiguous, and its mechanism has not been elucidated so far. Previous studies have shown that Prdx1 functions as tumor suppressor in several types of cancers, but other studies have indicated that it is overexpressed in some types of human cancers, and inhibition of Prdx1 by shRNA contributes to radiosensitivity and chemosensitivity. In this study, a suppression subtractive hybridization cDNA library between esophageal squamous cell carcinoma (ESCC) cell line EC9706 and noncancerous esophageal epithelial cell line Het-1A was constructed, and 11 tumorigenesis-associated genes including Prdx1 were isolated. In addition, we further confirmed that Prdx1 was overexpressed in ESCC cells at the level of protein compared with Het-1A (P < 0.05). Inhibition of Prdx1 by shRNA lentivirus decreased cell proliferation and invasion, and induced cell apoptosis, but did not affect cell cycle distribution of EC9706 cells (P > 0.05). Importantly, the total proteins of mTOR and p70S6K, as well as the activity of mTOR/p70S6K signaling pathway, were decreased in Prdx1-depletion EC9706 cells. Furthermore, the activity of mTOR/p70S6K signaling pathway was increased in Prdx1-overexpressing Het-1A cells. These findings mentioned above demonstrate that Prdx1 may be involved in tumorigenesis through regulation of mTOR/p70S6K pathway in ESCC.

Redox proteomics reveal stress responsive proteins linking peroxiredoxin-1 status in glioma to chemosensitivity and oxidative stress

The combined deletion of chromosomal arms 1p and 19q has been described as a prognostic marker for oligodendroglial tumors. These tumors show a better response to chemotherapy and radiotherapy. Recently, we found a lower abundance of peroxiredoxin 1 (PRDX1) in oligodendroglial tumors with 1p/19q deletion, suggesting a potential role of this enzyme in the clearance of therapy induced reactive oxygen species (ROS). Here, we confirmed the importance of PRDX1 in tumor cell survival by PRDX1 knockdown and overexpression in A-172 cells treated with the alkylating agent bis-chloroethyl nitrosourea (BCNU). Overexpression of PRDX1 resulted in a higher resistance of cells to BCNU treatment. In addition, BCNU challenged cells showed higher levels of ROS in PRDX1 knockdown cells. We applied a modified version of the redox two dimensional difference gel electrophoresis approach to analyze ROS mediated effects on protein thiols after BCNU treatment by labeling protein thiols with fluorescent dyes. Altogether eleven proteins were identified showing PRDX1 dependent altered labeling, many of them have been previously linked to stress response processes. Furthermore, 30 additional potentially redox active proteins were identified. The majority of them is involved in therapy associated processes like cellular stress response, DNA damage and regulation of cell death and therewith suggests that tumor cells maintain a network of redox sensitive proteins to escape chemotherapy. This article is part of a Special Issue entitled: Medical Proteomics.

Adenanthin targets peroxiredoxin I/II to kill hepatocellular carcinoma cells

Adenanthin, a natural diterpenoid isolated from the leaves of Isodon adenanthus, has recently been reported to induce leukemic cell differentiation by targeting peroxiredoxins (Prx) I and II. On the other hand, increasing lines of evidence propose that these Prx proteins would become potential targets to screen drugs for the prevention and treatment of solid tumors. Therefore, it is of significance to explore the potential activities of adenanthin on solid tumor cells. Here, we demonstrate that Prx I protein is essential for the survival of hepatocellular carcinoma (HCC) cells, and adenanthin can kill these malignant liver cells in vitro and xenografts. We also show that the cell death-inducing activity of adenanthin on HCC cells is mediated by the increased reactive oxygen species (ROS) levels. Furthermore, the silencing of Prx I or Prx II significantly enhances the cytotoxic activity of adenanthin on HCC, whereas the ectopic expression of Prx I and Prx II but not their mutants of adenanthin-bound cysteines can rescue adenanthin-induced cytotoxicity in Prxs-silenced HCC cells. Taken together, our results propose that adenanthin targets Prx I/II to kill HCC cells and its therapeutic significance warrants to be further explored in HCC patients.

Proteomic analysis of bladder cancer indicates Prx-I as a key molecule in BI-TK/GCV treatment system

In order to understand the molecular mechanisms of Bifidobacterium infantis thymidine kinase/nucleoside analogue ganciclovir (BI-TK/GCV) treatment system which was proven to exhibit sustainable anti-tumor growth activity and induce apoptosis in bladder cancer, a proteomic approach of isobaric tags for relative and absolute quantification (iTRAQ), followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used. 192 down-regulated and 210 up-regulated proteins were identified after treatment with BI-TK/GCV system in Sprague-Dawley (SD) rats. Western blot analysis and immunohistochemistry analysis confirmed that Peroxiredoxin-I (Prx-I) was significantly down-regulated in bladder cancer after treatment. Prx-I silencing by transfection of Prx-I shRNA significantly suppressed growth, promoted apoptosis and regulated the cell cycle in T24 cells and reduced the phospho-NF-κB p50 and p65 protein expression which revealed the links between Prx-I and NF-κB pathway implied by Ingenuity pathway analysis (IPA). These findings yield new insights into the therapy of bladder cancer, revealing Prx-I as a new therapeutic target and indicating BI-TK/GCV system as a prospective therapy by down-regulation of Prx-I through NF-κB signaling pathway.

Peroxiredoxin 1 is involved in disassembly of flagella and cilia

Cilia/flagella are evolutionarily conserved cellular organelles. In this study, we demonstrated that Dunaliella salina Peroxiredoxin 1 (DsPrdx1) localized to the flagella and basal bodies, and was involved in flagellar disassembly. The link between DsPrdx1 and flagella of Dunaliella salina (D. salina) encouraged us to explore the function of its human homologue, Homo sapiens Peroxiredoxin 1 (HsPrdx1) in development and physiology. Our results showed that HsPrdx1 was overexpressed, and cilia were lost in esophageal squamous cell carcinoma (ESCC) cells compared with the non-cancerous esophageal epithelial cells Het-1A. Furthermore, when HsPrdx1 was knocked down by short hairpin RNA (shRNA) lentivirus in ESCC cells, the phenotype of cilia lost can be reversed, and the expression levels of tumor suppressor genes LKB1 and p-AMPK were increased, and the activity of the oncogene Aurora A was inhibited compared with those in cells transfected with scrambe-shRNA lentivirus. These findings firstly showed that Prdx1 is involved in disassembly of flagella and cilia, and suggested that the abnormal expression of the cilia-related gene including Prdx1 may affect both ciliogenesis and cancernogenesis.