Coexpression of adult T-cell leukemia-derived factor, a human thioredoxin homologue, and human papillomavirus DNA in neoplastic cervical squamous epithelium

Thioredoxin Downregulation Enhances Sorafenib Effects in Hepatocarcinoma Cells

Sorafenib is the first-line recommended therapy for patients with advanced hepatocarcinoma (HCC) in de-differentiation stage (presenting epithelial-mesenchymal transition, EMT). We studied the role of the thioredoxin system (Trx1/TrxR1) in the sensitivity or resistance of HCC cells to the treatment with Sorafenib. As a model, we used a set of three established HCC cell lines with different degrees of de-differentiation as occurs in metastasis. By quantitative proteomics, we found that the expression levels of Trx1 and TrxR1 followed the same trend as canonical EMT markers in these cell lines. Treatment with Sorafenib induced thiol redox reductive changes in critical elements of oncogenic pathways in all three cell lines but induced drastic proteome reprograming only in HCC cell lines of intermediate stage. Trx1 downregulation counteracted the thiol reductive effect of Sorafenib on Signal Transducer and Activator of Transcription 3 (STAT3) but not on Mitogen-Activated Protein Kinase (MAPK) or Protein Kinase B (Akt) and transformed advanced HCC cells into Sorafenib-sensitive cells. Ten targets of the combined Sorafenib-siRNATrx1 treatment were identified that showed a gradually changing expression trend in parallel to changes in the expression of canonical EMT markers, likely as a result of the activation of Hippo signaling. These findings support the idea that a combination of Sorafenib with thioredoxin inhibitors should be taken into account in the design of therapies against advanced HCC.

Alantolactone promotes ER stress-mediated apoptosis by inhibition of TrxR1 in triple-negative breast cancer cell lines and in a mouse model

Triple‐negative breast cancer (TNBC) is a subtype of breast cancer with poor clinical outcome and currently no effective targeted therapies are available. Alantolactone (ATL), a sesquiterpene lactone, has been shown to have potential anti‐tumour activity against various cancer cells. However, the underlying mechanism and therapeutic effect of ATL in the TNBC are largely unknown. In the present study, we found that ATL suppresses TNBC cell viability by reactive oxygen species (ROS) accumulation and subsequent ROS‐dependent endoplasmic reticulum (ER) stress both in vitro and in vivo. Thioredoxin reductase 1 (TrxR1) expression and activity of were significantly up‐regulated in the TNBC tissue specimens compare to the normal adjacent tissues. Further analyses showed that ATL inhibits the activity of TrxR1 both in vitro and in vivo in TNBC and knockdown of TrxR1 in TNBC cells sensitized ATL‐induced cell apoptosis and ROS increase. These results will provide pre‐clinical evidences that ATL could be a potential therapeutic agent against TNBC by promoting ROS‐ER stress‐mediated apoptosis through partly targeting TrxR1.

Thioredoxin 1 mediates TGF-β-induced epithelial-mesenchymal transition in salivary adenoid cystic carcinoma

Epithelial-mesenchymal transition (EMT) plays an important role in the invasion and metastasis of salivary adenoid cystic carcinoma (SACC) which is characterized by wide local infiltration, perineural spread, a propensity to local recurrence and late distant metastasis. Our recent studies have disclosed that TGF-β is a crucial factor for EMT in metastatic SACC. In this study, we further uncovered small redox protein thioredoxin 1 (TXN) as a critical mediator of TGF-β induced EMT. Immunohistochemistry analysis revealed significantly higher expressions of TXN, thioredoxin reductase 1 (TXNRD1) and N-cadherin, and lower expression of E-cadherin in human metastatic SACC compared to non-metastatic SACC tissues. Consistently, cultured SACC cells with stable TXN overexpression had decreased E-cadherin and increased N-cadherin as well as Snail and Slug expressions. The enhanced migration and invasion potential of these cells was abrogated by Akt or TXNRD1 inhibitors. Expression of N-cadherin and Akt p-Akt decreased, whereas E-cadherin expression increased in a BBSKE (TXNRD1 inhibitor)-dose-dependent manner. In a xenograft mouse model, TXN overexpression facilitated the metastatic potential of SACC-83 cells to the lung. Our results indicate that TXN plays a key role in SACC invasion and metastasis through the modulation of TGF-β-Akt/GSK-3β on EMT. TXN could be a potential therapeutic target for SACC.

Redox Homeostasis and Cellular Antioxidant Systems: Crucial Players in Cancer Growth and Therapy

Reactive oxygen species (ROS) and their products are components of cell signaling pathways and play important roles in cellular physiology and pathophysiology. Under physiological conditions, cells control ROS levels by the use of scavenging systems such as superoxide dismutases, peroxiredoxins, and glutathione that balance ROS generation and elimination. Under oxidative stress conditions, excessive ROS can damage cellular proteins, lipids, and DNA, leading to cell damage that may contribute to carcinogenesis. Several studies have shown that cancer cells display an adaptive response to oxidative stress by increasing expression of antioxidant enzymes and molecules. As a double-edged sword, ROS influence signaling pathways determining beneficial or detrimental outcomes in cancer therapy. In this review, we address the role of redox homeostasis in cancer growth and therapy and examine the current literature regarding the redox regulatory systems that become upregulated in cancer and their role in promoting tumor progression and resistance to chemotherapy.

Thioredoxin, an antioxidant redox protein, in ovarian follicles of women undergoing in vitro fertilization

Oxidative stress has a bidirectional role in the development and maturation of zygotes and embryos. Reduction-oxidation reactions and regulatory proteins, such as thioredoxin (TRX) and thioredoxin reductase (TRXR), are intimately involved in the regulation of oxidative stress. The aim of this study was to determine the levels of TRX mRNA and protein in ovarian follicles collected from women undergoing in vitro fertilization (IVF) and to assess these levels relative to follicle size, presence of oocytes, and responsiveness to superovulation. Follicular fluid (FF) and/or granulosa cells (GCs) from large and small follicles were collected at the time of ovum pick-up from 42 IVF patients enrolled in this study. We divided the patients into normal and poor responders (NR and PR, respectively) based on the serum estradiol levels on the day of human chorionic gonadotropin (hCG) administration. We also compared the TRX concentration in FF (FF-TRX) between oocyte-containing follicles (Oc+) and empty follicles (Oc-). The transcript levels of TRX, but not TRXR, were significantly higher in GCs derived from follicles collected from NR than PR, as determined by semi-quantitative RT-PCR analysis. In NR, the FF-TRX was significantly higher in Oc+ follicles than in Oc- follicles and also in large Oc+ follicles than in large Oc- follicles. Unlike NR, PR exhibited no positive association with elevated FF-TRX and presence of oocytes. Based on its collective anti-oxidative, cytoprotective, and cytokine-like properties of TRX, TRX is likely to be involved in the optimal growth and maturation of ovarian follicles and responsiveness to hyperstimulation.

Thioredoxin 1 as a serum marker for ovarian cancer and its use in combination with CA125 for improving the sensitivity of ovarian cancer diagnoses

The serum levels of Trx1 in patients with ovarian cancer were significantly higher than those in normal persons and patients with non-cancer inflammatory diseases. The level of Trx1 increased with the Figo stage. Ovarian cancer patients who were determined to be negative for CA125, were observed to have serum Trx1 levels as high as those of CA125-positive patients. In addition, patients with non-cancer inflammatory diseases had lower plasma Trx1 1 levels than did controls, showing that Trx1 allows clear distinctions between ovarian cancer and these non-cancer diseases. Combinational analysis of CA125 with Trx1 for the detection of ovarian cancer suggests that the diagnostic capacity of CA125 alone for the early detection of ovarian cancer, especially regarding sensitivity, is significantly improved by its combination with Trx1. Taken together, we conclude that serum Trx1 is useful for the early diagnosis of ovarian cancer.

Thioredoxin 1 as a serum marker for breast cancer and its use in combination with CEA or CA15-3 for improving the sensitivity of breast cancer diagnoses

Background

The human cytosolic thioredoxin (Trx) contains a redox-active dithiol moiety in its conserved active-site sequence. Activation by a wide variety of stimuli leads to secretion of this cytoplasmic protein. Function of Trx1 has been implicated in regulating cell proliferation, differentiation, and apoptosis. The aim of this study was to assess the clinical significance of serum Trx1 level in patients with breast carcinoma.

Results

To clarify whether serum levels of Trx1 could be a serum marker for breast carcinoma, we measured the serum levels of Trx1 in patients with various carcinomas (breast, lung, colorectal, and kidney cancers) using an ELISA, and investigated its associations with the tumour grading from I to III. At the cut-off point 33.1725 ng/ml on the receiver operating characteristic curve (ROC) Trx1 could well discriminate breast carcinoma from normal controls with a sensitivity of 89.8%, specificity 78.0%, and area under the ROC (AUC) 0.901 ± 0.0252. The serum level was well correlated with the progress of the breast carcinoma. We also investigated the diagnostic capacity of CEA and CA15-3 for the early detection of metastatic breast cancer comparing that of Trx1. In contrast to the serum CEA and CA15-3 tumour markers, the serum Trx1 levels of the early cancer (grade I) patients were significantly higher than those of normal control subjects, showing a high diagnostic sensitivity and selectivity (89.4% sensitivity, and 72.0% specificity). The serum levels of Trx1 in various patients with lung, colorectal, and kidney carcinomas indicate that the level of Trx1 is significantly higher than those of other cancer patients. Combinational analysis of CEA or CA15-3 with Trx1 for the detection of breast cancer suggest that the diagnostic capacity of CEA or CA15-3 alone for the early detection of breast cancer, especially regarding sensitivity, is significantly improved by its combination with Trx1.

Conclusions

Taken together, we conclude that serum Trx1 is useful for the early diagnosis of breast cancer or the early prediction prognosis of breast cancer, and therefore has a valuable use as a diagnostic marker and companion marker to CEA and CA15-3 for breast cancer.

Thioredoxin and thioredoxin-interacting protein as prognostic markers for gastric cancer recurrence

AIM: To evaluate the potential of thioredoxin (TXN) and thioredoxin-interacting protein (TXNIP) expression as biomarkers for predicting gastric cancer recurrence.

METHODS: TXN and TXNIP expression levels were acquired from gene expression microarray data for 65 human gastric cancer tissues. We determined whether each gene expression level was associated with cancer recurrence and investigated the relationship between the two genes. For validation, the expression levels of TXN and TXNIP were measured by quantitative real-time reverse transcription polymerase chain reaction in 68 independent stage III gastric cancer patients. The correlation between gene expression and cancer prognosis was evaluated. Immunohistochemical staining was performed to investigate the protein expression levels of TXN and TXNIP and to characterize the expression patterns of each protein.

RESULTS: TXN was a prognosis-related gene (P = 0.009), whereas TXNIP, a TXN inhibitor, demonstrated a negative correlation with TXN in the gene expression microarray data. In the 68 stage III patients, the expression levels of both TXN and TXNIP had a statistically significant effect on recurrence-free survival (RFS, P = 0.008 and P = 0.036, respectively). The low TXN and high TXNIP expression group exhibited a better prognosis than the other groups, and the high TXN and low TXNIP expression group exhibited a poorer prognosis (P < 0.001 for RFS and P = 0.001 for overall survival). More than half of the patients in the simultaneously high TXN and low TXNIP expression group experienced a recurrence within 1 year after curative surgery, and the 5-year survival rate of the patients in this group was 29%, compared with 89% in the low TXN and high TXNIP expression group. The TXN protein was overexpressed in 65% of the gastric cancer tissues, whereas the TXNIP protein was underexpressed in 85% of the cancer cells. In a correlation analysis, TXN and TXNIP were highly correlated with many oncogenes and tumor suppressors as well as with genes related to energy, protein synthesis and autophagy.

CONCLUSION: TXN and TXNIP are promising prognostic markers for gastric cancer, and performing personalized adjuvant treatment based on TXN and TXNIP expression levels would be an effective practice in the treatment of gastric cancer.

Cloning, characterization, and expression analysis of a thioredoxin from orange-spotted grouper (Epinephelus coioides)

Thioredoxins (TRXs) are a family of small, highly conserved proteins that are essential for the maintenance of cellular homeostasis. In this study, a thioredoxin gene was cloned from orange-spotted grouper, Epinephelus coioides (designated as Ec-TRX). The full-length cDNA of Ec-TRX was comprised of 767bp with a 327bp open reading frame that encodes a putative protein of 108 amino acids. Quantitative real-time PCR analysis revealed that the Ec-TRX mRNA was distributed abundantly in grouper, E. coioides skin and liver, and the expression in liver was up-regulated after viral challenge with Singapore grouper iridovirus (SGIV). Recombinant Ec-TRX (rEc-TRX) was expressed in Escherichia coli BL21 (DE3) and purified for mouse anti-Ec-TRX serum preparation. The rEc-TRX fusion protein was demonstrated to possess the expected redox activity in enzymatic analysis, and scavenge free radicals and protect supercoiled DNA from oxidative damage induced by a metal-ion catalyzed oxidation reaction. Subcellular localization revealed that Ec-TRX was distributed in both cytoplasm and nucleus. Overexpression of Ec-TRX in grouper spleen (GS) cells could promote the growth of GS cells and inhibit the replication of SGIV. These results suggest that Ec-TRX could function as an important antioxidant in a physiological context, and perhaps is involved in the responses to viral challenge.

NMR structure of Carcinoscorpius rotundicauda thioredoxin-related protein 16 and its role in regulating transcription factor NF-κB activity

Thioredoxins (Trxs), which play a key role in maintaining a redox environment in the cell, are found in almost all organisms. Trxs act as potential reducing agents of disulfide bonds and contain two vicinal cysteines in a CXXC motif at the active site. Trx is also known to activate the DNA binding activity of NF-κB, an important transcription factor. Previously, Trx-related protein 16 from Carcinoscorpius rotundicauda (Cr-TRP16), a 16-kDa Trx-like protein that contains a WCPPC motif, was reported. Here we present the NMR structure of the reduced form of Cr-TRP16, along with its regulation of NF-κB activity. Unlike other 16-kDa Trx-like proteins, Cr-TRP16 contains an additional Cys residue (Cys-15, at the N terminus), through which it forms a homodimer. Moreover, we have explored the molecular basis of Cr-TRP16-mediated activation of NF-κB and showed that Cr-TRP16 exists as a dimer under physiological conditions, and only the dimeric form binds to NF-κB and enhances its DNA binding activity by directly reducing the cysteines in the DNA-binding motif of NF-κB. The C15S mutant of Cr-TRP16 was unable to dimerize and hence does not bind to NF-κB. Based on our finding and combined with the literature, we propose a model of how Cr-TRP16 is likely to bind to NF-κB. These findings elucidate the molecular mechanism by which NF-κB activation is regulated through Cr-TRP16.

Thiol redox transitions by thioredoxin and thioredoxin-binding protein-2 in cell signaling

The cellular thiol redox state is a crucial mediator of metabolic, signaling and transcriptional processes in cells, and an exquisite balance between the oxidizing and reducing states is essential for the normal function and survival of cells. Reactive oxygen species (ROS) are widely known to function as a kind of second messenger for intracellular signaling and to modulate the thiol redox state. Thiol reduction is mainly controlled by the thioredoxin (TRX) system and glutathione (GSH) systems as scavengers of ROS and regulators of the protein redox states. The thioredoxin system is composed of several related molecules interacting through the cysteine residues at the active site, including thioredoxin, thioredoxin-2, a mitochondrial thioredoxin family, and transmembrane thioredoxin-related protein (TMX), an endoplasmic reticulum (ER)-specific thioredoxin family. Thioredoxin couples with thioredoxin-dependent peroxidases (peroxiredoxin) to scavenge hydrogen peroxide. In addition, thioredoxin does not simply act only as a scavenger of ROS but also as an important regulator of oxidative stress response through protein-protein interaction. The interaction of thioredoxin and thioredoxin-binding proteins such as thioredoxin-binding protein-2 (TBP-2, also called as Txnip or VDUP1), apoptosis signal kinase (ASK-1), redox factor 1 (Ref-1), Forkhead box class O 4 (FoxO4), and nod-like receptor proteins (NLRPs) suggested unconventional functions of thioredoxin and a novel mechanism of redox regulation. Here, we introduce the central mechanism of thiol redox transition in cell signaling regulated by thioredoxin and related molecules.

Reduced levels of reactive oxygen species correlate with inhibition of apoptosis, rise in thioredoxin expression and increased bovine leukemia virus proviral loads

Background

Bovine Leukemia virus (BLV) is a deltaretrovirus that induces lymphoproliferation and leukemia in ruminants. In ex vivo cultures of B lymphocytes isolated from BLV-infected sheep show that spontaneous apoptosis is reduced. Here, we investigated the involvement of reactive oxygen species (ROS) in this process.

Results

We demonstrate that (i) the levels of ROS and a major product of oxidative stress (8-OHdG) are reduced, while the thioredoxin antioxidant protein is highly expressed in BLV-infected B lymphocytes, (ii) induction of ROS by valproate (VPA) is pro-apoptotic, (iii) inversely, the scavenging of ROS with N-acetylcysteine inhibits apoptosis, and finally (iv) the levels of ROS inversely correlate with the proviral loads.

Conclusion

Together, these observations underline the importance of ROS in the mechanisms of inhibition of apoptosis linked to BLV infection.

Overexpression of peroxiredoxin I and thioredoxin1 in human breast carcinoma

Background

Peroxiredoxins (Prxs) are a novel group of peroxidases containing high antioxidant efficiency. The mammalian Prx family has six distinct members (Prx I-VI) in various subcellular locations, including peroxisomes and mitochondria, places where oxidative stress is most evident. The function of Prx I in particular has been implicated in regulating cell proliferation, differentiation, and apoptosis. Since thioredoxin1 (Trx1) as an electron donor is functionally associated with Prx I, we investigated levels of expression of both Prx I and Trx1.

Methods

We investigated levels of expression of both Prx I and Trx1 in breast cancer by real-time polymerase chain reaction (RT-PCR) and Western blot.

Results

Levels of messenger RNA (mRNA) for both Prx I and Trx1 in normal human breast tissue were very low compared to other major human tissues, whereas their levels in breast cancer exceeded that in other solid cancers (colon, kidney, liver, lung, ovary, prostate, and thyroid). Among members of the Prx family (Prx I-VI) and Trx family (Trx1, Trx2), Prx I and Trx1 were preferentially induced in breast cancer. Moreover, the expression of each was associated with progress of breast cancer and correlated with each other. Western blot analysis of different and paired breast tissues revealed consistent and preferential expression of Prx I and Trx1 protein in breast cancer tissue.

Conclusion

Prx I and Trx1 are overexpressed in human breast carcinoma and the expression levels are associated with tumor grade. The striking induction of Prx I and Trx1 in breast cancer may enable their use as breast cancer markers.

Redox-regulated mechanisms in asthma

Homeostasis of the reduction-oxidation (redox) state is critical to protection from oxidative stress in the lungs. Therefore, the lungs have high levels of antioxidants, including glutathione, heme oxygenase, and superoxide dismutase. The numbers of inflammatory cells -- particularly eosinophils -- are increased in the airways of asthma patients, and these pulmonary inflammatory cells release large amounts of harmful reactive oxygen species and reactive nitrogen species. Human thioredoxin 1 (TRX1) is a redox-active protein of approximately 12 kDa that contains a (32)Cys-Gly-Pro-(35)Cys sequence necessary for its activity. The strong reducing activity of the sequence results from the cysteine residues acting as proton donors and cleaving disulfide (S-S) bonds in the target protein. Endogenous or exogenous TRX1 or both protect the lungs against ischemia-reperfusion injury, influenza infection, bleomycin-induced injury, or lethal pulmonary inflammation caused by interleukin-2 and interleukin-18. We showed that exogenous TRX1 inhibits airway hyperresponsiveness and pulmonary inflammation accompanied by eosinophilia in mouse models of asthma. Recently, we reported that exogenous TRX1 improves established airway remodeling in a prolonged antigen-exposure mouse asthma model. Exogenous and endogenous TRX1 also prevents the development of airway remodeling. Here, we discuss the role and clinical benefits of TRX1 in asthma.

Increased expression of thioredoxin-1, vascular endothelial growth factor, and redox factor-1 is associated with poor prognosis in patients with liver metastasis from colorectal cancer

We examined whether the expression of thioredoxin-1 (Trx-1) was associated with patient prognosis after liver resection for metastatic colorectal cancer. Eighty-four patients underwent resection of liver metastases from colorectal cancer, leaving no macroscopic evidence of residual tumor. Immunohistochemical study was performed to evaluate the relation among Trx-1, vascular endothelial growth factor (VEGF), and redox factor-1 (Ref-1) expression and the clinicopathologic characteristics and patient survival. Thirty-seven patients (44.0%) with Trx-1-positive metastases had shorter survival after primary liver resection (P = .0003) than the 47 patients (56.0%) with Trx-1-negative metastases. The percentage VEGF-positive and Ref-1-positive metastases was significantly higher in patients with Trx-1 expression (P = .0009 and .0002, respectively). Multivariate analysis revealed that Trx-1 expression was an independent prognostic factor. Expression of VEGF and Ref-1 is associated with Trx-1 overexpression, which is related to a poor prognosis in patients with liver metastases from colorectal cancer.

Reactive oxygen species and antioxidant mechanisms in human tissues and their relation to malignancies

Reactive oxygen species (ROS) are formed in mammalian cells as a consequence of aerobic respiration. Despite multiple conserved redox modulating systems, a given proportion of ROS continuously escape from the mitochondrial respiratory chain, being sufficiently potent to damage cells in various ways, including numerous carcinogenic DNA mutations. Oxidative stress resulting from an imbalanced ratio between ROS production and detoxification may also disturb physiological signal transduction, lead to chain reactions in lipid layers, and damage DNA repair enzymes. The significance of ROS and antioxidant systems in carcinogenesis is still complicated and in many ways contradictory. Enhanced antioxidant mechanisms in tumor cells in vivo have been implicated in chemoresistance and lead to poor prognosis, whereas most in vitro studies have reported tumor-suppressing properties of antioxidant enzymes. The present review aims to clarify the significance of oxidative stress and the role of cell redox state modulating systems in human malignancies in light of the current literature.

Regulation of the activity of the tumor suppressor PTEN by thioredoxin in Drosophila melanogaster

Human Thioredoxin-1 (hTrx-1) is a small redox protein with a molecular weight of 12 kDa that contains two cysteine residues found in its catalytic site. HTrx-1 plays an important role in cell growth, apoptosis, and cancer patient prognosis. Recently, we have demonstrated that hTrx-1 binds to the C2 domain of the human tumor suppressor, PTEN, in a redox dependent manner. This binding leads to the inhibition of PTEN lipid phosphatase activity in mammalian tissue culture systems. In this study, we show that over-expression of hTrx-1 in Drosophila melanogaster promotes cell growth and proliferation during eye development as measured by eye size and ommatidia size. Furthermore, hTrx-1 rescues the small eye phenotype induced by the over-expression of PTEN. We demonstrate that this rescue of the PTEN-induced eye size phenotype requires cysteine-218 in the C2 domain of PTEN. We also show that hTrx-1 over-expression results in increased Akt phosphorylation in fly head extracts supporting our observations that the hTrx-1-induced eye size increase results from the inhibition of PTEN activity. Our study confirms the redox regulation of PTEN through disulfide bond formation with the hTrx-1 in Drosophila and suggests conserved mechanisms for thioredoxins and their interactions with the phosphatidylinositol-3-kinase signaling pathway in humans and fruit flies.

Role of thioredoxin in cell growth through interactions with signaling molecules

The thioredoxin system helps maintain a reducing environment in cells, but thioredoxin functions as more than simply an antioxidant. Thioredoxin functions depend on the protein's redox state, as determined by two conserved cysteines. Key biologic activities of thioredoxin include antioxidant, growth control, and antiapoptotic properties, resulting from interaction with target molecules including transcription factors. Mechanisms by which thioredoxin regulates cell growth include binding to signaling molecules such as apoptosis signal-regulating kinase-1 (ASK-1) and thioredoxin-interacting protein (Txnip). The molecular interplay between thioredoxin, ASK-1, and Txnip potentially influences cell growth and survival in diverse human diseases such as cancer, diabetes, and heart disease. In this review, we focus on the structure of thioredoxin and its functional regulation of cell growth through the interactions with signaling molecules.

Evaluation of the molecular mechanisms involved in the gain of function of a Li-Fraumeni TP53 mutation

The TP53 tumor suppressor gene is the most frequent target for genetic alterations in human cancer. TP53 gene alterations may result in the gain of oncogenic functions such as neoangiogenesis and resistance to therapy. The TP53 germ line mutation c.659A>C (p.Y220S) was identified in stored DNA from related patients with Li-Fraumeni syndrome (LFS) who died after developing clinically aggressive tumors. All of the patients were treated with protocols that included doxorubicin hydrochloride (DX) as a pivotal drug. To define the in vitro mutational phenotype of this germ line mutation, we used murine fibroblasts explanted from wild-type (wt) and p53 knockout (KO) mice from the same littermate. p53Y220S and p53R175H fibroblasts, obtained from p53KO fibroblasts transfected with expression vectors encoding the human Y220S and R175H p53 mutants, respectively, exhibited resistance to DX treatment. Moreover, p53Y220S fibroblasts exhibited angiogenetic properties, and after DX treatment, p53Y220S failed to translocate into the nucleus and showed an increase in its cytosolic levels. DX treatment does not influence p53 distribution within the nuclear and cytosolic compartments in p53R175H fibroblasts. Peroxiredoxin II (Prx II), a protein that is involved in eliminating reactive oxygen species (ROS), showed increased expression intensity in p53Y220S fibroblasts after DX treatment, as observed by two-dimensional electrophoresis analysis. Moreover, Thioredoxin (Trx), a protein that cooperates with Prx II, is overexpressed in p53Y220S mutants under basal conditions. These data suggest a relationship between the presence of the p53Y220S mutation and enhanced levels of Prx II and Trx in mutant fibroblasts. Since one of the mechanisms of the DX antitumor effect has been ascribed to production of ROS, future studies will evaluate the involvement of PrxII and Trx in the chemoresistance of p53Y220S fibroblasts to DX.

Anti-proliferative and anti-tumor effects of antisense oligonucleotide GTI-2601 targeted against human thioredoxin

Human thioredoxin has been implicated in cancer as a growth stimulator through regulation of DNA replication and growth factor activity, as a modulator of transcription factor activity, and as an inhibitor of apoptosis. In the present study, the steady-state level of thioredoxin protein was examined in a number of cancer cell lines. Interestingly, thioredoxin expression is elevated in a variety of human tumor cell lines compared with normal cell lines. The altered expression of thioredoxin in tumor cells suggests it may be a target in the development of novel therapeutic agents for the treatment and prevention of cancer. Further to this possibility, 26 phosphorothioate antisense oligodeoxynucleotides (PS-AS-ODNs) were evaluated for the ability to inhibit thioredoxin expression in cell culture. One PS-AS-ODN, GTI-2601, specifically reduced the levels of thioredoxin mRNA and protein, exhibited potent anti-proliferative effects on colony formation in vitro, and had anti-tumor effects in human tumor xenograft mouse models in vivo. Sequence-specific decreases in thioredoxin expression levels were accompanied by significant suppression of tumor growth in mice. Taken together, these data suggest that thioredoxin may be a useful target for developing PS-AS-ODNs as drug candidates against human cancer.

Molecular pharmacology and antitumor activity of palmarumycin-based inhibitors of thioredoxin reductase

The cytosolic thioredoxin redox system composed of thioredoxin-1 and the NADPH-dependent thioredoxin reductase-1 reductase is an important regulator of cell growth and survival. Thioredoxin-1 is overexpressed in many human tumors where it is associated with increased cell proliferation, decreased apoptosis, and decreased patient survival. We hypothesized that thioredoxin reductase-1 provides a target to inhibit the activity of overexpressed thioredoxin-1 for the development of novel anticancer agents. We found that the naphthoquinone spiroketal fungal metabolite palmarumycin CP1 is a potent inhibitor of thioredoxin reductase-1, but attempts to exploit the activity of palmarumycin CP1 analogues as antitumor agents in vivo were hampered by their insolubility. We have therefore developed PX-916, a water-soluble prodrug of a palmarumycin CP1 analogue. PX-916 rapidly releases the parent compound at physiologic pH and in plasma but is stable at acid pH, allowing its i.v. administration. PX-916 is a potent inhibitor of purified human thioredoxin reductase-1 and of thioredoxin reductase-1 activity in cells and tumor xenografts when given to mice and inhibits the downstream targets of thioredoxin-1 signaling, hypoxia-inducible factor-1alpha, and vascular endothelial growth factor in tumors. PX-916 showed excellent antitumor activity against several animal tumor models with some cures. Thus, the study shows that water-soluble inhibitors of thioredoxin reductase-1, such as PX-916, can block thioredoxin-1 signaling in tumors producing marked inhibition of tumor growth.

High thioredoxin expression is associated with resistance to docetaxel in primary breast cancer

PURPOSE

Thioredoxin overexpression is suggested to be associated with resistance to several chemotherapeutic agents in vitro. In the present study, it has been studied whether or not high thioredoxin expression is associated with resistance to docetaxel therapy in breast cancer patients.

PATIENTS AND METHODS

Sixty-three primary breast cancer patients were treated with docetaxel (60 mg/m(2), q3w) for four cycles in the neoadjuvant setting. Expression of thioredoxin, estrogen receptor (ER), p53, BRCA-1, and Bcl-2 in tumor tissues obtained before docetaxel therapy was studied by immunohistochemistry (thioredoxin, p53, BRCA-1, and Bcl-2) and enzyme immunoassay (ER), and relationship of expression of these biomarkers with a pathologic response was investigated.

RESULTS

There was no significant correlation between the expression of p53, BRCA-1, or Bcl-2 and a response to docetaxel. However, tumors with high thioredoxin expression showed a significantly lower response rate (0%) than those with low thioredoxin expression (30.6%; P = 0.018) and ER-negative tumors showed a significantly higher response rate (32.4%) than ER-positive tumors (10.7%; P = 0.043). Thioredoxin expression significantly increased after docetaxel therapy (mean, 56.1%) as compared with that before docetaxel therapy (mean, 28.6%; P < 0.0001) but there was no significant association between the extent of increase in thioredoxin expression and response.

CONCLUSION

High thioredoxin expression in prechemotherapy tumor samples, but not the increase in thioredoxin expression induced by docetaxel, is associated with resistance to docetaxel in breast cancer. Thioredoxin and ER might be clinically useful in the prediction of a response to docetaxel.

Redox regulation of lung inflammation by thioredoxin

The lungs are the richest in oxygen among the various organs of the body and are always subject to harmful reactive oxygen species. Regulation of the reduction/oxidation (redox) state is critical for cell viability, activation, proliferation, and organ functions. Although the protective importance of various antioxidants has been reported, few antioxidants have established their clinical usefulness. Thioredoxin (TRX), a key redox molecule, plays crucial roles as an antioxidant and a catalyst in protein disulfide/dithiol exchange. TRX also modulates intracellular signal transduction and exerts antiinflammatory effects in tissues. In addition to its beneficial effects in other organs, the protective effect of TRX in the lungs has been shown against ischemia/ reperfusion injury, influenza infection, bleomycin-induced injury, or lethal inflammation caused by interleukin- 2 and interleukin-18. Monitoring of TRX in the plasma, airway, or lung tissue may be useful for the diagnosis and follow-up of pulmonary inflammation. Promotion/modulation of the TRX system by the administration of recombinant TRX protein, induction of endogenous TRX, or gene therapies can be a therapeutic modality for oxidative stress-associated lung disorders.

Immunohistochemical appearance of HNE-protein conjugates in human astrocytomas

Gliomas are tumors originating from astrocytes, oligodendrocytes or ependimal cells. Those of astrocytic origin are the most widespread of primary brain tumors and account for more then 60% of all CNS neoplasms. The current state of knowledge on the associations between tumor etiology and oxidative stress suggests that environmental factors that cause oxidative stress could also induce and promote cancer, especially in case of hereditary predisposition. Among mediators of oxidative stress, lipid peroxidation product 4-hydroxynonenal (HNE) is of particular relevance in oncology, as it is known to act as a growth-regulating factor and a signaling molecule. The aim of present study was to investigate by immunohistochemistry the presence of HNE-modified proteins in different types of astrocytoma. Our study comprised 45 astrocytic tumors. These tumors were graded in accordance with the WHO classification as diffuse astrocytomas (DA), anaplastic astrocytomas (AA) and glioblastomas (GB), while each group comprised 15 tumors. Slides of paraffin-embedded tumor tissue were stained with hematoxylin-eosin or were prepared for immunohistochemistry with monoclonal antibodies to HNE-histidine conjugate. Positive immunohistochemical reaction to HNE was analyzed semi-quantitatively. HNE positivity was proportional with malignancy of astrocytomas. The weakest presence of HNE-histidine adducts was found in DA, followed by AA and GB. Lowest intensity of HNE immunopositivity was present in tumor cells of almost all DA, predominantly around blood vessels. In malignant variants of astrocytoma, AA and GB, HNE positivity was moderate to strong, and diffusely distributed in all tumors.

Thioredoxin-1 binds to the C2 domain of PTEN inhibiting PTEN's lipid phosphatase activity and membrane binding: a mechanism for the functional loss of PTEN's tumor suppressor activity

Thioredoxin-1 (Trx-1) is a 12 kDa redox protein that is overexpressed in a large number of human tumors. Elevated Trx-1 is associated with increased tumor cell proliferation, inhibited apoptosis, aggressive tumor growth, and decreased patient survival. The molecular mechanisms for the promotion of tumorigenesis by Trx-1 are not known. PTEN is a major tumor suppressor of human cancer that acts by hydrolyzing membrane phosphatidylinositol (PtdIns)-3-phosphates, thus, preventing the activation of the survival signaling kinase Akt by PtdIns-3-kinase. We show that Trx-1 binds in a redox dependent manner to PTEN to inhibit its PtdIns-3-phosphatase activity which results in increased Akt activation in cells. Molecular docking and site-specific mutation studies show that the binding of Trx-1 to PTEN occurs through a disulfide bond between the active site Cys(32) of Trx-1 and Cys(212) of the C2 domain of PTEN leading to steric interference by bound Trx-1 of the catalytic site of PTEN and of the C2 lipid membrane-binding domain. The results of the study suggest that the increased levels of Trx-1 in human tumors could lead to functional inhibition of PTEN tumor suppressor activity providing an additional mechanism for tumorigenesis with loss of PTEN activity.

Thioredoxin is associated with proliferation, p53 expression and negative estrogen and progesterone receptor status in breast carcinoma

We investigated the expression of thioredoxin and thioredoxin reductase in a large set of breast invasive and in situ carcinomas by immunohistochemistry. Additionally, NF-kappa B, p53 and proliferating cell nuclear antigen (PCNA) expression was studied. Thioredoxin and thioredoxin reductase expression was located in both cytoplasmic and nuclear compartments of the cell. Cytoplasmic thioredoxin positivity was found in 67 % and nuclear in 59 % of the cases, while thioredoxin reductase was found in 55 % and 6 % of cases, respectively. Ductal carcinomas showed stronger cytoplasmic thioredoxin immunoreactivity than lobular ones. Nuclear thioredoxin positivity was more often found in in situ lesions, and lobular carcinomas were more often negative than ductal ones. Both cytoplasmic and nuclear thioredoxin-positive cases had a high proliferation measured by PCNA staining. Positive nuclear immunostaining was associated with negative estrogen and progesterone receptor status. Cases with high p53 expression showed significantly higher nuclear thioredoxin positivity, but lower thioredoxin reductase positivity. Whilst thioredoxin or thioredoxin reductase was not associated with patient survival, cases showing both cytoplasmic and nuclear thioredoxin reductase-positive tumours had a shorter disease-free interval than those with negative immunostaining.

Thioredoxin reductase and cancer cell growth inhibition by organotellurium compounds that could be selectively incorporated into tumor cells

The thioredoxins are small ubiquitous redox proteins with the conserved redox catalytic sequence-Trp-Cys-Gly-Pro-Cys-Lys, where the Cys residues undergo reversible NADPH dependent reduction by selenocysteine containing flavoprotein thioredoxin reductases. Thioredoxin expression is increased in several human primary cancers including lung, colon, cervix, liver, pancreatic, colorectal and squamous cell cancer. The thioredoxin/thioredoxin reductase pathway therefore provides an attractive target for cancer drug development. Organotellurium steroid, lipid, amino acid, nucleic base, and polyamine inhibitors were synthesized on the basis that they might be selectively or differentially incorporated into tumor cells. Some of the newly prepared classes of tellurium-based inhibitors (lipid-like compounds 3b and 3e, amino acid derivative 5b, nucleic base derivative 8b, and polyamine derivatives 14a and 14b) inhibited TrxR/Trx and cancer cell growth in culture with IC(50) values in the low micromolar range.

Increased expression of thioredoxin-1 in human colorectal cancer is associated with decreased patient survival

Thioredoxin-1 is a redox protein that, when overexpressed, causes increased cancer-cell growth and inhibited apoptosis. Thioredoxin-1 expression has been reported to be increased in several human primary tumors, but its relationship to tumor progression and patient survival has not been established. We studied the expression of thioredoxin-1 as measured with immunohistochemical staining in paraffin-embedded human normal colonic mucosa, adenomatous polyps, and primary and metastatic colorectal cancer. Thioredoxin-1 expression was not increased in 12 colorectal adenomatous polyps, compared with 8 samples of normal colonic mucosa, but was significantly increased in 12 primary colorectal cancers (P <.01). Thioredoxin-1 expression was not significantly different in primary lymph-node metastases and the primary colorectal cancer. Using colorectal cancer samples from 37 subjects for whom survival data was available, we found that thioredoxin-1 expression increased with Dukes stage, although the association was not statistically significant (P =.077). We noted a significant association between thioredoxin-1 expression and patient survival (P =.004); higher score was associated with decreased survival. When adjusted for Dukes stage, thioredoxin-1 expression showed a statistically significant association with survival (P =.012). The work shows that increased thioredoxin-1 expression is a relatively late event in colorectal carcinogenesis and provides evidence in a small group of subjects with colorectal cancer of Dukes stages A through D that thioredoxin-1 expression may be an independent marker of patient prognosis.

Thioredoxin reductase and cancer cell growth inhibition by organotellurium antioxidants

Thioredoxin (Trx) expression is increased in several human primary cancers and the Trx/Trx reductase (TrxR) system therefore provides an attractive target for cancer drug development. Novel organotellurium antioxidants, especially a primitive analog of vitamin E (compound 1d) and compounds 7, 9 and 10--all carrying highly functionalized 4-(dialkylamino)phenyltelluro groups to secure high antioxidative capacity--were found to inhibit TrxR with IC50 values in the low micromolar range. Whereas antioxidant 1d also inhibited the growth of MCF-7 human breast cancer cells in culture at a similar level (IC50 = 1.8 microM), the other TrxR inhibitors were inactive in concentrations below about 10 M.

DNA microarray reveals increased expression of thioredoxin peroxidase in thioredoxin-1 transfected cells and its functional consequences

The mammalian thioredoxins are a family of small redox proteins that undergo NADPH dependent reduction by thioredoxin reductase. Reduced thioredoxins reduce oxidized cysteine groups on proteins including transcription factors to increase their binding to DNA, and is a source of reducing equivalents for enzymes such as thioredoxin peroxidase which removes H2O2 and alkyl peroxides. Thioredoxin-1 is over expressed in many human tumors where it is associated with aggressive tumor growth, inhibited apoptosis and decreased patient survival. Transfection of cells with thioredoxin-1 has been shown to increase cell growth and inhibit apoptosis. We have used DNA micro array to investigate the effects of thioredoxin-1 transfection on the expression of a panel of 520 redox, apoptosis and cell growth related genes in MCF-7 human breast cancer cells. One of the genes whose expression was increased as a result of thioredoxin-1 over expression was thioredoxin peroxidase-2. This increase was confirmed by Northern blotting. Transfection of mouse WEHI7.2 thymoma cells with human thioredoxin peroxidase-2 was found to protect the cells from apoptosis induced by H2O2 but not from apoptosis induced by dexamethasone, doxorubicin or etoposide. Thus, increased thioredoxin peroxidase-2 expression does not explain the widespread antiapoptotic effects of thioredoxin-1.

Thioredoxin superfamily and thioredoxin-inducing agents

Mammalian thioredoxin (TRX) with redox-active dithiol in the active site plays multiple roles in intracellular signaling and resistance against oxidative stress. TRX is induced by a variety of stresses including infectious agents as well as hormones and chemicals. TRX is secreted from activated cells such as HTLV-I-transformed T-cells as a redox-sensitive molecule with cytokine-like and chemokine-like activities. The promoter of the TRX gene contains a series of stress-responsive elements. In turn, TRX promotes activation of transcription factors such as NF-kappa B, AP-1, and p53. We have reported that natural substances including estrogen, prostaglandins, and cAMP induce mRNA, protein, and secretion of TRX. These agents seemed to exert their physiological functions including cytoprotective actions partly through the induction of TRX without massive oxidative stress, which induces TRX strongly as well as other stress proteins. We report here a new TRX inducer substance, geranylgeranylacetone (GGA), which is originally derived from a natural plant constituent and has been used in the clinical field as an anti-ulcer drug. We have demonstrated that GGA induces the messenger RNA and protein of TRX and affects the activation of transcription factors, AP-1 and NF-kappa B, and that GGA blunted ethanol-induced cytotoxicity of cultured hepatocytes and gastrointestine mucosal cells. We will discuss a possible novel molecular mechanism of GGA, which is to protect cells via the induction of TRX and activation of transcription factors such as NF-kappa B and AP-1. Identification of the particular TRX-inducing components may contribute to the elucidation of the molecular basis of the "French Paradox," in which good red wines are beneficial for the cardiovascular system.

Thioredoxin post-transcriptional regulation by H19 provides a new function to mRNA-like non-coding RNA

Classically, the functional product of coding genes is a protein whose synthesis is directed by an mRNA-template. However, in the last few years several genes yielding an mRNA-like non-coding RNA as a functional product have been identified. In most cases these transcripts are synthesized by the RNA polymerase II, capped, spliced and polyadenylated, like classical mRNA. These latter have non-conserved open reading frames and seem to be untranslated. Consequently, it has been proposed and admitted that these genes act at the RNA level, and are so-called 'riboregulators'. H19 belongs to this class of gene and its role remains a matter of debate: for some authors it is an oncogene, for others a tumour suppressor. Here, we demonstrate, using a proteomic approach, that an H19 overexpression in human cancerous mammary epithelial cells stably transfected with genomic DNA containing the entire H19 gene is responsible for positively regulating at the post-transcriptional level the thioredoxin, a key protein of the cellular redox metabolism. Interestingly, this protein accumulates in many cancerous tissues, such as breast carcinomas in which we have also demonstrated an overexpression of the H19 gene.

Thioredoxin-mediated redox control of human T cell lymphotropic virus type I (HTLV-I) gene expression

Thioredoxin (TRX) is a small ubiquitous protein with multiple biological functions, including the thiol-mediated redox-regulation of gene expression. We have previously demonstrated that human TRX is overexpressed as a major protein oxidoreductase in human T cell lymphotropic virus type I (HTLV-I)-infected cells. In the present study, we investigated the relationship between TRX and viral gene expression in HTLV-I infection. To study the mechanism that causes overexpression of TRX in HTLV-I-infected cells, we first examined the effect of the HTLV-I transactivator, Tax, on TRX expression. Induction of HTLV-I Tax protein increased the expression of TRX protein in a Tax-transfected Jurkat cell line, JPX-9. Moreover, chloramphenicol acetyltransferase (CAT) analysis with a reporter gene containing the TRX promoter revealed that Tax activates the transcription of TRX gene. To study the role of overexpressed TRX in HTLV-I infection, we next examined the effect of TRX on HTLV-I long terminal repeat (LTR)-mediated transcription using CAT analysis. In an HTLV-I-infected human T cell line MT-2, the HTLV-I LTR transactivation was suppressed by the overexpression of wild-type TRX, but activated by the introduction of inactive mutant TRX. Moreover, in HTLV-I negative Jurkat T cells, the HTLV-I LTR transactivation induced by Tax was also repressed by overexpression of wild-type TRX. Because cellular redox changes were shown to affect the HTLV-I gene expression, it is likely that TRX modulates the HTLV-I gene expression by regulating cellular redox state. Taken together, these findings suggest that overexpressed TRX, which is induced by HTLV-I Tax, may play an important role in HTLV-I infection through the negative regulation of viral gene expression.

Properties and biological activities of thioredoxins

The mammalian thioredoxins are a family of small (approximately 12 kDa) redox proteins that undergo NADPH-dependent reduction by thioredoxin reductase and in turn reduce oxidized cysteine groups on proteins. The two main thioredoxins are thioredoxin- 1, a cytosolic and nuclear form, and thioredoxin-2, a mitochondrial form. Thioredoxin-1 has been studied more. It performs many biological actions including the supply of reducing equivalents to thioredoxin peroxidases and ribonucleotide reductase, the regulation of transcription factor activity, and the regulation of enzyme activity by heterodimer formation. Thioredoxin-1 stimulates cell growth and is an inhibitor of apoptosis. Thioredoxins may play a role in a variety of human diseases including cancer. An increased level of thioredoxin-1 is found in many human tumors, where it is associated with aggressive tumor growth. Drugs are being developed that inhibit thioredoxin and that have antitumor activity.

Thioredoxin peroxidase-1 (peroxiredoxin-1) is increased in thioredoxin-1 transfected cells and results in enhanced protection against apoptosis caused by hydrogen peroxide but not by other agents including dexamethasone, etoposide, and doxorubicin

Thioredoxin-1 (Trx-1) is a small redox oncoprotein whose expression is increased in a number of human primary cancers where it is associated with aggressive tumor growth, inhibition of apoptosis and decreased patient survival. We report that Trx-1-transfected MCF-7 human breast cancer cells have increased expression of thioredoxin peroxidase-1 (TrxP-1) a peroxiredoxin family member that scavenges H(2)O(2) using Trx-1 as a source of reducing equivalents. Our work shows that TrxP-1 is more effective than selenium-dependent glutathione peroxidase in protecting cells against H(2)O(2) damage. Transfection of mouse WEHI7.2 lymphoma cells with human TrxP-1 or TrxP-2, but not TrxP-4, protects the cells against H(2)O(2) induced apoptosis but does not protect against apoptosis induced by dexamethasone, etoposide, or doxorubicin. The results show that an increase in TrxP-1 expression contributes to the protection against H(2)O(2) induced apoptosis caused by Trx-1, but does not protect against apoptosis induced by other agents.

Properties and biological activities of thioredoxins

The mammalian thioredoxins are a family of small (approximately 12 kDa) redox proteins that undergo NADPH-dependent reduction by thioredoxin reductase and in turn reduce oxidized cysteine groups on proteins. The two main thioredoxins are thioredoxin-1, a cytosolic and nuclear form, and thioredoxin-2, a mitochondrial form. Thioredoxin-1 has been studied more. It performs many biological actions including the supply of reducing equivalents to thioredoxin peroxidases and ribonucleotide reductase, the regulation of transcription factor activity, and the regulation of enzyme activity by heterodimer formation. Thioredoxin-1 stimulates cell growth and is an inhibitor of apoptosis. Thioredoxins may play a role in a variety of human diseases including cancer. An increased level of thioredoxin-1 is found in many human tumors, where it is associated with aggressive tumor growth. Drugs are being developed that inhibit thioredoxin and that have antitumor activity.

Up-regulation of thioredoxin and thioredoxin reductase in human malignant pleural mesothelioma

Thioredoxin (Trx) with a redoxactive dithiol together with NADPH and thioredoxin reductase (TrxR) is a major disulfide reductase regulating cellular redox state and cell proliferation and possibly contributing to the drug resistance of malignant cells. We assessed the Trx system in malignant pleural mesothelioma cell lines, in nonmalignant pleural mesothelium and in biopsies of malignant pleural mesothelioma. The mRNA and immunoreactive proteins of Trx and cytosolic and mitochondrial TrxR were positive in all four human mesothelioma cell lines investigated. Six cases of nonmalignant, histologically healthy pleural mesothelium showed no Trx or TrxR immunoreactivity, whereas immunohistochemistry on 26 biopsies of human malignant pleural mesothelioma showed positive Trx in all cases and positive TrxR in 23 (88%) of the cases. Moderate or strong immunoreactivity for Trx or TrxR was detected in 85% (22 cases) and 61% (14 cases) of the mesothelioma cases, respectively. Both Trx and TrxR staining patterns were mainly diffuse and cytoplasmic, but in 39% of the mesothelioma cases prominent nuclear staining could also be detected. Although staining for Trx and TrxR was seen in tumor cells, no significant association could be demonstrated between Trx or TrxR expression and tumor cell proliferation or apoptosis in the biopsies of mesothelioma. There was no significant association between the intensity of Trx or TrxR immunoreactivity and patient survival, which may possibly be related to moderate or intense Trx and TrxR reactivity in most of the cases. Although the Trx system may have an important role in the drug resistance of malignant mesothelioma, these studies also suggest that multiple factors contribute to the promotion, cell proliferation and apoptosis of malignant mesothelioma cells in vivo.

Alternative Splicing Is Associated with Decreased Expression of the Redox Proto-oncogene Thioredoxin-1 in Human Cancers

Human thioredoxin-1 (Trx-1) is a small redox protein that is overexpressed in a number of human primary tumors, where it is associated with rapid cell proliferation and inhibited apoptosis. Mutation scanning denaturing high-performance liquid chromatography of Trx-1 mRNA in 58 human tumor cell lines found no evidence for changes in the base sequence of human Trx-1 mRNA. An alternatively spliced form of Trx-1 mRNA lacking exons 2 and 3 was found in 7 of the cell lines but it was not translated. The cell lines having the alternatively spliced Trx-1 mRNA had 73% lower total Trx-1 mRNA than the other cell lines, suggesting that alternative splicing may control the level of Trx-1 mRNA in some cancer cells.

Possible association of thioredoxin and p53 in breast cancer

Expression of thioredoxin (TRX), a dithiol-reducing enzyme, and mutations of p53 have been detected in various cancer tissues. We recently reported that TRX-dependent redox regulation plays a crucial role in DNA binding activity of p53. In this study, we investigated the possibility of functional association between TRX and p53 in breast cancer. First, we examined the expression of TRX and mutated p53 in 100 primary breast cancer tissues by immunohistochemistry. Expression of TRX was detected in cases of 84/100 (84%) and expression of p53, which means existence of mutated p53, in cases of 63/100 (63%). TRX positive cases was 89% (56/63) in mutant p53 positive cases. Next, we examined the expression of TRX and p53 in breast cancer cell line MCF-7 cells after CDDP treatment or irradiation. CDDP treatment or irradiation augmented expression of TRX and p53 in MCF-7 cells by western blotting. Immunofluorescence cell analysis by confocal microscopy showed that CDDP treatment induced translocation of TRX into nuclei. These results suggest the possible association of TRX with p53-dependent function including DNA repair in breast cancer.

The role of the redox protein thioredoxin in cell growth and cancer

The thioredoxins are ubiquitous proteins containing a conserved -Trp-Cys-Gly-Pro-Cys-Lys- redox catalytic site. Mammalian thioredoxin family members include thioredoxin-1 (Trx1), mitochondrial thioredoxin-2 (Trx2), and a larger thioredoxin-like protein, p32TrxL. Thioredoxin is reduced by NADPH and thioredoxin reductase and, in turn reduces oxidized cysteine groups on proteins. When thioredoxin levels are elevated there is increased cell growth and resistance to the normal mechanism of programmed cell death. An increase in thioredoxin levels seen in many human primary cancers compared to normal tissue appears to contribute to increased cancer cell growth and resistance to chemotherapy. Mechanisms by which thioredoxin increases cell growth include an increased supply of reducing equivalents for DNA synthesis, activation of transcription factors that regulate cell growth, and an increase in the sensitivity of cells to other cytokines and growth factors. The mechanisms for the inhibition of apoptosis by thioredoxin are just now being elucidated. Because of its role in stimulating cancer cell growth and as an inhibitor of apoptosis, thioredoxin offers a target for the development of drugs to treat and prevent cancer.

A redox-inactive thioredoxin reduces growth and enhances apoptosis in WEHI7.2 cells

Cancer cell lines transfected with thioredoxin show increased anchorage-independent growth and decreased sensitivity to induction of apoptosis by a number of anticancer drugs. The present studies were undertaken to evaluate further the role of thioredoxin in cell growth and drug-induced apoptosis. A redox-inactive mutant thioredoxin was stably transfected into WEHI7.2 mouse lymphocytic leukemia cells and two clones were examined for growth characteristics and the induction of apoptosis by dexamethasone, etoposide, doxorubicin, and staurosporine. These clones each exhibited a 71% increase in doubling time in solution and a 20 and 75% reduction in colony formation in soft agarose. The transfected cells also showed increased susceptibility to apoptosis induced by dexamethasone, etoposide, doxorubicin, and staurosporine compared with controls. The results of this study suggest that thioredoxin can regulate the growth rate of cells and that thioredoxin is a critical component in the pathway leading to drug-induced apoptosis in WEHI7.2 cells.

A possible interaction of thioredoxin with VDUP1 in HeLa cells detected in a yeast two-hybrid system

Human thioredoxin (hTrx), a small ubiquitous protein with strong reducing potential, has multiple biological functions, including signal transduction and regulation of the activity of transcription factors. hTrx expression is enhanced in HPV-transformed cancer cells; however, the role of hTrx in the malignant cells is not fully understood. We employed a yeast two-hybrid system to search for proteins that bind to hTrx in HeLa cells, a type of HPV-transformed human cervical cancer cell. In a screen of 1.62 x 10(6) yeast cotransformed with a HeLa cDNA library and an hTrx vector, 13 clones were identified as candidates for hTrx-binding proteins. Among them, 3 clones were found to code in frame for the carboxyl-terminal portion of VDUP1 protein, lacking at most the first 155 residues from the start codon. A reconstructed clone carrying the full-length VDUP1 coding sequence also showed the ability to bind to an hTrx fusion protein. Loss of interaction between VDUP1 and hTrx was observed either when two cysteines (Cys 32 and 35) in hTrx were substituted by serines or when the deletion in VDUP1 was extended from amino acid position 155 to 225 or beyond. The 71-mer peptide fragment (position 155-225) of VDUP-1 alone did not bind to hTrx.

Thioredoxin, a putative oncogene product, is overexpressed in gastric carcinoma and associated with increased proliferation and increased cell survival

Human thioredoxin is a putative oncogene that may confer both a growth and survival advantage to tumor cells. Overexpressed thioredoxin mRNA has been found in both primary human lung and colorectal cancers. To determine the intratumor distribution and amount of thioredoxin protein in human primary carcinomas, we developed an immunohistochemical assay for thioredoxin in paraffin-embedded tissue. We then studied 10 patients with primary high-risk gastric carcinoma. To further relate thioredoxin protein overexpression to cell death and survival, we used a paraffin-based in situ end-labeling (ISEL) assay. To delineate proliferation, we used the nuclear proliferation antigen detected by Ki-67. In this survey, we found that thioredoxin was localized to tumor cells and overexpressed compared with normal gastric mucosa in 8 of 10 gastric carcinomas. The thioredoxin was found at high levels in 5 of the 8 overexpressing carcinomas. The overexpression of thioredoxin was typically found in both a nuclear and cytoplasmic location in the neoplastic cells. There was a significant positive correlation (P = .0061) with cancer cell proliferation measured by Ki-67. There was a significant negative correlation (P = .0001) with DNA damage measured by the ISEL assay, suggesting decreased apoptosis and increased carcinoma cell survival. Thus, human primary gastric tumors that are highly expressive of thioredoxin have both a higher proliferative rate and a higher survival rate than tumors that do not express thioredoxin. With these newly developed assays in hand, it is now feasible to question whether this thioredoxin-related combined growth and survival advantage translates into poor clinical outcome.

Redox control of caspase-3 activity by thioredoxin and other reduced proteins

Caspases are cysteine proteinases that play a critical role in the execution phase of apoptosis. The active site cysteine residue must be reduced for caspase activity. Thioredoxins are redox proteins that catalyze the reduction of cysteine residues. We have examined the ability of various recombinant human thioredoxins to activate caspase-3. The EC(50) for caspase-3 activation by reduced thioredoxin-1 was 2.5 microM, by reduced glutathione 1.0 mM and by dithiothreitol 3.5 mM. A catalytic site redox-inactive mutant thioredoxin-1 was almost as active as thioredoxin-1 in activating caspase-3. Caspase activation was shown to correlate with the number of reduced cysteine residues in the thioredoxins. Reduced insulin and serum albumin were as effective on a molar basis as thioredoxin-1 in activating caspase-3. Thus, caspase-3 activation is not a specific effect of thioredoxins but is a property shared by other reduced proteins.

Detection of thioredoxin in gastric cancer: association with histological type

Thioredoxin (TRX) is a redox-active protein with multiple intra- and extracellular functions. This protein exists ubiquitously in all life forms, from primitive living cells, such as Escherichia coli and yeast, to higher mammals. Recently, augmentation of the expression and transcription level of TRX has been reported in tumors of various organs. In this study, we examined the expression of TRX in gastric cancer with respect to its histological type and depth of invasion. The association with cell proliferation was also studied. Results of histochemical analysis of surgical specimens as well as cytochemical analysis and Northern blot analysis of gastric cancer cell lines indicated that TRX is predominantly expressed in undifferentiated type gastric cancer rather than in the differentiated type. Neither the depth of tumor invasion nor cell proliferation significantly determined the staining intensity for TRX.

Thioredoxin-dependent redox regulation of p53-mediated p21 activation

Thioredoxin (TRX) is a dithiol-reducing enzyme that is induced by various oxidative stresses. TRX regulates the activity of DNA-binding proteins, including Jun/Fos and nuclear factor-kappaB. TRX also interacts with an intranuclear reducing molecule redox factor 1 (Ref-1), which enhances the activity of Jun/Fos. Here, we have investigated the role of TRX in the regulation of p53 activity. Electrophoretic mobility shift assay showed that TRX augmented the DNA binding activity of p53 and also further potentiated Ref-1-enhanced p53 activity. Luciferase assay revealed that transfection of TRX enhanced p53-dependent expression of p21 and further intensified Ref-1-mediated p53 activation. Furthermore, Western blot analysis revealed that p53-dependent induction of p21 protein was also facilitated by transfection with TRX. Overexpression of transdominant negative mutant TRX (mTRX) suppressed the effects of TRX or Ref-1, showing a functional interaction between TRX and Ref-1. cis-Diamminedichloroplatinum (II) (CDDP) induced p53 activation and p21 transactivation. The p53-dependent p21 transactivation induced by CDDP was inhibited by mTRX overexpression, suggesting that TRX-dependent redox regulation is physiologically involved in p53 regulation. CDDP also stimulated translocation of TRX from the cytosol into the nucleus. Hence, TRX-dependent redox regulation of p53 activity indicates coupling of the oxidative stress response and p53-dependent repair mechanism.

Identification of thioredoxin-binding protein-2/vitamin D(3) up-regulated protein 1 as a negative regulator of thioredoxin function and expression

Recent works have shown the importance of reduction/oxidation (redox) regulation in various biological phenomena. Thioredoxin (TRX) is one of the major components of the thiol reducing system and plays multiple roles in cellular processes such as proliferation, apoptosis, and gene expression. To investigate the molecular mechanism of TRX action, we used a yeast two-hybrid system to identify TRX-binding proteins. One of the candidates, designated as thioredoxin-binding protein-2 (TBP-2), was identical to vitamin D(3) up-regulated protein 1 (VDUP1). The association of TRX with TBP-2/VDUP1 was observed in vitro and in vivo. TBP-2/VDUP1 bound to reduced TRX but not to oxidized TRX nor to mutant TRX, in which two redox active cysteine residues are substituted by serine. Thus, the catalytic center of TRX seems to be important for the interaction. Insulin reducing activity of TRX was inhibited by the addition of recombinant TBP-2/VDUP1 protein in vitro. In COS-7 and HEK293 cells transiently transfected with TBP-2/VDUP1 expression vector, decrease of insulin reducing activity of TRX and diminishment of TRX expression was observed. These results suggested that TBP-2/VDUP1 serves as a negative regulator of the biological function and expression of TRX. Treatment of HL-60 cells with 1alpha, 25-dihydroxyvitamin D(3) caused an increase of TBP-2/VDUP1 expression and down-regulation of the expression and the reducing activity of TRX. Therefore, the TRX-TBP-2/VDUP1 interaction may be an important redox regulatory mechanism in cellular processes, including differentiation of myeloid and macrophage lineages.

Cloning, sequencing and functional expression of a novel human thioredoxin reductase

The DNA sequence encoding a novel human thioredoxin reductase has been determined. The protein is predicted to have 524 amino acids including a conserved -Cys-Val-Asn-Val-Gly-Cys catalytic site and a selenocysteine containing C-terminal -Gly-Cys-SeCys-Gly. The predicted molecular mass is 56.5. The newly identified TR sequence exhibits 54% identity to a previously reported human thioredoxin reductase and 37% identity to human glutathione reductase. Transient transfection of human embryonal kidney cells results in a 5-fold increase in thioredoxin reductase activity but no increase in glutathione reductase activity.