Isolation, characterization, and chromosomal mapping of a novel cDNA clone encoding human selenium binding protein

Withdrawal Notice

Withdrawal Notice: Zhu, Y, Pu, Q, Zhang, Q, et al. Selenium-binding protein 1 inhibits malignant progression and induces apoptosis via distinct mechanisms in non-small-cell lung cancer. Cancer Med. 2022; 00: 1-22. doi: 10.1002/cam4.5306. The above article, published online on 13th November 2022 in Wiley Online Library (https://onlinelibrary.wiley.com/doi/10.1002/cam4.5306), has been withdrawn by agreement between the journal Editor in Chief, Dr Stephen Tait, the Authors, and John Wiley & Sons, Ltd. The withdrawal has been agreed due to an editorial office error that led to the publication of the article without peer review. The revised article, which has undergone peer review may be read here: https://onlinelibrary.wiley.com/doi/10.1002/cam4.6309.

MicroRNAs as the pivotal regulators of cisplatin resistance in head and neck cancers

Although, there is a high rate of good prognosis in early stage head and neck tumors, about half of these tumors are detected in advanced stages with poor prognosis. A combination of chemotherapy, radiotherapy, and surgery is the treatment option in head and neck cancer (HNC) patients. Although, cisplatin (CDDP) as the first-line drug has a significant role in the treatment of HNC patients, CDDP resistance can be observed in a large number of these patients. Therefore, identification of the molecular mechanisms involved in CDDP resistance can help to reduce the side effects and also provides a better therapeutic management. MicroRNAs (miRNAs) as the post-transcriptional regulators play an important role in drug resistance. Therefore, in the present review we investigated the role of miRNAs in CDDP response of head and neck tumors. It has been reported that the miRNAs exerted their roles in CDDP response by regulation of signaling pathways such as WNT, NOTCH, PI3K/AKT, TGF-β, and NF-kB as well as apoptosis, autophagy, and EMT process. The present review paves the way to suggest a non-invasive miRNA based panel marker for the prediction of CDDP response among HNC patients. Therefore, such diagnostic miRNA based panel marker reduces the CDDP side effects and improves the clinical outcomes of these patients following an efficient therapeutic management.

Selenium-binding protein 1 inhibits malignant progression and induces apoptosis via distinct mechanisms in non-small cell lung cancer

BACKGROUND

Selenium is an essential trace element in the human body. In epidemiological and clinical studies, Se supplementation significantly reduced the incidence of lung cancer in individuals with low baseline Se levels. The significant action of selenium is based on the selenium-containing protein as a mediator. Of note, the previous studies reported that the expression of selenium-binding protein 1 (SELENBP1) was obviously decreased in many human cancer tissues including non-small cell lung cancer (NSCLC). However, its roles in the origin and development of NSCLC are still unclear.

METHODS

The expression of SELENBP1 was measured by qRT-PCR, Western blotting and IHC in our collected clinical NSCLC tissues and cell lines. Next, the CCK-8, colony formation, wound-haeling, Millicell, Transwell, FCM assay, and in vivo xenograft model were performed to explore the function of SELENBP1 in NSCLC. The molecular mechanisms of SELENBP1 were investigated by Western blotting or IF assay.

RESULTS

We further identified that the expression of SELENBP1 was significantly decreased in NSCLC tissues in TCGA database and 45 out of 59 collected clinical NSCLC tissues compared with adjacent nontumor tissues, as well as in four NSCLC cell lines compared with normal lung cells. Particularly, we unexpectedly discovered that SELENBP1 was obviously expressed in alveolar type 2 (AT-II) cells for the first time. Then, a series of in vitro experiments uncovered that overexpression of SELENBP1 inhibited the proliferation, migration, and invasion of NSCLC cells, and induced cell apoptosis. Moreover, overexpression of SELENBP1 also inhibited growth and induced apoptosis of NSCLC cells in vivo. Mechanistically, we demonstrated that overexpression of SELENBP1 inhibited the malignant characteristics of NSCLC cells in part via inactivating the PI3K/AKT/mTOR signal pathway. Meanwhile, we found that overexpression of SELENBP1 inducing the apoptosis of NSCLC cells was associated with the activation of caspase-3 signaling pathway under nonhigh level of oxidative stress, but overexpression of SELENBP1 facilitating the cell apoptosis might be related to its combining with GPX1 and colocalizing in the nucleus under high level of oxidative stress.

CONCLUSIONS

Our findings highlighted that SELENBP1 was an important tumor suppressor during the origin and development of NSCLC. It may help to discover novel biomarkers or drug therapy targets for NSCLC.

Effect of mechanical tension on fibroblast transcriptome profile and regulatory mechanisms of myocardial collagen turnover

Excess deposition of extracellular matrix in the myocardium is a predictor of reduced left ventricular function. Although reducing the hemodynamic load is known to improve myocardial fibrosis, the mechanisms underlying the reversal of the fibrosis have not been elucidated. We focused on the elasticity of myocardial tissue, which is assumed to influence the fibroblast phenotype. Normal and fibrotic myocardium were cultured in 16 kPa and 64 kPa silicone gel-coated dishes supplemented with recombinant TGFβ protein, respectively. Matrix-degrading myocardium was cultured in 64 kPa silicone gel-coated dishes with recombinant TGFβ protein and then in 16 kPa silicone gel-coated dishes. Cardiac fibroblasts were cultured in this three-part in vitro pathological models and compared. Fibroblasts differentiated into activated or matrix-degrading types in response to the pericellular environment. Comprehensive gene expression analysis of fibroblasts in each in vitro condition showed Selenbp1 to be one of the genes responsible for regulating differentiation of fibroblasts. In vitro knockdown of Selenbp1 enhanced fibroblast activation and inhibited conversion to the matrix-degrading form. In vivo knockdown of Selenbp1 resulted in structural changes in the left ventricle associated with progressive tissue fibrosis and left ventricular diastolic failure. Selenbp1 is involved in regulating fibroblast differentiation and appears to be one of the major molecules regulating collagen turnover in cardiac fibrosis.

The role of SELENBP1 and its epigenetic regulation in carcinogenic progression

The initiation and progression of cancer is modulated through diverse genetic and epigenetic modifications. The epigenetic machinery regulates gene expression through intertwined DNA methylation, histone modifications, and miRNAs without affecting their genome sequences. SELENBP1 belongs to selenium-binding proteins and functions as a tumor suppressor. Its expression is significantly downregulated and correlates with carcinogenic progression and poor survival in various cancers. The role of SELENBP1 in carcinogenesis has not been fully elucidated, and its epigenetic regulation remains poorly understood. In this review, we summarize recent findings on the function and regulatory mechanisms of SELENBP1 during carcinogenic progression, with an emphasis on epigenetic mechanisms. We also discuss the potential cancer treatment targeting epigenetic modification of SELENBP1, either alone or in combination with selenium-containing compounds or dietary selenium.

Altered Capacity for H2S Production during the Spontaneous Differentiation of Caco-2 Cells to Colonocytes Due to Reciprocal Regulation of CBS and SELENBP1

Hydrogen sulfide (H₂S) has been proposed to promote tumor growth. Elevated H₂S levels have been detected in human colorectal cancer (CRC) biopsies, resulting from the selective upregulation of cystathionine β-synthase (CBS). In contrast, the recently identified novel H₂S-generating enzyme, selenium-binding protein 1 (SELENBP1), is largely suppressed in tumors. Here, we provide the first comparative analysis of the four human H₂S-producing enzymes and the key H₂S-catabolizing enzyme, sulfide:quinone oxidoreductase (SQOR), in Caco-2 human colorectal adenocarcinoma cells. The gene expression pattern of proliferating Caco-2 cells parallels that of CRC, while confluent cells undergo spontaneous differentiation to a colonocyte-like phenotype. SELENBP1 and SQOR were strongly upregulated during spontaneous differentiation, whereas CBS was downregulated. Cystathionine γ-lyase and 3-mercaptopyruvate sulfurtransferase remained unaffected. Terminally differentiated cells showed an enhanced capacity to produce H₂S from methanethiol and homocysteine. Differentiation induced by exposure to butyrate also resulted in the upregulation of SELENBP1, accompanied by increased SELENBP1 promoter activity. In contrast to spontaneous differentiation, however, butyrate did not cause downregulation of CBS. In summary, SELENBP1 and CBS are reciprocally regulated during the spontaneous differentiation of Caco-2 cells, thus paralleling their opposing regulation in CRC. Butyrate exposure, while imitating some aspects of spontaneous differentiation, does not elicit the same expression patterns of genes encoding H₂S-modulating enzymes.

Investigation of the interaction of a papain-like cysteine protease (RD19c) with selenium-binding protein 1 (SBP1) in Arabidopsis thaliana

AtRD19c is a member of the papain-like cysteine proteases known for its participation in anther development after its maturation by βVPE (vacuolar processing enzyme). This papain-like cysteine protease was identified as an interacting protein of AtSBP1 (selenium binding protein 1) in a yeast two-hybrid screening. To confirm this interaction, we studied AtRD19c with respect to its expression and ability to interact with AtSBP1. The highest gene expression levels of AtRD19c were observed in the roots of 10-day-old seedlings, whereas minimum levels appeared in the hypocotyls of 10-day-old seedlings and flowers. AtRD19c expression was upregulated by selenium, and analysis of its promoter activity showed colocalization of a reporter gene (GUS) with AtSBP1. Additionally, the AtRD19c expression pattern was upregulated in the presence of selenite, indicating its participation in the Se response network. Confocal fluorescence microscopy revealed that AtRD19c localizes in the root tip, lateral roots, and leaf trichomes. Finally, we confirmed the physical interaction between AtRD19c and AtSBP1 and showed the importance of the first 175 aa of the AtSBP1 polypeptide in this interaction. Importantly, the AtRD19c-AtSBP1 interaction was also demonstrated in planta by employing bimolecular fluorescent complementation (BiFC) in a protoplast system.

Downregulation of SELENBP1 enhances oral squamous cell carcinoma chemoresistance through KEAP1-NRF2 signaling

PURPOSE

Limited value is achieved in systemic chemotherapy for oral squamous cell carcinoma (OSCC), due to cancer cell resistance against cytotoxic agents. Tumor suppressor activities of selenium-binding protein 1 (SELENBP1) have been shown in multiple human cancers except for OSCC. The aim of this study is to clarify the biological functions and potential mechanism of SELENBP1 in OSCC.

METHODS

SELENBP1 expression and its clinical significance in OSCC were analyzed from The Cancer Genome Atlas (TCGA) database. Quantitative polymerase chain reaction (qPCR) or western blot was applied to determine SELENBP1, NRF2 and KEAP1 mRNA or protein levels. Sulforhodamine B assay (SRB) was performed to examine the cytotoxic effects of 5-fluorouracil (5-FU) and cisplatin on OSCC cells. Luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay were conducted to investigate the role of SELENBP1 in KEAP1 transcription.

RESULTS

SELENBP1 downregulation is positively correlated with a poor prognosis for OSCC patients. SELENBP1 knockdown enhances resistance of OSCC cells to 5-FU and cisplatin, while SENENBP1 overexpression displays the opposite effects. Mechanistically, SELENBP1 reduces NRF2 protein levels by promoting its polyubiquitination and degradation. SELENBP1 induces KEAP1 transcription by binding to KEAP1 promoter. Downregulation of SELENBP1 is induced by miR-4786-3p binding to the 3' untranslated region (UTR) of SELENBP1.

CONCLUSION

SENENBP1 is identified as a novel protective biomarker for OSCC patients. Targeting at the miR-4786-3p-SELENBP1-KEAP1-NRF2 signaling axis may enhance the efficacy of chemotherapy for OSCC.

Hepatitis B Virus-X Downregulates Expression of Selenium Binding Protein 1

Selenium binding protein 1 (SELENBP1) has been known to be reduced in various types cancer, and epigenetic change is shown to be likely to account for the reduction of SELNEBP1 expression. With cDNA microarray comparative analysis, we found that SELENBP1 is markedly decreased in hepatitis B virus-X (HBx)-expressing cells. To clarify the effect of HBx on SELENBP1 expression, we compared the expression levels of SELENBP1 mRNA and protein by semi-quantitative RT-PCR, Northern blot, and Western blot. As expected, SELENBP1 expression was shown to be reduced in cells expressing HBx, and reporter gene analysis showed that the SELENBP1 promoter is repressed by HBx. In addition, the stepwise deletion of 5′ flanking promoter sequences resulted in a gradual decrease in basal promoter activity and inhibition of SELENBP1 expression by HBx. Moreover, immunohistochemistry on tissue microarrays containing 60 pairs of human liver tissue showed decreased intensity of SELENBP1 in tumor tissues as compared with their matched non-tumor liver tissues. Taken together, our findings suggest that inhibition of SELENBP1 expression by HBx might act as one of the causes in the development of hepatocellular carcinoma caused by HBV infection.

Investigation of the interaction of DAD1-LIKE LIPASE 3 (DALL3) with Selenium Binding Protein 1 (SBP1) in Arabidopsis thaliana

Phospholipase PLA₁-Iγ2 or otherwise DAD1-LIKE LIPASE 3 (DALL3) is a member of class I phospholipases and has a role in JA biosynthesis. AtDALL3 was previously identified in a yeast two-hybrid screening as an interacting protein of the Arabidopsis Selenium Binding Protein 1 (SBP1). In this work, we have studied AtDALL3 as an interacting partner of the Arabidopsis Selenium Binding Protein 1 (SBP1). Phylogenetic analysis showed that DALL3 appears in the PLA1-Igamma1, 2 group, paired with PLA1-Igammma1. The highest level of expression of AtDALL3 was observed in 10-day-old roots and in flowers, while constitutive levels were maintained in seedlings, cotyledons, shoots and leaves. In response to abiotic stress, DALL3 was shown to participate in the network of genes regulated by cadmium, selenite and selenate compounds. DALL3 promoter driven GUS assays revealed that the expression patterns defined were overlapping with the patterns reported for AtSBP1 gene, indicating that DALL3 and SBP1 transcripts co-localize. Furthermore, quantitative GUS assays showed that these compounds elicited changes in activity in specific cells files, indicating the differential response of DALL3 promoter. GFP::DALL3 studies by confocal microscopy demonstrated the localization of DALL3 in the plastids of the root apex, the plastids of the central root and the apex of emerging lateral root primordia. Additionally, we confirmed by yeast two hybrid assays the physical interaction of DALL3 with SBP1 and defined a minimal SBP1 fragment that DALL3 binds to. Finally, by employing bimolecular fluorescent complementation we demonstrated the in planta interaction of the two proteins.

Selenium-binding protein 1 transcriptionally activates p21 expression via p53-independent mechanism and its frequent reduction associates with poor prognosis in bladder cancer

Background

Recent studies have shown that selenium-binding protein 1 (SELENBP1) is significantly down-regulated in a variety of solid tumors. Nevertheless, the clinical relevance of SELENBP1 in human bladder cancer has not been described in any detail, and the molecular mechanism underlying its inhibitory role in cancer cell growth is largely unknown.

Methods

SELENBP1 expression levels in tumor tissues and adjacent normal tissues were evaluated using immunoblotting assay. The association of SELENBP1 expression, clinicopathological features, and clinical outcome was determined using publicly available dataset from The Cancer Genome Atlas bladder cancer (TCGA-BLCA) cohort. DNA methylation in SELENBP1 gene was assessed using online MEXPRESS tool. We generated stable SELENBP1-overexpression and their corresponding control cell lines to determine its potential effect on cell cycle and transcriptional activity of p21 by using flow cytometry and luciferase reporter assay, respectively. The dominant-negative mutant constructs, TAM67 and STAT1 Y701F, were employed to define the roles of c-Jun and STAT1 in the regulation of p21 protein.

Results

Here, we report that the reduction of SELENBP1 is a frequent event and significantly correlates with tumor progression as well as unfavorable prognosis in human bladder cancer. By utilizing TCGA-BLCA cohort, DNA hypermethylation, especially in gene body, is shown to be likely to account for the reduction of SELENBP1 expression. However, an apparent paradox is observed in its 3′-UTR region, in which DNA methylation is positively related to SELENBP1 expression. More importantly, we verify the growth inhibitory role for SELENBP1 in human bladder cancer, and further report a novel function for SELENBP1 in transcriptionally modulating p21 expression through a p53-independent mechanism. Instead, ectopic expression of SELENBP1 pronouncedly attenuates the phosphorylation of c-Jun and STAT1, both of which are indispensable for SELENBP1-mediated transcriptional induction of p21, thereby resulting in the G₀/G₁ phase cell cycle arrest in bladder cancer cell.

Conclusions

Taken together, our findings provide clinical and molecular insights into improved understanding of the tumor suppressive role for SELENBP1 in human bladder cancer, suggesting that SELENBP1 could potentially be utilized as a prognostic biomarker as well as a therapeutic target in future cancer therapy.

Selenium-Binding Protein 1 Indicates Myocardial Stress and Risk for Adverse Outcome in Cardiac Surgery

Selenium-binding protein 1 (SELENBP1) is an intracellular protein that has been detected in the circulation in response to myocardial infarction. Hypoxia and cardiac surgery affect selenoprotein expression and selenium (Se) status. For this reason, we decided to analyze circulating SELENBP1 concentrations in patients (n = 75) necessitating cardioplegia and a cardiopulmonary bypass (CPB) during the course of the cardiac surgery. Serum samples were collected at seven time-points spanning the full surgical process. SELENBP1 was quantified by a highly sensitive newly developed immunological assay. Serum concentrations of SELENBP1 increased markedly during the intervention and showed a positive association with the duration of ischemia (ρ = 0.6, p < 0.0001). Elevated serum SELENBP1 concentrations at 1 h after arrival at the intensive care unit (post-surgery) were predictive to identify patients at risk of adverse outcome (death, bradycardia or cerebral ischemia, "endpoint 1"; OR 29.9, CI 3.3-268.8, p = 0.00027). Circulating SELENBP1 during intervention (2 min after reperfusion or 15 min after weaning from the CPB) correlated positively with an established marker of myocardial infarction (CK-MB) measured after the intervention (each with ρ = 0.5, p < 0.0001). We concluded that serum concentrations of SELENBP1 were strongly associated with cardiac arrest and the duration of myocardial ischemia already early during surgery, thereby constituting a novel and promising quantitative marker for myocardial hypoxia, with a high potential to improve diagnostics and prediction in combination with the established clinical parameters.

Cell-Type Specific Analysis of Selenium-Related Genes in Brain

Selenoproteins are a unique class of proteins that play key roles in redox signaling in the brain. This unique organ is comprised of a wide variety of cell types that includes excitatory neurons, inhibitory neurons, astrocytes, microglia, and oligodendrocytes. Whereas selenoproteins are known to be required for neural development and function, the cell-type specific expression of selenoproteins and selenium-related machinery has yet to be systematically investigated. Due to advances in sequencing technology and investment from the National Institutes of Health (NIH)-sponsored BRAIN initiative, RNA sequencing (RNAseq) data from thousands of cortical neurons can now be freely accessed and searched using the online RNAseq data navigator at the Allen Brain Atlas. Hence, we utilized this newly developed tool to perform a comprehensive analysis of the cell-type specific expression of selenium-related genes in brain. Select proteins of interest were further verified by means of multi-label immunofluorescent labeling of mouse brain sections. Of potential significance to neural selenium homeostasis, we report co-expression of selenoprotein P (SELENOP) and selenium binding protein 1 (SELENBP1) within astrocytes. These findings raise the intriguing possibility that SELENBP1 may negatively regulate astrocytic SELENOP synthesis and thereby limit downstream Se supply to neurons.

Novel interactions of Selenium Binding Protein family with the PICOT containing proteins AtGRXS14 and AtGRXS16 in Arabidopsis thaliana

During abiotic stress the primary symptom of phytotoxicity can be ROS production which is strictly regulated by ROS scavenging pathways involving enzymatic and non-enzymatic antioxidants. Furthermore, ROS are well-described secondary messengers of cellular processes, while during the course of evolution, plants have accomplished high degree of control over ROS and used them as signalling molecules. Glutaredoxins (GRXs) are small and ubiquitous glutathione (GSH) -or thioredoxin reductase (TR)-dependent oxidoreductases belonging to the thioredoxin (TRX) superfamily which are conserved in most eukaryotes and prokaryotes. In Arabidopsis thaliana GRXs are subdivided into four classes playing a central role in oxidative stress responses and physiological functions. In this work, we describe a novel interaction of AtGRXS14 with the Selenium Binding Protein 1 (AtSBP1), a protein proposed to be integrated in a regulatory network that senses alterations in cellular redox state and acts towards its restoration. We further show that SBP protein family interacts with AtGRXS16 that also contains a PICOT domain, like AtGRXS14.

DNA Methylation of miR-122 Aggravates Oxidative Stress in Colitis Targeting SELENBP1 Partially by p65NF-κB Signaling

Aberrant microRNA (miRNA) expressions contribute to the development and progression of various diseases, including Crohn's disease (CD). However, the accurate mechanisms of miRNAs in CD are definitely unclear. We employed colonic tissue samples from normal volunteers and CD patients, an acute mice colitis model induced by 2,4,6-trinitro-benzene-sulfonic acid (TNBS), and a cellular oxidative stress model induced by H₂O₂ in HT-29 cells to determine the effects of oxidative stress on expressions of miR-122, selenium-binding protein 1 (SELENBP1, SBP1), p65 nuclear factor κB (p65NF-κB) signaling, and DNA methylation. We found that SBP1 was mainly located on epithelial cells and was significantly increased in patients with active CD. SBP1 was the target gene of miR-122. miR-122 expression was downregulated while SBP1 expression was upregulated under TNBS-induced colitis or oxidative stress. Pre-miR-122 or siRNA SBP1 (si-SBP1) treatment ameliorated acute TNBS-induced colitis and H₂O₂-induced oxidative stress. Cotreatment of pre-miR-122 and si-SBP1 enhanced these effects. Besides, pre-miR-122 and si-SBP1 obviously activated the p65NF-κB signaling by phosphorylation of IκBα. Bisulfite sequencing of the CpG islands in the promoter region of miR-122 showed that CpG methylation was significantly increased under oxidative stress. Treating cells with 5′-AZA which was well known as a DNA-demethylating agent significantly increased miR-122 expression. Our results suggest that oxidative stress-induced DNA methylation of miR-122 aggravates colitis targeting SELENBP1 partially by p65NF-κB signaling and may promote the progression of CD.

Selenium-Binding Protein 1 in Human Health and Disease

Selenium-binding protein 1 (SBP1) is a highly conserved protein that covalently binds selenium. SBP1 may play important roles in several fundamental physiological functions, including protein degradation, intra-Golgi transport, cell differentiation, cellular motility, redox modulation, and the metabolism of sulfur-containing molecules. SBP1 expression is often reduced in many cancer types compared to the corresponding normal tissues and low levels of SBP1 are frequently associated with poor clinical outcome. In this review, the transcriptional regulation of SBP1, the different physiological roles reported for SBP1, as well as the implications of SBP1 function in cancer and other diseases are presented.

Downregulation of plasma SELENBP1 protein in patients with recent-onset schizophrenia

Upregulation of selenium binding protein 1 (SELENBP1) mRNA expression has been reported in schizophrenia, primarily in the dorsolateral prefrontal cortex. However, peripheral blood studies are limited and results are inconsistent. In this study, we examined SELENBP1 mRNA expression in whole blood and protein expression in plasma from patients with recent-onset schizophrenia (n = 30), treatment-resistant schizophrenia (n = 71) and healthy controls (n = 57). We also examined the effects of SELENBP1 genetic variation on gene and protein expression. We found lower SELENBP1 plasma protein levels in patients with recent-onset schizophrenia (p = 0.042) but not in treatment-resistant schizophrenia (p = 0.81). Measurement of peripheral mRNA levels showed no difference between treatment-resistant schizophrenia and healthy controls (p = 0.234) but clozapine plasma levels (p = 0.036) and duration of illness (p = 0.028) were positively correlated with mRNA levels. Genetic variation was not associated with mRNA or protein expression. Our data represent the first peripheral proteomic study of SELENBP1 in schizophrenia and suggest that plasma SELENBP1 protein is downregulated in patients with recent-onset schizophrenia.

Tumor Suppressor Activity of Selenbp1, a Direct Nkx2-1 Target, in Lung Adenocarcinoma

The Nkx2-1 transcription factor promotes differentiation of lung epithelial lineages and suppresses malignant progression of lung adenocarcinoma. However, targets of Nkx2-1 that limit tumor growth and progression remain incompletely understood. Here, direct Nkx2-1 targets are identified whose expression correlates with Nkx2-1 activity in human lung adenocarcinoma. Selenium-binding protein 1 (Selenbp1), an Nkx2-1 effector that limits phenotypes associated with lung cancer growth and metastasis, was investigated further. Loss- and gain-of-function approaches demonstrate that Nkx2-1 is required and sufficient for Selenbp1 expression in lung adenocarcinoma cells. Interestingly, Selenbp1 knockdown also reduced Nkx2-1 expression and Selenbp1 stabilized Nkx2-1 protein levels in a heterologous system, suggesting that these genes function in a positive feedback loop. Selenbp1 inhibits clonal growth and migration and suppresses growth of metastases in an in vivo transplant model. Genetic inactivation of Selenbp1, using CRISPR/Cas9, also enhanced primary tumor growth in autochthonous lung adenocarcinoma mouse models. Collectively, these data demonstrate that Selenbp1 is a direct target of Nkx2-1, which inhibits lung adenocarcinoma growth in vivo Implications: Selenbp1 is an important suppressor of lung tumor growth that functions in a positive feedback loop with Nkx2-1, and whose loss is associated with worse patient outcome. Mol Cancer Res; 16(11); 1737-49. ©2018 AACR.

Mutations in SELENBP1, encoding a novel human methanethiol oxidase, cause extraoral halitosis

Selenium-binding protein 1 (SELENBP1) has been associated with several cancers, although its exact role is unknown. We show that SELENBP1 is a methanethiol oxidase (MTO), related to the MTO in methylotrophic bacteria, that converts methanethiol to H₂O₂, formaldehyde, and H₂S, an activity not previously known to exist in humans. We identified mutations in SELENBP1 in five patients with cabbage-like breath odor. The malodor was attributable to high levels of methanethiol and dimethylsulfide, the main odorous compounds in their breath. Elevated urinary excretion of dimethylsulfoxide was associated with MTO deficiency. Patient fibroblasts had low SELENBP1 protein levels and were deficient in MTO enzymatic activity; these effects were reversed by lentivirus-mediated expression of wild-type SELENBP1. Selenbp1-knockout mice showed biochemical characteristics similar to those in humans. Our data reveal a potentially frequent inborn error of metabolism that results from MTO deficiency and leads to a malodor syndrome.

Use of immunoproteomics to identify immunogenic proteins in a rat model of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a common and life‑threatening clinical syndrome, and seeking biomarkers of ARDS has been an area of continuing research. The present study hypothesized that alterations to certain immunogenic substances occur in injured lungs and are able to specifically bind with corresponding proteins in the blood, and that these proteins may be readily detected. To investigate this hypothesis, a rat model of ARDS was established by cecal ligation and puncture surgery, and an immunoproteomics approach, using serum as the primary antibody in a western blot analysis, was used with the aim of identifying immunogenic proteins in the injured lungs. Ingenuity Pathway Analysis (IPA) was used for bioinformatics analysis, and mass spectrometric analysis was used to identify a total of 38 differentially expressed immunogenic proteins. Bioinformatics analysis revealed that the top canonical pathways in which the identified proteins may be involved were gluconeogenesis I, glycolysis I, choline degradation I, NADH repair and heme degradation. IPA Biomarker Filter analysis with the terms 'acute respiratory distress syndrome/acute lung injury' was used to screen 13 proteins as candidate biomarkers. These proteins were described as antigens, and suggested that paired antibodies may be detected in the plasma of patients at high risk of ARDS. Analysis of these identified proteins may provide novel insights into the potential pathological mechanisms of ARDS.

Selenium-binding protein 1 in head and neck cancer is low-expression and associates with the prognosis of nasopharyngeal carcinoma

BACKGROUND

Selenium-binding protein 1 (SELENBP1) expression is reduced markedly in many types of cancers and low SELENBP1 expression levels are associated with poor patient prognosis.

METHODS

SELENBP1 gene expression in head and neck squamous cell carcinoma (HNSCC) was analyzed with GEO dataset and characteristics of SELENBP1 expression in paraffin embedded tissue were summarized. Expression of SELENBP1 in nasopharyngeal carcinoma (NPC), laryngeal cancer, oral cancer, tonsil cancer, hypopharyngeal cancer and normal tissues were detected using immunohistochemistry, at last, 99 NPC patients were followed up more than 5 years and were analyzed the prognostic significance of SELENBP1.

RESULTS

Analysis of GEO dataset concluded that SELENBP1 gene expression in HNSCC was lower than that in normal tissue (P < 0.01), but there was no significant difference of SELENBP1 gene expression in different T-stage and N-stage (P > 0.05). Analysis of pathological section concluded that SELENBP1 in the majority of HNSCC is low expression and in cancer nests is lower expression than surrounding normal tissue, even associated with the malignant degree of tumor. Further study indicated the low SELENBP1 expression group of patients with NPC accompanied by poor overall survival and has significantly different comparing with the high expression group.

CONCLUSION

SELENBP1 expression was down-regulated in HNSCC, but has no associated with T-stage and N-stage of tumor. Low expression of SELENBP1 in patients with NPC has poor over survival, so SELENBP1 could be a novel biomarker for predicting prognosis.

Downregulation of selenium-binding protein 1 is associated with poor prognosis in lung squamous cell carcinoma

Background

We found that selenium-binding protein 1 (SBP1) was progressively decreased in the human bronchial epithelial carcinogenic processes. Knockdown of SBP1 in immortalized human bronchial epithelial cell line 16HBE cells significantly increased the efficiency of B[a]P-induced cell transformation. However, the relationship between SBP1 expression and clinicopathological factors of patients has not been defined completely. The specific role of SBP1 in prognosis of lung squamous cell carcinoma (LSCC) is still unknown.

Methods

Tissue samples from 82 patients treated by pulmonary lobectomy for LSCC were used. Immunohistochemistry and western blotting were used to detect the expressions of SBP1 protein. The relationships between the expression level of SBP1 and the clinicopathological features of patients were analyzed. Cox proportional hazard regression analysis and Kaplan–Meier method were used to perform survival analysis.

Results

Expressions of SBP1 proteins were significantly lower in LSCC tissues than that in the corresponding normal bronchial epithelium (NBE) tissues (P = 0.000). In LSCC, The expression levels of SBP1 had not correlated with patients’ age, gender, smoking state, primary tumor stages (T), TNM clinical stages, and distant metastasis (M) (P > 0.05). However, downregulation of SBP1 was significantly associated with higher lymph node metastasis and lower overall survival rate (P < 0.05). Cox regression analysis indicated low expressions of SBP1 can be an independent prognostic factor for poor overall survival in LSCC patients (P = 0.002).

Conclusions

Downregulation of SBP1 may play a key role in the tumorigenic process of LSCC. SBP1 may be a novel potential prognostic factor of LSCC.

A Critical Role for Cysteine 57 in the Biological Functions of Selenium Binding Protein-1

The concentration of selenium-binding protein1 (SBP1) is often lower in tumors than in the corresponding tissue and lower levels have been associated with poor clinical outcomes. SBP1 binds tightly selenium although what role selenium plays in its biological functions remains unknown. Previous studies indicated that cysteine 57 is the most likely candidate amino acid for selenium binding. In order to investigate the role of cysteine 57 in SBP1, this amino acid was altered to a glycine and the mutated protein was expressed in human cancer cells. The SBP1 half-life, as well as the cellular response to selenite cytotoxicity, was altered by this change. The ectopic expression of SBP1^GLY also caused mitochondrial damage in HCT116 cells. Taken together, these results indicated that cysteine 57 is a critical determinant of SBP1 function and may play a significant role in mitochondrial function.

SELENBP1 expression in the prefrontal cortex of subjects with schizophrenia

Selenium binding protein 1 (SELENBP1) messenger RNA (mRNA) has previously been shown to be upregulated in the brain and blood from subjects with schizophrenia. We aimed to validate these findings in a new cohort using real-time PCR in Brodmann's Area (BA) 9, and to determine the disease specificity of increased SELENBP1 expression by measuring SELENBP1 mRNA in subjects with major depressive disorder and bipolar disorder. We then extended the study to include other cortical regions such as BA8 and BA44. SELENBP1 mRNA was higher in BA9 (P = 0.001), BA8 (P = 0.003) and BA44 (P = 0.0007) from subjects with schizophrenia. Conversely, in affective disorders, there was no significant difference in SELENBP1 mRNA in BA9 (P = 0.67), suggesting that the upregulation may be diagnosis specific. Measurement of SELENBP1 protein levels showed that changes in mRNA did not translate to changes in protein. In addition, chronic treatment of rats with antipsychotics did not significantly affect the expression of Selenbp1 in the cortex (P = 0.24). Our data show that elevated SELENBP1 transcript expression is widespread throughout the prefrontal cortex in schizophrenia, and confirm that this change is a consistent feature of schizophrenia and not a simple drug effect.

Does aberrant membrane transport contribute to poor outcome in adult acute myeloid leukemia?

Acute myeloid leukemia in adults is a highly heterogeneous disease. Gene expression profiling performed using unsupervised algorithms can be used to distinguish specific groups of patients within a large patient cohort. The identified gene expression signatures can offer insights into underlying physiological mechanisms of disease pathogenesis. Here, the analysis of several related gene expression clusters associated with poor outcome, worst overall survival and highest rates of resistant disease and obtained from the patients at the time of diagnosis or from previously untreated individuals is presented. Surprisingly, these gene clusters appear to be enriched for genes corresponding to proteins involved in transport across membranes (transporters, carriers and channels). Several ideas describing the possible relationship of membrane transport activity and leukemic cell biology, including the "Warburg effect," the specific role of chloride ion transport, direct "import" of metabolic energy through uptake of creatine phosphate, and modification of the bone marrow niche microenvironment are discussed.

Quantitative proteomic analysis reveals that anti-cancer effects of selenium-binding protein 1 in vivo are associated with metabolic pathways

Previous studies have shown the tumor-suppressive role of selenium-binding protein 1 (SBP1), but the underlying mechanisms are unclear. In this study, we found that induction of SBP1 showed significant inhibition of colorectal cancer cell growth and metastasis in mice. We further employed isobaric tags for relative and absolute quantitation (iTRAQ) to identify proteins that were involved in SBP1-mediated anti-cancer effects in tumor tissues. We identified 132 differentially expressed proteins, among them, 53 proteins were upregulated and 79 proteins were downregulated. Importantly, many of the differentially altered proteins were associated with lipid/glucose metabolism, which were also linked to Glycolysis, MAPK, Wnt, NF-kB, NOTCH and epithelial-mesenchymal transition (EMT) signaling pathways. These results have revealed a novel mechanism that SBP1-mediated cancer inhibition is through altering lipid/glucose metabolic signaling pathways.

Human selenium binding protein-1 (hSP56) is a negative regulator of HIF-1α and suppresses the malignant characteristics of prostate cancer cells

In the present study, we demonstrate that ectopic expression of 56-kDa human selenium binding protein-1 (hSP56) in PC-3 cells that do not normally express hSP56 results in a marked inhibition of cell growth in vitro and in vivo. Down-regulation of hSP56 in LNCaP cells that normally express hSP56 results in enhanced anchorage-independent growth. PC-3 cells expressing hSP56 exhibit a significant reduction of hypoxia inducible protein (HIF)-1α protein levels under hypoxic conditions without altering HIF-1α mRNA (HIF1A) levels. Taken together, our findings strongly suggest that hSP56 plays a critical role in prostate cells by mechanisms including negative regulation of HIF-1α, thus identifying hSP56 as a candidate anti-oncogene product. [BMB Reports 2014; 47(7): 411-416]

Revisão dos principais genes e proteínas associadas à demência frontotemporal tau-positiva

O objetivo desta revisão foi apresentar os genes APOE e MAPT e as proteínas ApoE e tau como marcadores genéticos que vêm sendo estudados na demência frontotemporal com inclusões tau-positivas, os quais poderão, futuramente, auxiliar no diagnóstico diferencial. A demência frontotemporal é um transtorno neurocognitivo marcado por disfunção dos lobos frontais e temporais, geralmente associada à atrofia dessas estruturas e relativa preservação das regiões cerebrais posteriores. Clinicamente, manifesta-se por volta dos 57 anos de idade, com igual incidência entre homens e mulheres. A demência frontotemporal tem início insidioso e caráter progressivo, com discreto comprometimento da memória episódica, mas com importantes alterações comportamentais, de personalidade e na linguagem. Devido às semelhanças possíveis entre as manifestações clínicas das demências inclusive a doença de Alzheimer, há grande dificuldade no diagnóstico diferencial, sendo necessário um exame clínico e neuropsicológico detalhado do indivíduo acometido, além de exames bioquímicos e de neuroimagem. O gene MAPT codifica a proteína tau e sua função principal é estabilizar os microtúbulos. Em células nervosas sadias, a proteína tau é normalmente encontrada nos axônios, ao contrário dos achados descritos nos transtornos neurocognitivos, em que a proteína se encontra distribuída no corpo celular e nos dendritos. A apolipoproteína E ApoE é uma glicoproteína polimórfica, codificada pelo gene APOE, que tem importante papel na absorção, transporte e redistribuição de colesterol, necessário ao reparo e manutenção do tecido nervoso. Com o aumento da expectativa de vida e controle da natalidade, o envelhecimento populacional tornou-se fato, trazendo consigo maior prevalência de doenças crônico-degenerativas, de modo que é de extrema importância conhecer melhor essas doenças, no sentido de buscar novas formas de tratamento, visto que as demências não dispõem ainda de cura. Sabe-se que o diagnóstico definitivo da maioria das síndromes demenciais depende do exame neuropatológico, mas conclui-se que, com o avanço tecnológico, bem como técnicas de biologia e genética molecular, novas perspectivas têm surgido para o diagnóstico diferencial e precoce das demências.

Reduction of selenium-binding protein 1 sensitizes cancer cells to selenite via elevating extracellular glutathione: a novel mechanism of cancer-specific cytotoxicity of selenite

Selenium is an essential trace element and has been extensively studied for preventive effects on cancers. Recent emerging evidence has also shown that selenium at supranutritional dosage has a preferential cytotoxicity in cancer cells and chemotherapeutic drug-resistant cells, but the underlying mechanisms remain largely unknown. This study was to investigate the roles of two distinct representatives of selenium-containing proteins, selenium-binding protein 1 (SBP1) and glutathione peroxidase 1 (GPX1), in selenite-mediated cancer-specific cytotoxicity. We found that there was a significantly inverse correlation between SBP1 and GPX1 protein level in human breast cancers and adjacent matched nontumor tissues (Pearson r=-0.4347, P=0.0338). Ectopic expression of GPX1 enhanced selenite cytotoxicity through down-regulation of SBP1, and SBP1 was likely to be a crucial determinant for selenite-mediated cytotoxicity. Reduction of SBP1 in cancer cells and epirubicin-resistant cells on selenite exposure resulted in a dramatic increase in the generation of hydrogen peroxide and superoxide anion, which in turn caused oxidative stress and triggered apoptosis. Furthermore, knockdown SBP1 by small interfering RNA increased selenite sensitivity by elevating extracellular glutathione (GSH), which spontaneously reacted with selenite and led to the rapid depletion of selenium (IV) in growth medium and the high-affinity uptake of selenite. In conclusion, these findings would improve our understanding of the roles of selenium-containing proteins in selenite-mediated cytotoxicity, and revealed a potent mechanism of the selective cytotoxicity of selenite in cancer cells and drug-resistant cells, in which SBP1 was likely to play an important role in modulating the extracellular microenvironment by regulating the levels of extracellular GSH.

Decreased selenium-binding protein 1 mRNA expression is associated with poor prognosis in renal cell carcinoma

BACKGROUND

The anticancer effects of selenium may be mediated by selenium-binding proteins, such as SELENBP1. The association between SELENBP1 expression levels and clinicopathologic parameters was assessed in renal cell carcinoma (RCC).

METHODS

SELENBP1 mRNA expression was measured with real-time quantitative polymerase chain reaction (qPCR) in 139 specimens of primary RCC and 59 specimens of donor-matched normal-appearing kidney tissues. The prognostic effect of SELENBP1 levels was evaluated with Kaplan-Meier and multivariate Cox regression analyses.

RESULTS

SELENBP1 mRNA levels were significantly lower in tumor tissues than in matched normal kidney tissues (P < 0.001) and significantly inversely correlated with pathologic (T-stage and Fuhrman grade) and prognostic variables (progression and cancer-specific death). Kaplan-Meier estimates showed that low SELENBP1 expression was significantly correlated with cancer-specific death (log-rank test, P = 0.014), and a multivariate Cox regression model revealed that SELENBP1 expression was an independent predictor of cancer-specific death (HR, 0.111; P = 0.006).

CONCLUSIONS

SELENBP1 might play a role in tumor suppression and could be a useful prognostic factor in RCC.

Molecular cross-talk between members of distinct families of selenium containing proteins

Dietary intake of selenium has been associated with reduced risk of several cancer types, and this is likely due to its role as a specific constituent of selenium containing proteins. One of these, selenium-binding protein 1 (SBP1), is a protein of unknown function that has been shown to be reduced in tumors of diverse tissue types as compared to the corresponding normal tissue. More importantly, SBP1 has also been reported to be a predictor of clinical outcome. Levels of SBP1 are inversely associated with the levels of another protein representative of a different class of selenoproteins, glutathione peroxidase1 (GPx-1). GPx-1 is an anti-oxidant, selenocysteine containing enzyme implicated in several diseases, including cancer, due to the association of specific alleles with disease risk. The relationship between SBP1 and GPx-1 represents a unique example of a molecular interaction between selenium containing proteins with a likely significant impact on human health and disease.

Selenium-binding protein 1 as a tumor suppressor and a prognostic indicator of clinical outcome

Selenium is a trace element that plays a critical role in physiological processes and cancer prevention, whose functions may be through its effects on selenium-containing proteins. Selenium-binding protein 1 (SBP1) is a member of an unusual class of selenium-containing proteins that may function as a tumor suppressor in multiple cancer types and whose levels have been shown to be lower in cancers as compared to corresponding normal tissues. This review is intended to summarize recent advances in gaining an understanding of the significance of SBP1 in carcinogenesis, and suggest that SBP1 could be developed as a potential biomarker for cancer progression and prognosis.

The link between selenium binding protein from Sinonovacula constricta and environmental pollutions exposure

Selenium binding proteins (SeBPs) play a crucial role in controlling the oxidation/reduction in many physiological processes. Here we reported the isolation and characterization of a cDNA of SeBP gene from Sinonovacula constricta (denoted as ScSeBP). The full-length cDNA of ScSeBP was of 2345 bp, consisting of a 5'UTR of 246 bp, a 3' UTR of 626 bp, and a complete ORF of 1473 bp encoding a polypeptide with 491 amino acid residues. The predicted molecular mass of deduced amino acid of ScSeBP was 54.85 kDa and the theoretical pI was 6.44. Tissue distribution analysis of the ScSeBP revealed that the mRNA transcripts of ScSeBP were constitutively expressed in all examined tissues with the higher expressions in gill, gonad and the haemocytes. The temporal expression of ScSeBP in gill and haemocytes after B[α]P and heavy metals exposure were recorded by qPCR. B[α]P exposure at 0.5 and 5 mg L(-1) caused significant increase in mRNA expression of ScSeBP in haemocytes, but down-regulated ScSeBP mRNA expression in gill. Concerning heavy metals stresses, the suppressed expression patterns were detected in gill and haemocyte except lower concentration of PbCl2 exposure in haemocytes at 12 h. All our results indicated that ScSeBP was one of key effectors in mediating B[α]P and heavy metals exposure.

Reduced selenium-binding protein 1 in breast cancer correlates with poor survival and resistance to the anti-proliferative effects of selenium

Supplemental dietary selenium is associated with reduced incidence of many cancers. The antitumor function of selenium is thought to be mediated through selenium-binding protein 1 (SELENBP1). However, the significance of SELENBP1 expression in breast cancer is still largely unknown. A total of 95 normal and tumor tissues assay and 12 breast cancer cell lines were used in this study. We found that SELENBP1 expression in breast cancer tissues is reduced compared to normal control. Low SELENBP1 expression in ER(+) breast cancer patients was significantly associated with poor survival (p<0.01), and SELENBP1 levels progressively decreased with advancing clinical stages of breast cancer. 17-β estradiol (E2) treatment of high SELENBP1-expressing ER(+) cell lines led to a down-regulation of SELENBP1, a result that did not occur in ER(-) cell lines. However, after ectopic expression of ER in an originally ER(-) cell line, down-regulation of SELENBP1 upon E2 treatment was observed. In addition, selenium treatment resulted in reduced cell proliferation in endogenous SELENBP1 high cells; however, after knocking-down SELENBP1, we observed no significant reduction in cell proliferation. Similarly, selenium has no effect on inhibition of cell proliferation in low endogenous SELENBP1 cells, but the inhibitory effect is regained following ectopic SELENBP1 expression. Furthermore, E2 treatment of an ER silenced high endogenous SELENBP1 expressing cell line showed no abolishment of cell proliferation inhibition upon selenium treatment. These data indicate that SELENBP1 expression is regulated via estrogen and that the cell proliferation inhibition effect of selenium treatment is dependent on the high level of SELENBP1 expression. Therefore, the expression level of SELENBP1 could be an important marker for predicting survival and effectiveness of selenium supplementation in breast cancer. This is the first study to reveal the importance of monitoring SELENBP1 expression as a potential biomarker in contributing to breast cancer prevention and treatment.

Evaluation of selenite effects on selenoproteins and cytokinome in human hepatoma cell lines

The need to explore new alternative therapeutic strategies and chemoprevention methods for hepatocellular carcinoma is growing significantly. Selenium is a trace element that plays a critical role in physiological processes, and is used in cancer chemoprevention. The aim of this work was to test in vitro the effect of sodium selenite on the human hepatoma cell lines, HepG2 and Huh7, to assess its effect on the expression of GPX1, SELK and SELENBP1 and also to evaluate its action on inflammation determinants such as cytokines. Our results show that: (i) the increase observed for the GPX1 and SELK expression is correlated with an increase in the sodium selenite concentration, also evidencing an inverse association between the levels of these two proteins and SELENBP1; (ii) the selenium concentrations evaluated in protein extracts increase in proportional way with the selenite concentrations used in the treatment, suggesting that other selenoproteins can also be modulated and should be evaluated in further studies, and (iii) some cytokines, VEGF and three pro-inflammatory cytokines, i.e., IL-6, IL-8, and IL-17, decreased with an increasing selenite concentration. Finally, interactomic studies show that GPX1 and SELK, and the four pro-inflammatory cytokines are functionally correlated evidencing a putative anti-inflammatory role for the selenite.

Decreased selenium-binding protein 1 enhances glutathione peroxidase 1 activity and downregulates HIF-1α to promote hepatocellular carcinoma invasiveness

PURPOSE

We aimed to characterize the role of selenium-binding protein 1 (SBP1) in hepatocellular carcinoma (HCC) invasiveness and underlying clinical significance.

EXPERIMENTAL DESIGN

SBP1 expression was measured in stepwise metastatic HCC cell lines by Western blotting. The role of SBP1 in HCC was investigated using siRNA. Immunofluorescence analyses were used to detect the interaction between SBP1 and glutathione peroxidase 1 (GPX1). Nineteen fresh tumor tissues and 323 paraffin-embedded samples were used to validate in vitro findings and to detect the prognostic significance of SBP1, respectively.

RESULTS

Inhibition of SBP1 effectively increased cell motility, promoted cell proliferation, and inhibited apoptosis only under oxidative stress; it also greatly enhanced GPX1 activity without altering GPX1 expression and downregulated hypoxia-inducible factor-1α (HIF-1α) expression. SBP1 and GPX1 formed nuclear bodies and colocalized under oxidative stress. In freshly isolated clinical HCC tissues, decreased SBP1 was linked with increased GPX1 activity and correlated with vascular invasion. Tumor tissue microarrays indicated that SBP1 was an independent risk factor for overall survival and disease recurrence; patients with lower SBP1 expression experienced shorter overall survival periods and higher rates of disease recurrence (P < 0.001). Further analyses indicated that the predictive power of SBP1 was more significant for patients beyond the Milan criteria than patients within the Milan criteria.

CONCLUSIONS

Decreased expression of SBP1 could promote tumor invasiveness by increasing GPX1 activity and diminishing HIF-1α expression in HCC; SBP1 could be a novel biomarker for predicting prognosis and guiding personalized therapeutic strategies, especially in patients with advanced HCC.

Proteomic profiling of follicular and papillary thyroid tumors

OBJECTIVE

Thyroid proteomics is a new direction in thyroid cancer research aiming at etiological understanding and biomarker identification for improved diagnosis.

METHODS

Two-dimensional electrophoresis was applied to cytosolic protein extracts from frozen thyroid samples (ten follicular adenomas, nine follicular carcinomas, ten papillary carcinomas, and ten reference thyroids). Spots with differential expression were revealed by image and multivariate statistical analyses, and identified by mass spectrometry.

RESULTS

A set of 25 protein spots significant for discriminating between the sample groups was identified. Proteins identified for nine of these spots were studied further including 14-3-3 protein beta/alpha, epsilon, and zeta/delta, peroxiredoxin 6, selenium-binding protein 1, protein disulfide-isomerase precursor, annexin A5 (ANXA5), tubulin alpha-1B chain, and α1-antitrypsin precursor. This subset of protein spots carried the same predictive power in differentiating between follicular carcinoma and adenoma or between follicular and papillary carcinoma, as compared with the larger set of 25 spots. Protein expression in the sample groups was demonstrated by western blot analyses. For ANXA5 and the 14-3-3 proteins, expression in tumor cell cytoplasm was demonstrated by immunohistochemistry both in the sample groups and an independent series of papillary thyroid carcinomas.

CONCLUSION

The proteins identified confirm previous findings in thyroid proteomics, and suggest additional proteins as dysregulated in thyroid tumors.

A possible predictive marker of progression for hepatocellular carcinoma

The correlation between decreased levels of selenium and increased DNA damage and oxidative stress shows the significance of this trace element. A number of studies have provided evidence for lower serum, plasma and tissue levels of selenium in patients with various diseases and types of cancer. In this study, liver selenium concentrations were measured in tissue samples of patients with hepatocellular carcinoma (HCC) by atomic absorption spectrometry. The results showed that the selenium concentrations decreased when the malignant grade increased. Furthermore, a significant correlation was found between selenium levels and human selenium binding protein-1 (SELENBP1) down-regulation in the liver. Therefore, we suggest that the evaluation of selenium and SELENBP1 concentrations can be used for improving the prognosis of HCC.

Structural and functional studies of the human selenium binding protein-1 and its involvement in hepatocellular carcinoma

The reduced expression of human selenium binding protein-1 (SELENBP1) has been reported for some human cancers. In this work we have estimated a reduced SELENBP1 expression by immunohistochemistry for the first time also in liver tissues of patients with hepatocarcinoma (HCC). Since the structure-function relationships of SELENBP1 are unknown, we have performed computational and experimental studies to have insight on the structural features of this protein focusing our attention on the properties of cysteines to assess their ability to interact with selenium. We have performed CD studies on the purified protein, modeled its three-dimensional structure, studied the energetic stability of the protein by molecular dynamics simulations, and titrated the cysteines by DTNB (5,5'-dithiobis (2-nitrobenzoic acid). The secondary structure content evaluated by CD has been found similar to that of 3D model. Our studies demonstrate that (i) SELENBP1 is an alpha-beta protein with some loop regions characterized by the presence of intrinsically unordered segments, (ii) only one cysteine (Cys57) is enough exposed to solvent, located on a loop and surrounded by charged and hydrophobic residues, and can be the cysteine able to bind the selenium. Furthermore, during the molecular dynamics simulation at neutral pH the loop containing Cys57 opens and exposes this residue to solvent, confirming that it is the best candidate to bind the selenium. Experimentally we found that only one cysteine is titratable by DTNB. This supports the hypothesis that Cys57 is a residue functionally important and this may open new pharmacological perspectives.

The expression of selenium-binding protein 1 is decreased in uterine leiomyoma

Background

Selenium has been shown to inhibit cancer development and growth through the mediation of selenium-binding proteins. Decreased expression of selenium-binding protein 1 has been reported in cancers of the prostate, stomach, colon, and lungs. No information, however, is available concerning the roles of selenium-binding protein 1 in uterine leiomyoma.

Methods

Using Western Blot analysis and immunohistochemistry, we examined the expression of selenium-binding protein 1 in uterine leiomyoma and normal myometrium in 20 patients who had undergone hysterectomy for uterine leiomyoma.

Results and Discussion

The patient age ranged from 34 to 58 years with a mean of 44.3 years. Proliferative endometrium was seen in 8 patients, secretory endometrium in 7 patients, and atrophic endometrium in 5 patients. Two patients showed solitary leiomyoma, and eighteen patients revealed 2 to 5 tumors. Tumor size ranged from 1 to 15.5 cm with a mean of 4.3 cm. Both Western Blot analysis and immunohistochemistry showed a significant lower level of selenium-binding protein 1 in leiomyoma than in normal myometrium. Larger tumors had a tendency to show a lower level of selenium-binding protein 1 than smaller ones, but the difference did not reach a statistical significance. The expression of selenium-binding protein 1 was the same among patients with proliferative, secretory, and atrophic endometrium in either leiomyoma or normal myometrium. Also, we did not find a difference of selenium-binding protein 1 level between patients younger than 45 years and older patients in either leiomyoma or normal myometrium.

Conclusions

Decreased expression of selenium-binding protein 1 in uterine leiomyoma may indicate a role of the protein in tumorigenesis. Our findings may provide a basis for future studies concerning the molecular mechanisms of selenium-binding protein 1 in tumorigenesis as well as the possible use of selenium in prevention and treatment of uterine leiomyoma.

Functional and physical interaction between the selenium-binding protein 1 (SBP1) and the glutathione peroxidase 1 selenoprotein

Selenium-binding protein (SBP) 1 is present in reduced levels in several cancer types as compared with normal tissues, and lower levels are associated with poor clinical prognosis. Another selenium-containing protein, glutathione peroxidase 1 (GPX1), has been associated with cancer risk and development. The interaction between these representatives of different classes of selenoproteins was investigated. Increasing SBP1 levels in either human colorectal or breast cancer cells by transfection of an expression construct resulted in the reduction of GPX1 enzyme activity. Increased expression of GPX1 in the same cell types resulted in the transcriptional and translational repression of SBP1, as evidenced by the reduction of SBP1 messenger RNA and protein and the inhibition of transcription measured using an SBP1 reporter construct. The opposing effects of SBP1 and GPX1 on each other were also observed when GPX1 was increased by supplementing the media of these tissue culture cells with selenium, and the effect of selenium on SBP1 was shown to be GPX1 dependent. Decreasing or increasing GPX1 levels in colonic epithelial cells of mice fed a selenium-deficient, -adequate or -supplemented diet resulted in the opposing effect on SBP1 levels. These data are explained in part by the demonstration that SBP1 and GPX1 form a physical association, as determined by coimmunoprecipitation and fluorescence resonance energy transfer assay. The results presented establish an interaction between two distinct selenium-containing proteins that may enhance the understanding of the mechanisms by which selenium and selenoproteins affect carcinogenesis in humans.

Selenium, but not lycopene or vitamin E, decreases growth of transplantable dunning R3327-H rat prostate tumors

Background

Lycopene, selenium, and vitamin E are three micronutrients commonly consumed and supplemented by men diagnosed with prostate cancer. However, it is not clear whether consumption of these compounds, alone or in combination, results in improved outcomes.

Methodology/Principal Findings

We evaluated the effects of dietary lycopene (250 mg/kg diet), selenium (methylselenocysteine, 1 mg/kg diet), and vitamin E (γ-tocopherol, 200 mg/kg diet) alone and in combination on the growth of androgen-dependent Dunning R3327-H rat prostate adenocarcinomas in male, Copenhagen rats. AIN-93G diets containing these micronutrients were prefed for 4 to 6 weeks prior to tumor implantation by subcutaneous injection. Tumors were allowed to grow for ∼18 weeks. Across diet groups, methylselenocysteine consumption decreased final tumor area (P = 0.003), tumor weight (P = 0.003), and the tumor weight/body weight ratio (P = 0.003), but lycopene and γ-tocopherol consumption intake did not alter any of these measures. There were no significant interactions among nutrient combinations on tumor growth. Methylselenocysteine consumption also led to small, but significant decreases in body weight (P = 0.007), food intake (P = 0.012), and body weight gain/food intake ratio (P = 0.022). However, neither body weight nor gain/food intake ratio was correlated with tumor weight. Methylselenocysteine, lycopene, and γ-tocopherol consumed alone and in combination did not alter serum testosterone or dihydrotestosterone concentrations; tumor proliferation or apoptosis rates. In addition, the diets also did not alter tumor or prostate androgen receptor, probasin, selenoprotein 15, selenoprotein P, or selenium binding protein 2 mRNA expression. However, using castration and finasteride-treated tissues from a previous study, we found that androgen ablation altered expression of these selenium-associated proteins.

Conclusions

Of the three micronutrients tested, only methylselenocysteine consumption reduced growth of transplantable Dunning R3327-H prostate tumors, albeit through an unresolved mechanism.

Reduced selenium-binding protein 1 is associated with poor survival rate in gastric carcinoma

Human selenium-binding protein 1 (SBP1) is known to play a key role in the development and progression of many cancers. The role of SBP1 expression in gastric carcinoma (GC) is far from being fully established. The aim of the present study was to evaluate the expression of SBP1 in GC and correlate the findings with several clinicopathological features and prognosis. Tissue samples from 65 patients treated by gastric resection for GC with clinical stage II and III were used. Each sample was matched with the corresponding nonneoplastic epithelia tissues removed during the same surgery. Reverse transcriptase-polymerase chain reaction, immunostaining and Western blot analyses were used to detect the expression of SBP1 at the mRNA and protein levels, respectively. The associations between SBP1 expressions and clinicopathological features were analyzed. Expressions of SBP1 at both mRNA and protein levels were significantly lower in GC than those in the corresponding nonneoplastic epithelia tissues (P = 0.000). SBP1-negative expression had a significant relationship with high clinical stage (P = 0.038). Prognosis of SBP1-negative patients was significantly poorer than that of SBP1-positive patients (P = 0.001), and multivariate analysis further confirmed that SBP1 was an independent prognostic factor (P = 0.004). Thus, down-regulation of SBP1 may play a key role in the tumorigenic process of human GC. The correlation of SBP1 reduction in GC with clinical stage and survival proposes a prognostic role in GC.

Decreased selenium-binding protein 1 in esophageal adenocarcinoma results from posttranscriptional and epigenetic regulation and affects chemosensitivity

PURPOSE

The chemopreventive effects of selenium have been extensively examined, but its role in cancer development or as a chemotherapeutic agent has only recently been explored. Because selenium-binding protein 1 (SELENBP1, SBP1, hSP56) has been shown to bind selenium covalently and selenium deficiency has been associated with esophageal adenocarcinoma (EAC), we examined its role in EAC development and its potential effect on chemosensitivity in the presence of selenium.

EXPERIMENTAL DESIGN

SELENBP1 expression level and copy number variation were determined by oligonucleotide microarrays, real-time reverse transcription-PCR, tissue microarrays, immunoblotting, and single-nucleotide polymorphism arrays. Bisulfite sequencing and sequence analysis of reverse transcription-PCR-amplified products explored epigenetic and posttranscriptional regulation of SELENBP1 expression, respectively. WST-1 cell proliferation assays, senescence-associated beta-galactosidase staining, immunoblotting, and flow cytometry were done to evaluate the biological significance of SELENBP1 overexpression in selenium-supplemented EAC cells.

RESULTS

SELENBP1 expression decreased significantly in Barrett's esophagus to adenocarcinoma progression. Both epigenetic and posttranscriptional mechanisms seemed to modulate SELENBP1 expression. Stable overexpression of SELENBP1 in methylseleninic acid-supplemented Flo-1 cells resulted in enhanced apoptosis, increased cellular senescence, and enhanced cisplatin cytotoxicity. Although inorganic sodium selenite similarly enhanced cisplatin cytotoxicity, these two forms of selenium elicited different cellular responses.

CONCLUSIONS

SELENBP1 expression may be an important predictor of response to chemoprevention or chemosensitization with certain forms of selenium in esophageal tissues. AACR.

Transcriptional regulation and biological functions of selenium-binding protein 1 in colorectal cancer in vitro and in nude mouse xenografts

Background

It has been shown that selenium-binding protein 1 (SBP1) is significantly downregulated in different human cancers. Its regulation and function have not yet been established.

Methodology and Principal Findings

We show that the SBP1 promoter is hypermethylated in colon cancer tissues and human colon cancer cells. Treatment with 5′-Aza-2′-deoxycytidine leads to demethylation of the SBP1 promoter and to an increase of SBP1 promoter activity, rescues SBP1 mRNA and protein expression in human colon cancer cells. Additionally, overexpression of SBP1 sensitizes colon cancer cells to H₂O₂-induced apoptosis, inhibits cancer cell migration in vitro and inhibits tumor growth in nude mice.

Conclusion and Significance

These data demonstrate that SBP1 has tumor suppressor functions that are inhibited in colorectal cancer through epigenetic silencing.

Hypoxia-inducible factor-1alpha suppresses squamous carcinogenic progression and epithelial-mesenchymal transition

Hypoxia-inducible factor-1 (HIF-1) is a known cancer progression factor, promoting growth, spread, and metastasis. However, in selected contexts, HIF-1 is a tumor suppressor coordinating hypoxic cell cycle suppression and apoptosis. Prior studies focused on HIF-1 function in established malignancy; however, little is known about its role during the entire process of carcinogenesis from neoplasia induction to malignancy. Here, we tested HIF-1 gain of function during multistage murine skin chemical carcinogenesis in K14-HIF-1alpha(Pro402A564G) (K14-HIF-1alphaDPM) transgenic mice. Transgenic papillomas appeared earlier and were more numerous (6 +/- 3 transgenic versus 2 +/- 1.5 nontransgenic papillomas per mouse), yet they were more differentiated, their proliferation was lower, and their malignant conversion was profoundly inhibited (7% in transgenic versus 40% in nontransgenic mice). Moreover, transgenic cancers maintained squamous differentiation whereas epithelial-mesenchymal transformation was frequent in nontransgenic malignancies. Transgenic basal keratinocytes up-regulated the HIF-1 target N-myc downstream regulated gene-1, a known tumor suppressor gene in human malignancy, and its expression was maintained in transgenic papillomas and cancer. We also discovered a novel HIF-1 target gene, selenium binding protein-1 (Selenbp1), a gene of unknown function whose expression is lost in human cancer. Thus, HIF-1 can function as a tumor suppressor through transactivation of genes that are themselves targets for negative selection in human cancers.

Expression of selenium-binding protein 1 characterizes intestinal cell maturation and predicts survival for patients with colorectal cancer

To identify candidate genes involved in the development of colorectal cancer, we used cDNA microarrays to analyze gene expression differences between human colorectal tumors and paired adjacent normal mucosa. We identified approximately 3.5-fold significant downregulation of selenium-binding protein 1 (SBP1) in colorectal tumors compared to normal mucosa (p = 0.003). Importantly, stage III colorectal cancer patients with low tumor-SBP1 expression had significantly shorter disease-free and overall survival as compared with those patients with high tumor-SBP1 expression (p = 0.04 and 0.03, respectively). We further characterized the role of SBP1 in colorectal cancer in vivo and in vitro. In normal tissue, SBP1 was maximally expressed in terminally differentiated epithelial cells on the luminal surface of crypts in the large intestine. Consistent with this in vivo localization, SBP1 was upregulated during in vitro colonic cell differentiation along the absorptive (Caco-2) and secretory (HT29 Clones 16E and 19A) cell lineages. Downregulation (approximately 50%) of SBP1 expression by small interfering RNA in colonic cancer cells was associated with reduced expression of another epithelial differentiation marker, carcinoembryonic antigen (CEA), although PCNA and p21(WAF1/cip1 )expression were not altered. These data demonstrate that higher expression of SBP1 is associated with differentiation of the normal colonic epithelia and may be a positive prognostic factor for survival in stage III colorectal carcinoma.