Selenium-binding Protein 1 Expression Research Articles

Tumor microenvironment-related gene selenium-binding protein 1 (SELENBP1) is associated with immunotherapy efficacy and survival in colorectal cancer

BackgroundSelenium-binding protein 1 (SELENBP1), a member of the selenium-containing protein family, plays an important role in malignant tumorigenesis and progression. However, it is currently lacking research about relationship between SELENBP1 and immunotherapy in colorectal cancer (CRC).MethodsWe first analyzed the expression levels of SELENBP1 based on the Cancer Genome Atlas (TCGA), Oncomine andUALCAN. Chisq.test, Fisher.test, Wilcoxon-Mann-Whitney test and logistic regression were used to analyze the relationship of clinical characteristics with SELENBP1 expression. Then Gene ontology/ Kyoto encyclopedia of genes and genomes (GO/KEGG), Gene set enrichment analysis (GSEA) enrichment analysis to clarify bio-processes and signaling pathways. The cBioPortal was used to perform analysis of mutation sites, types, etc. of SELENBP1. In addition, the correlation of SELENBP1 gene with tumor immune infiltration and prognosis was analyzed using ssGSEA, ESTIMATE, tumor immune dysfunction and rejection (TIDE) algorithm and Kaplan-Meier (KM) Plotter database. Quantitative real-time PCR (qRT-PCR) and western blotting (WB) were used to validate the expression of SELENBP1 in CRC samples and matched normal tissues. Immunohistochemistry (IHC) was further performed to detect the expression of SELENBP1 in CRC samples and matched normal tissues.ResultsWe found that SELENBP1 expression was lower in CRC compared to normal colorectal tissue and was associated with poor prognosis. The aggressiveness of CRC increased with decreased SELENBP1 expression. Enrichment analysis showed that the SELENBP1 gene was significantly enriched in several pathways, such as programmed death 1 (PD-1) signaling, signaling by interleukins, TCR signaling, collagen degradation, costimulation by the CD28 family. Decreased expression of SELENBP1 was associated with DNA methylation and mutation. Immune infiltration analysis identified that SELENBP1 expression was closely related to various immune cells and immune chemokines/receptors. With increasing SELENBP1 expression, immune and stromal components in the tumor microenvironment were significantly decreased. SELENBP1 expression in CRC patients affects patient prognosis by influencing tumor immune infiltration. Beside this, SELENBP1 expression is closely related to the sensitivity of chemotherapy and immunotherapy.ConclusionsSurvival analysis as well as enrichment and immunoassay results suggest that SELENBP1 can be considered as a promising prognostic biomarker for CRC. SELENBP1 expression is closely associated with immune infiltration and immunotherapy. Collectively, our study provided useful information on the oncogenic role of SELENBP1, contributing to further exploring the underlying mechanisms.

SELENBP1 inhibits progression of colorectal cancer by suppressing epithelial-mesenchymal transition.

Selenium-binding protein 1 (SELENBP1) is frequently dysregulated in various malignancies including colorectal cancer (CRC); however, its roles in progression of CRCs and the underlying mechanism remain to be elucidated. In this study, we compared the expression of SELENBP1 between CRCs and colorectal normal tissues (NTs), as well as between primary and metastatic CRCs; we determined the association between SELENBP1 expression and CRC patient prognoses; we conducted both in vitro and in vivo experiments to explore the functional roles of SELENBP1 in CRC progression; and we characterized the potential underlying mechanisms associated with SELENBP1 activities. We found that the expression of SELENBP1 was significantly and consistently decreased in CRCs than that in adjacent NTs, while significantly and frequently decreased in metastatic than primary CRCs. High expression of SELENBP1 was an independent predictor of favorable prognoses in CRC patients. Overexpression of SELENBP1 suppressed, while silencing of SELENBP1 promoted cell proliferation, migration and invasion, and in vivo tumorigenesis of CRC. Mechanically, SELENBP1 may suppress CRC progression by inhibiting the epithelial–mesenchymal transition.

SELENBP1 Inhibits Cell Proliferation and Migration in Colorectal Cancers by Suppressing EMT

Background: Selenium binding protein 1 (SELENBP1) is frequently dysregulated in various malignancies including colorectal cancer (CRC). Methods: Expression of SELENBP1 in colorectal normal tissues (NTs) and CRCs was determined using bioinformatics data and clinical samples. Correlation between SELENBP1 expression and patient survival was evaluated using the Kaplan-Meier method and log-rank test. Univariate and multivariate survival analyses were conducted with a Cox proportional hazards regression model. The impact of SELENBP1 on cell proliferation, migration and invasion, and in vivo tumorigenesis were investigated by Cell Counting Kit-8 (CCK8) assay and EdU assay, Transwell migration and invasion assays, and a subcutaneous xenograft model. The underlying mechanism was characterized for the suppressive roles of SELENBP1 in CRC carcinogenesis and progression. Findings: The expression of SELENBP1 was significantly and consistently decreased in CRCs than that in NTs, while significantly and frequently decreased in metastatic than primary CRCs. High expression of SELENBP1 was an independent predictor of favorable prognoses in CRC patients. Overexpression of SELENBP1 suppressed, while silencing of SELENBP1 promoted cell proliferation, migration and invasion, and in vivo tumorigenesis of CRC. Mechanically, SELENBP1 may suppress CRC carcinogenesis and progression by inhibiting the epithelial-mesenchymal transition (EMT). Interpretation: our results demonstrate that SELENBP1 could be a promising tumor suppressor which should be further investigated. Funding: This work was supported by Shanghai Fifth People’s Hospital (grant numbers 2016WYRC01 and 2017WYRCSG01); the Medical System of Shanghai Minhang District (grant number 2017MWDXK01); the Shanghai Minhang District Health and Family Planning Commission (grant number 2016MW03); and the Shanghai Minhang District Science and Technology Commission (grant numbers 2017MHZ02, 2019MHZ054, and 2020MHZ080). Declaration of Interest: The authors declare no competing interests. Ethical Approval: This study was approved by the Institutional Ethics Committee at Shanghai Fifth People’s Hospital and adhered to the principles listed in the Declaration of Helsinki.

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

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. 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. 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. 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.

Selenium-binding protein 1 alters energy metabolism in prostate cancer cells.

ObjectiveThe broad goal of the research described in this study was to investigate the contributions of selenium‐binding protein 1 (SBP1) loss in prostate cancer development and outcome.MethodsSBP1 levels were altered in prostate cancer cell lines and the consequences on oxygen consumption, expression of proteins associated with energy metabolism, and cellular transformation and migration were investigated. The effects of exposing cells to the SBP1 reaction products, H2O2 and H2S were also assessed. In silico analyses identified potential HNF4α binding sites within the SBP1 promoter region and this was investigated using an inhibitor specific for that transcription factor.ResultsUsing in silico analyses, it was determined that the promoter region of SBP1 contains putative binding sites for the HNF4α transcription factor. The potential for HNF4α to regulate SBP1 expression was supported by data indicating that HNF4α inhibition resulted in a dose‐response increase in the levels of SBP1 messenger RNA and protein, identifying HNF4α as a novel negative regulator of SBP1 expression in prostate cancer cells. The consequences of altering the levels of SBP1 were investigated by ectopically expressing SBP1 in PC‐3 prostate cancer cells, where SBP1 expression attenuated anchorage‐independent cellular growth and migration in culture, both properties associated with transformation. SBP1 overexpression reduced oxygen consumption in these cells and increased the activation of AMP‐activated protein kinase (AMPK), a major regulator of energy homeostasis. In addition, the reaction products of SBP1, H2O2, and H2S also activated AMPK.ConclusionsBased on the obtained data, it is hypothesized that SBP1 negatively regulates oxidative phosphorylation (OXPHOS) in the healthy prostate cells by the production of H2O2 and H2S and consequential activation of AMPK. The reduction of SBP1 levels in prostate cancer can occur due to increased binding of HNF4α, acting as a transcriptional inhibitor to the SBP1 promoter. Consequently, there is a reduction in H2O2 and H2S‐mediated signaling, inhibition of AMPK, and stimulation of OXPHOS and building blocks of biomolecules needed for tumor growth and progression. Other effects of SBP1 loss in tumor cells remain to be discovered.

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.

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

BackgroundRecent 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.MethodsSELENBP1 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.ResultsHere, 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.ConclusionsTaken 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 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.

Abstract P4-04-18: Estrogen receptor α-dependent transcriptional induction of selenium-binding protein 1 increases the sensitivity of tamoxifen treatment in breast cancer

Abstract Reduction of selenium-binding protein 1 (SELENBP1) has been frequently observed in various solid tumors, and associated with poor clinical prognosis, implicating SELENBP1 as a potential tumor suppressor. However, the molecular mechanism underlying the transcriptional regulation of SELENBP1 remains poorly understood. In this study, we first analyzed the relationship between SELENBP1 mRNA levels and clinical or pathological features of breast cancer in METABRIC datasets, and found that SELENBP1 mRNA levels were differentially expressed in PAM50 molecular subtypes with highest levels in Luminal A/B subtype and lowest levels in Basal-like/Claudin-low subtype, indicating that SELENBP1 might function as the downstream player of estrogen receptor α (ERα). Following the adjustment of clinicopathological characteristics including the menopausal status, ER/HR/ERBB2 status, TNM stage and histological grade, the Kaplan-Meier survival analysis surprisingly showed that patients with higher levels of SELENBP1 mRNA (n=43) had shorter survival time than those with moderate levels of SELENBP1 expression (n=102) in Luminal A subtype (Hazard Ratio 1.59; 95% CI 0.99-2.54; Logrank p=0.0367), although the patients with lower SELENBP1 levels were consistent the poor prognosis in Basal-like/Claudin-low subtype (Hazard Ratio 1.54; 95% CI 0.97-2.44; Logrank p=0.0356). To elucidate this controversy, we knocked down the expression of ERα in MCF-7 cells using shRNA targeting ERα, and found that knockdown of ERα resulted in the down-regulation of mRNA and protein expression of SELENBP1. In addition, SELENBP1 promoter-driven luciferase reporter assay reveled ERα regulated the expression of SELENBP1 at transcriptional level. Interestingly, we further found that the addition of 4-hydroxytamoxifen (4-OHT) led to a dramatic reduction of SELENBP1 protein expression in MCF-7 cells, while forced expression of SELENBP1 in MCF-7 cells significantly enhanced 4-OHT-mediated inhibition of anchor-independent cancer cell growth. Collectively, these results suggested that the transcriptional induction of SELENBP1 by ERα might function as a downstream tumor suppressor in breast cancer cells, but endocrine therapy led to the down-regulation of SELENBP1 expression due to the blocking of ERα signaling in the patients with Luminal subtype, which was likely to explain the observation of differential predictive value for SELENBP1 mRNA levels in the Luminal and Basal-like/Claudin-low subtypes. Further investigation in vitro and in vivo has been ongoing in our laboratory, and the results from which will help us better understand the clinical relevance for SELENBP1 as a promising therapeutic target in improving the efficacy of endocrine therapy. This study was supported in part by National Natural Science Foundation of China (8160111571) and Guangdong Natural Science Foundation (2016A030313768). Citation Format: Liao N, Wang Y, Zhang G, Cao L, Li K, Ren C-Y, Wen L-Z, Shi Y, Zhu W, Chen X. Estrogen receptor α-dependent transcriptional induction of selenium-binding protein 1 increases the sensitivity of tamoxifen treatment in breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-04-18.

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.

Loss of Selenium-Binding Protein 1 Decreases Sensitivity to Clastogens and Intracellular Selenium Content in HeLa Cells.

Selenium-binding protein 1 (SBP1) is not a selenoprotein but structurally binds selenium. Loss of SBP1 during carcinogenesis usually predicts poor prognosis. Because genome instability is a hallmark of cancer, we hypothesize that SBP1 sequesters cellular selenium and sensitizes cancer cells to DNA-damaging agents. To test this hypothesis, we knocked down SBP1 expression in HeLa cervical cancer cells by employing a short hairpin RNA (shRNA) approach. Reduced sensitivity to hydrogen peroxide, paraquat and camptothecin, reactive oxygen species content, and intracellular retention of selenium after selenomethionine treatment were observed in SBP1 shRNA HeLa cells. Results from Western analyses showed that treatment of HeLa cells with selenomethionine resulted in increased SBP1 protein expression in a dose-dependent manner. Knockdown of SBP1 rendered HeLa cells increased expression of glutathione peroxidase-1 but not glutathione peroxidase-4 protein levels and accelerated migration from a wound. Altogether, SBP1 retains supplemental selenium and sensitizes HeLa cancer cells to clastogens, suggesting a new cancer treatment strategy by sequestering selenium through SBP1.

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

BackgroundWe 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.MethodsTissue 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.ResultsExpressions 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).ConclusionsDownregulation of SBP1 may play a key role in the tumorigenic process of LSCC. SBP1 may be a novel potential prognostic factor of LSCC.

Sodium Selenite Inhibits Proliferation of Gastric Cancer Cells by Inducing SBP1 Expression.

Selenium is an essential trace element with an inhibitory effect on many types of human cancers, including gastric cancer. Selenium-binding protein 1 (SBP1) has been shown as a possible mediator of selenium's anti-cancer functions. Indeed, SBP1 was downregulated in gastric cancer, which is related with poor prognosis. However, the molecular mechanisms underlying the anti-tumor effects of SBP1 remain poorly understood. In this study, we aimed to assess the effects of selenium and/or SBP1 on the proliferation of gastric cancer cells. We used SGC7901 and N87 human gastric cancer cell lines and nude mice carrying subcutaneously implanted SGC7901 cells. Treatment with sodium selenite for 48 h caused the inhibition of cell proliferation and the increase in apoptosis of SGC7901 and N87 cells. Furthermore, sodium selenite increased the expression level of SBP1 and decreased the levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and the Wnt pathway components and its downstream targets, including β-catenin, GSK-3β, c-myc and cyclinD1 in these cell lines. However, these effects of sodium selenite were attenuated in SGC7901 and N87 cells by knockdown of SBP1 expression. Thus, the sodium selenite-induced SBP1 expression is associated with the inhibition of cell proliferation and with the induced apoptosis. Importantly, sodium selenite treatment retarded the growth of the transplanted SGC7901 cells in nude mice, with the induction of SBP1 expression, which was associated with the decrease of Nrf2 expression and the inactivation of the Wnt/β-catenin signaling pathway. We suggest that sodium selenite may have a potential application in gastric cancer treatment.

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.

Selenium-binding protein 1 is associated with the degree of colorectal cancer differentiation and is regulated by histone modification.

The aim of the present study was to examine the regulation of selenium binding protein 1 (SELENBP1) expression in colorectal cancer (CRC). Samples of cancer tissue and adjacent normal mucosa were collected from 83 CRC patients, and analyzed for SELENBP1 expression by 2D-DIGE, immunoblotting, RT-PCR and immunostaining. Expression levels of SELENBP1, carcinoembryonic antigen (CEA) and alkaline phosphatase (AKP) were determined in cultures of human colon cancer cell lines (SW480, SW620 and HT29) folllowing treatment with i) sodium butyrate (NaB, 2mM), a differentiation inducer; ii) Trichostatin A (TSA, 0.3µM), a histone deacetylase inhibitor; or iii) 5'-aza-2'-deoxycytidine (5-Aza-dC, 5µM), a DNA methylation inhibitor. SELENBP1 expression was found to be downregulated (2.54-fold) in the CRC samples as determined by 2D-DIGE and confirmed by immunoblotting and RT-PCR. SELENBP1 expression was correlated with the degree of differentiation, but not with TNM stage or lymph node metastasis, and was higher in benign polyps (1.97±0.57) than in CRC tissues (0.96±0.59). In the CRC cell lines, NaB treatment led to the upregulation of SELENBP1, CEA and AKP when compared with the untreated cells (2.24- to 4.82-fold). SELENBP1 was also upregulated in cells treated with TSA alone (1.25- to 3.64-fold), or in combination with 5-Aza-dC (1.32- to 4.13-fold). In CRC, the downregulated SELENBP1 expression was reactivated by inducing differentiation. Therefore, SELENBP1 is a potential pharmacological target for individualized CRC treatment.

The Function and Significance of SELENBP1 Downregulation in Human Bronchial Epithelial Carcinogenic Process

BackgroundOur quantitative proteomic study showed that selenium-binding protein 1 (SELENBP1) was progressively decreased in human bronchial epithelial carcinogenic process. However, there is little information on expression and function of SELENBP1 during human lung squamous cell cancer (LSCC) carcinogenesis.MethodsiTRAQ-tagging combined with 2D LC-MS/MS analysis was used to identify differentially expressed proteins in the human bronchial epithelial carcinogenic process. SELENBP1, member of selenoproteins family and progressively downregulated in this process, was selected to further study. Both Western blotting and immunohistochemistry were performed to detect SELENBP1 expression in independent sets of tissues of bronchial epithelial carcinogenesis, and ability of SELENBP1 for discriminating NBE (normal bronchial epithelium) from preneoplastic lesions from invasive LSCC was evaluated. The effects of SELENBP1 downregulation on the susceptibility of benzo(a)pyrene (B[a]P)-induced human bronchial epithelial cell transformation were determined.Results102 differentially expressed proteins were identified by quantitative proteomics, and SELENBP1 was found and confirmed being progressively decreased in the human bronchial epithelial carcinogenic process. The sensitivity and specificity of SELENBP1 were 80% and 79% in discriminating NBE from preneoplastic lesions, 79% and 82% in discriminating NBE from invasive LSCC, and 77% and 71% in discriminating preneoplastic lesions from invasive LSCC, respectively. Furthermore, knockdown of SELENBP1 in immortalized human bronchial epithelial cell line 16HBE cells significantly increased the efficiency of B[a]P-induced cell transformation.ConclusionsThe present data shows for the first time that decreased SELENBP1 is an early event in LSCC, increases B[a]P-induced human bronchial epithelial cell transformation, and might serve as a novel potential biomarker for early detection of LSCC.

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.

Selenium-binding protein 1 may decrease gastric cellular proliferation and migration

It has been reported that suppression of selenium‑binding protein 1 (SBP1) occurs in many human malignancies which is considered to play an important role in cancer development and progression. Despite its importance in cancer, the function and factors that regulate its expression are not known. Using cell proliferation assays, immunochemical staining and immunoblotting and flow cytometry methods and in a xenograft model, we evaluated the role of SBP1 in proliferation, migration, senescence and chemoresistance of gastric cancer cells (SGC7901 and BGC823) to cisplatin. It was noted that diminished SBP1 expression increased gastric cancer cell proliferation and cell migration and decreased cisplatin-induced apoptosis while its overexpression produced the opposite effects. These results suggest that SBP1 plays a significant role in gastric cancer cell proliferation and modulates its response to anticancer drugs. These results suggest that SBP1 can serve as a potential target to suppress gastric cancer.

Decreased Selenium-Binding Protein 1 Enhances Glutathione Peroxidase 1 Activity and Downregulates HIF-1α to Promote Hepatocellular Carcinoma Invasiveness

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

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.