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

Abstract

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-1a (HIF-1a) 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-1a expression in HCC; SBP1 could be a novel biomarker for predicting prognosis and guiding personalized therapeutic strategies, especially in patients with advanced HCC.

Biochemical and Biophysical Characterization of the Selenium-binding and Reducing Site in Arabidopsis thaliana Homologue to Mammals Selenium-binding Protein 1

“…Primer sequences were designed using QuikChange Primer Design software from Agilent Technology. Cys 21 and Cys 22 of AtSBP1 were replaced by Ser residues. PCR was performed using Phusion enzyme with 18 cycles as follow: 30 s at 98°C, 1 min at 55°C, and 1 min 40 s at 72°C.…”

“…5). Two additional Cys residues (Cys 21 and Cys 22 ) are conserved in all the photosynthetic organisms, and they aligned with a CXXC motif in mammals. We also investigated the three-dimensional structure of AtSBP1 to check whether two Cys residues not adjacent in the sequence could come into contact due to protein folding.…”

“…Isothermal titration calorimetry confirmed the 1:1 stoichiometry and revealed an unexpectedly large value of binding enthalpy suggesting a covalent bond between selenium and AtSBP1. Titration of reduced Cys residues and comparative mass spectrometry on AtSBP1 and the purified seleniumAtSBP1 complex identified Cys 21 and Cys 22 as being responsible for the binding of one selenium. These results were validated by site-directed mutagenesis.…”

“…In humans, down-regulation of SBP1 expression has been correlated with rapid tumor development in many organs (19 -27) and SBP1 expression is considered to be a predictor of clinical outcome. Recently, interaction of SBP1 and the selenoprotein glutathione peroxidase GPx-1 was observed, revealing a cross-talk between members of distinct families of selenium containing proteins (19,21,28). SBP1 was also characterized as a biomarker for schizophrenia as up-regulation of SBP1 is observed in the brains of patients with the disease (29,30).…”

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

“…The human selenium-binding protein 1 (SBP1, SELENBP1 or hSP56) gene is located at chromosome position 1q21-22 and is the homologue of the mouse SP56 gene (Yang and Diamond 2013). SBP1 has been shown to bind selenium covalently and has been found to be the possible mediator of selenium's anticancer functions (Porat et al 2000;Silvers et al 2010;Huang et al 2012). Selenium supplementation causes the increase in SBP1 expression, which affects cell viability and chemosensitivity of esophageal adenocarcinoma cells (Silvers et al 2010).…”