Decoy receptor 3: Its role as biomarker for chronic inflammatory diseases

Members of the tumor-necrosis factor-α(TNF-α) and TNF-α receptor(TNFR) superfamilies of proteins(TNFSF and TNFRSF, respectively) play important roles in the function of the immune system. Decoy receptor 3(Dc R3, TNFRSF6b) is a decoy receptor that binds to three TNFSF ligands, Fas L, LIGHT and TL1 A. Association to these ligands competes with the corresponding functional receptors and blocks downstream signaling, leading to immunomodulatory effects, including the prevention of apoptosis. Dc R3 lacks a transmembrane region and exists only as a secreted protein, which is detectable in biological fluids. Recent studies have shown that Dc R3 is upregulated and may be pathogenetically implicated in several and diverse chronic inflammatory diseases. The strongest associations have been described for rheumatological diseases, mainly systemic lupus erythematosus and rheumatoid arthritis, inflammatory bowel disease, and serious infectious conditions, including systemic inflammatory response syndrome. In the majority of these conditions, Dc R3 m RNA and protein expression is elevated both at the target tissues as well as in the systemic circulation. Dc R3 concentration in the serum is untraceable in the majority of healthy individuals but can be detected in patients with various inflammatory diseases. In mostsuch cases, soluble Dc R3 correlates with disease severity, as patients with severe forms of disease have significantly higher levels than patients with milder or no activity. In addition, effective anti-inflammatory treatment leads to the disappearance of soluble Dc R3 from the circulation. Taken together, current evidence suggests that serum Dc R3 may become a useful biomarker for chronic inflammatory disorders, as it is upregulated in response to inflammatory stimuli, and may serve both as a prognostic marker for disease severity and as a surrogate indicator of response to treatment.

Knockdown of Decoy Receptor 3 Impairs Growth and Invasiveness of Hepatocellular Carcinoma Cell Line of HepG2

Background：Decoy receptor 3 （DcR3） binds to Fas ligand （FasL） and inhibits FasL-induced apoptosis.The receptor is overexpressed in hepatocellular carcinoma （HCC）,and it is associated with the growth and metastatic spread of tumors.DcR3 holds promises as a new target for the treatment of HCC,but little is known regarding the molecular mechanisms underlying the oncogenic properties of DcR3.The present work,therefore,examined the role of DcR3 in regulating the growth and invasive property of liver cancer cell HepG2.Methods：HepG2 cells were stably transfected with lentivirus-based short hairpin RNA vector targeting DcR3.After the knockdown of DcR3 was confirmed,cell proliferation,clone formation,ability of migrating across transwell membrane,and wound healing were assessed in vitro.Matrix metalloproteinase-9 （MMP 9） and vascular epithelial growth factor （VEGF）-C and D expressions of the DcR3 knockdown were also studied.Comparisons between multiple groups were done using one-way analysis of variance （ANOVA）,while pairwise comparisons were performed using Student＇s t test.P 〈 0.05 was regarded statistically significant.Results：DcR3 was overexpressed in HepG2 compared to other HCC cell lines and normal hepatocyte Lo-2.Stable knockdown of DcR3 slowed down the growth of HepG2 （P 〈 0.05） and reduced the number of clones formed by 50% compared to those without DcR3 knockdown （P 〈 0.05）.The knockdown also reduced the migration of HepG2 across transwell matrix membrane by five folds compared to the control （P 〈 0.05） and suppressed the closure of scratch wound （P 〈 0.05）.In addition,the messenger RNA levels of MMP 9,VEGF-C,and VEGF-D were significantly suppressed by DcR3 knockdown by 90% when compared with the mock control （P 〈 0.05）.Conclusions：Loss of DcR3 impaired the growth and invasive property of HCC cell line of HepG2.Targeting DcR3 may be a potential therapeutic approach for the treatment of HCC.

Anti-apoptosis Effect of Decoy Receptor 3 in Cholangiocarcinoma Cell Line TFK-1

Background： Decoy receptor 3 （DcR3） is a protein with anti-apoptotic effect that belongs to the tumor necrosis factor receptor superfamily. DcR3 is highly expressed in a variety of malignant tumors including cholangiocarcinoma and its expression was found to be related to the clinical stage, the invasion, and tile metastasis of the tumor. This in vitro study aimed to investigate the effect ofdownregulated expression of DcR3 on cell viability, cell apoptosis, and cell cycle in cholangiocarcinoma cell line TFK-1. Methods： Three different cell lines were cultured： human cholangiocarcinoma TFK-I, human biliary epithelial carcinoma HuCCT-1, and human cholangiocarcinoma RBE. The cholangiocarcinoma cell line with the highest expression of DcR3 was selected for further investigation. The expression of DcR3 was silenced/knocked down by transfection with DcR3-siRNA in the selected cell line. Various biological phenotype parameters such as cell viability, apoptosis, and cell cycle were observed. Results： The mRNA and protein levels of DcR3 were measured in the three cell lines, and TFK-1 was selected. After the treatment with DcR3-siRNA for 48 h, DcR3 mRNA and protein expression in the treatment group were 38.45% （P 〈 0.01 ） and 48.03% （P 〈 0.05） of that of＇the control, respectively. It was found that the cell viability decreased to 61.87% of the control group （P 〈 0.01 ） after the downregulation of DcR3 in cholangiocarcinoma cell line TFK- 1 by transfection with DcR3-siRNA, while tile percentage ofapoptotic cells was 2.98 times as compared with the control group （P 〈 0.05）. Compared with the control group the ratio of G0/G1 increased, and the ratio of G2/M dccreased in the treatment group. However, the differences were not statistically significant. Conclusions： The effect of DcR3 on the growth and apoptosis ofcholangiocarcinoma has been demonstrated. DcR3 is not only a predictive marker for malignant tumor but it is also likely to be a potential target for cancer gene therapy. Further studies should focus on exploring the binding ligand of DcR3, the signaling pathway involved, and the molecular mechanism for the regulation of DcR3 expression in cholangiocarcinoma.