Abstract
Background: Decoy receptor 3 (DcR3) is a soluble secreted protein which belongs to TNF receptor superfamily, and inhibits Fas/Fas ligand (FasL) apoptotic pathway by binding to FasL competitively with Fas. Previous studies have reported that overexpression of DcR3 is detected in various human malignancies, and that DcR3 plays an important role on tumour progression. We previously reported that DcR3 overexpression was observed in human osteosarcoma and malignant fibrous histiocyoma (MFH) cells, however, the role of DcR3 in musculoskeletal tumours has not been studied. The purpose of this study was to evaluate the effect of DcR3 inhibition in Fas/FasL apoptotic pathway in human MFH cells. Methods: TNMY1, human MFH cell line that expresses the high level of DcR3, was used in this study. TNMY1 cells were transfected with either DcR3-siRNA or control siRNA. After siRNA transfection, each cell was cultured in medium with or without FasL, and cell proliferation assay was performed at 0, 24 and 48 hours of incubation. Also, cell lysate was collected from each transfected cell which was treated with or without FasL, and we performed immunoblot analysis to evaluate the expression of DcR3, Fas and apoptosis-related proteins, such as Caspases and PARP. Results: DcR3-siRNA transfection sufficiently suppressed DcR3 expression in TNMY1 cells compared with control cells without affecting Fas expression. FasL treatment significantly decreased cell proliferation in DcR3-siRNA transfected cells compared with control cells after 24 and 48 hours of incubation. Apoptosis-related proteins, cleaved Caspase-3 and cleaved PARP, were detected in cells which were treated with FasL after DcR3-siRNA transfection, however both proteins were not observed in control cells. Conclusions: Previous studies revealed that DcR3 blocks Fas/FasL apoptotic pathway by binding to FasL competitively with Fas, and that overexpression of DcR3 is associated with tumour progression in various human malignancies. However, the role of DcR3 in musculoskeletal tumours is still unknown. In this study, we demonstrated that FasL treatment with DcR3 inhibition caused a svnergistic cytotoxic effect and induced apoptosis in human MFH cells. These results suggest that DcR3 may have an anti-apoptotic effect via inhibiting Fas/FasL apoptosis pathway in human MFH, and that DcR3 may be a potent therapeutic target for human malignant musculoskeletal tumours.
Published Version
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