Ran-binding protein 9 overexpression induces apoptosis in osteosarcoma cells by activating endogenous mitochondrial pathway

Abstract

Objective To investigate the effect of overexpression of Ran-binding protein 9 (RanBP9) on apoptosis of osteosarcoma cells and the underlying mechanism. Methods Real-time PCR and Western blotting were used to detect the mRNA and protein expression of RanBP9 in cultured osteoblasts and different osteosarcoma cell lines (SaOS2, MG63, U2OS and HOS). In a SaOS2 cell model with stable RanBP9 overexpression induced by transfection with a lentiviral vector, the cell apoptotic rate was determined using flow cytometry and TUNEL assay, and the changes in mitochondrial transmembrane potential were analyzed. Results RanBP9 was positively expressed in cultured osteoblasts and in the 4 osteosarcoma cell lines. RanBP9 expression was significantly higher in the osteoblasts than in the osteosarcoma cells, and was significantly higher in osteosarcoma cell lines MG63 and HOS than in SaOS2 and U2OS cell lines that had higher levels of malignancy. In SaOS2 cells, overexpression of RanBP9 obviously suppressed cell proliferation and promoted cell apoptosis and significantly increased the expression levels of caspase-3 and Cytc and the ratio of Bax/Bcl-2, resulting also in the dissipation of mitochondrial transmembrane potential and activation of the mitochondrial pathway to induce cell apoptosis. Conclusion RanBP9 promotes osteosarcoma cell apoptosis via the endogenous mitochondrial pathway.

Keywords

• osteosarcoma
• ran-binding protein 9
• apoptosis
• proliferation
• chemotherapy