Objective      To explore the effect of Ran-binding protein 9 (RanBP9) expression on the proliferation

apoptosis and metastasis in human osteosarcoma cells

so as to discuss its biological functions in osteosarcoma cells.       Methods      Real-time PCR

immunofluorescence assay and Western blotting were used to examine RanBP9 mRNA and protein expression levels in osteosarcoma cell lines. Also we performed a series of biological tests using osteosarcoma SaOS2 cell line to study the effects of RanBP9 down-regulation on the proliferation

c

lone formation

apoptosis and metastasis in SaOS2 cells.        Results      We found that RanBP9 was highly expressed in human osteosarcoma cell lines and RanBP9 expression was significantly higher in MG63 cell line derived from low-grade osteosarcoma than in U2OS or SaOS2 cell lines derived from high-grade osteosarcoma (

P

0.05). Immunofluorescence assay and Western blotting also showed the same results. Low expression of RanBP9 in SaOS2 cell line not only markedly increased cell vitality

growth and colony formation

but also stimulated migration and invasion (

P

0.05) as compared with control cells (siCON-SaOS2). Consistently

down-regulated RanBP9 was associated with reduced basic apoptosis assayed by annexin APC-PI (

P

0.05).       Conclusion      Low expression of RanBP9 reduces apoptosis and increases osteosarcoma cell proliferation as well as metastasis

suggesting that RanBP9 may be a tumor-suppressor involving in the occurence and development of osteosarcoma.