Uncontrol cell growth and proliferation is acknowledged to responsible for cancer-related deaths by disorganizing the balance of growth promotion and growth limitation. Aberrant expression of microRNA play essential roles in cancer development, leads to cell proliferation, growth and survival, and promotes the development of various human tumors, including osteosarcoma. Elucidating the molecular mechanism of this abnormality in osteosarcoma carcinogenesis may improve diagnostic and therapeutic strategies for this malignancy.

The expression of miR-664 in osteosarcoma cell lines and osteosarcoma tissues was examined using real-time PCR. The effects of miR-664 on osteosarcoma cell proliferation were evaluated by 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, colony formation and Anchorage-independent growth ability assay. The effect of miR-664 on FOXO4 was determine by luciferase assays and western blot assay.

The expression of miR-664 was markedly upregulated in osteosarcoma cell lines and tissues, and upregulation of miR-664 enhanced, whereas downregulation of miR-664 inhibited the proliferation of osteosarcoma cells in vivo. Furthermore, using bioinformatics and biological approaches, we showed that miR-664 directly targeted and suppressed the expression of tumor suppressors FOXO4.

Our findings suggest that miR-664 functions as an oncogene miRNA and has an important role in promoting human osteosarcoma cell proliferation by suppressing FOXO4 expression. These data suggests that miR-664 may represent a novel therapeutic target of microRNA-mediated suppression of cell proliferation in osteosarcoma.