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Osteosarcoma is one of the most frequent types of primary malignant bone neoplasm in children and adolescents. Despite advancements developed in therapeutic modalities, the 5-year overall survival rates for patients with metastatic osteosarcoma disease remain poor. The present study aimed to investigate the expression level of microRNA-302a (miR-302a) in osteosarcoma tissues and cell lines, and the biological roles of miR-302a in osteosarcoma cells. In addition, the molecular mechanism underlying its tumor suppressive roles was evaluated. miR-302a expression in osteosarcoma tissues and cell lines was detected using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Following transfection of miR-302a mimics or IGF-1R siRNA, transwell migration and invasion, luciferase reporter assay RT-qPCR and western blot assays were conducted in osteosarcoma cells. In the present study, the data demonstrated that miR-302a was frequently reduced in osteosarcoma tissue and cell lines. In addition, the expression of miR-302a was correlated with metastatic features of patients with osteosarcoma. Restoration of miR-302a expression significantly inhibited the migration and invasion capacity of osteosarcoma cells. Mechanistic studies indicated that insulin-like growth factor 1 receptor (IGF-1R) was a direct target gene of miR-302a. Overexpression of miR-302a resulted in decreased expression of IGF-1R at the mRNA and protein levels. Furthermore, the knockdown IGF-1R mimicked the functions of miR-302a overexpression on osteosarcoma cell migration and invasion. Collectively, the results of the current study indicate that miR-302a acts as a metastasis suppressing miRNA and could be investigated as a therapeutic target for the treatment of patients with osteosarcoma to prevent metastasis. [ABSTRACT FROM AUTHOR]