C-Myc overexpression promotes osteosarcoma cell invasion via activation of MEK-ERK pathway. Osteosarcoma is a highly metastatic malignancy often with poor prognosis. c-Myc amplification is implicated in osteosarcoma pathogenesis. However, the role of c-myc overexpression in osteosarcoma cell invasion remains unexplored. This study showed that c-myc overexpression enhanced MG-63 and SAOS-2 osteosarcoma cell invasion. Treatment of MEK inhibitor PD98059 or PI3K inhibitor LY294002 decreased cell invasion along with downregulation of MMP-2 and MMP-9 expression. c-Myc overexpression stimulated MEK-ERK pathway whereas inhibited the activity of PI3K-AKT pathway. Specifically, inhibition of MEK-ERK pathway by PD98509 blocked the enhancement effect on cell invasion as well as MMP-2 and MMP-9 expression. The present study demonstrates that c-myc overexpression promotes osteosarcoma cell invasion, probably via activation of MEK-ERK pathway.