RAC1 and osteosarcoma: In the present study, we found that miR-124 was down-regulated in osteosarcoma cell lines and primary tumor samples, and miR-124 was further identified to be a tumor suppressor, as restoration of miR-124 expression in osteosarcoma cell lines was able to inhibit cell proliferation, promote cell cycle, and suppress cell invasion and metastasis by targeting Rac1.