ARL6IP5 and osteosarcoma: Unlike other members (PRAF1 and PRAF2) of the PRA family which promote tumor cell proliferation and migration and hence may function as oncogenes [11-13], PRAF3 is considered as a tumor suppressor since it could induce cell apoptosis and inhibit metastasis in tumors such as breast cancer, cervical cancer, melanoma and osteosarcoma [7,9,10].