Based on the studies of miR-513a-5p in osteosarcoma, we hypothesized that the downregulation of miR-513a-5p in osteosarcoma cells could be associated with the intrinsic radioresistance of osteosarcoma which has been reported to be due to the high expression of certain DNA repair proteins, including APE1. This evidence concerns the gene APEX1 and osteosarcoma.