MDM2 and osteosarcoma: Circular RNA sterile alpha motif domain containing 4A (circSAMD4A) is a newly identified circRNA, and Yanbin et al. found that circSAMD4A enhanced cell proliferation and the features of cancer stem cells in osteosarcoma by upregulating miR-1244-mediated MDM2 expression, suggesting the carcinogenic role of circSAMD4A in osteosarcoma [11].