TP53 and primitive neuroectodermal tumor: Upregulation of miRNA-125b suppresses the expression of p53 and the proapoptotic protein BAK, thereby preventing the induction of p53-dependent apoptosis and causing chemoresistance to doxorubicin, vincristine, and etoposide in EWS (Ewing sarcoma/primitive neuroectodermal tumor) cells [201].