CDK2 and Ewing sarcoma: Cyclin-E binds CDK2 to induce G1/S transition [33, 34], whereas p21 and p27 repress cyclin-E/CDK2 complex to inhibit the processes [35, 36]; therefore these results indicated that inhibition of SOX2 in Ewing’s sarcoma cells was induced by repression of cyclin-E and activation of p21 and p27.