The p53 activator Nutlin-3 induced MYBL2 degradation and G1 phase block by inhibition of the p53 suppressor MDM2 in primary leukemia cells as well as in p53-wildtype myeloid (OCI, MOLM) and lymphoblastoid cells (SKW6.4, EHEB) via miR-34a. The gene discussed is MYBL2; the disease is leukemia.