A feedback circuit of miR-34a/MDM4/p53 regulates apoptosis in chronic lymphocytic leukemia cells

BACKGROUND: Dysfunction of apoptosis is a significant characteristic in chronic lymphocytic leukemia (CLL). Murine double minute 4 (MDM4), miR-34a and TP53 are found to participate in modulating cellular apoptosis while the specific mechanism keeps unclear. This study was designed to investigate the potential feedback circuit among MDM4, miR-34a and TP53. METHODS: According to the bioinformatic approaches, there are 4 miR-34a candidate binding domains in MDM4. Use dual luciferase reporter gene to verify the regulation between miR-34a and MDM4. Flow cytometry was used to detect the change of apoptosis level in CLL cells before and after miR-34a mimics and shMDM4 were respectively transfected into primary CLL cells in vitro. Meanwhile, Real-time PCR was used to detect the change of RNA expression of MDM4, miR-34a and TP53. RESULTS: Up-regulated expression of miR-34a or down-regulated expression of MDM4 could increase apoptosis of CLL cells, inhibit expression of MDM4 and decrease expression of p53 in mRNA level compared to negative control (NC) or shNC (P<0.05). The luminescence of psiCHECK-2-MDM4 EXON 11 can be effectively inhibited by miR-34a (P<0.05). CONCLUSIONS: MiR-34a could modulate MDM4 by binding to MDM4 exon 11 instead of 3’UTR. This research thus highlights a forceful evidence for miR-34a/MDM4/p53 feedback circuit in CLL apoptosis.