Inhibition of MDM2 Using Idasanutlin (RG-7388) enhances the Chemo-sensitivity of B-ALL Cells to Daunorubicin

Background: Although significant advances have been made in the treatment of cancer, a significant number of patients with acute lymphoblastic leukemia (ALL) show resistance to treatment. Thus, it is necessary to seek novel therapeutic agents to overcome this problem. Studies have indicated that the expression level of mouse double minute 2 (MDM2), a negative regulator of p53, is markedly elevated in patients with refractory or recurrent ALL. Thus, targeting MDM2 using a specific inhibitor, Idasanutlin, can increase the activity of p53. This study evaluated the possible synergistic effect of Idasanutlin and Daunorubicin on the induction of apoptosis in NALM-6 cells. Materials and methods:  In this fundamental study, the anti-proliferative effects of Idasanutlin on NALM-6 cells, either alone or in combination with Daunorubicin, were confirmed by MTT(methyl-thiazol-tetrazolium) assay, Annexin/PI apoptosis assay, and cell cycle analysis. Quantitative reverse transcription-PCR (qRT-PCR) and Western blot analyses were applied to elucidate the molecular mechanisms underlying the anti-leukemic activity of Idasanutlin. Results: Idasanutlin synergistically enhanced Daunorubicin-induced apoptosis and activated caspase-3, thereby activating programmed cell death in a dose-dependent manner (P<0.001). The treatment of NALM-6 cells with Idasanutlin caused cell cycle arrest in the G1 phase by an increase in the expression of p21 (P<0.001).  Moreover, a significant increase was detected in the expression of pro-apoptotic genes (P<0.001), as well as a remarkable decrease in the expression of anti-apoptotic (P<0.01) and multidrug resistance1 (MDR1) genes (P<0.01). Conclusions: It seems that Idasanutlin can cooperatively promote daunorubicin-induced apoptosis in NALM-6 cells. These findings open up a new horizon in the application of Idasanutlin in combination with Daunorubicin to overcome drug resistance in patients with ALL.