NLS-RARα modulates acute promyelocytic leukemia NB4 cell proliferation and differentiation via the PI3K/AKT pathway

In patients with acute promyelocytic leukemia (APL), ~98% express the promyelocytic leukemia (PML)-retinoic acid receptor α (RARα) fusion protein. Previous studies have shown that, in primary leukemia cells of patients with APL, the cleavage of PML-RARα by neutrophil elastase is important for its ability to initiate APL. This cleavage separates the nuclear localization signal (NLS) from PML, leading to the formation of a novel protein, NLS-RARα, although its underlying mechanism in APL remains to be fully elucidated. In the present study, the role of NLS-RARα on the proliferation and differentiation of APL NB4 cells was investigated. Lentiviral vectors were constructed and transfected NLS-RARα in NB4 cells, puromycin was used to select the stable transfected cell lines. Cell Counting Kit-8 and flow cytometry analysis revealed that the efficient overexpression of NLS-RARα significantly promoted NB4 cell proliferation and inhibited all-trans retinoic acid-induced cell differentiation. Furthermore, the NLS-RARα protein promoted a significant increase in AKT and glycogen synthase kinase 3β (GSK-3β) phosphorylation. The protein levels of phosphorylated (p) AKT and pGSK-3β were decreased following pretreatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002. These findings suggested that NLS-RARα was an important molecule associated with the occurrence of APL via the PI3K-AKT signaling pathway, and indicated that the NLS-RARα protein may be a novel target for the treatment of APL.