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

Abstract

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.

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“…Normally, GSK activity is inhibited by AKT activation, but the activity of both AKT and GSK can be down-regulated under certain conditions. Song et al [58] demonstrated that a fusion protein NLS-RAR promoted both AKT and GSK-3β phosphorylation in NB4 cells (an acute promyelocytic leukemia cell line). The protein levels of both p-AKT and p-GSK-3β were decreased following pretreatment with the PI3K inhibitor LY294002 [58].…”

“…Song et al [58] demonstrated that a fusion protein NLS-RAR promoted both AKT and GSK-3β phosphorylation in NB4 cells (an acute promyelocytic leukemia cell line). The protein levels of both p-AKT and p-GSK-3β were decreased following pretreatment with the PI3K inhibitor LY294002 [58]. Jordan et al [59] showed that myristoylated AKT blocked o-sulfated AGF function in a bladder cancer cell line, but up-regulated both p-AKT and p-GSK.…”

Epigallocatechin-3-gallate promotes all-trans retinoic acid-induced maturation of acute promyelocytic leukemia cells via PTEN

“…For detection of the cell differentiation antigen, CD11 antigen-like family member B was used (CD11b), after 72 h of treatment, the cells were collected (1x10 6 /group) and washed with three times with pre-cooled PBS, then incubated with phycoerythrin (PE) conjugated CD11b antibody (12011342; eBioscience, Inc., San Diego, CA, USA) at 4˚C for 30 min in the dark (32). The cells were then analyzed using flow cytometry (BD FACSVantage; BD Biosciences, San Jose, CA, USA) and CellQuest Pro software version 5.1 (BD Biosciences).…”