Lentivirus-mediated RIG-I knockdown relieves cell proliferation inhibition, cell cycle arrest and apoptosis in ATRA-induced NB4 cells via the AKT-FOXO3A signaling pathway in vitro

Retinoic acid inducible gene I (RIG-I) is upregulated during all-trans retinoic acid (ATRA)-induced terminal granulocytic differentiation of NB4 acute promyelocytic leukemia (APL) cells. However, the function and mechanism of RIG-I in NB4 cells remains to be fully elucidated. In the present study, lentivirus-mediated RIG-I-knockdown was used to investigate the proliferation, cell cycle and apoptotic processes of ATRA-induced NB4 cells in vitro using an MTT assay and flow cytometry, respectively. The roles of RIG-I and the AKT-FOXO3A signaling pathway were investigated using western blot analysis. The results showed that the ATRA-induced expression of RIG-I was specifically and effectively knocked down at the mRNA and protein levels by lentivirus mediated RIG-I short hairpin RNA. In addition, silencing of RIG-I reduced the ATRA-induced inhibition of NB4 cell proliferation, cell cycle arrest and apoptosis. Further investigations indicated that with ATRA-induced expression of RIG-I, levels of phosphorylated (p)AKT-Thr308 and pForkhead Box (FOX) O3A-Thr32 were decreased, the expression levels of cell cycle arrest protein p27 and the apoptotic protein, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), directly transcribed by FOXO3A were increased. By contrast, following the knockdown of ATRA-induced expression of RIG-I, the levels of pAKT-Thr308 and pFOXO3A-Thr32 were increased, and the protein expression levels of p27 and TRAIL were decreased. Taken together, these results showed that the knockdown of RIG-I reduced the inhibition of cell proliferation, cell cycle arrest and apoptosis in the ATRA-induced NB4 cells via the AKT-FOXO3A signaling pathway.