Long noncoding RNA KCNQ1OT1 promotes apoptosis in neuroblastoma cells by regulating miR-296-5p/Bax axis

Long noncoding RNAs (lncRNAs) are emerging as important regulators of multiple cellular processes such as cell invasion, growth, apoptosis and differentiation. LncRNAs can function as competing endogenous RNAs (ceRNAs) which sponge and sequester microRNA (miRNA) to regulate specific targets. Previously, we found that the target genes of several miRNAs, including FADD, Fas, Casp and Bax, are related to neuronal apoptosis and form a regulatory network. Among several factors, microRNA-296-5p expression was found to be negatively correlated with caspase activity and apoptosis. Here, we aimed to investigate the role of miR-296-5p in neuroblastoma (NB) cells. By performing quantitative real-time PCR (qRT-PCR), western blot and flow cytometry assays we analysed the expression of apoptotic markers in NB cells transfected with miR-296-5p mimics or inhibitor. Pathway-specific PCR array allowed us to identify the target genes of miR-296-5p. Using LncBase online tool, we predicted lncRNA KCNQ1 opposite strand/antisense transcript 1 (KCNQ1OT1) as an upstream regulator of miR-296-5p. The binding of KCNQ1OT1 and miR-296-5p was validated via RNA immunoprecipitation and Biotin pull-down assays. We also demonstrate that miR-296-5p suppresses apoptosis of NB cells in vitro and in vivo. Mechanistically, miR-296-5p directly bound the 3'UTR of Bax mRNA, thus repressing Bax at the mRNA and protein level. Moreover, through bioinformatic analysis and molecular experiments, we showed that KCNQ1OT1 sponged miR-296-5p and impaired its effect on NB cell apoptosis. In summary, KCNQ1OT1 is a potent promoting factor of cell apoptosis, which acts by sponging miR-296-5p and upregulating Bax. Our findings identify a regulatory axis of cell fate in NB cells.