Transcription Factor FOXO3a Overexpression Inhibits the Progression of Neuroblastoma by Regulating the miR-21/SPRY2/ERK Axis.

Objective: Neuroblastoma is one of the most common extracranial solid tumors in children. The forkhead transcription factor FOXO3a has been implicated in the progression of a variety of human diseases. Here, we aim to identify the effects of FOXO3a on the malignancy of neuroblastoma.

Methods: Bioinformatics analysis was employed to identify differentially expressed genes related to neuroblastoma and the downstream regulator of FOXO3a. FOXO3a expression was examined in SH-SY5Y neuroblastoma cells. Interactions between FOXO3a and microRNA-21 (miR-21) were then identified using bioinformatics analysis and dual-luciferase reporter assay. After ectopic expression and depletion experiments in SH-SY5Y cells, cell malignant phenotypes were assessed by cell counting kit-8 and Transwell assays. FOXO3a-overexpressing neuroblastoma cells were xenografted into nude mice to validate the role of FOXO3a in tumor growth.

Results: Downregulated expression of FOXO3a was observed in neuroblastoma cells, with a negative correlation between FOXO3a and miR-21 expression. FOXO3a bound to the promoter region of miR-21 to downregulate its expression, resulting in inhibition of SH-SY5Y cell malignant phenotypes. Additionally, miR-21 targeted SPRY2 by binding to the 3'UTR of the mRNA encoding SPRY2, activating the extracellular signal-regulated kinase (ERK) pathway. FOXO3a disrupted the binding of miR-21 to SPRY2 and inactivated ERK to suppress the malignant phenotypes of SH-SY5Y cells as well as tumor growth in vivo.

Conclusions: In conclusion, FOXO3a may inhibit the progression of neuroblastoma by suppressing the miR-21 expression and facilitating SPRY2-dependent ERK pathway inactivation.