MYCN Directly Targets NeuroD1 to Promote Cellular Proliferation in Neuroblastoma

NeuroD1 is a neuronal differentiation factor that contains a basic helixloophelix (bHLH) motif. Recently, NeuroD1 was found to be associated with tumorigenesis in neuroblastoma (NB) and is known to promote cell proliferation and migration in these cells. Here we found that MYCN regulates the expression of NeuroD1 in NB cells and that the downregulation of MYCN using short hairpin RNAs (shRNA) results in the inhibition of cellular proliferation in NB cells. Moreover, the phenotype induced by MYCN shRNA was rescued by the exogenous expression of NeuroD1. Chromatin immunoprecipitation (ChIP) assay showed that MYCN directly binds to the E-box element in the NeuroD1 promoter region. In addition, our evaluation of two clinical databases showed that there was a positive correlation between the expression of MYCN and NeuroD1 in NB patients, which supports our in vitro data. In conclusion, this study demonstrates that MYCN-regulated NeuroD1 expression is one of the important mechanisms underlying enhanced cellular proliferation induced by the increase in MYCN expression in NB, and our results provide an important therapeutic target for NB in the future.