DKK3 and neuroblastoma: It is conceivable that these miRNAs act both in a MYCN negative regulatory feed-back loop as well as via repression of important neuroblastoma tumor suppressor genes: indeed, miR-19a-3p targets ESR1 [32], a ligand-inducible transcription factor implicated in neuronal differentiation, whereas miR-19b-3p represses DKK3 expression [33], a marker of tumor differentiation with elevated expression levels in favorable tumors.