RB1 and neuroblastoma: The effect of Mycn on the proliferation of adult nIPCs and neuroblasts is likely mediated by the axis of cyclin-dependent kinase (CDK)-retinoblastoma protein (RB)-E2F transcription factor family, a core transcriptional machinery that determines if a cell exits the G1 phase to enter the S phase of cell cycle [32], because CDK6, RB, and E2F1 are required for the proliferation of adult neuronal progenitors and immature newborn dentate granule cell neurons [33–35], and knockdown of MYCN resulted in downregulation of CDK6 and E2F1 in neuroblastoma cells [36].