NGF and neuroblastoma: IFRS1 cells retain an intrinsic ability to myelinate neurites in co-culture with primary cultured adult rat DRG neurons [11], nerve growth factor (NGF)-primed PC12 cells [12], mouse embryonic stem (ES) cell line-derived motor neurons [13], and the mouse neuroblastoma/mouse motor neuron hybrid NSC-34 cell line [14,15].