In vitro, retinoids arrest cell growth in the G1 phase of the cell cycle, and induce differentiation in human NB cell lines [30], [31] along neuronal- or glial-like lineages depending on the cell line [32] by regulating, for example, the expression of p27Kip1, a target gene of PHOX2A and PHOX2B that has major functions in controlling the cell cycle. This evidence concerns the gene PHOX2B and neuroblastoma.