The PRL gene, significantly up-regulated over 6-fold in response to depolarization, encodes a pregnancy hormone that is involved in regulating proliferation in many types of cells in the brain, including SVZ precursor cells [9], [19], astrocytes [20], neuroblastoma cells [21], oligodendrocyte precursor cells [22] and hippocampal precursor cells [12], [13]. This evidence concerns the gene PRL and neuroblastoma.