In 1994, the peptide prosaposin (PSAP) and its fragment Saposin C (Sap C) were identified as neurotrophic factors using the neuroblastoma NS20 line and specific binding of radio‐labeled Sap C with a Kd of 19 pM was demonstrated (O'Brien, Carson, Seo, Hiraiwa, & Kishimoto, 1994). The gene discussed is PSAP; the disease is neuroblastoma.