NRP2 and neuroblastoma: As a primary screening method to assess knockdown efficiency of endogenous Npn-1 and Npn-2 expression levels, F11 cells, a fusion cell line derived from of rat embryonal DRG and mouse neuroblastoma cells [25], were transduced with lentiviral vectors encoding green fluorescent protein (GFP) and an shRNAs directed against Npn-1 or Npn-2 (Figure 1a).