NCAM1 and neuroblastoma: On a cellular level, experiments with neuroblastoma cells and SVZ-derived neuroblasts revealed that removal of polySia, in addition to promoting NCAM1 homophilic interactions (Johnson et al., 2005), initiates heterophilic NCAM1 interactions, which activate the MAP kinase ERK1/2 pathway and promote neuronal differentiation (Seidenfaden et al., 2003; Röckle et al., 2008).