RARA and ganglioneuroblastoma: Using co-immunoprecipitation with an anti-GRP75 antibody and lysates derived from 30 human NB tumors, including 13 ganglioneuroblastomas (GNBs), 9 differentiating NBs (DNBs), and 8 undifferentiated NBs (UNBs), the interaction between GRP75 and RARα/RXRα was found to be significantly stronger in tumors with higher grades of histological differentiation (GNB and DNB) than in those with an undifferentiated histology (UNB) (Figure 7A, B and Figure S8).