GRIK1 and retinoblastoma: The presence of GluR5–7 subunits in human glioneuronal tumors (Aronica et al. 2001), GluR5–7 and KA1 in medulloblastomas, and additionally KA2 subunit in neuroblastoma cell lines (Yoshioka et al. 1996) or retinoblastoma cells (Takeda et al. 2000) has been reported.