GSK3B and neuroblastoma: They not only can compete at the same or at adjacent sites of the same protein in a reciprocal manner, but can also act synergistically: treatment of neuroblastoma cells with the wide range phosphatase inhibitor okadaic acid reduces O-GlcNAcylation (64), while inhibition of GSK3β increases O-GlcNAcylation of heat shock and cytoskeletal proteins but decreases the O-GlcNAcylation of other proteins such as transcription factors (65).