We have repeatedly observed distinct cellular origin of mPGES-1 and COX-2 in neuroblastoma44, experimental glioma49 and here in medulloblastoma, and demonstrated that inhibition of COX-2 has a therapeutic effect in vivo even though COX-2 and mPGES-1 are expressed in different cell types49. This evidence concerns the gene PTGES and medulloblastoma.