MAPK1 and glioblastoma: Leveraging the evidence that PTC-209 inhibits GBM formation in vivo28 and that PD325901 blocks ERK phosphorylation in the ventral striatum34 when administrated intraperitoneally (i.p.), we set out to assess whether PTC:PD combination treatment could represent a novel therapeutic approach in a preclinical in vivo model of MB.