MAPK3 and cancer: Aberrant activation of the MAP kinase or ERK kinase (MEK) 1/2 and extracellular signal-regulated kinases 1 and 2 (ERK1/2) occurs in many types of human cancers.5 Sustained ERK signaling is a requirement for S-phase entry and allows proliferation of tumor cells.6 GBMs often show constitutive activation of the pro-survival kinase AKT.7 The full activity of this kinase depends on Phosphoinositide-dependent protein kinase 1-mediated phosphorylation of T308 in the activation loop and mammalian target of rapamycin-triggered phosphorylation of S473 in the hydrophobic domain.