MAPK3 and central nervous system cancer: EGFR expression is increased in early GBM, and EGF ligand/EGFR signaling through extracellular signal-regulated kinases 1/2 (ERK1/2) and casein kinase2 (CK2) causes phosphorylation of β-catenin at serine 641 in glioma cells, which has been linked to glioma malignancy [26].