MAPK3 and glioblastoma: Moreover, it has been reported that gefitinib and other quinazoline TKIs, while inhibiting multiple EGFRvIII signaling pathways at high and repeated doses, when used at low concentrations, cause augmented homodimerization of the receptor, increased signaling to ERK1/2 and stimulation of proliferation and anchorage-independent growth of EGFRvIII-expressing GBM cells [41, 42].