A431-ΔRAF-1/ERTam- (A) and A431-myr-AKT/ERTam
(B) cells were incubated with 4-OHT, EGF (10 ng/ml) or cetuximab (1 μg/ml). (A) In the absence of 4-OHT, phosphorylation of EGFR and ERK was strongly induced by EGF. Cetuximab inhibited the ligand induced activation of EGFR downstream signaling. Upon pre-incubation with 4-OHT phosphorylation of ERK1/2 as marker of MAPK signaling was strongly induced, independently of incubation with EGF or cetuximab. (B) In the absence of 4-OHT, phosphorylation of EGFR and AKT/ERTam was strongly induced by EGF. Cetuximab inhibited the ligand induced activation of EGFR downstream signaling. Upon pre-incubation with 4-OHT phosphorylation of AKT/ERTam as marker of PI3K/AKT signaling was strongly induced, independently of incubation with EGF or cetuximab.