Figure 4. MAPK1 inhibition decreased sensitivity to erlotinib in MAPK1^E322K mutant HNSCC cells, while exogenous AREG restored erlotinib sensitivity.

HSC-6 cells and FaDu cells engineered to express MAPK1^E322K were pretreated with DMSO, VX-11e (0.5 μM) or combination of VX-11e (0.5 μM) and AREG (300 pg/ml) for 24 hours. Cells were then treated with two concentrations of erlotinib or a combination of VX-11e (0.5μM) and erlotinib or the triple combination of VX-11e (0.5 μM) and AREG (300pg/ml) and erlotinib for 48 hours. Cell survival was measured by crystal violet dye extraction growth assay and plotted relative to DMSO vehicle control (erlotinib alone) or VX-11e control (combination of VX-11e and erlotinib) or VX-11e and AREG control (combination of VX-11e, AREG and erlotinib). A. MAPK1 inhibition by VX-11e decreases sensitivity to erlotinib in HSC-6 cells, while exogenous AREG restored sensitivity. B. MAPK1 inhibition by VX-11e decreased sensitivity to erlotinib in FaDu cells engineered to express MAPK1^E322K, while exogenous AREG restored its sensitivity. Decreased sensitivity to erlotinib with MAPK1 inhibition was attenuated in vector control transfected FaDu cells C. and FaDu cells engineered to express MAPK1^WT D. (n = 3. *p < 0.05, **p < 0.01, ***p < 0.001). Similar results were obtained with triplicate wells in three independent experiments.