Fig. 5: Differential EGFR inhibitor toxicity is due to decreased ERK phosphorylation in the large intestine.

a Representative images of small and large intestine-derived monolayers treated with indicated erlotinib (ERL) concentration. Nuclei are stained with Hoechst. Scale bars, 100 µm. b Quantification of the percent change in total cells relative to untreated cells in small and large intestine-derived monolayers treated with 0.5 µM ERL, 0.8 µM gefitinib (GEF), and 0.4 µM osimertinib (OSI) for 48 h. n = 3 wells. Statistical significance was calculated by a two-way ANOVA followed by Sidak’s multiple comparison test. c Quantification of the percent change in total cells relative to untreated cells in small and large intestine-derived monolayers treated with the indicated concentration of PD0325901 for 48 h. n = 6 wells (vehicle) or n = 3 wells (PD0325901). All drug concentrations were statistically significant compared to control (p-value < 0.0001) as calculated by a two-way ANOVA followed by Sidak’s multiple comparison test. d Quantification of phospho-ERK (pERK) relative to total-ERK (tERK) in small and large intestine-derived monolayers treated with the indicated concentration of erlotinib for 6 h measured by ELISA. n = 2 technical replicates. e Representative images of EGFR expression in small and large intestine-derived monolayers grown in control media for 24 h. Scale bars, 40 µm. Density plot of EGFR intensity per cell. A.U.: arbitrary units. n = >50,000 cells pooled from 5 wells. Error bars mean ± SEM. SI: small intestine; LI: large intestine. ** indicates p-values < 0.01; **** indicates p-values < 0.0001.