Fig. 1
Acquired MEKi resistance is reversible after drug withdrawal. A Timeline of resistance formation and drug withdrawal classified by different passages (P) without constant MEKi treatment. B Bars represent the mean of two (na = two replicates in parental, three in resistant) or three independent cell viability measurements after 72 h in 300 nM MEKi ± standard deviation (SD). DMSO controls were performed for both the parental and the resistant cells and used for normalization. Statistics was calculated by a two-tailed unpaired Student’s t test on the log2 transformed DMSO-normalized values. C ERK phosphorylation in parental compared to MEKi resistant cell states assessed by Simple Western analysis (p < 0.0001, two-tailed paired Student’s t test on the log2 transformed ratios). The respective electropherograms and the derived recalculated images are shown in Additional file 2: Figs. S2 and S3. D Resistance reversibility upon drug withdrawal. The mean of three independent experiments after 72 h incubation ± SD is shown for cell line #3 as representative example. E Principal component analysis of RNA-seq data between parental (dark blue), resistant (red) and reverting (P5 and P12; light blue) cell states. Depictions in 2D are displayed in Additional file 2: Fig. S3. F Hierarchical clustering of significantly differentially expressed genes (adjusted p value < 0.01; log2 fold change > 1 or < − 1) between parental versus the union of resistant, P5, P12 and resistant versus the union of parental, P5, P12. G Principal component analysis of all abundances identified by LC-MS with more than one unique peptide. 2D presentations are shown in Additional file 2: Fig. S3. H–J Differentially expressed proteins determined by LC-MS between resistant and parental (H) or P12 (I) as well as between parental and P12 cells (J). Larger dots (blue and red) indicate significance (FDR < 0.05, log2 fold change < -1 or > 1) in ANOVA and post hoc test between the indicated groups and at least 2 unique peptides. Gray dots represent abundances only identified by 1 unique peptide. K Euler diagram summarizing the mass spectrometry results. Numbers indicate significantly different abundances of proteins per comparison identified with more than 1 unique peptide