Figure 8: MITF is a predictive biomarker also in NRAS mutant melanomas.

(a) RNA sequencing was performed on four MITF^endo_hi and four MITF^endo_lo NRAS mutant melanoma cell lines. The genes in the heatmap were selected based on the MITF expression, expression of MITF-target genes and expression of the mRNAs coding for the RTKs AXL, EGFR and PDGFRβ. (b) Treatment-naïve NRAS mutant melanoma cells were immunoblotted for MITF, RTKs and other proteins as indicated. HSP90 served as a loading control. WM1366-A/B refers to different batches of the same cell line. (c) A phospho-RTK array was performed comparing one NRAS mutant MITF^endo_hi and one MITF^endo_lo melanoma cell line. (d,e) MITF^endo_hi and MITF^endo_lo NRAS mutant melanoma cells were plated at low densities and treated with the MEKi trametinib (2.5 nM) (d) or ERKi SCH772984 (0.25 μM) (e) or left untreated for 6 days and stained by crystal violet. (f) Melanoma cells were plated at low density and treated with the AXLi R428 (0.5 μM), the ERKi SCH772984 (1 μM) or in combination. After 6 days of treatment, plates were stained with crystal violet. (g) Quantification of f, based on three biological replicates. Error bars represent s.d.; paired t-test was used for statistical analysis, *P<0.05. (h) A MEKi-resistant NRAS mutant melanoma cell line and its treatment-naïve counterpart were blotted for the indicated proteins. HSP90 served as a loading control.