Fig. 1: YAP1 confers MAPK pathway inhibitor resistance and induces the MITF^low/AXL^high phenotype.

a A TEAD luciferase reporter was used to quantify the transcriptional activity of YAP1 in engineered melanoma cell lines with constitutive YAP1 activity (YAP^5SA) and empty vector (EV) controls (mean + SD of three replicates is presented). b Cell viability assays were used to determine the sensitivity of cell lines lentivirally infected with YAP^5SA, transcriptionally inactive YAP^5SA/S94A, or EV controls toward a BRAF inhibitor (Vemurafenib) and a MEK inhibitor (Cobimetinib; mean ± SD of three replicates is presented). c SKMEL28-YAP^5SA cell lines were lentivirally infected with an sgRNA targeting YAP^5SA or a non-targeting (nt) control. Immunoblotting with indicated antibodies was used to quantify YAP1 protein levels and sensitivity toward Vemurafenib was assessed (mean ± SD of three replicates is presented). d A375-EV and A375-YAP^5SA cells were injected into NSG mice and established tumors were treated with Vemurafenib (Vem; 50 mg kg^–1 per day orally) or vehicle (mean ± SEM of fold change tumor volume compared to start of treatment is presented; p value from mixed-effect model. ***p < 0.001). e Analysis of MEK inhibition after treatment with 5 µM Vemurafenib for 24 h using immunoblotting with indicated antibodies. f GO term enrichment in genes significantly upregulated (p < 0.01) in A375-YAP^5SA and SKMEL28-YAP^5SA compared to respective EV controls as identified by RNA-seq. g Changes in expression of individual genes from the same experiment as f. h Immunoblotting of indicated antibodies for selected genes upregulated or suppressed upon YAP1 activation using protein lysates from A375-YAP^5SA and SKMEL28-YAP^5SA cell lines and corresponding EV controls. i Enrichment and depletion of gene sets for MITF targets, genes of the proliferative and invasive state, and NF-κB targets in SKMEL28-YAP^5SA and A375-YAP^5SA compared to EV controls. a–c, e, and h Experiments were performed at least two times independently, one representative experiment is shown. Western blot in c was performed once. f, g, i RNA was isolated from two biological replicates per cell line.