SCH722984 in BRAF-mutant melanoma cell lines with vemurafenib-acquired resistance. A. IC50 (nM) to SCH-722984 or vemurafenib. M398 and M376, two melanoma cell lines established from tumors progressing on vemurafenib, as well as six parental BRAF mutant melanoma cell lines and their paired in vitro derived vemurafenib-acquired resistance sublines (AR) were grown in the presence of 0–10 μM SCH-722984 (black bars) or vemurafenib (grey bars). Values are mean of three experiments, performed in duplicate (n = 6). Error bars are standard deviation. Bar at 1 μM denotes threshold between sensitive and intermediate. Resistant cell lines have IC50 higher than 2 μM. *: BRAF/NRAS double mutant, **: BRAF-splice variant, §: Receptor tyrosine kinase upreguation, +: resistance mechanism unknown. B. Effect of SCH722984 on MAPK signaling. Western blot analysis was performed to evaluate the effect of 24 hour exposure to 500 nM SCH&22984 (+) or DMSO (-) on phospho- or total MEK, ERK 1/2, RSK, AKT or beta-actin as loading control.