a, b Quantification of DUSP4 depletion following knockdown by siDUSP4_1 and siDUSP4_2 in: left, CHL-1 and right, SK-MEL-23 cells analysed by qRT-PCR (a) and western blot (b). Arrowhead: probable non-specific band not reduced by DUSP4 depletion. c Duration of DUSP4 knockdown in CHL-1 cells, analysed by western blotting at 3, 5 and 7 days after transfection. Representative results are shown for Allstars (AS) control siRNA and siDUSP4_1. ERK is shown as a loading control. d The effect of DUSP4 depletion by siDUSP4_1 and siDUSP4_2 on colony count in: left, CHL-1 and right, SK-MEL-23 cells (mean ± SEM of five independent experiments). e The effect of DUSP4 depletion by siDUSP4_1 and siDUSP4_2 on sensitivity of: left, CHL-1 and right, SK-MEL-23 cells to MEK inhibitors selumetinib and trametinib (mean ± SEM of triplicate values for a single representative experiment). Table 2 shows a summary of fold changes in MEK inhibitor sensitivity (pooled data from six experiments in each case).