Autoantibodies to BRAF activate the phosphorylation of MEK1. Purified anti-BRAF autoantibodies from patients were incubated with BRAF and MEK1. For each patient, we included one positive control (BRAF and MEK1) and one negative control (BRAF and MEK1 and C1 control antibody). Activation or inhibition of MEK1 phosphorylation was detected by measuring the ratio test OD/positive control OD. Ratio > 1 indicated activation, ratio < 1 indicated inhibition. Bars showed the mean ratio ± SD.