MAPK3 and myeloproliferative disorder: Most importantly, ERK1/2 inhibition enhanced JAK2 inhibitor efficacy dose-dependently with gradually reduced colony numbers in presence of ruxolitinib when LTT462 concentrations were further increased, indicating an additional corrective effect of ERK1/2 inhibition in human MPN settings (Fig. 6A, Supplementary Fig. 13B).