MAPK3 and melanoma: As shown in Fig. 4C, treatment with either 1.5 μM or 2.5 μM BCI treatment caused modest increase in Erk1/2 phosphorylation in all melanoma cells- MAPKi-sensitive MRA6, intrinsically MAPKi-resistant MRA5 and MRA6BR and MRA6MR cells with acquired MAPKi resistance.