MEK inhibition correlates with an increase in complex I expression also in human U87 glioblastoma cells (Supplementary Fig. 1C) and ipNF 04.4 plexiform neurofibroma cells (Supplementary Fig. 1D), both characterized by absence of neurofibromin and hence by Ras/MEK/ERK pathway induction. The gene discussed is MAP2K7; the disease is glioblastoma.