In the ex-vivo model of acute brain slices, already used for RB1 and RB3, we found that PD325901 showed an IC50 of 1.15 nM, similar to what previously reported by Pfizer (0.33 nM and 0.59 nM, for inhibiting MEK1 in a cell free system and blocking pERK in tumour cells, respectively) (Brown et al., 2007; Barrett et al., 2008) (Figure 6—figure supplement 1). Here, MAP2K1 is linked to neoplasm.