MAP2K7 and ductal breast carcinoma in situ: The highest MEK efficacy (lowest IC50 value) was observed in the MCF10.NeoT cells, which had relatively low levels of MEK activation, and lower efficacy (higher IC50 values) was seen in later stages of the model, which had higher basal pMEK levels (1.7-fold and 2.7-fold in MCF10.AT1 and MCF10.DCIS cells, respectively, p < 0.05 relative to MCF10.NeoT cells) (Fig. 3C,D and Fig. S7).