Combination therapy with MEK inhibitor trametinib and EGFR/HER2 dual inhibitor lapatinib has shown a synergistic effect and circumvented the resistance of MEK1‐mutated gastric cancer cells (Mizukami et al., 2015) and HER2‐positive breast cancer cells (Karakashev and Reginato, 2015) to MEK inhibitors. Here, MAP2K1 is linked to breast cancer.