ERBB2 and breast cancer: 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.