MAPK1 and breast cancer: For example GRB7 plays an important role in the signal transduction in response to EGF, promoting the activation of down-stream phosphorylation pathways (e.g. AKT1 and MAPK1) and its basal pre-treatment expression levels anticorrelate with the cellular response to Lapatinib not only in breast cancer cell lines (Pearson R = −0.64) but across the whole cell line panel (Pearson R = −0.39).