We also used breast cancer patient-derived tumor xenograft models for which both genomic information and drug responses are documented.37 Since there was a paucity of models with mutations in MAP3K1 or MAP2K4 in this collection, we selected four models having varying degrees of MAP3K1 and/or MAP2K4 copy number loss (Supplementary information, Table S4). The gene discussed is MAP2K4; the disease is breast carcinoma.