JIMT-1 (HER2 expressing cell line resistant to trastuzumab) and MDA-MB-468 (triple negative breast cancer) were selected as “difficult to treat” breast tumor prototypes and considered representative cell lines for advanced/metastatic breast cancer patients (Tanner et al., 2004; Chavez et al., 2010; Zeichner et al., 2016). The gene discussed is ERBB2; the disease is breast cancer.