We also gathered evidence for additional cross‐resistance, as several genes associated with ERBB2 expression or ERBB2 subtypes of breast cancer and genes involved in the response and resistance to chemotherapeutic agents such as fenretinide, fluorouracil, doxorubicin and the EGFR inhibitor Gefitinib were significantly dysregulated in the FIR20 cells (Fig. S2, Data S4). This evidence concerns the gene ERBB2 and breast cancer.