Increased expression of ErbB family members and cognate ligands such as EGFR/HER1 and EGF, TGFa, Hb-EGF, and heregulin has been demonstrated as a mechanism for acquired resistance to trastuzumab [12] and long-term trastuzumab exposure of primary resistant breast cancer cells is associated with HER1 reprogramming [13]. The gene discussed is EGF; the disease is breast carcinoma.