The preclinical data have demonstrated that gefitinib exerts positive therapeutic effects in models of HER2 overexpressing breast cancer which have been attributed to blocking activity of the PI3K/AKT and the MAPK pathways, increased apoptosis, induction of cytostasis through G1/G0 cell cycle arrest and downregulation of cyclin D1, as well as inhibiting angiogenesis [12-14,20,21]. The gene discussed is PIK3CA; the disease is breast cancer.