The role played by CAFs in the development and progression of breast cancer relies on their ability to produce stromal ECM (extracellular matrix) proteins and secrete many growth factors and hormones, including insulin like growth factor (IGF)-I, IGF-II, epidermal growth factor (EGF), transforming growth factor (TGF)-α, TGF-β (3). The gene discussed is EGF; the disease is breast cancer.