Previous studies have demonstrated that Epo and EpoR are not only produced or expressed in the kidneys, but also in other cells and tissues, including macrophages (6), vascular endothelial cells (7), neurons (8), myoblasts (9), the uterus, ovaries (10) and mammary glands (11), and in various malignant tumors, including angioblastomas (12), meningiomas (13), uterine or ovarian cancer (14) and breast cancer (15). The gene discussed is EPO; the disease is breast cancer.