The characterization of EPO variants that mediate the non-hematopoietic biologic effects of EPO without inducing signaling in hematopoietic cells [46] suggests that strategies to develop EPO-EPOR antagonists to selectively target non-hematopoietic cells- possibly including cancer cells and tumor vasculature- without causing anemia might be feasible, particularly when the exact structure of the cell surface receptor that mediates erythropoietin signaling in non-hematopoietic cells is ascertained [47]. This evidence concerns the gene EPO and anemia (phenotype).