EPO and acquired polycythemia vera: To investigate whether this pro-proliferative effect was confined to erythroblasts derived from the spleens of AML mice, we cocultured AML cells with erythroblasts isolated from the spleens of other mouse models known to induce splenic EMH, such as polycythemia vera (PV), erythropoietin-treated (EPO-treated), and phenylhydrazine-treated (PHZ-treated) mice (Supplemental Figure 1I).