SCF-, IL-3-, and Epo-dependent mitogenesis in FDCW2 and FDCW2ER cells. Proliferative responses of factor-dependent FDCW2 and FDCW2ER cell lines to SCF, IL-3, and Epo were assayed based on rates of cytokine-stimulated incorporation of [methyl-3H]thymidine. To account for any minor differences in plating, values were normalized based on maximal responsiveness to IL-3.