d392 EpoR expressing Ba/F3 cells die via apoptosis when Epo is the only mitogen present. (A) Long-term proliferation assays were performed with Ba/F3-WT cells in 5 U/mL Epo plus 10% FCS (▪), and in 5 U/mL plus SS (□) and with Ba/F3-d392 cells in 5 U/mL Epo plus 10% FCS (▴) and 5 U/mL plus SS (▵). Data points for A, B, and C represent the mean ± standard error (SE) of triplicate determinations. (B) Agarose gel electrophoresis of DNA taken 24 hours after culture from Ba/F3-WT cells grown in FCS (1) and SS (2) and from Ba/F3-d392 cells grown in FCS (3) and SS (4). All cultures contained 5 U/mL Epo.