Effect of overexpression of Fli-3 on the differentiation and proliferation of HB60–5 cells by Epo. (A) Schematic diagram of the Fli-3-mir-92 and Fli-3-mir-17–92 expression vectors. The right panel shows the ectopic expression of Fli-3 in HB60–5 cells and NIH-3T3 cells detected by Northern blot using the Fli-3 probe. (B) Fli-3 ectopic expression blocks differentiation of HB60–5 cells. HB60–5 cells infected with Fli-3-mir-92, Fli-3-mir-17–92, or empty vector retrovirus were grown in medium containing 1 U/mL Epo and subjected to Northern blot analysis using the Fli-3 and α-globin probe. Hybridization of the same blot with a GAPDH probe was used to show equal loading. (C) Ectopic expression of Fli-3 promotes proliferation of HB60–5 cells. Triplicate cultures of HB60–5 cells (10⁴) infected with either Fli-3-mir-92, Fli-3-mir-17–92, or empty vector were grown in media containing Epo (1 U/mL) and the number of viable cells was determined at indicated days. Error bars are SD.