Overexpression of Gfi-1B in human CD36⁺/GPA^– cells induces expression of GPA in the absence of EPO. CD34⁺ from PB were cultured in the presence of EPO, SCF, IL3, and DXM. The cells were then transduced twice with the different retroviral vector (MIGR, full-length Gfi-1B, or SNAG-deleted Gfi-1B, Δ1) at day 4 and day 5 of the culture. Infected CD36⁺/GPA^– cells were sorted at day 6 of culture in the presence of IL3, EPO, SCF, and DXM and cultured in the presence of SCF, without EPO. GPA expression and BZD staining were evaluated 48 and 72 hours after EPO removal. (A) Flow cytometry analysis of the cells 48 hours after cell sorting (one representative experiment). In cells overexpressing full-length Gfi-1B, expression of GPA was higher than in cells transduced with the empty vector MIGR or with the SNAG-deleted Gfi-1B cDNA. (B) Induction 48 hours after cell sorting of erythroid markers determined by flow cytometry using antibody against GPA (i) (MIGR versus Gfi-1B: P = .01, n = 4; MIGR versus Δ1: P > .05) and by benzidine staining (ii) (MIGR versus Gfi-1B: P = .001, n = 4; MIGR versus Δ1: P > .05). Data are expressed as mean ± SD.