C/EBPα-ER impairs growth and expansion and induces differentiation of leukemic cells. (A) Cumulative growth cultures of AML cells (n = 7) on MS5 cells in the presence or absence of 500 nM 4-OHT. Half of the cultures were harvested weekly, and fresh medium was added to the culture. A representative example (AML no. 7) is shown, and all expansion data are summarized in Table 2. (B) Representative phase-contrast microscopy images of AML (no. 11) cocultures in the presence or absence of 500 nM 4-OHT on MS5 cells at week 3. Note the absence of phase bright suspension cells from C/EBPα-ER–transduced culture after treatment with 500 nM 4-OHT. One representative example is shown. (n = 7). (C) Flow cytometric analysis of suspension cells from week-1 leukemic MS5 cocultures in the presence of 500 nM 4-OHT. One representative example is shown. Also refer to Table 2. Indicated are the percentages of CD14⁺, CD15⁺, or CD71⁺ cells within the Venus⁻ or Venus⁺ fractions. (n = 7). (D) RT-PCR analysis of neutrophil elastase (NE) expression in 3 AML samples after treatment with 500 nM 4-OHT in Venus-transduced cells (−) or in C/EBPα-ER–transduced cells (+). GAPDH expression is shown as loading control. −RT-PCRs were performed as negative control. (E) Morphologic analysis of suspension cells at week 1 of AML no. 3 was performed by MGG staining of cytospins. See “Materials and methods; Microscopy and cytospins.”