C/EBPs suppress growth and induce partial differentiation of FDC-P1 cells.

FDC-P1 cells grown continuously in IL-3 were transduced on 2 sequential days with control, hC/EBPα, or hC/EBPε retroviruses. For these experiments, day 0 is considered to begin 24 hours after the second round of retroviral transduction. (A) The growth of C/EBPα- and C/EBPε-infected FDC-P1 cells was suppressed. Equal numbers of cells were plated on day 0. The growth curves represent the number of transduced FDC-P1 cells at days 0, 2, 4, and 6. At each time point, cells were counted and the percentage of cells with GFP expression was assessed. The number of GFP⁺ cells is shown on this graph. Results shown are means ± SDs from 3 independent experiments. (B) Both C/EBPα and C/EBPε induced expression of myeloid markers by FDC-P1 cells. Transduced FDC-P1 cells were stained for Gr-1 (Ly-6G) and Mac-1 (CD11b). Results shown in histograms are of live (based on forward scatter versus side scatter) GFP⁺ cell populations. These data are representative of 2 independent experiments. (C) C/EBP-transduced FDC-P1 cells were partially differentiated toward more mature forms. GFP⁺FDC-P1 cells were sorted at day 4 (6 days after the first round of transduction) with the FACSVantage cell sorter. Cytospins of 25 000 sorted cells of each transduction were stained with Wright Giemsa. Images were captured with × 40 objectives.