Figure 1

Exogenous C/EBPbeta-2 expression confers EGF-independent growth in MCF10As. Micrographs of untreated (panels A and C) and C/EBPbeta-2 overexpressing (panels B and D) MCF10A cultures are shown one (panels A and B) and two (panels C and D) days after growth in medium lacking EGF. Cells were plated on day 0 at 5 × 10⁵ per 60 mm dish and the same location was imaged on both days. The bar represents 600 microns. Cell cycle profiles of control MCF10A(untreated), MCF10A cells infected with LZRS-Lac-Z virus (+ Beta-Gal), and MCF10A cells infected with LZRS-His-C/EBPbeta-2 virus (+ C/EBPbeta-2) were determined after growth in the presence or absence of EGF for 3 days. Results are shown as the mean of 4 separate experiments. Error bars indicate ± standard error of the mean (SEM). Solid black bars indicate the percentage of cells present in G0/G1, gray-filled bars the percentage in S-phase, and white-filled bars the percentage in G2/M. When compared to control MCF10A and MCF10A + Beta-Gal cell populations grown in the absence of EGF, the cell cycle distribution of MCF10A + C/EBPbeta-2 grown under identical conditions was determined to be statistically significant (p < 0.0001 for G0/G1 and G2/M and p < 0.0085 for S-phase). In contrast, there was no significant difference in the cell cycle distribution of MCF10A + C/EBPbeta-2 cells cultured in the absence of EGF compared to any of the MCF10A-based cells grown in the presence of EGF.