FIGURE 1.

Increase in C/EBPβ isoforms as well as LAP/LIP ratio in differentiating THP-1 premonocytic cells, accompanied by impaired proliferation. A, premonocytic THP-1 cells were incubated with 100 nm PMA up to 72 h. Nuclear C/EBPβ levels were measured by Western blot analysis. The C/EBPβ isoforms LAP*, LAP, and LIP are indicated by arrows. TBP was used as a loading control. n.s., nonspecific bands. B, the LAP/LIP ratio was determined by densitometry in which the respective ratio in unstimulated cells at 0 h was defined as 1 (mean ± S.D. (error bars), n = 3). Statistical significance with p ≤ 0.05 (*) or p ≤ 0.01 (**) is indicated. C, ATP proliferation assays were performed using the experimental conditions described above. The respective proliferation value at 0 h was defined as 1, and the relative proliferation values were calculated (mean ± S.D., n = 3). The asterisks indicate statistical significance with p ≤ 0.05.