FIGURE 7.

PMA induces cyclin D1 transcription in colon cancer cells. A, induction of cyclin D1 by PMA in DLD1 cells requires new transcription. DLD1 cells were pretreated with 5 μg/ml actinomycin D (Act D) or vehicle (DMSO) for 30 min prior to the addition of PMA (P) or vehicle (C) for 4 h, and levels of cyclin D1 and β-actin were determined by Western blot analysis. Data are representative of more than three independent experiments. B, PMA activates the proximal cyclin D1 promoter in colorectal cancer cells. DLD1 cells were transfected with the −963CD1Luc or −163CD1Luc cyclin D1 promoter-luciferase constructs and treated with PMA for 5 h. The activity of cyclin D1 promoter fragments was measured by the Dual-Luciferase assay and is normalized to the activity in control cells treated with vehicle for 5 h. Data are averages ± S.E. (error bars) of nine independent experiments for the −163 bp CD1-Luc construct and of two independent experiments for the −963 bp CD1-Luc construct. *, statistically different from vehicle (EtOH)-treated control cells (p < 0.05).