TGF-β1-induced suppression of COX-2 expression by transcriptional repression.

<p>(A) Time-dependent decrease of COX-2 mRNA expression by treatment with TGF-β1 (5 ng/mL). COX-2 mRNA level was measured by real-time RT-PCR as described in Materials and Methods. (B) Cells were pretreated with actinomycin D (5 µg/mL) for 1 h and incubated with or without TGF-β1 (5 ng/mL) for the indicated times. TGF-β1 did not affect decrease of COX-2 mRNA by actinomycin D. COX-2 expression levels were normalized for GAPDH expression levels and expressed as a percentage of that in non-treated cells (control). Each value represents the mean ± SE (n = 3). (C) Cells were incubated with CHX (50 µg/mL) or CHX plus TGF-β1 (5 ng/mL) for the indicated times and COX-2 protein expression was detected by immunoblotting. TGF-β1 did not affect decrease of COX-2 protein by CHX. The band intensities were quantified and COX-2/actin values were expressed as relative to those of control. Each value represents the mean ± SE (n = 4).