Figure 1.
ET-743 inhibits activation of the transfected and endogenous MDR1 promoter by multiple inducers. (A) Structure of ET-743. (B–D) SW620 cells stably transfected with an MDR1 promoter/luciferase construct were treated with 100 ng/ml trichostatin A (TSA; B), 2 mM sodium butyrate (C), or 10 J/m2 UV irradiation (D) without (white bars) or with (black bars) 50 nM ET-743. The stably transfected cells were treated as indicated for 24 h, and luciferase activity was determined. The data represent the results of three independent experiments performed in triplicate. (E) Nuclease protection analysis of MDR1 RNA from untreated SW620 cells (lane 1) or cells treated with 100 ng/ml TSA (lane 2), 2 mM sodium butyrate (lane 3), 50 ng/ml ET-743 (lane 4), 50 nM TSA and 50 ng/ml ET-743 (lane 5), or 2 mM sodium butyrate and 50 ng/ml ET-743 (lane 6). Total RNA was extracted from cells, and nuclease protection assays were performed with MDR1 or glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene-specific ribonucleotide probes (6) by using 20 μg and 0.66 μg RNA, respectively.