Effects of cycloheximide on the induction of CYP1A1 gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in three human breast cancer cell lines.
Treatment of MCF-7, MDA-MB-231 and Hs578-T human breast cancer cell lines with 10(-9) M 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces CYP1A1 gene expression in the MCF-7 but not in the MDA-MB-231 or Hs578-T cells. Pretreatment of the cells with 10(-5) M cycloheximide results in significantly increased P4501A1 mRNA levels in all three cells lines. However, in cells co-treated with 10(-5) M cycloheximide plus 10(-9) M TCDD, an induced response by TCDD was observed in the MCF-7 and MDA-MB-231 but not in Hs578-T cells. Gel-retardation assays of nuclear extracts from the three cell lines complexed with a 32P-labeled dioxin-responsive element (DRE) gave a TCDD-inducible retarded band only in the MCF-7 and MDA-MB-231 cells. A retarded band with a similar mobility was observed in nuclear extracts from Hs578-T cells treated with either 10(-9) M TCDD or DMSO (solvent control). These results suggest that aryl hydrocarbon non-responsive MDA-MB-231 and Hs578-T human breast cancer cell lines contain the CYP1A1 gene and treatment with cycloheximide increases both constitutive and TCDD-induced CYP1A1 gene expression.
Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station 77843-4466.
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Arellano
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Wang
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D001483:Base Sequence; D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics*; D003513:Cycloheximide / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D004967:Estrogens / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D008969:Molecular Sequence Data; D009376:Neoplasms, Hormone-Dependent / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D004967:Estrogens; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug; D003577:Cytochrome P-450 Enzyme System; D003513:Cycloheximide