Potentiation of CYP1A1 gene expression in MCF-7 human breast cancer cells cotreated with 2,3,7,8-tetrachlorodibenzo-p-dioxin and 12-O-tetradecanoylphorbol-13-acetate. 1993

M Moore, and T R Narasimhan, and M A Steinberg, and X Wang, and S Safe
Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station 77843-4466.

In MCF-7 cells treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 12-O-tetradecanoylphorbol-13-acetate (TPA) causes a time- and concentration-dependent modulation of TCDD-induced CYP1A1 gene expression. Treatment of MCF-7 cells with 1 nM TCDD for 24 h resulted in the induction of ethoxyresorufin O-deethylase (EROD) activity and CYP1A1 mRNA levels. In cells treated with TCDD for 24 h and 100 ng/ml TPA for 26 and 30 h, the TCDD-induced CYP1A1 gene expression was detected. For example, TCDD-induced EROD activity decreased from 122 pmol/min/mg to 25.5 pmol/min/mg after treatment of MCF-7 cells with TPA for 26 h and this was also paralleled by a 44% decrease in CYP1A1 mRNA levels. There was also a decrease in nuclear Ah receptor levels and the binding of nuclear extracts to a 32P-labeled dioxin responsive element (DRE) in a gel mobility shift assay. In parallel studies which measured EROD activities, similar TCDD/TPA interactions were observed in wild-type Hepa 1c1c7 cells, whereas no interactive effects were observed in T47-D human breast cancer cells. In MCF-7 cells treated with TPA for 36 or 48 h, the TCDD-induced EROD activity and CYP1A1 mRNA levels were restored and in cells exposed to TPA for 72 or 96 h superinducibility of CYP1A1 gene expression was observed; there was a 2.8- and 2.2-fold increase in EROD activity and CYP1A1 mRNA levels, respectively, compared to MCF-7 cells treated with TCDD alone. The biphasic temporal effects of TPA on TCDD-induced CYP1A1 gene expression in MCF-7 cells were paralleled by comparable changes in nuclear Ah receptor levels and binding to a synthetic DRE. In contrast, prolonged exposure of the wild-type Hepa 1c1c7 or T47-D cells to both TCDD plus TPA gave results similar to those observed after 24 h. These data show that the effects of TPA on TCDD-induced expression of CYP1A1 are cell-specific and suggest that the proposed protein kinase C (PKC)-dependent activation of the nuclear Ah receptor complex may not be required in MCF-7 cells since TPA downregulates PKC activity within 11 h and this inactivation persists for at least 96 h.

UI MeSH Term Description Entries
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D009687 Nuclear Proteins Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus. Nucleolar Protein,Nucleolar Proteins,Nuclear Protein,Protein, Nuclear,Protein, Nucleolar,Proteins, Nuclear,Proteins, Nucleolar
D009838 Oligodeoxyribonucleotides A group of deoxyribonucleotides (up to 12) in which the phosphate residues of each deoxyribonucleotide act as bridges in forming diester linkages between the deoxyribose moieties. Oligodeoxynucleotide,Oligodeoxyribonucleotide,Oligodeoxynucleotides
D010088 Oxidoreductases The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9) Dehydrogenases,Oxidases,Oxidoreductase,Reductases,Dehydrogenase,Oxidase,Reductase
D011955 Receptors, Drug Proteins that bind specific drugs with high affinity and trigger intracellular changes influencing the behavior of cells. Drug receptors are generally thought to be receptors for some endogenous substance not otherwise specified. Drug Receptors,Drug Receptor,Receptor, Drug
D001943 Breast Neoplasms Tumors or cancer of the human BREAST. Breast Cancer,Breast Tumors,Cancer of Breast,Breast Carcinoma,Cancer of the Breast,Human Mammary Carcinoma,Malignant Neoplasm of Breast,Malignant Tumor of Breast,Mammary Cancer,Mammary Carcinoma, Human,Mammary Neoplasm, Human,Mammary Neoplasms, Human,Neoplasms, Breast,Tumors, Breast,Breast Carcinomas,Breast Malignant Neoplasm,Breast Malignant Neoplasms,Breast Malignant Tumor,Breast Malignant Tumors,Breast Neoplasm,Breast Tumor,Cancer, Breast,Cancer, Mammary,Cancers, Mammary,Carcinoma, Breast,Carcinoma, Human Mammary,Carcinomas, Breast,Carcinomas, Human Mammary,Human Mammary Carcinomas,Human Mammary Neoplasm,Human Mammary Neoplasms,Mammary Cancers,Mammary Carcinomas, Human,Neoplasm, Breast,Neoplasm, Human Mammary,Neoplasms, Human Mammary,Tumor, Breast
D003577 Cytochrome P-450 Enzyme System A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism. Cytochrome P-450,Cytochrome P-450 Enzyme,Cytochrome P-450-Dependent Monooxygenase,P-450 Enzyme,P450 Enzyme,CYP450 Family,CYP450 Superfamily,Cytochrome P-450 Enzymes,Cytochrome P-450 Families,Cytochrome P-450 Monooxygenase,Cytochrome P-450 Oxygenase,Cytochrome P-450 Superfamily,Cytochrome P450,Cytochrome P450 Superfamily,Cytochrome p450 Families,P-450 Enzymes,P450 Enzymes,Cytochrome P 450,Cytochrome P 450 Dependent Monooxygenase,Cytochrome P 450 Enzyme,Cytochrome P 450 Enzyme System,Cytochrome P 450 Enzymes,Cytochrome P 450 Families,Cytochrome P 450 Monooxygenase,Cytochrome P 450 Oxygenase,Cytochrome P 450 Superfamily,Enzyme, Cytochrome P-450,Enzyme, P-450,Enzyme, P450,Enzymes, Cytochrome P-450,Enzymes, P-450,Enzymes, P450,Monooxygenase, Cytochrome P-450,Monooxygenase, Cytochrome P-450-Dependent,P 450 Enzyme,P 450 Enzymes,P-450 Enzyme, Cytochrome,P-450 Enzymes, Cytochrome,Superfamily, CYP450,Superfamily, Cytochrome P-450,Superfamily, Cytochrome P450
D004268 DNA-Binding Proteins Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases. DNA Helix Destabilizing Proteins,DNA-Binding Protein,Single-Stranded DNA Binding Proteins,DNA Binding Protein,DNA Single-Stranded Binding Protein,SS DNA BP,Single-Stranded DNA-Binding Protein,Binding Protein, DNA,DNA Binding Proteins,DNA Single Stranded Binding Protein,DNA-Binding Protein, Single-Stranded,Protein, DNA-Binding,Single Stranded DNA Binding Protein,Single Stranded DNA Binding Proteins
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man

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