title: 3',4'-dimethoxyflavone as an aryl hydrocarbon receptor antagonist in human breast cancer cells.
abstract: Treatment of MCF-7 and T47D human breast cancer cells with 3', 4'-dimethoxyflavone (3',4'-DMF) alone did not induce CYP1A1-dependent ethoxyresorufin O:-deethylase (EROD) activity or reporter gene activity in cells transfected with an aryl hydrocarbon (Ah)-responsive construct (pRNH11c). In contrast, 1 nM 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) induced up to a 50- to 80-fold increase in EROD and reporter gene activity in MCF-7 and T47D cells. In cells cotreated with 1 nM TCDD plus 0.1-10 microM 3',4'-DMF, there was a concentration-dependent decrease in the TCDD-induced responses, with 100% inhibition observed at the 10 microM concentration. Gel mobility shift assays using rat liver cytosol and breast cancer cell nuclear extracts showed that 3',4'-DMF alone did not transform the AhR to its nuclear binding form, but inhibited TCDD-induced AhR transformation in rat liver cytosol and blocked TCDD-induced formation of the nuclear AhR complex in MCF-7 and T47D cells. TCDD also inhibited estrogen-induced transactivation in MCF-7 cells, and this response was also blocked by 3',4'-DMF, confirming the AhR antagonist activity of this compound in breast cancer cells.
authors: Department of Veterinary Physiology & Pharmacology, Texas A&M University, 4466 TAMU, College Station, Texas 77843, USA.
authors: J E
authors: JE
authors: Lee
authors: S
authors: S
authors: Safe
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors*; D013329:Structure-Activity Relationship; D015533:Transcriptional Activation / Q000187:drug effects
chemical_list: D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D019363:Cytochrome P-450 CYP1A1