title: Aryl hydrocarbon receptor activation of an antitumor aminoflavone: basis of selective toxicity for MCF-7 breast tumor cells.
abstract: Aminoflavone (4H-1-benzopyran-4-one, 5-amino-2-(4-amino-3-fluorophenyl)-6,8-difluoro-7-methyl; NSC 686288) demonstrates differential antiproliferative activity in the National Cancer Institute's anticancer drug screen. We demonstrate here that MCF-7 human breast cancer cells are sensitive to aminoflavone both in vitro and when grown in vivo as xenografts in athymic mice. As previous work has indicated that aminoflavone requires metabolic activation by cytochrome P450 1A1 (CYP1A1), we investigated the effect of aminoflavone on CYP1A1 expression and on the aryl hydrocarbon receptor (AhR), a transcriptional regulator of CYP1A1. In aminoflavone-sensitive but not aminoflavone-resistant cells, the drug caused a 100-fold induction of CYP1A1 mRNA and a corresponding increase in ethoxyresorufin-O-deethylase activity. An AhR-deficient variant of the MCF-7 breast carcinoma, AH(R100), with diminished CYP1A1 inducibility, exhibits cellular resistance to aminoflavone and is refractory to CYP1A1 mRNA induction by the drug. The increase in CYP1A1 mRNA in the aminoflavone-sensitive MCF-7 breast tumor cell results from transcriptional activation of xenobiotic-responsive element (XRE)-controlled transcription. Aminoflavone treatment causes a translocation of the AhR from the cytoplasm to the nucleus with subsequent formation of AhR-XRE protein DNA complexes. In contrast to the aminoflavone-sensitive MCF-7 cells, the resistant cell lines (MDA-MB-435, PC-3, and AH(R100)) demonstrated constitutive nuclear localization of AhR. Additionally, aminoflavone failed to induce ethoxyresorufin-O-deethylase activity, CYP1A1 transcription, AhR-XRE complex formation, and apoptosis in aminoflavone-resistant cells. These results suggest that the cytotoxicity of aminoflavone in a sensitive breast tumor cell line is the result of the engagement of AhR-mediated signal transduction.
authors.affiliation: Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute-Frederick, Building 322, Room 104, Frederick, MD 21702, USA.
authors.forename: Andrea I
authors.initials: AI
authors.lastname: Loaiza-Pérez
authors.forename: Susan
authors.initials: S
authors.lastname: Kenney
authors.forename: Jamie
authors.initials: J
authors.lastname: Boswell
authors.forename: Melinda
authors.initials: M
authors.lastname: Hollingshead
authors.forename: Michael C
authors.initials: MC
authors.lastname: Alley
authors.forename: Curtis
authors.initials: C
authors.lastname: Hose
authors.forename: Henry P
authors.initials: HP
authors.lastname: Ciolino
authors.forename: Grace C
authors.initials: GC
authors.lastname: Yeh
authors.forename: Jane B
authors.initials: JB
authors.lastname: Trepel
authors.forename: David T
authors.initials: DT
authors.lastname: Vistica
authors.forename: Edward A
authors.initials: EA
authors.lastname: Sausville
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D004790:Enzyme Induction / Q000187:drug effects; D005419:Flavonoids / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D011401:Promoter Regions, Genetic / Q000235:genetics; D021381:Protein Transport / Q000187:drug effects; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D005419:Flavonoids; D018336:Receptors, Aryl Hydrocarbon; C413760:aminoflavone; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; C585498:Cyp1b1 protein, mouse; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1