title: Role of Cyp1A1 in modulation of antitumor properties of the novel agent 2-(4-amino-3-methylphenyl)benzothiazole (DF 203, NSC 674495) in human breast cancer cells.
abstract: 2-(4-Amino-3-methylphenyl)benzothiazole (DF 203, NSC 674495) is a candidate antitumor agent with potent and selective activity against human-derived tumor cell lines in vitro and in vivo. Only sensitive cell lines (e.g., MCF-7) were able to accumulate and metabolize DF 203, forming the main inactive metabolite, 2-(4-amino-3-methylphenyl)-6-hydroxybenzothiazole (6-OH 203). Selective metabolism may therefore underlie its antitumor profile. DF 203 6-hydroxylase activity by MCF-7 cells was not constitutive but induced only after pretreatment of cells with DF 203, 3-methylcholanthrene, or beta-naphthoflavone. 6-Hydroxylation was strongly inhibited by either goat antirat cytochrome P450 1A1 (CYP1A1) serum or alpha-naphthoflavone. Both alpha-naphthoflavone and 6-OH 203 abrogated DF 203-induced growth inhibition. Microsomes from genetically engineered human B-lymphoblastoid cells expressing CYP1A1, CYP1B1, or CYP2D6 metabolized DF 203 to 6-OH 203. Immunoblot analysis detected significantly enhanced CYP1A1 protein in a panel of sensitive breast cancer cell lines after exposure to DF 203. Neither constitutive expression nor induction of CYP1A1 protein was detected in nonresponsive breast (HBL 100, MDA-MB-435, and MCF-7/ADR) and prostate (PC 3 and DU 145) cancer cell lines. The expression of CYP1B1 was also modulated by DF 203 in the same sensitive cell lines. However, of the two isoforms, only CYP1A1 activity was irreversibly inhibited by DF 203 and significantly inhibited by 6-OH 203. In sensitive cell lines only, [14C]DF 203-derived radioactivity bound covalently to a Mr 50,000, protein which was immunoprecipitated by CYP1A1 antiserum. The covalent binding of [14C]DF 203 to recombinant CYP1A1 enzyme was NADPH-dependent and reduced by 6-OH 203 and glutathione. CYP1A1 appears essential for the metabolism of DF 203 and may have a pivotal, yet undefined, role in its antitumor activity.
authors.affiliation: Cancer Research Laboratories, School of Pharmaceutical Sciences, University of Nottingham, United Kingdom.
authors.forename: M S
authors.initials: MS
authors.lastname: Chua
authors.forename: E
authors.initials: E
authors.lastname: Kashiyama
authors.forename: T D
authors.initials: TD
authors.lastname: Bradshaw
authors.forename: S F
authors.initials: SF
authors.lastname: Stinson
authors.forename: E
authors.initials: E
authors.lastname: Brantley
authors.forename: E A
authors.initials: EA
authors.lastname: Sausville
authors.forename: M F
authors.initials: MF
authors.lastname: Stevens
mesh_terms: D000814:Aniline Compounds / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D001189:Aryl Hydrocarbon Hydroxylases; D001571:Benzoflavones / Q000494:pharmacology; D052160:Benzothiazoles; D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology*; D019363:Cytochrome P-450 CYP1A1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006900:Hydroxylation; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000096:biosynthesis / Q000378:metabolism; D011485:Protein Binding; D013379:Substrate Specificity; D013844:Thiazoles / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000814:Aniline Compounds; D000970:Antineoplastic Agents; D001571:Benzoflavones; D052160:Benzothiazoles; D004791:Enzyme Inhibitors; D007527:Isoenzymes; C122062:NSC 674495; D013844:Thiazoles; C011512:alpha-naphthoflavone; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1