title: Time and dose-dependent modulation of phase 1 and phase 2 gene expression in response to treatment of MCF-7 cells with a natural anti-cancer agent.
abstract: Several known anti-cancer agents have been shown to lead to increased expression of phase 2 metabolic enzymes without affecting phase 1 enzymes. Phase 1 cytochrome P450 (CYP) enzymes are relevant in cancer studies in that they are involved in oxidative metabolism, biotransformation and detoxification, whereas phase 2 enzyme catalysis leads to clearance. In this study, we obtained semi-quantitative measurements of cytochrome P450 (phase 1) and phase 2 microsomal epoxide hydrolase (mEH) gene expression levels in response to treatment of MCF-7 breast cancer cells with water-soluble Vernonia amygdalina (V.A.) extract. V.A., a vegetable grown in Nigeria, has potential as an anti-cancer agent. The results of Western blot and RT-PCR analyses show that V.A. extract acts as a monofunctional inducer within exposure times ranging from 2-16 hr and dose ranges from 3-100 microg/ml of V.A. Exposure of cells to low doses of V.A. did not affect expression levels of CYP1A1/1A2 mRNA, but lead to induction of mEH, thus supporting the chemotherapeutic potential of VA. However, in parallel studies, CYP3A4 gene expression was also induced, suggesting potential intermediates which influence drug-drug interactions. These data are useful toward further validating V.A. extract as a potential clinically useful natural anti-cancer agent and provide some support for the concept that modulation in CYP3A4 expression in response to treatment is relevant to prognosis.
authors.affiliation: Breast Cancer Research Laboratory, Department of Biology, Center for Environmental Health, Jackson State University, 1400 J R Lynch Street, Jackson, Mississippi 39217, USA. carolyn.b.howard@jsums.edu
authors.forename: C B
authors.initials: CB
authors.lastname: Howard
authors.forename: J
authors.initials: J
authors.lastname: Stevens
authors.forename: E B
authors.initials: EB
authors.lastname: Izevbigie
authors.forename: A
authors.initials: A
authors.lastname: Walker
authors.forename: O
authors.initials: O
authors.lastname: McDaniel
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004851:Epoxide Hydrolases / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D032264:Veronica
chemical_list: D010936:Plant Extracts; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D004851:Epoxide Hydrolases