title: Phytochemical regulation of the tumor suppressive microRNA, miR-34a, by p53-dependent and independent responses in human breast cancer cells.
abstract: The tumor suppressive microRNA miR-34a is transcriptionally regulated by p53 and shown to inhibit breast cancer cell proliferation as well as being a marker of increased disease free survival. Indole-3-carbinol (I3C) derived from cruciferous vegetables, artemisinin, extracted from the sweet wormwood plant, and artesunate, a semi-synthetic derivative of artemisinin, are phytochemicals with anti-tumorigenic properties however, little is known about the role of microRNAs in their mechanism of action. Human breast cancer cells expressing wild-type (MCF-7) or mutant p53 (T47D) were treated with a concentration range and time course of each phytochemical under conditions of cell cycle arrest as detected by flow cytometry to examine the potential connection between miR-34a expression and their anti-proliferative responses. Real-time PCR and western blot analysis of extracted RNA and total protein revealed artemsinin and artesunate increased miR-34a expression in a dose-dependent manner correlating with down-regulation of the miR-34a target gene, CDK4. I3C stimulation of miR-34a expression required functional p53, whereas, both artemisinin and artesunate up-regulated miR-34a expression regardless of p53 mutational status or in the presence of dominant negative p53. Phytochemical treatments inhibited the luciferase activity of a construct containing the wild-type 3'UTR of CDK4, but not those with a mutated miR-34a binding site, whereas, transfection of miR-34a inhibitors ablated the phytochemical mediated down-regulation of CDK4 and induction of cell cycle arrest. Our results suggest that miR-34a is an essential component of the anti-proliferative activities of I3C, artemisinin, and artesunate and demonstrate that both wild-type p53 dependent and independent pathways are responsible for miR-34a induction.
authors: Department of Molecular and Cell Biology, The Cancer Research Laboratory, University of California at Berkeley, Berkeley, California.
authors: Kris G
authors: KG
authors: Hargraves
authors: Department of Molecular and Cell Biology, The Cancer Research Laboratory, University of California at Berkeley, Berkeley, California.
authors: Lin
authors: L
authors: He
authors: Department of Molecular and Cell Biology, The Cancer Research Laboratory, University of California at Berkeley, Berkeley, California.
authors: Gary L
authors: GL
authors: Firestone
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D037621:Artemisinins / Q000494:pharmacology; D000077332:Artesunate; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D051358:Cyclin-Dependent Kinase 4 / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D037621:Artemisinins; D007211:Indoles; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D000077332:Artesunate; C031327:artemisinin; C016517:indole-3-carbinol; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4
keywords: CDK4; Indole-3-carbinol; anti-proliferative response; artemisinin; artesunate