title: Induction of apoptosis by 1,25-dihydroxyvitamin D3 in MCF-7 Vitamin D3-resistant variant can be sensitized by TPA.
abstract: Vitamin D(3) compounds offer an alternative approach to anti-hormonal therapies for human breast cancer. 1,25-Dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) acts through the nuclear Vitamin D(3) receptor (VDR), a phosphoprotein and ligand-dependent transcription factor. Our lab has shown that 1,25-(OH)(2)D(3) induces apoptosis in MCF-7 cells by disruption of mitochondrial function which is associated with Bax translocation to mitochondria, cytochrome c release, and production of reactive oxygen species (ROS). TPA, a protein kinase C (PKC) activator, does not induce cytochrome c release or Bax translocation, thus demonstrating that it has no effect on mitochondria and apoptosis on its own. However, when the MCF-7(D(3)Res) cells (a Vitamin D(3)-resistant variant) are treated with 1,25-(OH)(2)D(3) in the presence of TPA, the cells displayed apoptotic morphology and redistribution of both cytochrome c and Bax. TPA pretreatment greatly enhances 1,25-(OH)(2)D(3) stimulated 24-hydroxylase luciferase activity and VDR protein expression, although transactivation is lower in the MCF-7(D(3)Res) cells compared to the parental cell line. The observation that the phorbol ester TPA sensitizes the Vitamin D(3)-resistant variant to the effects of 1,25-(OH)(2)D(3) suggests an important role for phosphorylation in dictating sensitivity to Vitamin D(3)-mediated apoptosis. This study demonstrates that the effects of 1,25-(OH)(2)D(3) on mitochondrial disruption might be sensitized through activators of PKC.
authors.affiliation: Department of Biological Sciences, University of Notre Dame, IN 46556, USA.
authors.forename: Carmen J
authors.initials: CJ
authors.lastname: Narvaez
authors.forename: Belinda M
authors.initials: BM
authors.lastname: Byrne
authors.forename: Saara
authors.initials: S
authors.lastname: Romu
authors.forename: Meggan
authors.initials: M
authors.lastname: Valrance
authors.forename: JoEllen
authors.initials: J
authors.lastname: Welsh
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D017209:Apoptosis; D002117:Calcitriol / Q000494:pharmacology*; D002273:Carcinogens; D002462:Cell Membrane / Q000378:metabolism; D002762:Cholecalciferol / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species; D013250:Steroid Hydroxylases / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate; D013997:Time Factors; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D065668:Vitamin D3 24-Hydroxylase; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; D002273:Carcinogens; D003574:Cytochrome c Group; D008024:Ligands; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D002762:Cholecalciferol; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D008156:Luciferases; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D011493:Protein Kinase C; D000469:Alkaline Phosphatase; D002117:Calcitriol; D013755:Tetradecanoylphorbol Acetate