title: 3,3'-Diindolylmethane is a novel mitochondrial H(+)-ATP synthase inhibitor that can induce p21(Cip1/Waf1) expression by induction of oxidative stress in human breast cancer cells.
abstract: Epidemiologic evidence suggests that high dietary intake of Brassica vegetables, such as broccoli, cabbage, and Brussels sprouts, protects against tumorigenesis in multiple organs. 3,3'-Diindolylmethane, one of the active products derived from Brassica vegetables, is a promising antitumor agent. Previous studies in our laboratory showed that 3,3'-diindolylmethane induced a G(1) cell cycle arrest in human breast cancer MCF-7 cells by a mechanism that included increased expression of p21. In the present study, the upstream events leading to p21 overexpression were further investigated. We show for the first time that 3,3'-diindolylmethane is a strong mitochondrial H(+)-ATPase inhibitor (IC(50) approximately 20 micromol/L). 3,3'-Diindolylmethane treatment induced hyperpolarization of mitochondrial inner membrane, decreased cellular ATP level, and significantly stimulated mitochondrial reactive oxygen species (ROS) production. ROS production, in turn, led to the activation of stress-activated pathways involving p38 and c-Jun NH(2)-terminal kinase. Using specific kinase inhibitors (SB203580 and SP600125), we showed the central role of p38 and c-Jun NH(2)-terminal kinase (JNK) pathways in 3,3'-diindolylmethane-induced p21 mRNA transcription. In addition, antioxidants significantly attenuated 3,3'-diindolylmethane-induced activation of p38 and JNK and induction of p21, indicating that oxidative stress is the major trigger of these events. To further support the role of ROS in 3,3'-diindolylmethane-induced p21 overexpression, we showed that 3,3'-diindolylmethane failed to induce p21 overexpression in mitochondrial respiratory chain deficient rho(0) MCF-7 cells, in which 3,3'-diindolylmethane did not stimulate ROS production. Thus, we have established the critical role of enhanced mitochondrial ROS release in 3,3'-diindolylmethane-induced p21 up-regulation in human breast cancer cells.
authors.affiliation: Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720, USA.
authors.forename: Yixuan
authors.initials: Y
authors.lastname: Gong
authors.forename: Heesook
authors.initials: H
authors.lastname: Sohn
authors.forename: Ling
authors.initials: L
authors.lastname: Xue
authors.forename: Gary L
authors.initials: GL
authors.lastname: Firestone
authors.forename: Leonard F
authors.initials: LF
authors.lastname: Bjeldanes
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000187:drug effects; D025261:Mitochondrial Proton-Translocating ATPases / Q000037:antagonists & inhibitors*; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D007211:Indoles; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D016160:Retinoblastoma Protein; D000255:Adenosine Triphosphate; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D025261:Mitochondrial Proton-Translocating ATPases; C016392:3,3'-diindolylmethane