title: Low concentrations of diindolylmethane, a metabolite of indole-3-carbinol, protect against oxidative stress in a BRCA1-dependent manner.
abstract: The indole-3-carbinol (I3C) metabolite 3,3'-diindolylmethane (DIM) is a proposed cancer prevention agent for various tumor types, including breast cancer. Here, we show that DIM up-regulates expression of the tumor suppressor protein BRCA1 in carcinoma and normal cell types. Up-regulation of BRCA1 was dose and time dependent, and it was observed at physiologically relevant micromolar and submicromolar DIM concentrations when cells were exposed for 72 hours. Treatment with the parent compound (I3C) or DIM (1 micromol/L) protected against cell killing due to H(2)O(2) and other oxidants, and the protection was abrogated by knockdown of BRCA1. DIM stimulated signaling by the antioxidant transcription factor NFE2L2 (NRF2) through the antioxidant response element in a BRCA1-dependent manner. We further showed that DIM rapidly stimulated phosphorylation of BRCA1 on Ser (1387) and Ser (1524) and that these phosphorylations are required for protection against oxidative stress. DIM-induced phosphorylation of BRCA1 on Ser (1387) was dependent on ataxia-telangiectasia mutated. Finally, in our assay systems, H(2)O(2)-induced cell death was not due to apoptosis. However, a significant component of cell death was attributable to autophagy, and both DIM and BRCA1 inhibited H(2)O(2)-induced autophagy. Our findings suggest that low concentrations of DIM protect cells against oxidative stress via the tumor suppressor BRCA1 by several distinct mechanisms.
authors.affiliation: Department of Oncology, Georgetown University, Washington, District of Columbia200 57, USA.
authors.forename: Saijun
authors.initials: S
authors.lastname: Fan
authors.forename: Qinghui
authors.initials: Q
authors.lastname: Meng
authors.forename: Tapas
authors.initials: T
authors.lastname: Saha
authors.forename: Fazlul H
authors.initials: FH
authors.lastname: Sarkar
authors.forename: Eliot M
authors.initials: EM
authors.lastname: Rosen
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects; D019313:BRCA1 Protein / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology*; D051379:Mice; D018384:Oxidative Stress / Q000187:drug effects*; D010766:Phosphorylation / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D019313:BRCA1 Protein; D007211:Indoles; D034741:RNA, Small Interfering; D006861:Hydrogen Peroxide; C016517:indole-3-carbinol; C016392:3,3'-diindolylmethane