title: Inhibition of mitochondrial fusion is an early and critical event in breast cancer cell apoptosis by dietary chemopreventative benzyl isothiocyanate.
abstract: Benzyl isothiocyanate (BITC) is a highly promising phytochemical abundant in cruciferous vegetables with preclinical evidence of in vivo efficacy against breast cancer in xenograft and transgenic mouse models. Mammary cancer chemoprevention by BITC is associated with apoptotic cell death but the underlying mechanism is not fully understood. Herein, we demonstrate for the first time that altered mitochondrial dynamics is an early and critical event in BITC-induced apoptosis in breast cancer cells. Exposure of MCF-7 and MDA-MB-231 cells to plasma achievable doses of BITC resulted in rapid collapse of mitochondrial filamentous network. BITC treatment also inhibited polyethyleneglycol-induced mitochondrial fusion. In contrast, a normal human mammary epithelial cell line (MCF-10A) that was derived from fibrocystic breast disease, was resistant to BITC-mediated alterations in mitochondrial dynamics as well as apoptosis. Transient or sustained decrease in levels of proteins engaged in regulation of mitochondrial fission and fusion was clearly evident after BITC treatment in both cancer cell lines. A trend for a decrease in the levels of mitochondrial fission- and fusion-related proteins was also observed in vivo in tumors of BITC-treated mice compared with control. Immortalized mouse embryonic fibroblasts from Drp1 knockout mice were resistant to BITC-induced apoptosis when compared with those from wild-type mice. Upon treatment with BITC, Bak dissociated from mitofusin 2 in both MCF-7 and MDA-MB-231 cells suggesting a crucial role for interaction of Bak and mitofusins in BITC-mediated inhibition of fusion and morphological dynamics. In conclusion, the present study provides novel insights into the molecular complexity of BITC-induced cell death.
authors.affiliation: Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: Anuradha
authors.initials: A
authors.lastname: Sehrawat
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Claudette St
authors.initials: CS
authors.lastname: Croix
authors.affiliation: Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Baty
authors.affiliation: Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: Simon
authors.initials: S
authors.lastname: Watkins
authors.affiliation: School of Life Sciences, Central University of Gujarat, Gandhinagar, Gujarat, India.
authors.forename: Dhanir
authors.initials: D
authors.lastname: Tailor
authors.affiliation: School of Life Sciences, Central University of Gujarat, Gandhinagar, Gujarat, India; Cancer and Radiation Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Rana P
authors.initials: RP
authors.lastname: Singh
authors.affiliation: Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA. Electronic address: singhs@upmc.edu.
authors.forename: Shivendra V
authors.initials: SV
authors.lastname: Singh
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001943:Breast Neoplasms / Q000473:pathology; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D017879:Isothiocyanates / Q000494:pharmacology*; D018345:Mice, Knockout; D063154:Mitochondrial Dynamics / Q000187:drug effects*
chemical_list: D000970:Antineoplastic Agents; D017879:Isothiocyanates; C031403:benzyl isothiocyanate
keywords: Apoptosis; Benzyl isothiocyanate; Breast cancer; Chemoprevention; Mitochondrial dynamics