title: 3,3'-Diindolylmethane (DIM) and its ring-substituted halogenated analogs (ring-DIMs) induce differential mechanisms of survival and death in androgen-dependent and -independent prostate cancer cells.
abstract: We recently reported that novel ring-substituted analogs of 3,3'-diindolylmethane (ring-DIMs) induce apoptosis and necrosis in androgen-dependent and -independent prostate cancer cells. In this paper, we have focused on the mechanism(s) associated with ring-DIM-mediated cell death, and on identifying the specific intracellular target(s) of these compounds. The 4,4'- and 7,7'-dichloroDIMs and 4,4'- and 7,7'-dibromoDIMs induced the death of LNCaP, C42B and DU145 prostate cancer cells, but not that of immortalized normal human prostate epithelial (RWPE-1) cells. Ring-DIMs caused the early loss of mitochondrial membrane potential (MMP) and decreased mitochondrial ATP generation in prostate cancer cells. Cyclosporin A, an inhibitor of the mitochondrial permeability transition pore, inhibited ring-DIM-mediated cell death, and salubrinal, an inhibitor of ER stress, inhibited cell death mediated only by 4,4'-dihaloDIMs. We found that although salubrinal did not inhibit the onset of ER stress, it prevented 4,4'-dibromoDIM mediated loss of MMP. Salubrinal potentiated cell death in response to 7,7'-dihaloDIMs and DIM, and this effect concurred with increased loss of MMP. Using in silico 3-D docking affinity analysis, we identified Ca2+/calmodulin-dependent kinase II (CaMKII) as a potential direct target for the most toxic ring-DIM, 4,4'-dibromoDIM. An inhibitor of CaMKII, KN93, but not its inactive analog KN92, abrogated cell death mediated by 4,4'-dibromoDIM. The ring-DIMs induced ER stress and autophagy, but these processes were not necessary for ring-DIM-mediated cell death. Inhibition of autophagy with bafilomycin A1, 3-methyladenine or by LC3B gene silencing sensitized LNCaP and C42B, but not ATG5-deficient DU145 cells to ring-DIM- and DIM-mediated cell death. We propose that autophagy induced by the ring-DIMs and DIM has a cytoprotective function in prostate cancer cells.
authors.affiliation: INRS-Institut Armand-Frappier, Laval, Québec, Canada.|Critical Care Division and Meakins-Christie Laboratories, Faculty of Medicine, McGill University, Montreal, Quebec H3A 1A1, Canada.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Goldberg
authors.affiliation: INRS-Institut Armand-Frappier, Laval, Québec, Canada.|Department of Biochemistry, National Research Centre, Dokki, Cairo, Egypt.
authors.forename: Hossam
authors.initials: H
authors.lastname: Draz
authors.affiliation: Environmental and Computational Chemistry Group, University of Cartagena, Colombia.
authors.forename: Diana
authors.initials: D
authors.lastname: Montes-Grajales
authors.affiliation: Environmental and Computational Chemistry Group, University of Cartagena, Colombia.
authors.forename: Jesus
authors.initials: J
authors.lastname: Olivero-Verbél
authors.affiliation: Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX, United States.
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Safe
authors.affiliation: INRS-Institut Armand-Frappier, Laval, Québec, Canada.
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Sanderson
keywords: C42B; DU145; LNCaP; mitochondrial function; prostate cancer