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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.

Goldberg AA, Draz H, Montes-Grajales D, Olivero-Verbél J, Safe SH, Sanderson JT - Genes Cancer (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.


Related in: MedlinePlus

Salubrinal modulates mitochondrial activity in prostate cancer cells treated with 4,4′-dihaloDIMsThe percentage of intact LNCaP (A) and C42B (B) cells was calculated after a 24 hour exposure to toxic concentrations of 4,4′-Br2DIM, 7,7′-Br2DIM, 4,4′-Cl2DIM, 7,7′-Cl2DIM, DIM with or without a 4 h pre-treatment with salubrinal. TMRE fluorescence of LNCaP (C) and C42B (D) cells after a 4 hour exposure to 4,4′-Br2DIM or 4,4′-Cl2DIM with or without a 4 h pre-treatment with salubrinal. (E) Phosphorylation of eIF2α, and levels of ER stress proteins after a 24 hour exposure to 4,4′-Br2DIM with or without a 4 hour pre-treatment with salubrinal.
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Figure 4: Salubrinal modulates mitochondrial activity in prostate cancer cells treated with 4,4′-dihaloDIMsThe percentage of intact LNCaP (A) and C42B (B) cells was calculated after a 24 hour exposure to toxic concentrations of 4,4′-Br2DIM, 7,7′-Br2DIM, 4,4′-Cl2DIM, 7,7′-Cl2DIM, DIM with or without a 4 h pre-treatment with salubrinal. TMRE fluorescence of LNCaP (C) and C42B (D) cells after a 4 hour exposure to 4,4′-Br2DIM or 4,4′-Cl2DIM with or without a 4 h pre-treatment with salubrinal. (E) Phosphorylation of eIF2α, and levels of ER stress proteins after a 24 hour exposure to 4,4′-Br2DIM with or without a 4 hour pre-treatment with salubrinal.

Mentions: Salubrinal is an inhibitor of ER stress that blocks dephosphorylation of eIF2α, and we investigated the effects of this compound on the cytotoxicity of the ring-DIMs and DIM. Pre-treatment of LNCaP and C42B cells with 20 μM of salubrinal inhibited cell death caused by 4,4′-dihaloDIMs, but not 7,7′-dihaloDIMs or DIM (Fig 4A, B); in DU145 cells salubrinal pre-treatment also completely prevented 4,4′-Br2DIM-induced cell death (Supplementary Fig. S1E).


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.

Goldberg AA, Draz H, Montes-Grajales D, Olivero-Verbél J, Safe SH, Sanderson JT - Genes Cancer (2015)

Salubrinal modulates mitochondrial activity in prostate cancer cells treated with 4,4′-dihaloDIMsThe percentage of intact LNCaP (A) and C42B (B) cells was calculated after a 24 hour exposure to toxic concentrations of 4,4′-Br2DIM, 7,7′-Br2DIM, 4,4′-Cl2DIM, 7,7′-Cl2DIM, DIM with or without a 4 h pre-treatment with salubrinal. TMRE fluorescence of LNCaP (C) and C42B (D) cells after a 4 hour exposure to 4,4′-Br2DIM or 4,4′-Cl2DIM with or without a 4 h pre-treatment with salubrinal. (E) Phosphorylation of eIF2α, and levels of ER stress proteins after a 24 hour exposure to 4,4′-Br2DIM with or without a 4 hour pre-treatment with salubrinal.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4482247&req=5

Figure 4: Salubrinal modulates mitochondrial activity in prostate cancer cells treated with 4,4′-dihaloDIMsThe percentage of intact LNCaP (A) and C42B (B) cells was calculated after a 24 hour exposure to toxic concentrations of 4,4′-Br2DIM, 7,7′-Br2DIM, 4,4′-Cl2DIM, 7,7′-Cl2DIM, DIM with or without a 4 h pre-treatment with salubrinal. TMRE fluorescence of LNCaP (C) and C42B (D) cells after a 4 hour exposure to 4,4′-Br2DIM or 4,4′-Cl2DIM with or without a 4 h pre-treatment with salubrinal. (E) Phosphorylation of eIF2α, and levels of ER stress proteins after a 24 hour exposure to 4,4′-Br2DIM with or without a 4 hour pre-treatment with salubrinal.
Mentions: Salubrinal is an inhibitor of ER stress that blocks dephosphorylation of eIF2α, and we investigated the effects of this compound on the cytotoxicity of the ring-DIMs and DIM. Pre-treatment of LNCaP and C42B cells with 20 μM of salubrinal inhibited cell death caused by 4,4′-dihaloDIMs, but not 7,7′-dihaloDIMs or DIM (Fig 4A, B); in DU145 cells salubrinal pre-treatment also completely prevented 4,4′-Br2DIM-induced cell death (Supplementary Fig. S1E).

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.


Related in: MedlinePlus