Diindolylmethane and its halogenated derivatives induce protective autophagy in human prostate cancer cells via induction of the oncogenic protein AEG-1 and activation of AMP-activated protein kinase (AMPK)

Cell Signal. 2017 Dec;40:172-182. doi: 10.1016/j.cellsig.2017.09.006. Epub 2017 Sep 18.

Abstract

3,3'-Diindolylmethane (DIM) and its synthetic halogenated derivatives 4,4'-Br2- and 7,7'-Cl2DIM (ring-DIMs) have recently been shown to induce protective autophagy in human prostate cancer cells. The mechanisms by which DIM and ring-DIMs induce autophagy have not been elucidated. As DIM is a mitochondrial ATP-synthase inhibitor, we hypothesized that DIM and ring-DIMs induce autophagy via alteration of intracellular AMP/ATP ratios and activation of AMP-activated protein kinase (AMPK) signaling in prostate cancer cells. We found that DIM and ring-DIMs induced autophagy was accompanied by increased autophagic vacuole formation and conversion of LC3BI to LC3BII in LNCaP and C42B human prostate cancer cells. DIM and ring-DIMs also induced AMPK, ULK-1 (unc-51-like autophagy activating kinase 1; Atg1) and acetyl-CoA carboxylase (ACC) phosphorylation in a time-dependent manner. DIM and the ring-DIMs time-dependently induced the oncogenic protein astrocyte-elevated gene 1 (AEG-1) in LNCaP and C42B cells. Downregulation of AEG-1 or AMPK inhibited DIM- and ring-DIM-induced autophagy. Pretreatment with ULK1 inhibitor MRT 67307 or siRNAs targeting either AEG-1 or AMPK potentiated the cytotoxicity of DIM and ring-DIMs. Interestingly, downregulation of AEG-1 induced senescence in cells treated with overtly cytotoxic concentrations of DIM or ring-DIMs and inhibited the onset of apoptosis in response to these compounds. In summary, we have identified a novel mechanism for DIM- and ring-DIM-induced protective autophagy, via induction of AEG-1 and subsequent activation of AMPK. Our findings could facilitate the development of novel drug therapies for prostate cancer that include selective autophagy inhibitors as adjuvants.

Keywords: AEG-1; AMPK; Autophagy; C42B; LNCaP; Prostate cancer.

MeSH terms

  • AMP-Activated Protein Kinases / genetics*
  • AMP-Activated Protein Kinases / metabolism
  • Apoptosis / drug effects
  • Autophagy / drug effects
  • Carcinogenesis / drug effects
  • Carcinogenesis / genetics
  • Cell Adhesion Molecules / genetics*
  • Cell Adhesion Molecules / metabolism
  • Cell Line, Tumor
  • Halogenation / drug effects
  • Humans
  • Indoles / administration & dosage*
  • Indoles / chemistry
  • Male
  • Membrane Proteins
  • Prostatic Neoplasms / drug therapy*
  • Prostatic Neoplasms / genetics
  • Prostatic Neoplasms / pathology
  • RNA, Small Interfering / genetics
  • RNA-Binding Proteins
  • Signal Transduction / drug effects
  • Signal Transduction / genetics

Substances

  • Cell Adhesion Molecules
  • Indoles
  • MTDH protein, human
  • Membrane Proteins
  • RNA, Small Interfering
  • RNA-Binding Proteins
  • PRKAA1 protein, human
  • AMP-Activated Protein Kinases
  • 3,3'-diindolylmethane