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)

• Published in: Cellular signalling 2017-12, Vol.40, p.172-182
• Main Authors: Draz, Hossam, Goldberg, Alexander A., Titorenko, Vladimir I., Tomlinson Guns, Emma S., Safe, Stephen H., Sanderson, J. Thomas
• Format: Article
• Language: English
• Subjects: AEG-1; AMP-Activated Protein Kinases; AMP-Activated Protein Kinases - genetics; AMP-Activated Protein Kinases - metabolism; AMPK; Apoptosis; Apoptosis - drug effects; Autophagy; Autophagy - drug effects; C42B; Carcinogenesis; Carcinogenesis - drug effects; Carcinogenesis - genetics; Cell Adhesion Molecules; Cell Adhesion Molecules - genetics; Cell Adhesion Molecules - metabolism; Cell Line, Tumor; Halogenation; Halogenation - drug effects; Humans; Indoles; Indoles - administration & dosage; Indoles - chemistry; Life Sciences; LNCaP; Male; Prostate cancer; Prostatic Neoplasms; Prostatic Neoplasms - drug therapy; Prostatic Neoplasms - genetics; Prostatic Neoplasms - pathology; RNA, Small Interfering; RNA, Small Interfering - genetics; Signal Transduction; Signal Transduction - drug effects; Signal Transduction - genetics
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/j.cellsig.2017.09.006

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. •DIM and ring-DIMs induce the formation of autophagic vacuoles in prostate cancer cells.•AEG-1/AMPK downregulation sensitizes prostate cancer cells to death in presence of subtoxic concentrations of (ring-)DIM.•DIM- and ring-DIM-induced protective autophagy is mediated by the induction of AEG-1 and subsequent activation of AMPK.•Downregulation of AEG-1 induces senescence in prostate cancer cells.