Cannabinoid action induces autophagy-mediated cell death through stimulation of ER stress in human glioma cells
María Salazar, … , Patricia Boya, Guillermo Velasco
María Salazar, … , Patricia Boya, Guillermo Velasco
Published May 1, 2009; First published April 1, 2009
Citation Information: J Clin Invest. 2009;119(5):1359-1372. https://doi.org/10.1172/JCI37948.
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Categories: Research Article Oncology

Cannabinoid action induces autophagy-mediated cell death through stimulation of ER stress in human glioma cells

Abstract

Autophagy can promote cell survival or cell death, but the molecular basis underlying its dual role in cancer remains obscure. Here we demonstrate that Δ9-tetrahydrocannabinol (THC), the main active component of marijuana, induces human glioma cell death through stimulation of autophagy. Our data indicate that THC induced ceramide accumulation and eukaryotic translation initiation factor 2α (eIF2α) phosphorylation and thereby activated an ER stress response that promoted autophagy via tribbles homolog 3–dependent (TRB3-dependent) inhibition of the Akt/mammalian target of rapamycin complex 1 (mTORC1) axis. We also showed that autophagy is upstream of apoptosis in cannabinoid-induced human and mouse cancer cell death and that activation of this pathway was necessary for the antitumor action of cannabinoids in vivo. These findings describe a mechanism by which THC can promote the autophagic death of human and mouse cancer cells and provide evidence that cannabinoid administration may be an effective therapeutic strategy for targeting human cancers.

Authors

María Salazar, Arkaitz Carracedo, Íñigo J. Salanueva, Sonia Hernández-Tiedra, Mar Lorente, Ainara Egia, Patricia Vázquez, Cristina Blázquez, Sofía Torres, Stephane García, Jonathan Nowak, Gian María Fimia, Mauro Piacentini, Francesco Cecconi, Pier Paolo Pandolfi, Luis González-Feria, Juan L. Iovanna, Manuel Guzmán, Patricia Boya, Guillermo Velasco

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Figure 3

THC induces autophagy via ER stress–evoked p8 and TRB3 upregulation.

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THC induces autophagy via ER stress–evoked p8 and TRB3 ...
(A and B) Effect of ISP-1 (1 μM) on THC-induced eIF2α phosphorylation (A; 3 h; n = 3) and LC3 immunostaining (B, left panels; 18 h; percentage of cells with LC3 dots relative to the total cell number, mean ± SD; n = 3; scale bar: 20 μm) in U87MG cells. sip8, p8-selective siRNA; siTRB3, TRB3-selective siRNA. (C) Effect of THC on p8, ATF4, CHOP, and TRB3 mRNA levels of eIF2α WT and eIF2α S51A MEFs as determined by real-time quantitative PCR (8 h; n = 3). Numbers indicate the mean fold increase ± SD relative to vehicle-treated eIF2α WT MEFs. (D) Top: Analysis of p8 and TRB3 mRNA levels. Results from a representative RT-PCR experiment are shown. The numbers indicate gene expression levels as determined by real-time quantitative PCR (mean fold change ± SD relative to siC-transfected cells; n = 5). Bottom: Effect of THC on LC3 immunostaining (green) of U87MG cells transfected with siC, sip8, or siTRB3 (18 h; n = 4). The percentage of cells with LC3 dots relative to cells cotransfected with a red fluorescent control siRNA is shown in each panel (mean ± SD). Scale bar: 20 μm. (E) Effect of THC on LC3 lipidation in U87MG cells transfected with siC, sip8, or siTRB3 (18 h; n = 6). (F) Effect of THC on LC3 lipidation (top; 18 h; n = 5) and LC3 immunostaining (bottom; 18 h; percentage of cells with LC3 dots relative to the total cell number, mean ± SD; n = 4; scale bar: 40 μm) in p8+/+ or p8–/– MEFs. *P < 0.05 and **P < 0.01 compared with THC-treated U87MG (B), eIF2α WT (C), or p8+/+ (F) cells and compared with siC-transfected, THC-treated U87MG cells (D).