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 April 1, 2009
Citation Information: J Clin Invest. 2009;119(5):1359-1372. https://doi.org/10.1172/JCI37948.
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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 1

Inhibition of autophagy prevents THC-induced cancer cell death.

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Inhibition of autophagy prevents THC-induced cancer cell death. (A–C) Ef...
(A–C) Effect of THC on U87MG cell morphology. Representative electron microscopy photomicrographs are shown (6 h). Scale bars: 500 nm. Note the presence of early (A, open arrows, and B) and late (A, filled arrows, and C) autophagosomes in THC-treated but not vehicle-treated (veh-treated) cells. (D) Top: Effect of SR141716 (SR1; 1 μM) and THC on LC3 immunostaining (green) in U87MG cells (18 h; n = 3). The percentage of cells with LC3 dots relative to the total cell number is shown in the corner of each panel (mean ± SD). Scale bar: 20 μm. Bottom: Effect of SR1 and THC on LC3 lipidation in U87MG cells (18 h; n = 3). (E) Effect of E64d (10 μM) and pepstatin A (PA; 10 μg/ml) on THC-induced LC3 lipidation in U87MG cells (18 h; n = 3). (F and G) Effect of THC treatment and transfection with control siRNAs (siC) or ATG1-selective siRNAs (siATG1) on cell viability (F; mean ± SD; n = 3), LC3 immunostaining (G, left panels; 18 h; percentage of cells with LC3 dots relative to the total number of cells cotransfected with a red fluorescent control siRNA, mean ± SD; n = 3; scale bar: 20 μm), and LC3 lipidation (G, right panel; 18 h; n = 3) in U87MG cells. (H and I) Effect of THC on cell viability (H; mean ± SD; n = 3), LC3 immunostaining (I, left panels; 18 h; percentage of cells with LC3 dots relative to the total cell number, mean ± SD; n = 3; scale bar: 20 μm), and LC3 lipidation (I, right panel; 18 h; n = 3) in Atg5+/+ and Atg5–/– RasV12/T-large antigen MEFs. *P < 0.05 and **P < 0.01 compared with THC-treated U87MG (D) and Atg5+/+ (H and I) cells and compared with siC-transfected, THC-treated U87MG cells (F and G). THC concentration was 6 μM.