Pellerito Ornella, Notaro Antonietta, Sabella Selenia, De Blasio Anna, Vento Renza, Calvaruso Giuseppe, Giuliano Michela
Laboratory of Cellular and Developmental Genetics, Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, PROTEO and IBIS, Université Laval, Quebec, QC, Canada.
Apoptosis. 2014 Jun;19(6):1029-42. doi: 10.1007/s10495-014-0985-0.
Cannabinoids have been reported to possess anti-tumorigenic activity in cancer models although their mechanism of action is not well understood. Here, we show that the synthetic cannabinoid WIN55,212-2 (WIN)-induced apoptosis in colon cancer cell lines is accompanied by endoplasmic reticulum stress induction. The formation of acidic vacuoles and the increase in LC3-II protein indicated the involvement of autophagic process which seemed to play a pro-survival role against the cytotoxic effects of the drug. However, the enhanced lysosomal membrane permeabilization (LMP) blocked the autophagic flux after the formation of autophagosomes as demonstrated by the accumulation of p62 and LC3, two markers of autophagic degradation. Data also provided evidence for a role for nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) in cannabinoid signalling. PPARγ expression, at both protein and mRNA levels, was significantly down-regulated after WIN treatment and its inhibition, either by specific antagonists or by down-regulation via gene silencing, induced effects on cell viability as well as on ER stress and autophagic markers similar to those obtained in the presence of WIN. Moreover, the observation that the increase in p62 level and the induction of LMP were also modified by PPARγ antagonists seemed to indicate that PPARγ down-regulation was crucial to determinate the block of autophagic flux, thus confirming the critical role of PPARγ in WIN action. In conclusion, at our knowledge, our results are the first to show that the reduction of PPARγ levels contributes to WIN-induced colon carcinoma cell death by blocking the pro-survival autophagic response of cells.
据报道，大麻素在癌症模型中具有抗肿瘤活性，但其作用机制尚不清楚。在此，我们表明合成大麻素WIN55,212-2（WIN）诱导结肠癌细胞系凋亡的同时伴有内质网应激诱导。酸性空泡的形成和LC3-II蛋白的增加表明自噬过程的参与，这似乎对药物的细胞毒性作用起到了促生存作用。然而，溶酶体膜通透性增强（LMP）在自噬体形成后阻断了自噬流，这通过自噬降解的两个标志物p62和LC3的积累得以证明。数据还为核受体过氧化物酶体增殖物激活受体γ（PPARγ）在大麻素信号传导中的作用提供了证据。WIN处理后，PPARγ在蛋白质和mRNA水平的表达均显著下调，通过特异性拮抗剂或基因沉默下调其表达，对细胞活力以及内质网应激和自噬标志物产生的影响与在WIN存在下获得的影响相似。此外，PPARγ拮抗剂也改变了p62水平的升高和LMP的诱导，这一观察结果似乎表明PPARγ下调对于确定自噬流的阻断至关重要，从而证实了PPARγ在WIN作用中的关键作用。总之，据我们所知，我们的结果首次表明PPARγ水平的降低通过阻断细胞的促生存自噬反应导致WIN诱导的结肠癌细胞死亡。
