β-Caryophyllene Inhibits Cell Proliferation through a Direct Modulation of CB2 Receptors in Glioblastoma Cells

Glioblastomas are aggressive cancers characterized by uncontrolled proliferation and inflammation. b-caryophyllene (BCP) is a cannabinoid receptor 2 (CB2) agonist that showed an important anti-inflammatory effect through the interaction of CB2 and peroxisome proliferator-activated receptor gamma (PPARg) receptors. BCP effects were investigated in an in vitro model of glioblastoma. U-373 and U87, derived from a human glioblastoma, and human glioma stem-like cells (GSCs) were treated with BCP at different doses and time-points. AM360, a specific CB2 antagonist, was added 2 h before BCP treatment. BCP showed a significant anti-proliferative effect, reducing cell viability, inhibiting cell cycle, and increasing apoptosis, as demonstrated by Tunel assay, caspase-3 and caspase -9 activation. In addition, the pro-apoptotic BAX expression was increased, whereas the anti-apoptotic Bcl-2 expression was reduced. Treatment with BCP decreased Beclin-1, LC3 and p62/SQSTM1 expression, indicating a possible switch of autophagy to apoptosis. BCP's anti-inflammatory effect was demonstrated by NF-kappa B reduction, PPARg activation and TNF-a decrease; BCP significantly reduced Jun N-Terminal Kinase (JNK) expression as a consequence of TNF-alpha inhibition. AM360 abrogated BCP effects, thus demonstrating the BCP mechanism of action through the CB2 receptor. These findings let us hypothesize that BCP may act as a tumor suppressor in glioblastoma, acting on CB2 receptor and modulating JNK.