Abstract
“The antitumorigenic mechanism of cannabidiol (CBD) is still controversial. This study investigates the role of cyclooxygenase-2 (COX-2) and peroxisome proliferator activated receptor γ (PPARγ) in CBDs proapoptotic and tumor-regressive action. In lung cancer cell lines (A549, H460) and primary cells from a lung cancer patient CBD elicited decreased viability associated with apoptosis. Apoptotic cell death by CBD was suppressed by NS-398 (COX-2 inhibitor), GW-9662 (PPARγ antagonist) and siRNA targeting COX-2 and PPARγ. CBD-induced apoptosis was paralleled by upregulation of COX-2 and PPARγ mRNA and protein expression with a maximum induction of COX-2 mRNA after 8 h and continuous increases of PPARγ mRNA when compared to vehicle. In response to CBD tumor cell lines exhibited increased levels of COX-2-dependent prostaglandins (PGs) among which PGD2 and 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2) caused a translocation of PPARγ to the nucleus and induced a PPARγ-dependent apoptotic cell death. Moreover, in A549-xenografted nude mice CBD caused upregulation of COX-2 and PPARγ in tumor tissue, and tumor regression that was fully reversible by GW-9662. Together, our data demonstrate a novel proapoptotic mechanism of CBD involving initial upregulation of COX-2 and PPARγ and a subsequent nuclear translocation of PPARγ by COX-2-dependent PGs.”