R(+)-Methanandamide-Induced Apoptosis of Human Cervical Carcinoma Cells Involves A Cyclooxygenase-2-Dependent Pathway

Purpose  Cannabinoids have received renewed interest due to their antitumorigenic effects. Using human cervical carcinoma cells (HeLa), this study investigates the role of cyclooxygenase-2 (COX-2) in apoptosis elicited by the endocannabinoid analog R(+)-methanandamide (MA). Methods  COX-2 expression was assessed by RT-PCR and Western blotting. PGE₂/PGD₂ levels in cell culture supernatants and DNA fragmentation were measured by ELISA. Results  MA led to an induction of COX-2 expression, PGD₂ and PGE₂ synthesis. Cells were significantly less sensitive to MA-induced apoptosis when COX-2 was suppressed by siRNA or the selective COX-2 inhibitor NS-398. COX-2 expression and apoptosis by MA was also prevented by the ceramide synthase inhibitor fumonisin B₁, but not by antagonists to cannabinoid receptors and TRPV1. In line with the established role of peroxisome proliferator-activated receptor γ (PPARγ) in the proapoptotic action of PGs of the D and J series, inhibition of MA-induced apoptosis was also achieved by siRNA targeting lipocalin-type PGD synthase (L-PGDS) or PPARγ. A role of COX-2 and PPARγ in MA-induced apoptosis was confirmed in another human cervical cancer cell line (C33A) and in human lung carcinoma cells (A549). Conclusion  This study demonstrates COX-2 induction and synthesis of L-PGDS-derived, PPARγ-activating PGs as a possible mechanism of apoptosis by MA. Karin Eichele and Robert Ramer contributed equally to this work.