Abstract 2128: Cyclooxygenase-2 regulates anandamide-induced endoplasmic reticulum stress in tumorigenic keratinocytes.
Authors: Soliman Eman , Danell Allison , Van Dross Rukiyah 
Published: August 2014

Non-melanoma skin cancer (NMSC) is the most common cancer in the United States. NMSC and other epithelial tumors overexpress cyclooxygenase-2 (COX-2), differentiating them from normal epithelial cells. COX-2 metabolizes arachidonic acid to prostaglandins of the E-, F-, D-, and J-series. While E-series prostaglandins promote tumor cell proliferation, J-series prostaglandins induce apoptosis by various mechanisms including the induction of endoplasmic reticulum (ER) stress. In response to excessive ER stress, sensors such as PKR-like ER kinase (PERK) and activating transcription factor 6 (ATF6) are activated and initiate the apoptotic cascade by increasing the expression of C/EBP homologous protein (CHOP 10). Anandamide (AEA) is an endogenous cannabinoid neurotransmitter which induces apoptotic cell death in a variety of tumor cell types. AEA is metabolized by COX-2 to ethanolamide conjugates of E-, F-, and D-series prostaglandins. Data from our previous study showed that J-series prostaglandins are also metabolic products of AEA however, the identity of the specific J-series prostaglandins produced was unknown. In the current study, we identify the J-series prostaglandins produced by AEA and test the hypothesis that these ethanolamide conjugates of J-series prostaglandins (PGJ2-EA) initiate AEA-induced ER stress in NMSC cells.

To determine if AEA induces ER stress in NMSC cells we examined the phosphorylation of PERK and eukaryotic initiation factor 2 alpha (eIF2α), the induction of CHOP 10 expression and the nuclear translocation of ATF 6 by Western blot or immunocytochemical analysis. Our data show that AEA increased PERK and eIF2α phosphorylation, CHOP 10 expression and ATF 6 nuclear localization. To determine whether COX-2 and J-series prostaglandins are necessary for AEA-induced ER stress, non-tumorigenic HaCaT keratinocytes, which express low basal levels of COX-2, were transfected with a plasmid containing human COX-2 cDNA or an empty vector and the cells treated with AEA or drug vehicle. We observed that AEA-induced phosphorylation of PERK and eIF2α occurred only in the presence of COX-2. To identify the specific J-series PGs synthesized from AEA in NMSC cells, JWF2 keratinocytes were treated with AEA, the PGs extracted from the culture media of treated cells, and the samples analyzed using LC/MS. Our data show that ethanolamide conjugates of 15-deoxyΔ 12, 14PGJ2, Δ12PGJ2, and PGJ2 are metabolic products of AEA.

These findings suggest that COX-2 mediates the induction of ER stress by AEA. Therefore, the initiation of ER stress may be responsible for the pro-apoptotic activity of AEA in tumor cells. As such, AEA or chemical derivatives of AEA could be ideal topical agents for the eradication of non-melanoma skin tumors that overexpress COX-2.

Citation Format: Eman Soliman, Allison Danell, Rukiyah Van Dross. Cyclooxygenase-2 regulates anandamide-induced endoplasmic reticulum stress in tumorigenic keratinocytes. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2128. doi:10.1158/1538-7445.AM2013-2128