Abstract 123: A novel J-series prostamide mediates D-series prostamide-induced apoptosis in skin cancer: receptor-independent signaling

Abstract

Abstract Non-melanoma skin cancer (NMSC) is the most common cancer in the United States. The absence of selective toxicity is a major problem that limits the utility of chemotherapeutic and radiation therapy for NMSCs. Our previous data showed that the endocannabinoid, anandamide, selectively induced apoptosis in non-melanoma skin cancer (NMSC) cells which overexpress cyclooxygenase-2. The cytotoxic effect of anandamide was mediated by the production of ethanolamide-conjugated D- and J-series prostaglandins (PGs), also known as prostamide D2 (PMD2) and prostamide J2 (PMJ2), respectively. The aim of the current study was to determine if tumorigenic keratinocytes are more sensitive to PMD2 than non-tumorigenic cells and to examine whether the cytotoxicity of PMD2 is mediated by its downstream metabolite PMJ2. To determine if PMD2 demonstrates preferential toxicity, tumorigenic (JWF2) and non-tumorigenic (HaCaT) keratinocytes were utilized. A significant reduction in cell viability was observed in JWF2 but not in HaCaT cells treated with PMD2. In tumorigenic keratinocytes, PMD2 induced apoptotic cell death, oxidative stress and increased the expression of apoptotic ER stress protein, C/EBP homologous protein-10 (CHOP10). In addition, use of the antioxidant, trolox, and ER stress inhibitor, salubrinal, inhibited the cytotoxic effect of PMD2. Furthermore, the use of prostaglandin D receptor (DP1 and DP2) antagonists did not inhibit PMD2-induced apoptosis indicating that the activity was mediated by a receptor-independent pathway. Similar effects were observed in keratinocytes treated with the structurally-related arachidonic acid metabolite, prostaglandin D2 (PGD2). Interestingly, PMD2 increased the production of J-series prostaglandins in both tumorigenic and non-tumorigenic keratinocytes. LC-ESI-MS/MS analysis detected ethanolamide- conjugated J series PG (15-deoxy, Δ12,14 prostamide J2, 15d-PMJ2) in PMD2-treated cell culture media. Since selective inhibitors of the J-series prostaglandins are not available, 15d-PMJ2 was synthesized to examine its direct activity. Exogenous 15d-PMJ2 mimicked the activity of PMD2 demonstrating preferential cytotoxicity towards tumorigenic compared to non-tumorigenic keratinocytes. In addition, 15d-PMJ2 induced oxidative stress, ER stress and apoptosis in tumorigenic keratinocytes. These findings suggest that the cytotoxicity of PMD2 is mediated by 15dPMJ2. Since PMD2 and its metabolite 15d-PMJ2 are preferentially toxic towards tumorigenic cells, PMD2 or 15d-PMJ2 may be an ideal topical treatment for NMSC that will elicit minimal toxicity in healthy surrounding skin cells. Citation Format: Eman Soliman, Daniel Ladin, Hussam Albassam, Ahmed E. Elhassanny, Andrew Morris, Allison Danell, Rukiyah Van Dross. A novel J-series prostamide mediates D-series prostamide-induced apoptosis in skin cancer: receptor-independent signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 123. doi:10.1158/1538-7445.AM2017-123