New oleyl glycoside as anti-cancer agent that targets on neutral sphingomyelinase

We designed and synthesized two anomeric oleyl glucosaminides as anti-cancer agents where the presence of a trifluoroacetyl group close to the anomeric center makes them resistant to hydrolysis by hexosaminidases. The oleyl glycosides share key structural features with synthetic and natural oleyl derivatives that have been reported to exhibit anti-cancer properties. While both glycosides showed antiproliferative activity on cancer cell lines, only the α-anomer caused endoplasmic reticulum (ER) stress and cell death on C6 glioma cells. Analysis of sphingolipids and glycosphingolipds in cells treated with the glycosides showed that the α-anomer caused a drastic accumulation of ceramide and glucosylceramide and reduction of lactosylceramide and GM3 ganglioside at concentrations above a threshold of 20 μM. In order to understand how ceramide levels increase in response to α-glycoside treatment, further investigations were done using specific inhibitors of sphingolipid metabolic pathways. The pretreatment with 3-O-methylsphingomyelin (a neutral sphingomyelinase inhibitor) restored sphingomyelin levels together with the lactosylceramide and GM3 ganglioside levels and prevented the ER stress and cell death caused by the α-glycoside. The results indicated that the activation of neutral sphingomyelinase is the main cause of the alterations in sphingolipids that eventually lead to cell death. The new oleyl glycoside targets a key enzyme in sphingolipid metabolism with potential applications in cancer therapy.We appreciate the help of Noelia Villarrubia Migallón (Flow cytometry and cell sorting unit, Instituto Cajal, CSIC) with flow cytometry determinations in cell death/apoptosis experiments. We acknowledge Dr. Ron Prywes, Columbia University for providing UPRE-pGL3 (previously called 5xATF6-pGL3) reporter plasmid. We greatly appreciate the financial support provided by the FISCAM-Servicio de Salud of Castilla-La Mancha (SESCAM) (PI2008/19 and PI2009/51), the Ministry of Economy and Competitiveness (PI11/00592, PI11/01436, SAF2009-11257 and SAF2012-40126), the Comunidad de Madrid (S2009/PPQ-1752), the CSIC (201280E091) and the Generalitat of Catalunya (Grant 2009SGR-1072) was greatly appreciated.Peer Reviewe