title: Sphingomyelin synthase as a potential target for D609-induced apoptosis in U937 human monocytic leukemia cells.
abstract: Tricyclodecan-9-yl-xanthogenate (D609) is a selective tumor cytotoxic agent. However, the mechanisms of action of D609 against tumor cells have not been well established. Using U937 human monocytic leukemia cells, we examined the ability of D609 to inhibit sphingomyelin synthase (SMS), since inhibition of SMS may contribute to D609-induced tumor cell cytotoxicity via modulating the cellular levels of ceramide and diacylglycerol (DAG). The results showed that D609 is capable of inducing U937 cell death by apoptosis in a dose- and time-dependent manner. The induction of U937 cell apoptosis was associated with an inhibition of SMS activity and a significant increase in the intracellular level of ceramide and decrease in that of sphingomyelin (SM) and DAG, which resulted in an elevation of the ratio between ceramide and DAG favoring the induction of apoptosis. In addition, incubation of U937 cells with C(6)-ceramide and/or H7 (a selective PKC inhibitor) reduced U937 cell viability; whereas pretreatment of the cells with a PKC activator, PMA or 1-oleoyl-2-acetylglycerol (OAG), attenuated D609-induced U937 cell apoptosis. These results suggest that SMS is a potential target of D609 and inhibition of SMS may contribute to D609-induced tumor cell death via modulation of the cellular levels of ceramide and DAG.
authors.affiliation: Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Aimin
authors.initials: A
authors.lastname: Meng
authors.forename: Chiara
authors.initials: C
authors.lastname: Luberto
authors.forename: Patrick
authors.initials: P
authors.lastname: Meier
authors.forename: Aiping
authors.initials: A
authors.lastname: Bai
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Yang
authors.forename: Yusuf A
authors.initials: YA
authors.lastname: Hannun
authors.forename: Daohong
authors.initials: D
authors.lastname: Zhou
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001952:Bridged-Ring Compounds / Q000494:pharmacology*; D002518:Ceramides / Q000378:metabolism / Q000494:pharmacology; D003603:Cytotoxins / Q000494:pharmacology; D004075:Diglycerides / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007948:Leukemia, Monocytic, Acute / Q000188:drug therapy* / Q000201:enzymology; D009636:Norbornanes; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013859:Thiocarbamates; D013871:Thiones / Q000494:pharmacology*; D017855:Transferases (Other Substituted Phosphate Groups) / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020298:U937 Cells; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D000970:Antineoplastic Agents; D001952:Bridged-Ring Compounds; D002518:Ceramides; D003603:Cytotoxins; D004075:Diglycerides; D004791:Enzyme Inhibitors; D009636:Norbornanes; D013859:Thiocarbamates; D013871:Thiones; C101954:N-caproylsphingosine; C046498:tricyclodecane-9-yl-xanthogenate; C038237:1-oleoyl-2-acetylglycerol; D011493:Protein Kinase C; D017855:Transferases (Other Substituted Phosphate Groups); C070186:phosphatidylcholine-ceramide phosphocholine transferase; D013755:Tetradecanoylphorbol Acetate