title: Antitumor activity of sphingosine kinase inhibitors.
abstract: Sphingosine kinase (SK) is an oncogenic sphingolipid-metabolizing enzyme that catalyzes the formation of the mitogenic second messenger sphingosine-1-phosphate (S1P) at the expense of proapoptotic ceramide. Thus, SK is an attractive target for cancer therapy because blockage of S1P formation leads to inhibition of proliferation, as well as the induction of apoptosis in cancer cells. We have recently identified novel SK inhibitors with nanomolar to low micromolar potencies toward recombinant human SK. This study describes the continuing analysis of these inhibitors through in vitro and in vivo experiments. All three structurally diverse SK inhibitors tested showed antitumor activity in mice without exhibiting toxicity. Blood and tumor inhibitor concentrations exceeded in vitro potency levels. Cell signaling analyses in vitro revealed mixed inhibition of mitogen-activated protein kinase kinase and Akt phosphorylation by the SK inhibitors. Importantly, 4-[4-(4-chloro-phenyl)-thiazol-2-ylamino]-phenol (SKI-II) is orally bioavailable, detected in the blood for at least 8 h, and showed a significant inhibition of tumor growth in mice. These compounds are the first examples of nonlipid selective inhibitors of SK with in vivo antitumor activity and provide leads for further development of inhibitors of this important molecular target.
authors.affiliation: Apogee Biotechnology Company, P.O. Box 916, Hershey, PA 17033, USA. kjfrench@apogeebiotech.com
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: French
authors.forename: John J
authors.initials: JJ
authors.lastname: Upson
authors.forename: Staci N
authors.initials: SN
authors.lastname: Keller
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhuang
authors.forename: Jong K
authors.initials: JK
authors.lastname: Yun
authors.forename: Charles D
authors.initials: CD
authors.lastname: Smith
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000493:pharmacokinetics; D001682:Biological Availability; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000493:pharmacokinetics / Q000494:pharmacology*; D005260:Female; D006207:Half-Life; D008246:Lysophospholipids / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors*; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology; D000099157:Sphingosine Kinase
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D008246:Lysophospholipids; D020928:Mitogen-Activated Protein Kinases; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); D051057:Proto-Oncogene Proteins c-akt; D013110:Sphingosine; D013844:Thiazoles; D000099157:Sphingosine Kinase; C525025:4-(4-(4-chloro-phenyl)thiazol-2-ylamino)phenol; C060506:sphingosine 1-phosphate; C421109:multidrug resistance-associated protein 1