Abstract LB-39: Sphingosine kinase activity is not required for tumor cell viability.

Abstract

Sphingosine kinase activity is not required for tumor cell viability Holger Wesche, Matthew L. Brown, Timothy J. Carlson, Angela Coxon, Brendon Frank, Darin J. Gustin, Shawn Jeffries, Shyun Li, Yihong Li, Kurt Morgenstern, Matthew Plant, Karen Rex, Joanna Schmidt, Shanling Shen, Nigel Walker, Dineli Wickramasinghe, Mariwil Wong, Guifen Xu Contribution from the Departments of Oncology Research, Medicinal Chemistry, Molecular Structure and Characterization and Pharmacokinetics and Drug Metabolism, Amgen Inc., South San Francisco, 1120 Veterans Blvd., South San Francisco, Ca, 94080. Sphingosine kinases (SPHKs) are enzymes that phosphorylate the lipid sphingosine, leading to the formation of sphingosine-1-phosphate (S1P). In addition to the well established role of extracellular S1P as a mitogen and potent chemoattractant, SPHK activity has been postulated to be an important intracellular regulator of apoptosis. According to the proposed rheostat theory, SPHK activity shifts the intracellular balance from the pro-apoptotic sphingolipids ceramide and sphingosine to the mitogenic S1P, thereby determining the susceptibility of a cell to apoptotic stress. Despite numerous publications with supporting evidence, a clear experimental confirmation of the impact of this mechanism on tumor cell viability in vitro and in vivo has been hampered by the lack of suitable tool reagents. Utilizing a structure based design approach, we developed potent and specific SPHK1/2 inhibitors. These compounds completely inhibited intracellular S1P production in human cells and attenuated vascular permeability in mice, but did not lead to reduced tumor cell growth in vitro or in vivo. These results show that the SPHK rheostat does not play a major role in tumor cell viability, and that SPHK inhibition may not offer an advantage over S1P neutralization in the treatment of cancer. Citation Format: Holger Wesche, Matthew L. Brown, Timothy J. Carlson, Angela Coxon, Brendon Frank, Darin J. Gustin, Shawn Jeffries, Shyun Li, Yihong Li, Kurt Morgenstern, Kurt Morgenstern, Matthew Plant, Karen Rex, Joanna Schmidt, Shanling Shen, Nigel Walker, Dineli Wickramasinghe, Guifen Xu. Sphingosine kinase activity is not required for tumor cell viability. [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 LB-39. doi:10.1158/1538-7445.AM2013-LB-39