Abstract 3280: The sphingosine-1-phosphate receptor modulator FTY720 synergistically inhibits colon cancer cell growth with 5-fluorouracil, irinotecan and oxaliplatin.

Introduction: Despite the appearance of new cancer chemotherapeutics during the last decade, the five-year survival rate of advanced colon cancer remains low. Sphingosine-1-phosphate (S1P), a bioactive lipid mediator, plays critical roles in cancer biology by regulating cell proliferation, migration, metastasis and angiogenesis. S1P exerts most of its functions via its specific cell surface receptors. The immunosuppressive drug, FTY720 (fingolimod), is a functional antagonist of S1P receptor 1 and is approved by FDA for treatment of multiple sclerosis. Although there have been some reports on the effects of FTY720 on breast and prostate cancers, its effects on colon cancer have not yet been examined. The aim of this work was to determine whether FTY720 suppresses survival of colon cancer cell lines either alone or in combination with 5-fluorouracil (5-FU), irinotecan, or oxaliplatin the most commonly used chemotherapies for colon cancer. Methods: The effects of FTY720 on cell survival of multiple cancer types were assessed with the NCI-60 panel. Colon cancer cell lines, human well-differentiated (DLD-1), human moderately differentiated (HT29), and human poorly differentiated (HCT-116) were seeded at a density of 2000 cells per well in 96-well culture plates and FTY720 and 5-FU, or irrinotecan, or oxaliplatin or both were added after 24 hours. Effects on cell viability were examined by WST-8 assay 48 hours later. Results: Among the 9 types of cancers tested in the NCI-60 cell line panel, colon cancer and leukemia were the only ones in which all cell lines responded to FTY720. FTY720 completely suppressed growth of DLD-1 and HCT-116 cells at a concentration of 5 μM or greater in a dose dependent manner. The half maximal (50%) inhibitory concentrations (IC50) of FTY720 were less than 1.8 uM in the 3 colon cancer cell lines. The IC50 values for 5-FU, irinotecan, and oxaliplatin alone were about 8.0 uM, 5.8uM,and 1.1uM respectively, in the same 3 colon cancer cell lines. The combined treatment with FTY720 and 5FU synergistically suppressed survival. Also the combination treatment of FTY720 and irinotecan synergistically suppressed survival of these cell lines, except for HT29 cells. As for the combination treatment with FTY720 and oxaliplatin, it synergically suppressed survival HT29 cells. Conclusion: Our results demonstrate that FTY720 has a synergistic cell killing effect with 5-FU, irinotecan, and oxaliplatin on colon cancer cell lines. Further studies will focus on delineating the mechanisms determining susceptibility to these drugs. This work was supported by NIH (R01CA160688 to KT and R01CA61774 to SS). M.N. is a Japan Society for the Promotion of Science Postdoctoral Fellow. Citation Format: Tomoyoshi Aoyagi, Akimitsu Yamada, Masayuki Nagahashi, Sheldon Milstien, Sarah Spiegel, Kazuaki Takabe. The sphingosine-1-phosphate receptor modulator FTY720 synergistically inhibits colon cancer cell growth with 5-fluorouracil, irinotecan and oxaliplatin. [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 3280. doi:10.1158/1538-7445.AM2013-3280