Abstract 316: FTY720 enhances the efficacy of paclitaxel and of carboplatin in drug-resistant ovarian cancer cells

Abstract

Abstract Objectives: Our long-term goal is to develop effective therapies for ovarian cancer by targeting molecules that contribute to drug resistance in this tumor type. Preliminary RNA-seq data were generated using a patient-derived xenograft model. These data identified the sphingosine-1-phosphate (S1P) signaling pathway as one of the pathways most affected by carboplatin and paclitaxel, the current standards of care for ovarian cancer. We then examined whether a synthetic analog of sphingosine, FTY720, enhanced the cytotoxicity of platinum and taxane resistant ovarian cancer cell lines. Methods: To assess the efficacy of FTY720 + carboplatin and of FTY720 + paclitaxel, we exposed three pairs of parental and drug resistant human ovarian cancer cell lines to each combination. The cell lines used were: SKOV3-ip1 and SKOV3-TR (taxane resistant), A2780 and A2780-CP20 (platinum resistant), and HeyA8 and HeyA8-MDR (taxane-platinum resistant). We used alamarBlue cell proliferation assays to determine the efficacy of FTY720 as a single agent or in combination with paclitaxel or carboplatin, and immunoblots to assess the expression of proteins involved in the S1P pathway. Results: FTY720 as a single agent decreased cell viability in a dose-dependent manner in all three pairs of cell lines, with IC50 values ranging from 5 to 8 μM. When cells were exposed to the IC50 of FTY720 + a range of concentrations of carboplatin or paclitaxel, FTY720 had little effect in any of the three parental cell lines and in SKOV3-TR cells. Interestingly, however, FTY720 decreased the IC50 of carboplatin 15- to 16-fold and the IC50 of paclitaxel 20- to 90- fold in A2780-CP20 and HeyA8-MDR cells, respectively. We also observed that FTY720 altered the expression of sphingosine kinase2, S1P lyase, and acid ceramidase, each of which contributes to the ceramide-sphingosine-S1P rheostat that tightly regulates expression of S1P pathway proteins. Conclusions: Our data show that FTY720 sensitized drug resistant ovarian cancer cell lines A2780-CP20 and HeyA8-MDR to carboplatin and to paclitaxel 15- to 90-fold. The data suggest that the S1P pathway may contribute to carboplatin and paclitaxel resistance in this cell type. We propose that proteins of the S1P pathway merit further study as effective molecular targets in drug resistant ovarian cancer cells. Citation Format: Kelly M. Kreitzburg, Ronald D. Alvarez, Charles N. Landen, Karina J. Yoon. FTY720 enhances the efficacy of paclitaxel and of carboplatin in drug-resistant ovarian cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 316.