A. P. Williams1, L. L. Stafman1, J. M. Aye2, H. R. Markert1, J. E. Stewart1, E. A. Beierle1 1University Of Alabama at Birmingham,Surgery,Birmingham, Alabama, USA 2University Of Alabama at Birmingham,Hematology And Oncology,Birmingham, Alabama, USA
Introduction: Fingolimod, or FTY720, is a sphingosine phosphate receptor modulator that is currently approved for treatment of pediatric multiple sclerosis, but has also demonstrated a potential for therapeutic use in various malignancies. Previous studies in our laboratory demonstrated that FTY720 had an anti-tumor effect on medulloblastoma cells both in vitro and in vivo. A subgroup of medulloblastoma cells with the cell surface marker CD133 have been shown to act as stem cell like cancer cells (SCLCCs) and are believed to play a role in resistance and relapse. We sought to demonstrate the efficacy of FTY720 against medulloblastoma SCLCCs, thereby demonstrating its potential as a therapy for medulloblastoma.
Methods: Two well-established human group 3 medulloblastoma patient-derived xenografts (PDXs), D425 and D341, were used for experimentation. Magnetic cell sorting was used to separate CD133-enriched cells (SCLCCs) from the CD133-depleted population. CellTiter96 and alamarBlue assays were used to demonstrate the effect of FTY720 on proliferation and survival, respectively. An extreme limiting dilution assay was used to assess tumorsphere formation, an indicator of tumor cell stemness, and cell motility was measured using migration and invasion assays.
Results: Following treatment with FTY720, both CD133-enriched and CD133-depleted cells had a significant decrease in proliferation and survival (Figure). Cells that were CD133-enriched were more likely to form tumorspheres than their CD133-depleted counterparts at baseline, but following treatment with FTY720, both populations had a significant decrease the tumorsphere formation. In D341, FTY720 significantly decreased invasion in both the CD133-enriched and CD133-depleted populations, but significantly decreased migration in only the CD133-depleted population. In the D425 cells there was a trend toward decreased migration and invasion for both the CD133-enriched and depleted cells, but this was only statistically significant for migration of the CD133-depleted cells.
Conclusion: FTY720 decreased cell survival, proliferation, ability to form tumorspheres, and motility in both CD133-enriched and CD133-depleted medulloblastoma cell populations, demonstrating that the SCLCC population was not resistant to this therapy. These data establish the potential of FTY720 as a therapeutic option for patients with resistant or relapsed medulloblastoma.
