Abstract 2108: Differential signaling and efficacy responses to SDF-1 and plerixafor in neuroblastoma cells.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Purpose: We have previously demonstrated that CXCR4 is widely but heterogeneously expressed in neuroblastoma cells and that the selective CXCR4 drug Plerixafor has preclinical efficacy for reducing growth of ectopic neuroblastomas in mice. Despite this reports exist which show Plerixafor can exhibit positive effects on growth in other cancers. Knowledge of the biochemical effect of CXCR4 occupancy by SDF-1 or Plerixafor in neuroblastoma cells and how this might vary based on CXCR4 isotype is largely unknown. The purpose of this study is to evaluate the efficacy response of neuroblastoma cells to SDF-1 or Plerixafor and determine if any differences exist and is so are these differences influenced by CXCR4 isotype. Additionally, we seek to identify signaling pathways activated in neuroblastoma cells by SDF-1 and Plerixafor. Experimental Design: Patient-derived neuroblastoma cell lines that differ by level and nature of CXCR4 isoform expressed were evaluated for their response to SDF-1 or Plerixafor. Serum-starved cells were treated with either agent in microplates and calcium mobilization or cell growth was measured using FluoForte and MTT assay kits respectively. For measurement of Akt activation total protein was extracted from stimulated cells, followed by western blot detection of Phosphorylated Akt using phospho-specific antibody and enhanced chemiluminescence (ECL). Results: We observed dose-dependent increases in calcium-mobilization in response to SDF-1 and Plerixafor treatment in all cell lines. Effects on cell growth were heterogeneous and variable in response to SDF-1 stimulation. High-CXCR4 expressing cell line SK-N-SH showed a dose-dependent increase in growth subsequent to SDF-1stimulation, while the low-CXCR4 expressing cell lines SH-SY5Y and SK-N-AS showed stimulation and inhibition at different doses. Plerixafor treatment of SK-N-SH cells resulted in a dose-dependent inhibition of cell growth while the low-CXCR4 expressing lines showed differential efficacy responses, with lower doses stimulating growth and higher doses inhibiting growth. Both SDF-1 and Plerixafor stimulation resulted in increased phosphorylation of Akt. Conclusion: In neuroblastoma cells signaling through CXCR4 occurs in response to Plerixafor as well as SDF-1; signaling by these two agents involves utilization of similar downstream signals including activation of the PI3K/Akt pathway. Neuroblastoma cells show differential efficacy responses to both SDF-1 and Plerixafor with respect to cell growth and this response appears to be dependent on CXCR4 expression type. In addition to its inhibitory effect Plerixafor is partially agonistic as well, underscoring the fact that further understanding of the mechanisms associated with differential efficacy response to Plerixafor is critical to developing effective treatment strategies for neuroblastoma based on this modality. Citation Format: Waleed A. Osman, Jacqueline N. Shanks, Charise M. White, Alex J. Carlisle. Differential signaling and efficacy responses to SDF-1 and plerixafor in neuroblastoma cells. [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 2108. doi:10.1158/1538-7445.AM2013-2108