TBIO-16. AUTOMATED CELL ENRICHMENT AND DIGITAL CELL SORTING USING DIELECTROPHORETIC ARRAYS FOR ISOLATION OF CIRCULATING TUMOR CELLS IN PEDIATRIC BRAIN TUMOR PATIENTS

INTRODUCTION: Liquid biopsy has the potential to revolutionize diagnosis and management of cancer. In brain tumors, detection of cell free tumor DNA (ctDNA) and circulating tumor cells (CTC) is challenging due to low level of the circulating material. We present a novel workflow for detection and capture of CTCs. METHODS: Peripheral blood was obtained from five pediatric patients with astrocytoma (n=2), ependymoma (n=1), dysembryoplastic neuroepithelial tumor (n=1), and medulloblastoma (n=1) at initial resection (n=3) and relapse (n=2). Samples were enriched using the ClearBridge ClearCell FX1 system and the suspension stained with antibodies against CD56 and CD45. Samples were analyzed using Silicon Biosystems DEPArray to capture single and pooled CTCs. CTCs were identified by CD56 positivity, while leukocytes were positive for CD45 and NK cells double-positive for CD56 and CD45. RESULTS: CTCs were identified in all 5 patient samples. The number of CD56-positive cells isolated from each sample ranged from 1 to 25 (mean 9). The CD56-positive cells were on average 11.8 µm in diameter (range 9.0-15.7 µm), and CD45-positive cells were on average 10.8 µm in diameter (range 8.9-15.9 µm). Single CTCs and CTC pools are amenable to molecular analysis after whole genome amplification. CONCLUSION: We report a novel integrated workflow for capturing CTCs in pediatric patients with brain tumors. While rare, CTCs circulate in peripheral blood of patients with brain tumors regardless of their grade and are amenable for molecular analysis. This method has the potential to serve as a non-invasive diagnostic and monitoring method for pediatric brain tumors.