Ex vivo propagation and characterization of circulating tumor cell clusters from late stage prostate cancer patients.

314 Background: Cells shed by a tumor into the bloodstream upon metastasis present an opportunity to study the properties of these cells for biomarker discovery, drug development, and personalized therapy. Enrichment and expansion of circulating tumor cells (CTCs) in culture enables molecular characterization not readily available for rare cells. Here, we demonstrate the successful identification and culture of rare circulating tumor cell clusters from peripheral blood of metastatic castration resistant prostate cancer patients (mCRPC). Methods: The approach to isolate CTC clusters relies on nucleated cell enrichment via Ficoll-based centrifugation from 15 mL of peripheral blood. A collagen-based cell-binding substrate was used to capture cell clusters with preferential affinity for collagen (i.e. epithelial-like cells). Hypoxic and pressurized culturing conditions were used to maintain and propagate adhered CTC clusters. After 7 days in culture, immunofluorescence imaging, qPCR and/or mRNAseq were perfor...