Isolation of circulating tumor cells using a novel EMT-based capture method.

Abstract

10533 Background: Circulating tumor cells (CTCs) have potential prognostic, predictive and surrogate implications in oncology. In patients with metastatic castration-resistant prostate cancer (CRPC) and breast cancer (BC), we have shown that CTCs isolated using epithelial cell adhesion molecule (EpCAM) ferromagnetic capture express mesenchymal markers, including N- and O-cadherin, suggesting phenotypic plasticity and the presence of epithelial-mesenchymal transitions (EMT). Therefore, we postulate that during metastasis, tumor cells exist as a spectrum of epithelial to mesenchymal phenotypes and may not be captured with existing EpCAM-based CTC technology. The goal of this study is to identify CTCs in CRPC and BC patients using a novel mesenchymal-based capture method. Methods: In patients with advanced CRPC and BC, two EDTA and one CellSave tube of blood are collected. Using the CellSearch system (Veridex, USA), CTCs are captured with either anti-N-cadherin (N-cad) or anti-O-cadherin (O-cad) ferrofluid and detected cells (events) are defined as beta-catenin and DAPI positive, CD45 negative intact cells. We evaluated the performance of these EMT-based ferrofluids in healthy volunteers, control cells, and in a pilot study of patients with CRPC, and compared enumeration of cells using novel vs. standard EpCAM-based capture methods. Results: In healthy volunteers, rare events were detected using the novel capture methods. In CRPC patients, O-cad capture detected more events in 3 of 5 subjects than EpCAM-based capture, and the majority of captured cells were cytokeratin negative. See table below. Conclusions: These preliminary results suggest that a novel CTC phenotype exists in CRPC based on EMT properties, particularly overexpression of O-cadherin. Further characterization of these cells from patients with advanced PC, BC, and other solid tumors will provide insight into EMT and metastasis biology. [Table: see text]