Circulating tumor cells, tumor-derived extracellular vesicles and plasma cytokeratins in castration-resistant prostate cancer patients

// Afroditi Nanou 1 , Frank A.W. Coumans 2 , Guus van Dalum 3 , Leonie L. Zeune 1, 4 , David Dolling 6 , Wendy Onstenk 5 , Mateus Crespo 6 , Mariane Sousa Fontes 6, 7 , Pasquale Rescigno 6, 7 , Gemma Fowler 6 , Penny Flohr 6 , Christoph Brune 4 , Stefan Sleijfer 5 , Johann S. de Bono 6, 7 and Leon W.M.M. Terstappen 1 1 Department of Medical Cell BioPhysics, MIRA Institute, University of Twente, Enschede, the Netherlands 2 Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, the Netherlands 3 Department of General, Visceral and Pediatric Surgery, University Hospital and Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany 4 Department of Applied Mathematics, MIRA Institute and Faculty of EEMCS, University of Twente, Enschede, the Netherlands 5 Department of Medical Oncology, Erasmus MC – Cancer Institute, Rotterdam, The Netherlands 6 Division of Clinical Studies, The Institute of Cancer Research, London, United Kingdom 7 Prostate Cancer Targeted Therapies Group, The Royal Marsden NHS Foundation Trust, London, United Kingdom Correspondence to: Afroditi Nanou, email: a.nanou@utwente.nl Leon W.M.M. Terstappen, email: l.w.m.m.terstappen@utwente.nl Keywords: circulating tumor cells (CTCs); tumor-derived Extracellular Vesicles (tdEVs); cytokeratin 18 (CK18); caspase-cleaved cytokeratin 18 (ccCK18); castration-resistant prostate cancer (CRPC) Received: November 07, 2017      Accepted: March 17, 2018      Published: April 10, 2018 ABSTRACT Purpose: The presence of Circulating Tumor Cells (CTCs) in Castration-Resistant Prostate Cancer (CRPC) patients is associated with poor prognosis. In this study, we evaluated the association of clinical outcome in 129 CRPC patients with CTCs, tumor-derived Extracellular Vesicles (tdEVs) and plasma levels of total (CK18) and caspase-cleaved cytokeratin 18 (ccCK18). Experimental Design: CTCs and tdEVs were isolated with the CellSearch system and automatically enumerated. Cut-off values dichotomizing patients into favorable and unfavorable groups of overall survival were set on a retrospective data set of 84 patients and validated on a prospective data set of 45 patients. Plasma levels of CK18 and ccCK18 were assessed by ELISAs. Results: CTCs, tdEVs and both cytokeratin plasma levels were significantly increased in CRPC patients compared to healthy donors (HDs). All biomarkers except for ccCK18 were prognostic showing a decreased median overall survival for the unfavorable groups of 9.2 vs 21.1, 8.1 vs 23.0 and 10.0 vs 21.5 months respectively. In multivariable Cox regression analysis, tdEVs remained significant. Conclusions: Automated CTC and tdEV enumeration allows fast and reliable scoring eliminating inter- and intra- operator variability. tdEVs provide similar prognostic information to CTC counts.