Abstract 4964: The isolation of prostate cancer specific circulating tumor cells in the blood of patients with metastatic castration-resistant prostate cancer

Abstract

Abstract Background: Circulating tumor cells (CTC) consist of a heterogeneous population of very rare cells of the primary tumor or its own metastases. A growing amount of evidence has shown that subpopulations of carcinoma cells undergo epithelial-to-mesenchymal transitions (EMT), resulting in their increased motility which facilitates their intravasation into the blood circulation. Gold standard of CTC-isolation is the CellSearchSystem based on epithelial cell adhesion molecule (EpCAM) enrichment, though it is known that EpCAM is downregulated in al advanced prostate cancers and in all CTCs. Furthermore these CTC isolation techniques are not able to isolate organ specific CTCs. The aim of this pilot study is the development of a prostate cancer specific functionalized wire, which detects prostate cancer specific circulating tumor cells (PCTC) in metastatic PCa patients. The CTC detection rate will be compared between an EpCAM functionalized wire and a PCa specific functionalized wire. Methods: We combined 4 antibodies against Prostate specific membrane antigen (PSMA), Prostate specific antigen (PSA), Prostate specific stem cell antigen (PSCA) and epithelial cell adhesion molecule (EpCAM). Evaluations of these antibodies were performed by immunofluorescence analysis of the human prostate cancer cell lines PC3 and LNCaP. PCa specific functionalization of the wire was determined with spiking experiments. Blood samples from healthy donors were spiked with PC-3 and LNCaP cells to test the wire for cell-binding. Afterwards blood of 15 metastatic castration-resistant prostate cancer (CRPC) patients with metastatic progression, documented by prostate-specific antigen or radiologic criteria, was investigated. These samples were simultaneously analyzed in the flow system with two different functionalized wires. The captured CTC and PCTC were identified by immunofluorescence staining using pan cytokeratin and Hoechst-33258 positive signals as well as CD45 negative criteria. Results: The spiking experiments indicate that a sensitive ex vivo isolation with different functionalized wires is possible. In summary, PCTC counts ranged from 0-122 per PCTC (median 9) and CTC counts ranged from 0-22 per CTC (median 3). Our data shows that a more sensitive isolation of PCTC′s is possible using prostate cancer specific functionalized wire compared to EpCAM functionalized wire (p ≤ 0,001). The CTC isolation sensitivity was about 86% for PCa-functionalized wire and about 73% for EpCAM functionalized wire. Conclusions: PCTC can be isolated with prostate cancer-specific functionalization of the wire. Simultaneously CTC that underwent EMT can be isolated. These organ specific subpopulations might have a prognostic effect on the clinical outcome and on the development of personalized medicine. This proof of concept shows how important it is to optimize the EpCam based CTC-detection. Citation Format: Gerit Theil, Stefanie Schmidt, Kersten Fischer, Klaus Lücke, Paolo Fornara. The isolation of prostate cancer specific circulating tumor cells in the blood of patients with metastatic castration-resistant prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4964.