Abstract 3077: Label free prostate cancer cell isolation from blood by acoustic standing wave technology - acoustophoresis
Authors: Magnusson Cecilia , Augustsson Per , Haflidadottir Benedikta , Lenshof Andreas , Ceder Yvonne , Laurell Thomas , Lilja Hans 
Published: May 2015

Abstract
There is intense search for disease biomarkers that can reliably detect lethal prostate cancer (PCa) at early stage, monitor response to treatment, detect disease recurrence, and predict survival. Enrichment, enumeration, and transcriptional profiling of rare circulating tumor cells (CTCs) can predict survival of patients with disseminated tumors, and may provide clinical benefit in predicting treatment responses of targeted therapies.
We exploit ultrasound radiation forces to enable label free diversion of cancer cells from nucleated blood cells in a temperature-controlled, microfluidic continuous flow system (acoustophoresis). A third generation, standing-wave ultrasound microchip (silicon/glass) incorporated a cell pre-alignment channel, and a microchannel with a trifurcated inlet and outlet. The system is driven by compressed air (500 mBar) to mitigate and minimize continuous flow-fluctuations and provide more reproducible and reliable discrimination of tumor cells from nucleated blood cells compared to previous syringe driven setups, and allow us to process clinically relevant sample volumes of blood (5-10 mL).
We fixed, spiked, and processed 50 or more PCa cells per mL in undiluted white blood cells (WBC) in the acoustic microchip. The separation system is very flexible and the ratio between cancer cell recovery and cell contamination can be tuned by changing the sample flow rates or the acoustic energy. A consistent and reproducible recovery of cancer cells above 90% with less than 0.4% contamination of WBC was provided using flow rates of 100 l/min. We also found that about 90% of the contaminating WBCs were granulocytes, whereas the vast majority of lymphocytes were reliably diverted. Our results were consistent using different PCa cell lines (DU145, LNCaP, PC3) along with the breast cancer cell line (MCF7).
The isolation of cancer cells by acoustophoresis is a label free method that consistently enables high recovery of cancer cells independent of the expression of surface antigens. This allows for separation of EpCAM negative populations of CTCs, mesenchymal cells along with cancer stem cells, which can be identified with subsequent qRT-PCR analysis. In acoustophoresis, cells are separated according to size, density and compressibility (dV/dp), where size is the major factor. Using non-fixed samples, we can separate viable from dead cells, since dead cells display significantly different acoustic properties to their live counterpart. Acoustophoresis is a gentle separation method and does not affect cell viability, allowing post isolation ex vivo cultivation of CTCs. This allows functional assays to test CTCs ability to form metastasis. It is therefore a promising method for future non-invasive molecular interrogation of metastatic cancers and the characterization of CTCs will relate CTCs to disease outcome and predict for sensitivity to treatment and match patient to drug response.
Citation Format: Cecilia Magnusson, Per Augustsson, Benedikta Haflidadottir, Andreas Lenshof, Yvonne Ceder, Thomas Laurell, Hans Lilja. Label free prostate cancer cell isolation from blood by acoustic standing wave technology - acoustophoresis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3077. doi:10.1158/1538-7445.AM2014-3077