Abstract 7498: Acoustophoresis enriches tumor cell clusters from patients with metastatic prostate cancer
Authors: Magnusson Cecilia , Augustsson Per , Lenshof Andreas , Josefsson Andreas , Bjartell Anders , Ceder Yvonne , Lilja Hans , Laurell Thomas 
Published: March 2024

Abstract
Purpose: A subset of aggressive prostate cancers (PCa) progress to invade surrounding tissue to form distant metastases by shed of circulating tumor cells (CTCs). However, due to the scarcity of CTCs among the millions of nucleated blood cells, there is an unmet need to improve CTC isolation assays. Our technique Acoustophoresis uses standing ultrasound waves in a flow-through microfluidic chamber to discriminate cells based on their size, density, and compressibility.
Method: We analyzed the effectiveness of acoustophoretic circulating tumor cell (CTC) isolation from 6 mL PFA fixed red blood cell lysed blood from 12 metastatic prostate cancer patients and 20 healthy control subjects and compared it to the golden standard CellSearch. For acoustic cell separation, cells were diluted in 12 mL PBS based buffer and separated by acoustophoresis and analyzed by imaging flow cytometry using a standardized antibody panel (EpCAM, cytokeratin, CD45, CD66b, DAPI). Generally, CTCs, and clusters migrate faster than white blood cells (WBCs) when exposed to ultrasound in the microchannel during acoustophoresis and can therefore be separated from nucleated blood cells.
Major findings: Our pilot study shows that acoustophoresis finds both singlets and clusters of CTCs in patients as well as aggregates of CTCs and WBCs. In total, 67 cancer cell containing cell clusters were identified. Most identified cell clusters were small, containing less than 4 cells. In addition, acoustophoresis is a label-free separation technique, and could therefore identify additional subclasses of CTCs among the detected CTCs with e.g., EpCAM low/- expression. Further, we provide extensive data for the effect of storage time on acoustophoretic separation performance for fixed prostate cancer cell line cells and WBCs. Demonstrating that sample processing can be done up to 72 hours after blood sampling. We believe this is to date the most comprehensive study of acoustic separation of CTCs in patients and control subjects.
Conclusion: Label-free acoustophoresis is a potential method for future non-invasive molecular interrogation of metastatic cancers. We believe Acoustophoresis is a promising technology for CTC enrichment with the possibility to detect new subclasses of CTCs as well as cell clusters not detectable with CellSearch. CTC-clusters has previously been proposed as a promising and potent predictor to monitor progressive disease and is associated with earlier onset of metastatic disease and poor prognosis, which makes acoustophoresis ability to identify clusters of high interest.
Citation Format: Cecilia Magnusson, Per Augustsson, Andreas Lenshof, Andreas Josefsson, Anders Bjartell, Yvonne Ceder, Hans Lilja, Thomas Laurell. Acoustophoresis enriches tumor cell clusters from patients with metastatic prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7498.