Acoustic enrichment of heterogenous circulating tumor cells and clusters from patients with metastatic prostate cancer

Abstract

BackgroundThere are important unmet clinical needs to develop cell enrichment technologies to enable unbiased label-free isolation of both single cell and clusters of circulating tumor cells (CTCs) manifesting heterogeneous lineage specificity. Here, we report a pilot study based on microfluidic acoustophoresis enrichment of CTCs using the CellSearch CTC assay as a reference modality.MethodsAcoustophoresis uses an ultrasonic standing wave field to separate cells based on biomechanical properties (size, density, and compressibility) resulting in inherently label-free and epitope-independent cell enrichment. Following red blood cell lysis and paraformaldehyde fixation, 6 mL of whole blood from 12 patients with metastatic prostate cancer and 20 healthy controls were processed with acoustophoresis and subsequent image cytometry.ResultsAcoustophoresis enabled enrichment and characterization of phenotypic CTCs (EpCAM+, Cytokeratin+, DAPI+, CD45-/CD66b-) in all patients with metastatic prostate cancer and detected CTC-clusters composed of only CTCs or heterogenous aggregates of CTCs clustered with various types of white blood cells in 9 out of 12 patients. By contrast, CellSearch did not detect any CTC-clusters, but detected comparable numbers of phenotypic CTCs as acoustophoresis, with trends of finding higher number of CTCs using acoustophoresis.ConclusionOur preliminary data indicate that acoustophoresis provides excellent possibilities to detect and characterize CTC-clusters as a putative marker of metastatic disease and outcomes. Moreover, acoustophoresis enables sensitive label-free enrichment of cells with epithelial phenotype in blood and offers opportunities to detect and characterize CTCs undergoing epithelial-to-mesenchymal transitioning and lineage plasticity.