Functional profiling of circulating tumor cells with an integrated vortex capture and single-cell protease activity assay

TLDR

Current liquid biopsy paradigms rely on CTC counts and genomics for actionable data, but functional approaches like protease activity profiling can illuminate metastasis and enable companion diagnostics. The study introduces a functional assay that quantifies protease secretion from live CTCs at single‑cell resolution. The assay uses an integrated microfluidic device to capture, wash, and encapsulate CTCs into nanoliter droplets containing fluorogenic substrates, enabling rapid, physiologic measurement of protease activity. Data reveal outlier CTCs with high protease activity that correlate with metastatic progression and may drive metastasis or immune evasion.

Abstract

Significance The current paradigm in liquid biopsies focuses on circulating tumor cell (CTC) count and genomics to provide clinically actionable information. We push beyond current capabilities to introduce a functional assay that quantifies protease secretion from live CTCs with single-cell resolution. In this assay, an integrated microfluidic device captures CTCs from blood and washes and encapsulates them into nanoliter-scale droplets with fluorogenic substrates within minutes, maintaining physiologic conditions. Our data support the presence of outlier CTCs with high protease activity that may drive metastasis or immune evasion. We reveal an intriguing correlation between CTC protease activity and metastatic progression. Such functional liquid biopsy approaches provide avenues to understand the metastatic process and potential for companion diagnostics.