Optofluidic real-time cell sorter for longitudinal CTC studies in mouse models of cancer


Despite the usefulness of genetically engineered mouse models in cancer research, their small total blood volume and the rarity of circulating tumor cells (CTCs) preclude the use of existing liquid biopsy techniques for longitudinal CTC studies in mice. We have devised a method for collecting CTCs from an unanesthetized mouse longitudinally, spanning multiple days or weeks, to study acute perturbations (e.g., drug treatment) or potentially long-term phenotypes (e.g., tumor progression) within the same mouse. Here, we show that our optofluidic-based approach eliminates confounding biases driven by intermouse heterogeneity that can occur when CTCs are collected across different mice.Circulating tumor cells (CTCs) play a fundamental role in cancer progression. However, in mice, limited blood volume and the rarity of CTCs in the bloodstream preclude longitudinal, in-depth studies of these cells using existing liquid biopsy techniques. Here, we present an optofluidic system that continuously collects fluorescently labeled CTCs from a genetically engineered mouse model (GEMM) for several hours per day over multiple days or weeks. The system is based on a microfluidic cell sorting chip connected serially to an unanesthetized mouse via an implanted arteriovenous shunt. Pneumatically controlled microfluidic valves capture CTCs as they flow through the device, and CTC-depleted blood is returned back to the mouse via the shunt. To demonstrate the utility of our system, we profile CTCs isolated longitudinally from animals over 4 days of treatment with the BET inhibitor JQ1 using single-cell RNA sequencing (scRNA-Seq) and show that our approach eliminates potential biases driven by intermouse heterogeneity that can occur when CTCs are collected across different mice. The CTC isolation and sorting technology presented here provides a research tool to help reveal details of how CTCs evolve over time, allowing studies to credential changes in CTCs as biomarkers of drug response and facilitating future studies to understand the role of CTCs in metastasis.

Proceedings of the National Academy of Sciences