An Optofluidic Real-Time Cell Sorter for Longitudinal CTC Studies in Mouse Models of Cancer

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 for several hours per day over multiple days or weeks. The system is based on a microfluidic cell-sorting chip connected serially to an un-anesthetized 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 a four-day treatment with the BET inhibitor JQ1 using single-cell RNA-Seq (scRNA-Seq) and show that our approach eliminates potential biases driven by inter-mouse 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 change 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. Single-cell RNA-Sequencing of CTCs and primary tumors from a murine model of non-small cell-lung cancer