Abstract 5598: Microfluidic isolation and capture of circulating tumor cells and clusters from mouse blood
Authors: Macaraniag Celine , Zhou Jian , Papautsky Ian , Li Jing , Putzbach William , Hay Nissim 
Published: April 2023

Abstract
Background. Circulating tumor cells (CTCs) and their clusters have been regarded as potential targets for therapies and subjects for identifying certain mechanisms of cancer metastasis. Mouse models have been especially useful tools to investigate the process of metastasis, since they are easier to control and are less variable compared to clinical patient samples. Therefore, it is of interest to extract and study CTCs and CTC clusters from such mouse models. However, most isolation systems are designed and tested for human blood and cell lines. Sized-based methods of CTC isolation have been optimized for human cell lines, but mouse CTCs are generally smaller in size (i.e., ~14 µm EO771 breast cancer cells). Therefore, mouse cell separation necessitates a varied protocol for CTC isolation. We used mouse blood and EO771, a mouse breast cancer cell line, to demonstrate the isolation of mouse CTCs from mouse blood using a sized-based microfluidic device. We also validated the presence of endogenous CTCs and CTC-neutrophil clusters in a tumor bearing mouse model.
Methods. Our microfluidic device employs inertial migration in a straight channel segment (150 µm × 50 µm × 24 mm) to isolate CTCs from blood samples. We spiked 100 and 1000 ZsGreen-expressing EO771 cells in 5 × diluted blood containing tdTomato-expressing neutrophils, easily distinguishing CTCs from the red-colored neutrophils. To enumerate the recovered cells, we used Cytospin to concentrate the cells into a glass slide. Lastly, we used hydrodynamic traps to capture CTC clusters from tumor-bearing mouse blood. The blood was extracted from the posterior vena cava of the mice at the endpoint experiment.
Results. We achieved an overall recovery rate of 22-29%, which combines the recovery of the isolation device and the Cytospin. Here, we enumerate cells only after their extraction from the collection tube outside of the isolation device. Other methods with higher capture efficiency enumerate the recovered CTCs before they are harvested from the isolation device which is not always representative of the number of cells that are analyzed. We were also able to discover endogenous CTC-neutrophil clusters from tumor-bearing mice which we distinguished apart with anti-EpCAM staining of CTCs (green) and anti-Ly6G (red) staining of neutrophils.
Conclusion. We demonstrated and optimized a procedure for isolating mouse-derived CTCs from naïve mice blood and CTC-neutrophil clusters from tumor-bearing mice with our microfluidic isolation devices, as opposed to the isolation of human CTCs as in other sized-based isolation systems. In future studies, we aim to continue to use our microfluidic devices to capture and study CTC and CTC clusters.
Citation Format: Celine Macaraniag, Jian Zhou, Ian Papautsky, Jing Li, William Putzbach, Nissim Hay. Microfluidic isolation and capture of circulating tumor cells and clusters from mouse blood. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5598.