Abstract 2216: Circulating tumor cell isolation based on both physical & biological properties
Authors: Fan Hugh , Chen Kangfu , Dopico Pablo , George Thomas 
Published: August 2019

Abstract
Isolation and detection of circulating tumor cells (CTCs) in peripheral blood have been used for cancer prognosis and treatment monitoring. Most CTC isolation methods are based on either physical property (e.g. size) or biological property (e.g. immunoaffinity) of CTCs. However, it is well known that CTCs are very heterogeneous and their properties are not uniform. For immunoaffinity-based approaches such as the FDA-approved CellSearch® that employs antibodies against epithelial cell adhesion molecule (EpCAM), they cannot detect those CTCs expressing little or no EpCAM (due partially to epithelial-to-mesenchymal transition). For size-based methods such as those using microfilters, CTCs with a smaller size are not detected while a large number of normal blood cells are retained by the filters. To address the challenge, isolation methods based on both physical and biological properties of CTCs have been explored.
We report here a microfluidic device that contains a serpentine main channel and an array of lateral microfilters. The key difference of the device from the conventional microfilter devices is that our filters are not in the direction of the main flow. The unique design of the device layout produces a two-dimensional flow that allows the majority of a sample to pass by while all cells have opportunities to interact with filters, resulting in a larger throughput, reduced cell clogging, and increased purity of cells isolated. The device is further functionalized by immobilizing antibodies on the surfaces of microfilters to achieve a platform that combines filtration-based CTC isolation with immunoaffinity-based isolation.
We first tested the device for the isolation of L3.6pl cells (pancreatic cancer cells) spiked in a buffer or blood, and compared the antibody-immobilized device with the same device containing filters only. Without antibody, the device has a capture efficiency from 69.8% to 83.9%, depending on the flow rate we used. With antibody, the device with combined CTC isolation mechanisms can accomplish a capture efficiency of (98.7 ± 1.2)% at a flow rate of 1.8 mL/h. Other tumor cells with different sizes have also been evaluated in the device.
Further we employed the device for enumerating CTCs from blood samples of pancreatic and colorectal cancer patients. We compared this integrated device with a previously reported device containing herringbone-based micromixers. We found that the new device generally detected a higher number of CTCs.
In summary, a microfluidic device has been developed to integrate filtration-based CTC isolation with immunoaffinity-based isolation. The device offers better performance than those based on one isolation mechanism only, with a potential to address CTC heterogeneity and detect CTCs with different size (single versus cluster) and/or various expression level (epithelial versus mesenchymal).
Citation Format: Hugh Fan, Kangfu Chen, Pablo Dopico, Thomas George. Circulating tumor cell isolation based on both physical & biological properties [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2216.