Capture and Characterization of Circulating Tumor Cells (CTCs) in Early Lung Cancer Using a Novel High-throughput Affinity-based Microfluidic Device.

Abstract

Circulating tumor cells or CTCs are believed to be the seeds for metastases, which cause the majority of cancer-related deaths. They have been proven to be clinically useful as they can inform tumor biology, and be harnessed for patient-specific treatment monitoring and outcomes related to cancer. However, studies are limited by their low yields of 1-10 CTCs per ml of blood in a background of millions of blood cells. Microfluidic platforms using antibody-based capture of CTCs have demonstrated high sensitivity in isolating these cells. Capture is achieved by targeting antigens such as EpCAM present on the surface of CTCs. As such most microfluidic affinity-based platforms that depend on optimal antigen-antibody binding for CTC capture, operate at a low throughput of 1-3 ml/hr. Herein, we developed a high-throughput affinity-based microfluidic device, the OncoBean Chip, operating on a radial flow principle, in contrast to previously reported linear flow devices. Radial flow enables a continuous decrease in velocity, which is conducive to CTC capture. The device was optimized for a capture efficiency of 80% at 10 ml/hr. The OncoBean Chip was used to assess CTCs from the pulmonary vein (PV) or the tumor draining vein of early stage lung cancer patients, in addition to multiple draws of peripheral vein (Pe) blood. As hypothesized, PV had a higher CTC abundance than Pe, and gene expression profiling revealed higher expression of epithelial-mesenchymal transition related genes in the PV than Pe CTCs. CTC clusters, which are capable of more aggressive metastases than single CTCs, were found in the early stage specimens, and were also indicative of disease recurrence. Ki67 was found to be a promising biomarker that may be assessed in CTCs to indicate tumor progression. Future studies will involve single cell analysis of CTC clusters and single CTCs to study their significance in metastasis. The OncoBean Chip was also applied toward CTC capture from melanoma patients, and is thus a versatile device that can be applied to CTC applications in solid cancers.