Abstract

Identification of Different Subpopulations of Circulating Tumor Cells in the Blood of Localized and Metastatic Cancer Patients Using Microfluidics

Steve Soper, Foundation Distinguished Professor; Director, Center of BioModular Multi-scale System for Precision Medicine, Adjunct Professor, Ulsan National Institute of Science & Technology, The University of Kansas

Liquid biopsies are becoming an attractive source of biomarkers that can be used to manage a variety of cancer-related diseases. One of the principle biomarkers for oncology-related diseases found in blood is circulating tumor cells (CTCs). The challenge associated with using CTCs as biomarkers for many cancer-related diseases has been the modest clinical sensitivity demonstrated using the FDA-approved platform. CTCs expressing invasive phenotypes down-regulate epithelial antigens, such as the epithelial cell adhesion molecule – EpCAM, which is typically used for the affinity selection of CTCs. As such, CTCs may have a continuum of phenotypes and thus, a single selection marker may not address all cells comprising the tumor microenvironment. We have developed a CTC selection strategy that employs two polymeric microfluidic chips modified with antibodies and connected in series with each selecting a distinct CTC subpopulation from a single blood sample. In addition to the common marker used for CTC positive selection (EpCAM), Fibroblast Activation Protein alpha (FAPa) expressing CTCs can also be selected. Using the dual selection strategy, both CTC types were detected from patients with clinical sensitivity that showed significant improvement compared to selection in which only EpCAM was used. Approximately 90% of the selected CTCs were found not to co-express both antigens. Due to the high purity (>80%) and clinical yields (>95% recovery) of the dual selection strategy, molecular analysis of both EpCAM and FAP-alpha CTCs could be carried out including next generation sequencing, and droplet digital PCR. Our results suggest FAP-alpha and EpCAM CTCs can be used in concert to guide therapeutic decisions for cancer patients. In this presentation, I will discuss the microfluidic chips we use for the selection of CTCs, the clinical results secured using these chips, and the molecular profiling of both CTC subpopulations.