Microfluidic techniques for isolation, formation, and characterization of circulating tumor cells and clusters

Abstract

Circulating tumor cell (CTC) clusters that are shed from the primary tumor into the bloodstream are associated with a poor prognosis, elevated metastatic potential, higher proliferation rate, and distinct molecular features compared to single CTCs. Studying CTC clusters may give us information on the differences in the genetic profiles, somatic mutations, and epigenetic changes in circulating cells compared to the primary tumor and metastatic sites. Microfluidic systems offer the means of studying CTC clusters through the ability to efficiently isolate these rare cells from the whole blood of patients in a liquid biopsy. Microfluidics can also be used to develop in vitro models of CTC clusters and make possible their characterization and analysis. Ultimately, microfluidic systems can offer the means to gather insight on the complexities of the metastatic process, the biology of cancer, and the potential for developing novel or personalized therapies. In this review, we aim to discuss the advantages and challenges of the existing microfluidic systems for working with CTC clusters. We hope that an improved understanding of the role microfluidics can play in isolation, formation, and characterization of CTC clusters, which can lead to increased sophistication of microfluidic platforms in cancer research.

Role of Epithelial-to-Mesenchymal Transition for the Generation of Circulating Tumors Cells and Cancer Cell Dissemination

“…However, CTCs are difficult to detect and analyze, particularly due to their genetic and phenotypic heterogeneity and their scarcity in blood samples. Whole blood can contain less than 100 and sometimes even less than 10 clusters of CTCs per 10 7 leukocytes and 500 × 10 7 erythrocytes [ 66 , 67 ]. Despite being a rare event, CTCs offer great potential in liquid biopsy, which allows safe, inexpensive, and reproducible sampling as an alternative to invasive biopsy [ 68 ].…”

Circulating Tumour Cells, Cell Free DNA and Tumour-Educated Platelets as Reliable Prognostic and Management Biomarkers for the Liquid Biopsy in Multiple Myeloma

“…Microfluidic techniques have the possibility of investigating CTC clusters via the capability to proficiently separate these cells from the peripheral blood of patients in a liquid biopsy. Microfluidics can also be employed in in vitro experimental models of CTC clusters and allow their identification and study [ 59 , 60 , 61 , 62 ].…”

Microfluidic vascular models of tumor cell extravasation

“…It has been found that clusters of circulating tumor cells (CTCs) have a greater propensity to cause metastases than single cells (3). Several studies have therefore included perfused tumor cell clusters, in addition to single CTCs, into microfluidic vasculature to mimic circulating tumor cluster transportation in vivo (59,90).…”

“…Cancer metastasis often begins when tumor cells undergo an epithelial-to-mesenchymal transition (EMT), in which they acquire higher motility and invasiveness and break away from the primary tumor (2). Then, these tumor cells invade surrounding tissues, intravasate to the nearby microvasculature as either single cells or cell clusters, and become circulating tumor cells (CTCs), often aggregating with platelets or monocytes, enabling them to withstand fluid shear stress or anoikis (3) and avoid attack by circulating NK cells. Surviving CTCs can then adhere to the endothelium and extravasate into the distant secondary organ and subsequently progress into metastatic tumors (Figure 1).…”