Enhanced capture system for mesenchymal-type circulating tumor cells using a polymeric microfluidic device 'CTC-Chip' incorporating cell-surface vimentin

CellSearch, the only approved epithelial cell adhesion molecule (EpCAM)-dependent capture system approved for clinical use, overlooks circulating tumor cells (CTCs) undergoing epithelial-mesenchymal transition (EMT-CTCs), which is considered a crucial subtype responsible for metastasis. To address this limitation, a novel polymeric microfluidic device 'CTC-chip' designed for the easy introduction of any antibody was developed, enabling EpCAM-independent capture. In this study, antibodies against EpCAM and cell surface vimentin (CSV), identified as cancer-specific EMT markers, were conjugated onto the chip (EpCAM-chip and CSV-chip, respectively), and the capture efficiency was examined using lung cancer (PC9, H441 and A549) and colon cancer (DLD1) cell lines, classified into three types based on EMT markers: Epithelial (PC9), intermediate (H441 and DLD1) and mesenchymal (A549). PC9, H441 and DLD1 cells were effectively captured using the EpCAM-chip (average capture efficiencies: 99.4, 88.8 and 90.8%, respectively) when spiked into blood. However, A549 cells were scarcely captured (13.4%), indicating that EpCAM-dependent capture is not suitable for mesenchymal-type cells. The expression of CSV tended to be higher in cells exhibiting mesenchymal properties and A549 cells were effectively captured with the CSV-chip (72.4 and 88.4% at concentrations of 10 and 100 mu g/ml, respectively) when spiked into PBS. When spiked into blood, the average capture efficiencies were 27.7 and 46.8% at concentrations of 10 and 100 mu g/ml, respectively. These results suggest that the CSV-chip is useful for detecting mesenchymal-type cells and has potential applications in capturing EMT-CTCs.