Abstract 2370: Development of microcavity array system for size- and deformability-based isolation of circulating tumor cells

Background: EpCAM-based enumeration of circulating tumor cells (CTCs) has prognostic value in solid tumors such as advanced breast, colon and prostate cancers. However, currently poor sensitivity has limited the use of CTCs in other types of cancers including non-small cell lung cancer (NSCLC). We have developed a microcavity array (MCA) system integrated with microfluidic device for recovery and enumeration of CTC regardless of EpCAM expression level, allowing isolation of tumor cells on the basis of differences in the size and deformability between tumor and hematologic cells. Shapes and sizes of the cavity were optimized in order to trap tumor cells while letting blood cells flow through the microcavities during whole blood filtration. Enrichment of CTCs, fixation, permeabilization, staining, and counting process were implemented in a microfluidic assay within one integrated device. In this study, we evaluated the sensitivity of the MCA system in detecting CTCs with a preclinical model using cell lines and conducted a clinical feasibility study in NSCLC patients. Methods: A wide range of cancer cell lines derived from breast (MCF-7, Hs578T), colon (SW620), gastric (AGS, SNU-1) and lung (A549, HCC-827, NCI-H358, NCI-H441, NCI-H1650, NCI-H1975, NCI-H69, NCI-H82) were used for spike-in experiments. Cells were spiked into 1 mL of healthy donor blood and then introduced into the MCA system. Trapped cells were stained with Hoechst 33342, FITC-labeled anti-pan cytokeratin antibody and PE-labeled anti-CD45 antibody for subsequent imaging analysis. CTCs were defined as cells with round to oval morphology, a visible nucleus, positive staining for pan-cytokeratin and negative staining for CD45. For the clinical evaluation, 16 advanced NSCLC patients were enrolled into the study and we conducted a head-to-head comparison study with CellSearch system. Results: We obtained a quite high recovery rate regardless of tumor types ranging from 80 to 99% in the cell line spike-in experiments containing EpCAM-negative cell lines (Hs578T, SNU-1). Most of recovered cells were viable and were able to proliferate even after isolation process, suggesting the potential for further biological and molecular analyses of CTCs. In the clinical part of the study, CTCs were detectable in 12 out of 16 patients (count β1 per 7.5 ml) with our system. More CTCs were detected by MCA system (median 13, range 0-313 cells/7.5ml blood) than by CellSearch system (median 0, range 0-37 cells/7.5ml b