Label-Free Isolation of Low-Adhesion Cells with Stem Properties for Cancer Stem Cell-Specific Drug Evaluation.

Isolating and obtaining sufficient numbers of cancer stem-like cells from bulk cancer cells for cancer stem cells (CSCs)-specific drug evaluation remain challenging due to the rarity and their relative instability in culture. Here, we report a label-free microfluidic method to isolate low-adhesion cells (LACs) with stem properties based on a cell adhesion microfluidic chip (CA-chip) using cell adhesion differences. In this chip, suspended cells are driven by hydrodynamic force to flow through microchannels coated with basement membrane extract (BME). By manipulating the hydrodynamic force, heterogeneous tumor cells can be separated into different adhesive cell subpopulations. LACs flow out first and are collected from the outlet, while high-adhesion cells (HACs) are captured into the chip and can be recovered by washing with a cell dissociation buffer. We found that the isolated LACs showed cancer stem-like properties, which were further utilized as rare CSC candidates to evaluate CSC-specific drugs. The results showed that only CSC-specific drugs had complete inhibition of sphere formation, demonstrating the feasibility of evaluating the specificity of CSC drugs. The label-free method is highly versatile as it employs cell adhesion as a unique phenotypic marker to effectively isolate cancer stem-like cells and offers an opportunity to evaluate on the large scale CSC-specific drugs, making it applicable to the analysis of certain cancer types, especially CSC-specific biomarkers that have not been identified.