Brain-endothelium-adhesion-based selection of breast cancer cells. (a) The illustration of in vitro system for brain-endothelium-adhesion-based selection of breast cancer cells (created with biorender.com). (b,c) The adhesion of tumor cells to the brain endothelium under various levels of fluid shear stress. WT cells were labeled with red cell tracker and perfused into the flow chamber slides to adhere to the brain endothelium under 0.25, 0.5, 1, 2.5, and 5 dyn/cm2 shear stress for 15 min. The number of adhered cells was counted under a fluorescence microscope. Scale bar = 100 μm. n = 3. (d,e) The FAS cells exhibited enhanced adhesion ability under shear stress. WT cells (labeled with red cell tracker) and FAS cells or SAS cells (labeled with green cell tracker) were equally mixed and perfused into the flow chamber at the rate of 1 dyn/cm2 to adhere to the brain endothelium for 15 min. The number of adhered cells was counted under a microscope and normalized to the WT group. Scale bar = 100 μm. n = 3. All data are represented by mean ± SEM. The statistics among groups were analyzed using one-way ANOVA with the post hoc Bonferroni test. (ns: no significance, *** p < 0.001, **** p < 0.0001).