Deformability of breast cancer cells in correlation with surface markers and cell rolling

Although the cancer stem cell (CSC) hypothesis has been around for many years, the reliability of cell-surface markers to classify CSCs has remained debatable. The finding that cancerous cells are significantly more deformable than healthy ones has provided motivation to consider mechanical properties as a possible biomarker for stemness. In this study, using the micropipette aspiration technique, mechanical properties of multiple breast cancer cell lines were investigated and correlated with breast cancer stem cell (BCSC) marker, CD44(+)/CD24(-)/ALDH1(+). The results indicated that Hs578T and MDA-MB-231 cell lines with CD44(+)/CD24(-)/ALDH1(+) phenotype were significantly more deformable than the MDA-MB-468 cell line, which did not express the BCSC marker. The BT-20 cell line with intermediate deformability did not express any CD44(+)/CD24(-) phenotype, but it expressed aldehyde dehydrogenase-1 activity. In addition, more-deformable cell lines were found to roll with shear-independent velocities on E-selectin-coated substrates in a parallel-plate flow chamber, which might be a mediating factor for firm adhesion of CSCs to endothelium during metastasis. Our results indicate that rheological properties can be considered as a biomechanical marker in addition to, or as a complement of, surface markers to find more-definitive evidence of CSC characteristics within tumors.