Evaluating Mechanical Invasiveness of Breast Cancer Stem Cells

Cancer stem cells are a small subpopulation of highly tumorigenic tumors cells that drive tumor progression and are able to self-renew and to differentiate. We propose that cancer stem cells also play a major role in invasion, having a high mechanical invasiveness capacity. Previously, we have identified invasive subpopulations of metastatic cells through their forceful interaction with synthetic gels leading to measurable gel-indentations, specifically the amounts of indenting cells and attained depths indicate their mechanical invasiveness. Here, we correlate the mechanical invasiveness of cell subpopulations with the expression of cancer stem cell markers (ALDH and CD44) and their high/low combinations (ALDH^highCD44^high, ALDH^highCD44^low, ALDH^lowCD44^high). We use Fluorescence-activated cell sorting (FACS) to collect cell subpopulations from highly metastatic breast cancer cell lines from similar genetic (MDA-MB-231 and LM2-4). We show that cancer stem cells are capable of large indentations that reveal their functional role in metastatic invasion.