For example, in breast cancer, collagen I and collagen VI could induce the expression of CSCs markers, while collagen IV and vitronectin promote CSCs differentiation, leading to a decreased CD44+ /CD24- CSCs population.10 ECM compounds such as fibronectin and hyaluronic acid were also reported to promote the enrichment of CD44+ glioblastoma stem cells.11,12 Increasing investigations provide evidence that ECM composition dynamically regulates CSCs development and dormancy, which determines drug resistance and tumor relapse occurrence. The gene discussed is CD44; the disease is breast cancer.