Thus, here we isolate by FACS the enriched population of BCSCs (ESA+-CD44+-CD24-/Low cells, from now on CD24-) and the so-called tumor-differentiated cells (ESA+-CD44+-CD24+ cells, from now on CD24+) from MCF7-Tet-On-SrcDN [24], and test their capacity of self-renewal. This evidence concerns the gene CD44 and neoplasm.