Studies to identify the OS cancer stem cells (CSCs) or tumor-initiating cells (TICs) highlight a number of available techniques used to isolate and enrich TICs: (1) the sphere culture assay (or sarcosphere assay) 18; (2) cell sorting for CD133, high-ALDH activity, SP cells, or CD117 in combination with Stro-1 19–22; (3) identification of cells that express the embryonic stem cell gene Oct-4 23; and (4) resistance to chemotherapeutic drugs using U2OS and MG63 cell lines 24,25. This evidence concerns the gene KIT and neoplasm.