To validate that tumor-initiating cells in tumors originating from single in vitro colonies both resembled parental tumors and were derived from a single cell, UM-C4 cells were transduced with a lentivirus carrying GFP-Luciferase, tumors were generated, and single colonies obtained from ESA+CD44+CD166+ cells were transplanted into mice. This evidence concerns the gene CD44 and neoplasm.