SOX2 and acute myeloid leukemia: While it has been published that CSL cells in AML can be detected and/or purified by using various cell surface or cytoplasmic markers (e.g., CD34+/CD38−, CD200) and ALDH [6,7,8], we chose to study CSL cells in AML using the SORE6 (Sox2/Oct4 response element) reporter system, which contains six repeats of the consensus sequences for Sox2/Oct4 [5].