CD34 and leukemia: As shown in the data, three subsets of LKS+ HSCs, namely, LT-HSCs (LKS+CD34− or LKS+CD150+CD48−), ST-HSCs (LKS+CD34+Flk2−) and MPPs (LKS+CD34+Flk2+), all suffered progressive decreases in absolute numbers during leukemia development (Additional file 4: Figure S4A).