IL-6–induced pY-STAT3 is increased in the leukemia stem cell enriched (LSCe) subpopulation. (A) Histograms of sorted subpopulations of a representative diagnostic AML BM sample. Constitutive (yellow) and IL-6–induced (blue) pY-STAT3 are shown for the non–stem AML population (left) and the LSCe population (right). (B) A significant difference in the mean percentage of cells with IL-6–induced pY-STAT3 in the LSCe subpopulation compared with the non–stem AML subpopulation was found. No differences were seen in constitutive pY-STAT3 between sorted populations (n = 8). Bar graphs show mean ± standard error of the mean. *P < .05. PE, phycoerythrin.