IL1RAP is overexpressed on stem cells of patients with AML with monosomy 7, AML with normal karyotype, and high-risk MDS. (A) IL1RAP gene expression in phenotypically defined HSCs (Lin−CD34+CD38−) in HCs (n = 10), AML with monosomy 7 (n = 10), and AML with normal karyotype (n = 8). *Differences compared with the HC group are statistically significant (P < .05 in both cases). (B) IL1RAP protein expression was determined in Lin−CD34+CD38− cells in MDS patients (n = 7: 3 with low-risk and 4 with high-risk MDS). An isotype control was used to define IL1RAP positivity in each experiment. Percentages of IL1RAP+ cells are shown. *P < .05. (C) IL1RAP mRNA expression in CD34+ cells of different types of MDS (n = 183 total) with refractory anemia (RA), refractory anemia with ringed sideroblasts (RARS), and refractory anemia with excess blast types 1 (RAEB1) and 2 (RAEB2), and CD34+ cells of HCs (n = 17). ***P < .001.