IL1RAP protein is aberrantly expressed on distinct stem and progenitor cell compartments of AML patients with −7/7q−. Detection of IL1RAP expression at the protein level by flow cytometry in bone marrow-derived cells from HCs (n = 5) and AML patients with −7/7q− (n = 8). (A) Representative histograms show the distribution of IL1RAP protein (cell surface) expression (fluorescence intensity) within phenotypically defined cell compartments of HC (dotted line) and AML (solid line) samples measured using IL1RAP antibody. Gray histograms correspond to the isotype control. (B) Ratios of IL1RAP geometric mean fluorescence intensity relative to the isotype control (arbitrary unit = 1, indicated by the dotted line) for HSCs in blue, progenitors in red, and lineage-positive cells in yellow. Error bars represent SD. (C) Box-and-whisker plots represent the percentage of IL1RAP-positive cells in each cellular compartment, phenotypic HSCs in blue, progenitors in red, and lineage-positive cells in yellow, in HC and AML bone marrow. An isotype control was used to define positive expression in each experiment. The central box represents the values from the 25th to 75th percentile. The middle square represents the mean; and horizontal line, median. A line extends from the minimum to the maximum value. Black star indicates significant difference with HC counterparts. (D) FISH of sorted IL1RAP-positive and IL1RAP-negative cells of an AML patient bearing monosomy 7 hybridized with the Vysis LSI D7S486 (7q31) SpectrumOrange/CEP 7 SpectrumGreen Probe. Bar graph represents the number of nuclei with normal karyotype (NK) and monosomy 7 (−7) for each group (n = 100 nuclei analyzed per group). P < .001 (χ²). The scoring threshold is indicated. (E) Representative FISH image. The arrows indicate a NK FISH pattern with 2 individual green (centromere chromosome 7) and 2 orange (7q31) signals per nuclear section (top), and monosomy 7(−7) with 1 green and 1 orange signal (bottom), respectively.