CMP and MPP undergo premature granulomonocytic differentiation in CMML. (A) Proportion of MPP (CD34⁺/CD38⁻/CD45RA⁻/CD90⁻, top panel) and CMP (bottom panel, CD34⁺/CD38⁺/CD45RA⁻/CD123⁺) by flow cytometry among total BM CD34⁺ cells from patients with CMML (n = 33) or aged-matched healthy control participants (n = 15). Bar: median; Mann-Whitney U test. (B) Proportion of mixed (CFU-M, white), granulomonocytic (CFU-G/M: total of CFU-G, CFU-M, and CFU-GM; black) and erythroid colonies (BFU-E, gray) colonies from 250 MPP (top) or CMP (bottom) grown in triplicate in methylcellulose for 14 days with 30% FBS and cytokines (SCF, IL-3, G-CSF, and EPO); χ² test for mean proportions from CMML (CMP: n = 18; MPP: n = 9) and control (CMP: n = 5; MPP: n = 3) samples. (C) 5 × 10⁴ CMP from healthy (n = 4) or CMML (n = 8) samples were cultivated in bulk for 3 days in the presence of 10% FBS and cytokines (SCF, FLT3-L, TPO, IL-3, IL-6, G-CSF, GM-CSF, and EPO) and then were analyzed by flow cytometry for CD34, CD38, CD45RA, and CD123 expression. Representation of the ratio of events with a GMP (CD34⁺/CD38⁺/CD45RA⁺/CD123⁺) phenotype to cells with an MEP CD34⁺/CD38⁺/CD45RA⁻/CD123⁻) phenotype; bar: median. (D) Gene expression levels (relative to HPRT expression) of PU.1 (top panel) and GATA1 (bottom) in sorted CMP fractions: mean and SEM from 4 control and 5 CMML samples each analyzed in duplicate. Unpaired t tests. *P < .05; **P < .01; ***P < .001. (E) Correlation between the percentage of granulomonocytic colonies from CMP of 16 CMML samples and the corresponding patient’s hemoglobin level (g/dL). Spearman test, slope from linear regression.