HSPC subsets are diminished in the BM of MM patients. The subset composition of HSPCs including HSC (Lin⁻, CD34⁺, CD38⁻), CMP (Lin⁻, CD34⁺, CD38⁺, IL-3α^lo, CD45RA⁻), GMP (Lin⁻, CD34⁺, CD38⁺, IL-3Rα^lo, CD45RA⁺), and MEP (Lin⁻, CD34⁺, CD38⁺, IL-3Rα⁻, CD45RA⁻) was determined in BM samples of 5 healthy donors and 12 MM patients. (A) Contour plots of representative experiments are shown. HSPC subset concentrations were calculated based on the number of total nucleated cells (TNC) per microliter of BM aspirate. Bar charts represent the (B) mean proportions and (C) absolute cell counts of HSPC subsets in healthy donors (□) and MM patients (■). Error bars represent SEM. The Student t test was used to detect statistically significant differences. *P < .05; **P < .01; ***P < .001. (D) Computer simulation of HSPC subset composition in (left) healthy donors and (right) MM patients based on microarray datasets.