American Society of Hematology

Figure 1.

$Mutation burden of CD34+ BM populations is significantly lower in patients with MDS-RS with asymptomatic anemia than in patients with TN. (A) Study overview. BM samples from patients with MDS-RS were taken at diagnosis, at onset of TN, during successful ESA treatment, and in a refractory state. Fluorescence-activated cell sorting (FACS) was used to isolate defined HSPC compartments. VAF was determined in all populations using ddPCR. (B) VAF of SF3B1 mutations measured in different HPSC subpopulations in patients with NTN (blue) and in patients with TN (yellow): bulk BM mononuclear cells (BMMNCs; n = 13), CD34+ BMMNCs (n = 12 NTN; n = 10 TN), CD34+CD38– BMMNCs (n = 15 NTN; n = 8 TN), CD34+CD38+ BMMNCs (n = 13 NTN; n = 10 TN), HSCs (n = 11 NTN; n = 14 TN), MPP cells (n = 10 NTN; n = 14 TN), CMP cells (n = 11 NTN; n = 14 TN), GMP cells (n = 11 NTN; n = 14 TN), and MEP cells (n = 12 NTN; n = 14 TN). The numbers of investigated subpopulations in each graph reflect subpopulations with enough cells to allow for statistical comparison. A dotted horizontal line is added at 50% VAF to indicate the theoretical maximum VAF of heterozygous SF3B1 mutation. Error bars indicate the standard deviation. (C) VAF of SF3B1 mutations measured in paired samples from patients with TN: before EPO treatment (n = 9; light green), during successful EPO treatment (n = 9; dark green), and in patients who had become refractory to EPO (n = 6; red). The response samples were taken at a median of 21 months (range, 6-71 months) from start of EPO treatment. (D) VAF analysis of SF3B1 mutations in paired sequential samples from patients (n = 8) taken before and during successful EPO treatment. Analysis was performed in HSCs, and MPP, CMP, GMP, and MEP cells. Significance was tested with paired two-tailed Wilcoxon tests. Mann-Whitney U test: *P < .05; ***P < .001. CMP, common myeloid progenitor; GMP, granulocyte-macrophage progenitor; LMPP, lymphoid-primed multipotent progenitor; MEP, megakaryocyte-erythroid progenitor; MPP, multipotent progenitor; ns, not significant.$

Mutation burden of CD34⁺ BM populations is significantly lower in patients with MDS-RS with asymptomatic anemia than in patients with TN. (A) Study overview. BM samples from patients with MDS-RS were taken at diagnosis, at onset of TN, during successful ESA treatment, and in a refractory state. Fluorescence-activated cell sorting (FACS) was used to isolate defined HSPC compartments. VAF was determined in all populations using ddPCR. (B) VAF of SF3B1 mutations measured in different HPSC subpopulations in patients with NTN (blue) and in patients with TN (yellow): bulk BM mononuclear cells (BMMNCs; n = 13), CD34⁺ BMMNCs (n = 12 NTN; n = 10 TN), CD34⁺CD38^– BMMNCs (n = 15 NTN; n = 8 TN), CD34⁺CD38⁺ BMMNCs (n = 13 NTN; n = 10 TN), HSCs (n = 11 NTN; n = 14 TN), MPP cells (n = 10 NTN; n = 14 TN), CMP cells (n = 11 NTN; n = 14 TN), GMP cells (n = 11 NTN; n = 14 TN), and MEP cells (n = 12 NTN; n = 14 TN). The numbers of investigated subpopulations in each graph reflect subpopulations with enough cells to allow for statistical comparison. A dotted horizontal line is added at 50% VAF to indicate the theoretical maximum VAF of heterozygous SF3B1 mutation. Error bars indicate the standard deviation. (C) VAF of SF3B1 mutations measured in paired samples from patients with TN: before EPO treatment (n = 9; light green), during successful EPO treatment (n = 9; dark green), and in patients who had become refractory to EPO (n = 6; red). The response samples were taken at a median of 21 months (range, 6-71 months) from start of EPO treatment. (D) VAF analysis of SF3B1 mutations in paired sequential samples from patients (n = 8) taken before and during successful EPO treatment. Analysis was performed in HSCs, and MPP, CMP, GMP, and MEP cells. Significance was tested with paired two-tailed Wilcoxon tests. Mann-Whitney U test: *P < .05; ***P < .001. CMP, common myeloid progenitor; GMP, granulocyte-macrophage progenitor; LMPP, lymphoid-primed multipotent progenitor; MEP, megakaryocyte-erythroid progenitor; MPP, multipotent progenitor; ns, not significant.

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