Page 133 - Haematologica Vol. 110 - January 2025

ARTICLE - CITE-seq analysis of HU effects on CML cells Discussion
Although many CML patients currently receive a course of cytoreductive treatment with HU prior to starting TKI therapy, this is to our knowledge the first study to report effects of this treatment on the SPC. As HU pre-treatment is indicated only in a subgroup of patients (those with high white blood cell counts or high platelet counts7,25), HU-related effects on the SPC compartment may affect conclusions of CML studies utilizing diagnostic samples from patients who have or have not received prior HU treatment. In this study, detailed proteo-transcriptomic CITE-sequencing analysis of SPC obtained from chronic phase CML patients before or after HU treatment indicated
H. Komic et al.
multiple HU-induced transcriptional changes within this compartment, including (i) increased erythroid maturation, and (ii) an increased proportion of cells in S/G2/M phase. Paired and unpaired comparisons of SPC from peripheral blood and BM samples implied increased frequencies of cells appearing in the most mature hemoglobin subunit-express- ing erythroid clusters (EP-II/EP-IV) following HU treatment, which is in line with previous studies linking HU treatment to erythroid differentiation, in part via NO-induced GATA1 activation, in other contexts.13,26 A recent study by Krishnan et al. suggested that CML patients with a high degree of erythroid differentiation prior to TKI treatment were more likely to respond favorably to the TKI therapy; however, it did not take prior HU treatment into account.27 In our
A
Figure 7. Hydroxyurea increases the fraction of cells in S/G2/M phase among the most immature leukemic stem cells. (A) Anno- tation of CD14-CD34+CD38- cells in the paired CITE-sequencing dataset based on cell label transfer from a previously published dataset of CD14-CD34+CD38- healthy/chronic phase chronic myeloid leukemia bone marrow cells (Nilsson et al.19). (B) Distribution of cells annotated as immature HSC-I, HSC-II, LSC-I, and LSC-II across the uniform manifold approximation and projection (UMAP). (C, D) Proportion of (C) stem cells annotated as HSC (HSC-I and HSC-II), LSC-I and LSC-II in each analyzed sample (after HU samples were collected after 7-9 days of hydroxyurea treatment), and (D) cells in G0/G1 versus S/G2/M phase in each stem cell subset. CP-CML: chronic phase chronic myeloid leukemia; BCP: B-cell progenitors; EP: erythroid progenitors; EBMP: eosinophil/ basophil/mast cell progenitors; HSC: hematopoietic stem cells; LMP: lympho-myeloid progenitors; LSC: leukemic stem cells; MDP: monocyte/dendritic cell progenitors; MEP: megakaryocytic/erythroid progenitors; MKP: megakaryocytic progenitors; NP: neutrophil progenitors; HU: hydroxyurea.
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