Background Tyrosine kinase inhibitor (TKI) resistance is a significant challenge in chronic myeloid leukemia (CML). Data of endothelial progenitor cells (EPCs) from bone marrow microenvironment in TKI resistance are limited.

Aims To explore whether EPCs are associated with TKI resistance in patients with CML.

Methods EPCs were isolated from TKI-sensitive or resistant patients with CML using Ficoll-Hypaque density-gradient centrifugation for co-culture with K562 cells ± TKIs. The number of EPCs and apoptosis level of K562 were detected by flow cytometry. Tube formation and migration assays were performed to evaluate the functions of EPCs. RNA sequencing was employed to analyze gene expression profiles of EPCs and K562 cells.

Results Compared with those from TKI-sensitive patients, the number of EPCs from TKI-resistant patients was reduced (0.07% ± 0.01% vs. 0.11% ± 0.02%, p = 0.139), tube formation (17005 ± 3561 vs. 41084 ± 3693, p = 0.003) and migration ability of the EPCs were impaired (103.2 ± 17.41 vs. 202.0 ± 14.59, p < 0.001). Moreover, EPCs from TKI-resistant patients exhibited higher level of reactive oxygen species (2683 ± 158 vs. 2170 ± 320, p = 0.211). Co-culture experiments demonstrated that contact-dependent endothelial-mediated resistance to imatinib was observed in the EPCs from TKI-resistant patients, characterized by reduced K562 apoptosis (22.51% ± 1.52% vs. 36.58% ± 1.88%, p < 0.001) and G0/G1 phase (31.30% ± 3.05% vs. 43.10% ± 3.59%) compared with that from TKI-sensitive patients, and similar phenomenon also occurred when nilotinib or ponatinib replaced imatinib. KEGG pathway enrichment analyses showed that cell adhesion, immune and inflammatory related pathways were enriched in EPCs from TKI-resistant patients and K562 cells co-cultured with TKI-resistant EPCs.

Conclusions Our findings suggested that EPCs from TKI resistant CML patients were dysfunctional which might contribute to TKI resistance.

Disclosures

No relevant conflicts of interest to declare.

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2024
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