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IL-4 contributes to thrombocytopenia in AML
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Figure 6. Targeting interleukin-4 cooperates with chemotherapy to enhance platelet recovery in acute myeloid leukemia mice. (A) Diagram of the experimental design: mice transplanted with CD45.1+ leukemic cells were treated with cytarabine (AraC) (60 mg/kg/day) for 1 week from day 15, with or without anti-interleukin- 4 (anti-IL-4) (10 mg/kg/day) for 5 days. The peripheral blood (PB) analysis was performed on day 22. (B) Percentage engraftment of CD45.1+ leukemic cells in mice untreated (AML Ctrl) or treated as in (A): engraftment assessed in the PB. Five mice per group, three independent experiments. (C) Counts of platelets (Plt), erythro- cytes (RBC) and leukocytes (WBC) in PB of mice injected with AraC alone or combined with anti-mIL-4. Five mice per group, three independent experiments. (D) Survival curves of recipient mice given different treatments as shown in (A). Five mice per group, three independent experiments. *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001. ns, no significant difference. Error bars represent the standard error of mean.
comparison of the megakaryocytic differentiation land- scape between leukemia and healthy control mice revealed a marked reduction of MK differentiation from MPP2 and LT-HSC via both the canonical and non-canon- ical pathways, which was fundamentally responsible for the decreased MK in AML BM. Transcriptome analysis of MK from animals with AML showed severely impaired maturation and platelet-producing capacity. Additionally, we discovered an excessive production of IL-4 by BM endothelial cells and found that this had a striking role in suppressing MK differentiation from MPP2 and MK mat- uration in vivo, which might contribute to the thrombocy- topenia of mice with AML. Finally, our preclinical data using pharmacological approaches to inhibit IL-4 in com- bination with AraC treatment showed that targeting IL-4
represents a promising strategy to improve the therapeu- tic responses in AML.
By performing colony assays on whole BM cells, Capitano et al.45 recently found that IL-4, in synergy with transforming growth factor-β1, could inhibit hematopoi- etic progenitor cell colony formation. Our results further demonstrated that IL-4 had a unique inhibitory effect on colony-forming unit-MK formation without affecting other lineages, which was consistent with a previous study that assessed human CD34+ cells.37 NF-E2 transcrip- tion factor has been identified as an essential factor for terminal MK maturation and normal platelet production.46 It has been shown that IL-4 downmodulated the expres- sion of NF-E2 transcription factor at both the mRNA and protein levels in normal maturing megakaryocytic cells
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