Year: 2026
Type: article
Abstract: FLT3-ITD is associated with poor prognosis in acute myeloid leukemia (AML) and has been implicated in immune dysregulation. Whether FLT3-ITD alone is sufficient to modulate NK-cell functional ligands before overt leukemic transformation remains unknown. We investigated this question using a preleukemic Flt3-ITD knock-in mouse model. Peripheral blood counts were performed in Flt3WT (n=8), Flt3HET (n=18), and Flt3HOMO (n=6) mice to characterize the hematologic phenotype. Subsequently, bone marrow from a representative subset of animals (Flt3WT, n=3; Flt3HET, n=2; Flt3HOMO, n=2) was analyzed by multiparameter flow cytometry. A standardized flow cytometry panel was used to identify hematopoietic stem/progenitor cells (LSK; Lin−Sca-1+c-Kit+) and simultaneously evaluate both the frequency of ligand-positive cells and the mean fluorescence intensity (MFI) of activating (CD80, CD86, RAE-1, CD112, and CD155) and inhibitory (Qa-1, PD-L1, and Galectin-9) NK-cell ligands. Peripheral blood analysis demonstrated an early myeloid phenotype characterized by increased granulocyte and reduced lymphocyte frequencies, particularly in Flt3HOMO mice, whereas erythroid parameters, platelet counts, and monocyte counts remained unchanged, consistent with the preleukemic stage of the model. LSK frequencies were comparable among Flt3WT, Flt3HET, and Flt3HOMO mice, indicating preservation of the hematopoietic stem/progenitor compartment. Flow cytometric analysis showed no consistent genotype-associated differences in either the frequency of ligand-positive cells or ligand expression (MFI). Although the frequency of CD86-positive LSK cells was reduced in Flt3HOMO mice (p<0.05), no corresponding differences in MFI or in the remaining activating and inhibitory ligands were observed, supporting preservation of the overall NK-ligand profile. These findings indicate that, despite early hematopoietic alterations associated with Flt3-ITD, the mutation alone is insufficient to broadly modulate NK-cell functional ligands on hematopoietic progenitors before leukemic transformation. These results suggest that additional leukemogenic events and/or microenvironmental remodeling are required to establish the NK-cell immune landscape characteristic of overt AML. This work was supported by the São Paulo Research Foundation (FAPESP; Grant Nos. 2021/06841-3, 2023/17838-9, 2026/01063-6, and 2024/13669-0), the National Council for Scientific and Technological Development (CNPq; Grant No. 311364/2022-5 and a PIBIC undergraduate research scholarship), and the Coordination for the Improvement of Higher Education Personnel (CAPES).
Institution: Universidade de São Paulo
Language: English
Subfield: Hematology
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W7223108878