IFITM3 promotes an M2-like tumor-supportive microenvironment in acute myeloid leukemia

Interferon-induced transmembrane protein 3 (IFITM3) is overexpressed in acute myeloid leukemia (AML) and is associated with poor prognosis. Previous studies implicate IFITM3 in oncogenic processes and immune modulation; however, the mechanisms by which IFITM3 contributes to leukemogenesis and shapes the AML immune microenvironment remain unclear. Here, we integrated single-cell RNA sequencing (scRNA-seq) and bulk gene expression analyses with macrophage polarization assays using IFITM3^high AML cell lines and their corresponding IFITM3 knockdown models, together with gain-of-function experiments in IFITM3^low HL-60 cells, alongside functional assays and pharmacologic perturbations, to define the immunological function of IFITM3 in AML. Our results revealed for the first time that IFITM3^high AML cell lines polarize M0 macrophages toward a M2-like phenotype. IFITM3 knockdown significantly reduced the M2 marker CD163 and increased the M1 marker CD80. Consistently, IFITM3-deficient AML cells decreased M2-associated gene expression and diminished secretion of TGF-β and IL-10, together with lower viability and G1/G0 cell-cycle arrest. Conversely, enforced IFITM3 expression in HL-60 cells biased macrophages toward a predominantly M2-like state, whereas vector controls promoted a mixed M1/M2 pattern. Mechanistically, loss of IFITM3 reduced total PI3K and AKT protein levels and markedly decreased PI3K/AKT phosphorylation. Pharmacologic PI3K inhibition with LY294002 suppressed PI3K/AKT phosphorylation and specifically attenuated IFITM3-dependent M2 polarization and associated cytokine programs, while also reducing leukemic cell proliferation in co-culture. Clinically, we extended the adverse prognostic effect of IFITM3 to AML patients with intermediate molecular risk. These findings provide comprehensive evidence that IFITM3 contributes to a tumor-supportive AML microenvironment by driving M2 macrophage polarization, highlighting IFITM3 as a potential therapeutic target in IFITM3^high AML.