Investigation of the role of IFITM3 and the PI3K/Akt axis in the acute myeloid leukemia tumor microenvironment.

6522 Background: Interferon-induced transmembrane protein 3 (IFITM3) is overexpressed in acute myeloid leukemia (AML) and is associated with poor prognosis. Previous studies have implicated IFITM3 in oncogenic processes and immune modulation; however, the mechanisms through which IFITM3 contributes to leukemogenesis and shapes the immune microenvironment in AML remain unclear. Methods: The clinical and immunological significance of IFITM3 in AML was analyzed using scRNA-seq and bulk transcriptomic datasets. IFITM3-knockdown Kasumi-1 and ME-1 cells were established to evaluate their impact on cell proliferation and cycle progression via MTT and flow cytometry. A Transwell co-culture system was employed to assess AML-induced M0 macrophage polarization, quantified by surface markers (CD80/CD163) and cytokine profiling (ELISA/qRT-PCR). Mechanistically, GSEA were performed to identify downstream pathways, followed by Western blot validation. The functional role of the PI3K/Akt axis was further verified using the specific inhibitor LY294002. Results: Our results revealed for the first time that IFITM3high AML cell lines polarize M0 macrophages into an M2-like phenotype. Knockdown of IFITM3 led to a significant reduction of the M2 marker CD163, accompanied by an increase of the M1 marker CD80. In parallel, IFITM3-deficient AML cells exhibited decreased M2-associated gene expression and diminished secretion of TGF-β and IL-10, together with lower viability and G0/G1 cell-cycle arrest. Molecular mechanism studies revealed that loss of IFITM3 markedly reduced Akt and p-Akt protein levels. Crucially, pharmacological inhibition of the PI3K/Akt pathway using a PI3K inhibitor rescued the IFITM3-mediated effects, suppressing AML cell proliferation and M2 macrophage polarization. Clinically, we extended the adverse prognostic effect of IFITM3 to AML patients with intermediate molecular risk. Conclusions: These findings provide comprehensive evidence that IFITM3 promotes leukemic cell proliferation and contributes to a tumor-supportive AML microenvironment by driving M2 macrophage polarization via the PI3K/Akt signaling axis. These results highlight IFITM3 as a promising therapeutic target and suggest that PI3K inhibitors may offer a precision medicine approach for AML patients with elevated IFITM3 expression.