MMRN1-EGFR drives sialylglycan-Siglec immune evasion in AML leukemia stem cells.

Leukemia stem cells (LSCs) drive acute myeloid leukemia (AML) relapse and therapy resistance, predominantly through immune evasion. Here, we identify multimerin 1 (MMRN1) as being highly and specifically expressed in LSCs. Mechanistically, MMRN1 activates the epidermal growth factor receptor (EGFR)/signal transducer and activator of transcription 1 (STAT1) pathway via its epidermal growth factor (EGF)-like domain, suppressing Neu5Ac degradation to drive sialylglycan accumulation, which forms glycoimmune checkpoints functionally akin to programmed death 1 (PD-1)/the cytotoxic T-lymphocyte antigen-4 (CTLA-4). These sialylglycans activate the sialylglycan-Siglec immune checkpoint axis, impairing T/natural killer (NK) cell activity and enabling LSC immune evasion. Additionally, MMRN1 sustains LSC self-renewal via the EGFR/STAT5/CD9 pathway. Genetic ablation of MMRN1 markedly suppresses AML progression and synergizes with anti-PD-L1/CTLA-4 therapy. In a clinical trial (ChiCTR2500097714), erlotinib (an EGFR inhibitor) combined with azacitidine plus the HAG regimen, which consists of homoharringtonine, a low dose of cytarabine, and granulocyte colony-stimulating factor priming, achieves a remission rate of 75% in relapsed/refractory AML, likely via MMRN1/EGFR axis blockade. Our findings establish MMRN1 as a dual-functional target for LSC maintenance and immune evasion and propose that disrupting MMRN1 or EGFR remodels the immunosuppressive tumor microenvironment, offering a promising strategy for AML immunotherapy.