IFITM1 is an interferon-induced antiviral protein that functions as a potent restriction factor against multiple viruses by inhibiting viral entry into host cell cytoplasm 12. It blocks fusion and release of viral contents following endocytosis, acting against influenza A, SARS-CoV-2, HIV-1, hepatitis C virus, and others 12. IFITM1 inhibits viral spike protein-mediated entry and, in hepatocytes, coordinates with other IFITM family members to target enveloped virions for lysosomal degradation 1. Mechanistically, IFITM1 prevents membrane fusion events critical for viral and extracellular vesicle entry 3. Beyond antiviral functions, IFITM1 regulates cell growth arrest via p53-dependent mechanisms and promotes osteoblast differentiation 2. However, in cancer contexts, IFITM1 is frequently upregulated and promotes tumor progression through enhanced cell proliferation, invasion, metastasis, and therapeutic resistance across multiple cancer types including gastric, esophageal, and colorectal cancers 45. In lung adenocarcinoma, IFITM1 upregulation via STING-TBK1-IRF3 signaling amplifies oncogenic FoxM1 signaling and facilitates immune escape through PD-L1 upregulation 6. Clinically, elevated IFITM1 expression predicts poor prognosis in multiple malignancies, suggesting therapeutic targeting of IFITM1 may improve cancer outcomes 54. Notably, IFITM1 also exhibits context-dependent roles in some coronavirus infections and pregnancy complications, highlighting its pleiotropic effects 7.