IFITM1 is an interferon-induced antiviral protein that restricts viral entry by blocking fusion of viral and cellular membranes after endocytosis, rather than preventing viral uptake. It is active against multiple enveloped viruses including influenza A, SARS-CoV and SARS-CoV-2, Marburg, Ebola, dengue, West Nile, HIV-1, and hepatitis C virus. Beyond its antiviral role, IFITM1 participates in cell growth control through interferon-gamma signaling and osteoblast differentiation. In cancer contexts, IFITM1 is overexpressed in multiple tumor types including gallbladder carcinoma, esophageal adenocarcinoma, colorectal cancer, and gastric cancer, where it serves as an independent prognostic biomarker 1. High IFITM1 expression promotes tumor cell proliferation, invasion, metastasis, angiogenesis, and therapeutic resistance to endocrine, chemotherapy, and radiation treatments 1. In lung adenocarcinoma, IFITM1 upregulation through STING-TBK1-IRF3 signaling amplifies invasive FoxM1-mediated tumor-associated macrophage polarization and immune escape 2. IFITM1 is identified as a diagnostic gene for Helicobacter pylori-associated gastric cancer in transcriptomic studies 3. During pregnancy, elevated IFITM1 impairs placental syncytiotrophoblast formation and promotes fetal demise in the context of congenital infections 4. Targeting IFITM1 represents a potential therapeutic strategy for cancer treatment.