SPINT1 (serine peptidase inhibitor, Kunitz type 1) is a membrane-anchored serine protease inhibitor that regulates pericellular proteolysis across multiple tissues. Primary function: SPINT1 inhibits serine proteases including HGFAC 1, matriptase/ST14 2, and TMPRSS13 3 through its BPTI/Kunitz inhibitor domain. Mechanism: SPINT1 modulates epithelial development and function by controlling E-cadherin expression in epithelial cells, including those of the choroid plexus 4. In pancreatic β cells, SPINT1 regulates glucose homeostasis and insulin production via HEPSIN/MAFA signaling; pancreas-specific disruption causes glucose intolerance and diminished islet mass 5. Disease relevance: SPINT1 expression increases in prediabetic human islets 5, suggesting involvement in diabetes pathogenesis. In triple-negative breast cancer, SPINT1 is a component of the Malignant Cell Index prognostic model 6. SPINT1/SPINT2 upregulation in breast carcinoma correlates with poor prognosis and HER2-positive status 7. Elevated SPINT1 expression associates with drug sensitivity to STAT3/STAT5 degraders in T-prolymphocytic leukemia 8. Clinical significance: SPINT1 represents a potential prognostic biomarker and therapeutic target in multiple malignancies and metabolic disorders.