Extracellular SPON2 Protein Inhibits Metabolism by Blocking Glutamine Uptake to Coordinate Mammary Morphogenesis and Cancer Suppression
This study identifies the basal-derived extracellular protein SPON2 as a metabolic checkpoint that suppresses mammary morphogenesis and breast cancer by directly binding the glutamine transporter SLC38A1 to restrict nutrient uptake, thereby inhibiting mTORC1 signaling and epithelial expansion.