PGF and neoplasm: The Tag protein comprises a super-folded green fluorescent protein dimer (diGFP) fused to the heparin-binding domain (HBD) of placental growth factor-2 (PlGF-2), achieving dual functional advantages: (1) The HBD facilitates binding to tumor-associated extracellular matrix components such as collagen, fibronectin, and heparan sulfate proteoglycans (HSPGs), thereby restricting protein diffusion to enhance localization specificity and systemic safety; (2) The diGFP moiety serves as a synthetic antigen that promotes CAR-T cell polarization and amplifies anti-tumor cytotoxicity.