SDC2 (syndecan-2) is a cell surface heparan sulfate proteoglycan that functions as a co-receptor regulating cell signaling and extracellular matrix interactions 1. Structurally, SDC2 contains PDZ domain-binding regions and functions in dendrite morphogenesis and synapse assembly 2. Mechanistically, SDC2 serves as a co-receptor for growth factors including FGF2 and VEGF, facilitating signaling pathway activation 3. In human spermatogenesis, PTN-SDC2 interactions activate GFRA1 expression and HIF-1 signaling, promoting spermatogonial stem cell proliferation and self-renewal 2. In cancer biology, SDC2 exhibits oncogenic potential. In gastric cancer, SDC2 upregulation correlates with poor prognosis and promotes AKT pathway activation through PDK1 interaction, facilitating tumor growth and invasion 3. High SDC2 expression in cancer-associated fibroblasts is linked to aggressive phenotypes and poor survival 4. In colorectal cancer, fecal SDC2 gene methylation shows 93.33% sensitivity and AUC of 0.981, outperforming conventional tumor markers for early detection 5. Combined detection of SDC2 with SFRP2 and Fusobacterium nucleatum improves early CRC screening efficacy 6. Clinically, SDC2 represents a promising diagnostic biomarker and therapeutic target. USP14-mediated SDC2 stabilization offers a druggable pathway; USP14 inhibitors decrease SDC2 abundance in cancer cells 3. In pulmonary fibrosis, SDC2-derived peptides activate CD148 phosphatase, reducing fibroblast activation 7. These findings establish SDC2 as a multi-functional oncogenic protein with diagnostic and therapeutic significance across multiple cancer types.