SDC1 and breast cancer: Abnormal GAG accumulation, especially of chondroitin sulfate, is associated with poor prognosis in both BC and TC (Yen et al., 2024; Sui et al., 2024), while SDC-1, a heparan sulfate proteoglycan, promotes invasion via cell-cell and cell-ECM adhesion (Bologna-Molina et al., 2010; Hassan et al., 2023).