ST6GAL1 and breast cancer: These cells can serve as monitoring biomarkers or key elements in blood-based non-invasive liquid biopsies, providing crucial diagnostic and treatment-related information to guide personalized treatment decisions.239 Research indicates that CTCs in multicellular clusters, which exhibit stem cell properties, have a 20-100-fold higher metastatic potential compared to individual cells.240 In BC patients, dynamic alterations in CTCs involving low sialylation or ST6GAL1 defects promote the seeding of CTCs in cluster form and enable evasion of paclitaxel therapy.