ST6GAL1 and cancer: The ST6GAL1 membrane-bound form is packed in sEVs from bone metastatic C4-2B cells but not from DU145 cells, which do not metastasize to bone; we thus propose that the ST6GAL1 membrane-bound form in sEVs may help the donor cancer cells to promote bone metastasis by targeting local cells, as osteoblasts or osteoclasts [47].