GPC1 and breast carcinoma: As such, the upregulation of two cell-surface PGs, glypican-1 (GPC1) and syndecan-1 (SDC1), and of the extracellular sulfatase Sulf-2, have been described in malignant breast cancer tissues [9,10] whilst the downregulation of some genes including SULF1 and HS3ST2 has also been reported [11-13].