Glypican-3 (GPC3) is the first glypican that was cloned (Filmus et al. 1988). Initially named OCI-5, GPC3 was identified in 1988 as a gene whose expression was developmentally regulated in the intestine. Two years later, the cloning of Glypican-1 (GPC1) was reported. This report characterized GPC1 as a glycosylphosphatidylinositol (GPI)-anchored heparan sulfate proteoglycan (HSPG), but it did not indicate that GPC1 displays significantly homology with GPC3 (David et al. 1990). This homology was noticed 4 years later in a study that reported the cloning of Glypican-2 (initially called cerebroglycan) (Stipp et al. 1994). This study established for the first...