Human embryonal carcinoma tumor antigen, Gp200/GCTM-2, is podocalyxin.
We previously characterized a peanut agglutinin-binding tumor antigen, gp200, a surface membrane glycoprotein expressed on human embryonal carcinoma, a malignant stem cell of testicular tumors. Gp200 is remarkably similar to another embryonal carcinoma antigen, GCTM-2, a cell differentiation marker that is also detected in blood of testis cancer patients, yet neither molecular identity is known. We now report the identity of gp200 as podocalyxin. Protein sequence results of gp200 peptides match with podocalyxin sequence. Furthermore, two distinct monoclonal antibodies, specific for podocalyxin, react positively with gp200. Therefore, gp200 is a testicular tumor form of podocalyxin, a surface membrane glycoprotein that was originally discovered as a scaffolding extracellular matrix protein of kidney podocyte cells. Podocalyxin is also expressed on subsets of hematopoietic cells where it has a putative function as a cell adhesion protein. This is the first report of podocalyxin expression on malignant cells.
Schopperle
W Michael
WM
Division of Urology, Urological Research Laboratory, Beth Israel Deaconess Medical Center, Dana 838, 330 Brookline Ave., Boston, MA 02115, USA. wschoppe@caregroup.harvard.edu
Kershaw
David B
DB
DeWolf
William C
WC
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology; D000951:Antigens, Neoplasm / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D018236:Carcinoma, Embryonal / Q000276:immunology*; D006801:Humans; D008297:Male; D019887:Peanut Agglutinin / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012795:Sialoglycoproteins / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D013736:Testicular Neoplasms / Q000276:immunology*; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D019887:Peanut Agglutinin; D012795:Sialoglycoproteins; C001643:podocalyxin