Targeting the neurophysin-related cell surface antigen on small cell lung cancer cells using a monoclonal antibody against the glycopeptide region (MAG-1) of provasopressin.
The vasopressin (VP) gene is largely expressed in hypothalamic neurons, where the resultant pro-VP protein is enzymatically cleaved into its peptide hormone components, which include the neuropeptide VP, VP-associated neurophysin, and VP-associated glycopeptide (VAG). Small cell lung cancer (SCLC) tumors also express the VP gene, but the tumor pro-VP protein can remain intact and localize to the cell surface membrane. Previous studies have shown that polyclonal antibodies directed against different regions of the pro-VP protein bind specifically to the surface of cultured SCLC cells and recognize proteins of approximately 20 and approximately 40 kDa in cultured SCLC whole-cell lysate. Thus, these proteins have been designated neurophysin-related cell surface antigen (NRSA). A monoclonal antibody (mAb) designated MAG-1 was raised in this laboratory using a synthetic peptide representing the COOH-terminal sequence of VAG. The MAG-1 mAb recognizes NRSA in SCLC cell and tissue lysates by Western analysis, whereas immunofluorescent cytometric and microscopic analyses indicate that MAG-1 reacts specifically with NRSA on the surface of viable SCLC cells of both the classical and the variant subtype. Immunohistochemical analysis demonstrates that MAG-1 reacts with human SCLC tumor, but not with normal pulmonary epithelial cells in lung tissue. Additionally, a MAG-1 Fab fragment was generated that was also able to recognize NRSA. This is the first study to demonstrate that a mAb directed to the VAG region of the pro-VP protein has the potential for development into an in vivo diagnostic and therapeutic tool that targets plasma membrane-incorporated NRSA.
Keegan
Brendan P
BP
Departments of Physiology, Dartmouth Medical School, Lebanon, New Hampshire 03756, USA.
Memoli
Vincent A
VA
North
William G
WG
D000818:Animals; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000032:analysis*; D000954:Antigens, Surface / Q000032:analysis*; D001127:Arginine Vasopressin; D015153:Blotting, Western; D018288:Carcinoma, Small Cell / Q000276:immunology*; D006023:Glycoproteins / Q000276:immunology*; D007124:Immunoenzyme Techniques; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008175:Lung Neoplasms / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009481:Neurophysins / Q000276:immunology*; D010121:Oxytocin; D011498:Protein Precursors / Q000276:immunology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D014667:Vasopressins / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D006023:Glycoproteins; D009481:Neurophysins; D011498:Protein Precursors; D014667:Vasopressins; D001127:Arginine Vasopressin; D010121:Oxytocin