Forskolin increases the expression of the pancreatic tumor antigen, Nd2, and uptake of Nd2 antibody.
Nd2 antibody recognizes an antigen that is tumor specific in pancreas. It has been used successfully in clinical radioimmunodetection studies to identify exocrine pancreatic tumors. In the present study we show that the uptake of radiolabeled Nd2 antibody by SW1990 pancreatic carcinoma cells was increased by the adenyl cyclase activator, forskolin. Dibutyryl cyclic AMP and forskolin were both effective in increasing the level of Nd2 antigen in SW1990 cells. Immunoprecipitation studies showed that the Nd2 epitope is associated with MUC1 mucin. Forskolin increased Nd2/MUC1 antigen in both a membrane fraction and a high buoyant density mucin-like fraction. Nd2 immunoreactivity was reduced by treatment of mucins with proteases and beta-mercaptoethanol. Immunohistochemical studies showed that periodate catalyzed beta-elimination greatly reduced Nd2 immunoreactivity. These results suggest that the Nd2 epitope is unusual in having characteristics of both a peptide and a carbohydrate, protease and conformation sensitivities and involvement of O-linked oligosaccharides. Nd2 antibody does not react with several known pancreatic cancer antigens. In summary, activation of the cyclic AMP pathway increased cellular uptake of Nd2 antibody and the cellular expression of the tumor-specific, mucin-associated Nd2 antigen. These results suggest a means of improving the effectiveness of monoclonal antibodies in targeting tumor antigens for the diagnosis and treatment of malignancy.
Ho
J J
JJ
Gastrointestinal Research Laboratory (151 M2), Veterans Affairs Medical Center, San Francisco, CA 94121, USA. jjl@itsa.ucsf.edu
Farrelly
E R
ER
Hong
J
J
Pan
P
P
Kim
Y S
YS
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D000912:Antibodies, Neoplasm / Q000276:immunology*; D000951:Antigens, Neoplasm / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D002236:Carbohydrate Conformation; D021441:Carcinoma, Pancreatic Ductal / Q000276:immunology / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010450:Endopeptidases / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000939:Epitopes / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006031:Glycosylation; D006801:Humans; D007124:Immunoenzyme Techniques; D008623:Mercaptoethanol / Q000494:pharmacology; D008969:Molecular Sequence Data; D018396:Mucin-1 / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D010084:Oxidation-Reduction; D010190:Pancreatic Neoplasms / Q000276:immunology / Q000378:metabolism*; D010504:Periodic Acid / Q000494:pharmacology; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D000951:Antigens, Neoplasm; D004791:Enzyme Inhibitors; D000939:Epitopes; D018396:Mucin-1; D010504:Periodic Acid; D005576:Colforsin; D008623:Mercaptoethanol; C009288:metaperiodate; D017868:Cyclic AMP-Dependent Protein Kinases; D010450:Endopeptidases