CHARACTERIZATION OF A PROSTATE CARCINOMA MUCIN-LIKE ANTIGEN (PMA)

A recently identified, high m.w. human tumor antigen, reactive with mo noclonal antibody (MAb) PD41 and designated prostate mucin antigen (PM A), was found to have expression highly restricted to prostate carcino mas. Both biochemical and immunological characteristics of this antige n and its relationship to other tumor-associated mucins and various sp ecies of submaxillary mucins were evaluated. Immunohistochemical exami nation of submaxillary tissues revealed differential expression of thi s antigen and other human tumor-associated mucins, with MAb, PD41 expr ession found only in bovine submaxillary gland serous cells. Neuramini dase treatment enhanced antibody binding by 50%, suggesting partial ma sking of the PD41 epitope by sialic acid. Antigenicity was reduced by treatment with alkaline-borohydride, sodium metaperiodate, beta-galact osidase, O-glycanase, and various proteolytic enzymes. MAb PD41 antibo dy binding also could be significantly reduced by selected lectins and sugars suggesting that: the immunodominant carbohydrate involved in t he epitope was an O-linked oligosaccharide containing N-acetyl galacto samine as a major component. This antigen was further distinguished fr om T, Tn, or Sialyl-Tn antigens and blood group carbohydrate antigens by radioimmunometric analyses. Cross-blocking and double determinant W A experiments also showed a distinction between the PD41 epitope and s everal well-characterized tumor-associated mucin antigens such as MUC1 , CEA, M344, OC125, and AR3 as well as bovine submaxillary core protei n. Our results indicate that the PD41-reactive epitope is a non-acidic O-linked carbohydrate or glycopeptide epitope with restricted express ion in prostate carcinomas and bovine submaxillary glands. This expres sion is distinct from other mucin-like tumor-associated antigens ident ified in human prostate carcinomas. (C) 1995 Wiley-Liss, Inc.