Recombinant breast carcinoma-associated mucins expressed in a baculovirus system contain a tumor specific epitope

Mucins are highly immunogenic glycoproteins that are abundantly expressed by breast and other adenocarcinomas. In order to progress in the understanding of the structure immunity relationship of the breast tumor associated mucin and normal tissue mucin, two forms of breast carcinoma associated mucin, muc7-BV and pem-BV, were expressed in a baculovirus expression system. The muc7-BV was constructed by inserting the seven tandem repeats of mucin core cDNA fragment into transfer vector pAc360, forming a fusion protein containing 14 amino acids of the baculovirus polyhedrin N-terminus. The pem-BV was constructed by cloning full-length mucin cDNA into the transfer vector pVL1392. The recombinant mucins were purified using immunoaffinity chromatography. The purified muc7-BV and pem-BV had molecular weights of 28 and 59 kd, respectively. No carbohydrate was detected on these recombinant mucins and is speculated to explain why both forms of recombinant mucin showed strong affinity to tumor-specific monoclonal antibody SM3. These recombinant mucins may have the potential value to develop vaccines against breast and other adenocarcinomas and to induce cytotoxic T-lymphocyte lines for immunotherapy of the same.