[Molecular biological analyses of mucin core proteins and their clinical application]

Recent molecular biological approach has revealed the primary structure of some mucin core proteins. Most prominent characteristic is tandemly repeated sequences. cDNA cloning of 6 kinds of mucin core proteins, MUC1-6, have thus been performed. Among them, the entire structure was revealed on MUC1 and 2. MUC 1 is a type I transmembrane protein with a large number of tandem repeat consisting of 20 amino acids. We have found that mouse MoAb MUSE11 against adenocarcinoma, which detects circulating MUC1 in patients with gastrointestinal and pancreatic cancers, recognizes part of the tandem repeat of MUC1 using synthetic peptides. To date, some of the MoAbs to adenocarcinoma which were prepared for the last decade have been shown to react with the tandem repeat of MUC1(MUC1 epitope), suggesting that MUC1 epitope could be highly immunogenic in human. Recently, cytotoxic T-cells against MUC1 epitope were established from breast and pancreas cancer patients. We could also induce those T-cells from the patient with multiple myeloma. Interestingly, CTL functions in a HLA-unrestricted manner, and may be of use as an adoptive immunotherapy. In addition, we have found antibody against MUC1 epitope in patients with ulcerative colitis or colon cancer. EB virus-transformed B-cell clone producing antibody against MUC1 epitope has been established from a cancer patient. Thus, MUC1 is now considered as a targeting molecule for immunotherapy. Indeed, Longenecker's group in Canada has recently tried the basic evaluation for immunotherapy using synthetic peptides of MUC1.