A monoclonal antibody CIBr17 recognizes a myoepithelium-specific antigen in human mammary gland

A murine monoclonal antibody (MAb) CIBr17, raised against the human breast carcinoma cell line PMC42, reacts specifically with myoepithelial cells in normal human breast. This IgGl antibody recognizes a approximately 110kDa glycoprotein that is expressed on the cell surface and junctional membranes of PMC42 monolayer cultures. The CIBr17 antigen is present in two major glycosylated forms with approximate pls of 5.2 and 5.5 respectively in PMC42 cells. The tissue specificity of CIBr17 was assessed on frozen sections of PLP-fixed tissues by means of a 4-layer immunoperoxidase technique. CIBr17 has reacted with a variety of epithelium-derived tissues and some smooth muscle cells. Within many epithelial tissues, CIBr17 has demonstrated specific staining of particular epithelial cell types. Within normal breast and most benign breast lesions, antibody CIBr17 stained only myoepithelial cells. No staining of luminal epithelium, basement membranes or stromal elements was observed. In sclerosing adenosis, CIBr17 stained areas of pronounced myoepithelial differentiation, while in duct epitheliosis variable staining of proliferating cells was observed. In breast carcinomas, CIBr17 demonstrated variable antigen expression. In most tumors, CIBr17 either did not stain any tumor cells or stained only a small number of tumor cells spread randomly throughout the tumor. In several ductal carcinomas, however, CIBr17 stained the majority of tumor cells.