Polymorphic epithelial mucins (PEM): molecular characteristics and association with breast cancer

Human mammary cells express at their surfaces polymorphic epithelial mucins (PEM) which are developmentally regulated and are aberrantly expressed in tumours. These molecules have been identified as target antigens for a variety of monoclonal antibodies raised against materials such as products from human milk and breast tumour extracts. Anti-PEM antibodies have been shown to display useful tumour-related reactivity and their application in immunoassays for circulating mucin in cancer patients provides information relevant to assessing tumour burden and response to therapy. Further, these antibodies have yet to realise their full potential for in vivo diagnosis by immunoscintigraphy and in treatment by radioimmunotherapy. The development of anti-PEM monoclocal antibodies has been central to investigations on the nature and characteristics of PEM molecules as well as their exploitation in a clinical context. Not only have these antibodies proved of value in defining antigen expression in tissues and established the bases for antigen immunoassay, but they have provided insight and understanding at the molecular level of antibody specificity for malignant cells.