A Mr 46,000 human milk fat globule protein that is highly expressed in human breast tumors contains factor VIII-like domains.

The human milk fat globule has proved to be a good source of antigenic material for production of antibodies against surface components of breast epithelial cells. Monoclonal antibodies against one of the major components of the human milk fat globule, which identify a glycoprotein with an apparent molecular weight of 46,000, have been found to be useful for both breast cancer diagnosis and therapy. In order to characterize this Mr 46,000 glycoprotein, specific monoclonal antibodies were used to select complementary DNAs from a lambda gt11 expression library from lactating breast.