The mucin antigens: what are we measuring?

Serum of breast cancer patients contains high molecular weight, mucin-like glycoproteins which are held to be differentiation markers for certain types of normal epithelia, in particular mammary epithelium. These components have primarily been identified using monoclonal antibodies raised against human milk fat globule membranes, tumour extracts or purified mucins. Even so, many of the antibodies produced react with a discrete region of the mucin protein core involving the hydrophilic turn domain APDTRPAP. The present investigation using the anti-urinary mucin antibody, C595, illustrates both the clinical potential of the mucin antigens in breast cancer studies as well as the exquisite specificity of immune recognition of a complex polymorphic glycoprotein at the level of the individual amino acids.