Objective: To investigate the expression of the neu protein antigen in non-neoplastic, mammary epithelial cells of prepartum and actively lactating women.
Methods: Formalin-fixed, paraffin-embedded sections from breast biopsies obtained from four prepartum and seven postpartum, lactating women were stained for neu antigen with one commercially available monoclonal antibody (Ab 3), one commercially available polyclonal antibody (Ab-1), and another independently prepared polyclonal antibody (21N). Antigen competition experiments were carried out alongside as negative controls, and two strongly neu-positive breast carcinomas were included as positive controls.
Results: Membranes and cytoplasmic elements of two of the four prepartum and four of the seven lactating specimens stained as strongly or nearly as strongly for neu antigen as did those of the breast carcinomas.
Conclusion: Our results demonstrate the expression of neu antigen by mammary epithelial cells just before and during lactation and suggest a possible role for this receptor in the lactational differentiation of the normal female breast.