Molecular expression of epitopes recognized by monoclonal antibodies HMFG-1 and HMFG-2 in human breast cancers: diversity, variability and relationship to prognostic factors

Epitopes recognised by the monoclonal antibodies HMFG-1 and HMFG-2 are found on glycoprotein components in human breast cancers. This study used immunoblotting techniques to ascertain their molecular diversity, assess their relationship to known prognostic factors, and investigate their expression in sequential samples of breast tumours from individual patients. Both epitopes were expressed on components of a wide variety of molecular weights (HMFG-1, 130 to 450kDa; HMFG-2, 90 to 450kDa). The HMFG-2 epitope was expressed more frequently on components of less than 200kDa (p less than 0.0001). Progesterone receptors (PR), small tumour size and low histological grade correlated significantly with HMFG components greater than or equal to 300kDa. Higher staining intensity was associated with increased likelihood of PR positivity. Paired sequential samples were taken, with a median interval of 8 days, from 38 patients, 23 of whom were administered tamoxifen. In the majority of tumours profiles of expression of components carrying the epitopes were identical in both samples (HMFG-1, 30/38; HMFG-2, 22/38). Overall the results suggested that there was no consistent relationship between the differences observed and tamoxifen administration. We conclude that expression of the HMFG-1 and HMFG-2 epitopes is relatively constant in most tumours, but variable (and possibly subject to modulation) in others, and that their expression, particularly on high molecular weight components, is related to factors associated with good prognosis (PR, small size, low grade), and may be of independent prognostic value.