Enzyme immunoassay and radioimmunoassay using monoclonal antibody for the determination of estrogen receptors in human breast cancer

: Enzymeimmunoassay (EIA) with monoclonal antibody against human estrogen receptor (ER) from MCF-7 breast cancer cells and radioimmunoassay (RIA) with monoclonal antibody against ER D-5 antigen from human myometrium were applied to human breast tumor, and the results were compared to those of steroid binding assay using the dextran coated charcoal (DCC) method. The rates of coincidence of positivity and negativity of ER between the DCC method and EIA or RIA in 30 human breast tumors were 96.7% (29/30) and 86.7% (26/30), respectively. A highly significant positive correlation was observed between ER values obtained by the DCC method and those by EIA (r = 0.87, P less than 0.001). On the other hand, the correlation between ER values obtained by the DCC method and those by RIA was less significant (r = 0.41, P less than 0.05). The discrepancy between these ER values may be due to the difference of the monoclonal antibody used in each new assay. The above results indicate that EIA and RIA with monoclonal antibody for human ER are useful for clinical use, although the reason for the partial discrepancy of the data between the DCC method and RIA remains to be elucidated.