BIOCHEMICAL AND IMMUNOHISTOCHEMICAL DETECTION OF THE EPIDERMAL GROWTH-FACTOR RECEPTOR (EGF-R) IN BREAST-TUMOR SPECIMENS

Analyses of the level of expression of the epidermal growth factor rec eptor (EGF-R) of breast cancer tumors may add independent information about the prognosis of individual patients. Furthermore, the use of mo noclonal antibodies directed against EGF-R as therapeutic tools (e.g., Mab 425) requires a reliable evaluation of the individual EGF-R conte nt. Various analytical methods have been published, including (Scarff RW and Torloni H: World Health Organization, Geneva, 1968), biochemica l detection of EGF-R by a radiolabeled physiologic ligand I-125!EGF, (Early Breast Cancer Trialists' Collaborative Group: Lancet 329: 1-15, 1992) biochemical analyses of EGF-R content with a monoclonal antibod y, and (McGuire WL and Clark GM: N Engl J Med 326: 1756-1761, 1992) im munohistochemical EGF-R detection. We measured the EGF-R content in me mbrane pellets derived from routine processing for evaluation of estro gen (ER, ER-EIA) and progesterone receptor (PgR; PgR-EIA) in 185 breas t cancers and 18 benign breast samples, using a single-point saturatio n assay (RBA). Simultaneously, ER (ER-ICA), PgR (PgR-ICA), and EGF-R i mmunohistochemistry was performed on frozen sections of the same tumor s. Various cell lines and normal skin tissue samples served as EGF-R p ositive or negative controls. The results of the two different EGF-R a nalyzing methods were compared with other biological characteristics o f the tumors. 37% of the tumors were EGF-R positive. There was an inve rse correlation between the ER or PgR and the EGF-R content. EGF-R ove rexpression correlated with high tumor grade. Analyses of EGF-R conten t in membrane pellets of breast cancer samples by single point saturat ion assay as well as the evaluation of tumor sections by immunohistoch emistry can be performed routinely. The results obtained with both ana lytical methods did not differ significantly. but the immunohistochemi stry proved to be more difficult to perform and to interpret. Thus, we prefer to perform both analytical methods simultaneously to provide i nformation potentially useful for clinical management of individual ca ncer patients.