MODIFICATION OF THE ROUTINE BIOCHEMICAL-ANALYSIS OF THE EPIDERMAL GROWTH-FACTOR RECEPTOR (EGF-R) ON BREAST-TUMOR SPECIMENS

Analyses of the level of expression of the epidermal growth factor rec eptor (EGF-R) in breast cancer specimens may add independent informati on on the prognosis for individual patients. Furthermore, the use of t he therapeutic potential of monoclonal antibodies (e. g., Mab 425) dir ected against EGF-R requires a reliable evaluation of the EGF-R conten t. Various analytical methods have been published, including (1) bioch emical detection of EGF-R by a radioactively labeled physiologic ligan d of [I-125]EGF, (2) biochemical analysis EGF-R content with a monoclo nal antibody, and/or (3) immunohistochemical detection and localizatio n. We measured the EGF-R content in membrane pellets derived from rout ine processing for evaluation of estrogen (ER) and progesterone recept or (PgR) in 100 breast cancer samples by using a modified single-point saturation assay. This modified assay method was tested on tumor samp les derived from EGF-R-expressing, xenotransplanted tumors and on memb ranes from the squamous vulvar carcinoma cell line, A431. The results of the EGF-R analyses were compared with other biological characterist ics of the tumors, such as ER and PgR, and with their histopathologic grading. Thirty-three of the tumors examined were EGF-R-positive accor ding to the cut off point, which we employed. There was a positive cor relation between EGF-R content and tumor grade; this correlation was m ore pronounced in premenopausal than in postmenopausal patients. The c orrelation between ER/PgR and EGF-R content was inverse. Analyses of E GF-R content in membrane pellets of breast cancer samples can be perfo rmed routinely with the modified single-point saturation assay.