EPIDERMAL GROWTH-FACTOR RECEPTOR EXPRESSION BY NORTHERN ANALYSIS AND IMMUNOHISTOCHEMISTRY IN BENIGN AND MALIGNANT PROSTATIC TUMORS

Epidermal growth factor receptor (EGFR) expression in 44 benign prosta tic hyperplasia (BPH) and 55 prostatic carcinoma specimens has been in vestigated using Northern blot analysis and immunohistochemistry. The values obtained for the EGFR mRNA in the BPH and carcinoma specimens w ere not significantly different and in the latter there was no correla tion with grade. In the immunohistochemical assays, two antibodies to the external and one to the internal domain of EGFR were used. The for mer ones stained the basal cell membranes intensely whilst cytoplasmic staining of secretory epithelium was seen in BPH specimens with the l atter. In the carcinoma specimens, the intensity of membrane staining correlated with the two external domain antibodies, r = 0.640, P<0.001 , but neither of these correlated with the EGFR mRNA results. All thre e antibodies demonstrated a trend towards elevated expression of EGFR with dedifferentiation which reached significance only with the intern al domain antibody results, P<0.02. No correlation was observed with t umour EGFR mRNA values and the EGFR immunohistochemical results. The E GFR immunoreaction with the external domain antibody in 14 treated hig h-grade tumours was comparable to that obtained in 15 untreated anapla stic prostatic tumours. In 5 patients, both pre- and post-treatment sa mples were available and these exhibited little or no difference in EG FR expression with therapy.