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 prostatic hyperplasia (BPH) and 55 prostatic carcinoma specimens has been investigated using Northern blot analysis and immunohistochemistry. The values obtained for the EGFR mRNA in the BPH and carcinoma specimens were not significantly different and in the latter there was no correlation with grade. In the immunohistochemical assays, two antibodies to the external and one to the internal domain of EGFR were used. The former ones stained the basal cell membranes intensely whilst cytoplasmic staining of secretory epithelium was seen in BPH specimens with the latter. 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 three antibodies demonstrated a trend towards elevated expression of EGFR with dedifferentiation which reached significance only with the internal domain antibody results, P<0.02. No correlation was observed with tumour EGFR mRNA values and the EGFR immunohistochemical results. The EGFR immunoreaction with the external domain antibody in 14 treated high-grade tumours was comparable to that obtained in 15 untreated anaplastic prostatic tumours. In 5 patients, both pre- and post-treatment samples were available and these exhibited little or no difference in EGFR expression with therapy.