Comparative analysis of mRNA and protein expression for epidermal growth factor receptor and ligands relative to the...

The expression of epidermal growth factor receptor (EGF-R), transforming growth factor alpha (TGFalpha), and epidermal growth factor (EGF) was evaluated in a series of prostate cancer (CaP; n = 55) and benign prostate hyperplasia (BPH; n = 44) specimens using immunocytochemistry (ICC) and Northern blotting. In situ hybridization (ISH), performed on a subgroup of these specimens, proved to be a more informative technique for the assessment of messenger RNA (mRNA) in this heterogeneous tissue. A comparative analysis was made in relation to the proliferative index, assessed using the MIB-1 antibody. Elevated levels of EGF-R and TGFalpha, mRNA, and protein were observed in carcinoma cells compared with benign, secretory epithelium using in situ hybridization and immunocytochemistry. In carcinoma specimens evidence of an autocrine growth loop is provided by a correlation between EGF-R and TGFalpha, mRNA (P < .0001), and protein expression (P < .01). A trend toward increased expression of EGF-R and TGFalpha protein with dedifferentiation and a similar trend in the growth fraction suggest a role in tumor progression. Although there was a correlation between EGF-R and the proliferative index (P < .01), no relationship was found between this latter parameter and TGFalpha immunoreactivity (P > .05), indicating that this growth factor may be linked with other aspects of malignant activity rather than directly stimulating proliferation.