Zonal biochemical and morphological characteristics in BPH

To compare androgen, oestrogen, progesterone and epidermal growth factor receptor concentrations in the transition zone and peripheral zone of the prostate in benign prostatic hyperplasia (BPH), and to relate these findings to epithelial and stromal composition.

Tissue from both the transition and peripheral zone of the prostate was obtained from 26 patients undergoing transurethral prostatectomy for benign prostatic obstruction and used for both receptor binding studies and morphometric analysis. Androgen receptor (AR), oestrogen receptor (ER), progesterone receptor (PR) and epidermal growth factor receptor (EGFR) concentrations were assayed by saturation binding with a competitive inhibitor. The epithelial, stromal and luminal composition of the tissue was determined using a Zeiss AxioHOME microscope workstation.

The epithelial content was significantly greater in the transition zone than in the peripheral zone. No overall zonal difference in AR concentration was detected; however, when values were expressed relative to the epithelial component, the AR content was significantly higher in the peripheral zone. Conversely, overall EGFR concentrations were significantly greater in the transition zone, although not when expressed per unit epithelium. Higher concentrations of oestrogen receptor were measured in the transition zone per unit stroma. No zonal difference in PR was detected. However, there was a significant correlation between AR and PR in the peripheral zone and between EGFR and AR in the transition zone.

These data demonstrate that receptor concentrations should be related to tissue composition. Concentrations of AR were higher in the peripheral zone epithelium than in transition zone epithelium, suggesting greater androgen dependence. This may be important in determining its greater propensity for malignancy. Although EGFR concentrations were greater in the transition zone, there was no zonal difference after correction for the amount of epithelium. Finally, higher concentrations of ER were detected in the transition zone stroma which may reflect important zonal differences in regulating growth and provides further evidence of a role for oestrogens in BPH.