Heterogeneity of 5 alpha-reductase gene expression in benign prostatic hyperplasia

The search for molecular markers of benign prostatic hyperplasia in general is based on an analysis of a limited number of biopsy samples. Little is known about the homogeneity of the expression of key genes in different zones of the prostate. We studied the intraprostatic (that is within the same gland) and inter-prostatic (that is between glands) variability of 5 alpha-reductase 2 (5aR2) gene expression.

Ten tissue samples removed by open prostatectomy were the source of tissue specimens. Two frozen sections were generated from each of several random biopsies taken from each adenoma immediately after enucleation, 1 of which was used for 5aR2 gene expression analysis and 1 for morphometric analysis. Results among biopsies were compared using the 5 alpha-reductase index (ratio of 5 alpha-reductase expression to an internal standard measured as electrophoretic band intensity). Morphometric composition was determined for smooth muscle, collagen, epithelium and glandular lumens. Statistical comparisons were performed with ANOVA by pairwise multiple comparison (Dunn) and Spearman's rank correlation procedure.

For the 71 biopsies analyzed mean 5 alpha-reductase index was 0.23 +/- 0.16 and overall tissue distribution was smooth muscle 34%, collagen 35%, epithelium 14% and glandular lumens 17%. Inter-prostate and intraprostate variability in 5 alpha-reductase index was statistically significant (p = 0.004) as was the variability in stromal-to-epithelial ratio (p = 0.012). The 5 alpha-reductase index showed strong correlation with stroma (%) and negative correlation with epithelium (%).

Benign prostatic hyperplasia is heterogeneous in terms of tissue morphometry and expression of single important genes. This finding limits the use of single biopsy based markers to predict biological behavior, and has significant impact on the ability of distinguishing longitudinal changes in tissue composition from sampling artifacts.