Gene expression profiling of prostate tissue based on variable expression of 5-alpha reductase 2.

Abstract

143 Background: Androgen signaling plays a central role in the pathophysiology of both benign and malignant prostatic disease. We previously showed that some men carry epigenetic modifications of the 5-alpha reductase (AR) promoter that modulate gene expression, raising the hypothesis that there may be molecular heterogeneity underlying the variability in clinical response to 5-AR inhibitors for management of benign and malignant prostatic diseases. In this study, we performed whole-genome expression profiling of prostatic tissue based on variable expression of 5-AR2 to determine whether molecular subtypes of clinical relevance could be identified. Methods: Prostatic tissue specimens were obtained from 22 patients with symptomatic BPH undergoing prostate debulking surgery. 5-AR2 protein expression was measured by immunohistochemistry, and 5-AR2 promoter methylation determined by PCR. RNA was extracted from each specimen and whole-genome expression profiling was performed using Illumina Human BeadChip Arrays. Gene expression data was analyzed by unsupervised hierarchical clustering and Gene Set Enrichment Analysis. Results: Unsupervised hierarchical clustering identified two subtypes of patients with distinct gene expression signatures. Among the most differentially expressed genes were several notable androgen-regulated genes, including TMPRSS2, NKX3-1, AZGP1, KLK3 (encoding the PSA protein) and multiple other members of the kallikrein family of serine proteases (all P< 0.001, FDR < 0.02). Multiple gene sets composed of androgen-regulated genes and androgen receptor target genes were found to be significantly enriched in one of the two subtypes. Interestingly, patients from this Androgen-Up subtype were also noted to have a higher frequency of 5-AR2 promoter methylation (though not statistically significant). Conclusions: Our findings suggest that there are distinct molecular subtypes among prostatic tissues with variable expression of 5-AR2, driven by differences in androgen gene regulation. These differences may partially explain the variable response to 5-AR inhibitors and thereby inform clinical strategies for devising therapies for benign and malignant prostatic disease.