Goserelin and bicalutamide treatments alter the expression of microRNAs in the prostate.

BACKGROUND: Although endocrine therapy has been used for decades, its influence on the expression of microRNAs (miRNAs) in clinical tissue specimens has not been analyzed. Moreover, the effects of the TMPRSS2:ERG fusion on the expression of miRNAs in hormone naïve and endocrine-treated prostate cancers are poorly understood. METHODS: We used clinical material from a neoadjuvant trial consisting of 28 men treated with goserelin (n = 8), bicalutamide (n = 9), or no treatment (n = 11) for 3 months prior to radical prostatectomy. Freshly frozen specimens were used for microarray analysis of 723 human miRNAs. Specific miRNA expression in cancer, benign epithelium and stromal tissue compartments was predicted with an in silico Bayesian modeling tool. RESULTS: The expression of 52, 44, and 34 miRNAs was affected >1.4-fold by the endocrine treatment in the cancer, non-malignant epithelium, and stromal compartments, respectively. Of the 52 miRNAs, only 10 were equally affected by the two treatment modalities in the cancer compartment. Twenty-six of the 52 genes (50%) showed AR binding sites in their proximity in either VCaP or LNCaP cell lines. Forty-seven miRNAs were differentially expressed in TMPRSS2:ERG fusion positive compared with fusion negative cases. Endocrine treatment reduced the differences between fusion positive and negative cases. CONCLUSIONS: Goserelin treatment and bicalutamide treatment mostly affected the expression of different miRNAs. The effect clearly varied in different tissue compartments. TMPRSS2:ERG fusion positive and negative cases showed differential expression of miRNAs, and the difference was diminished by androgen ablation.

Chemical castration and anti-androgens induce differential gene expression in prostate cancer.

Endocrine therapy by castration or anti-androgens is the gold standard treatment for advanced prostate cancer. Although it has been used for decades, the molecular consequences of androgen deprivation are incompletely known and biomarkers of its resistance are lacking. In this study, we studied the molecular mechanisms of hormonal therapy by comparing the effect of bicalutamide (anti-androgen), goserelin (GnRH agonist) and no therapy, followed by radical prostatectomy. For this purpose, 28 men were randomly assigned to treatment groups. Freshly frozen specimens were used for gene expression profiling for all known protein-coding genes. An in silico Bayesian modelling tool was used to assess cancer-specific gene expression from heterogeneous tissue specimens. The expression of 128 genes was > two-fold reduced by the treatments. Only 16% of the altered genes were common in both treatment groups. Of the 128 genes, only 24 were directly androgen-regulated genes, according to re-analysis of previous data on gene expression, androgen receptor-binding sites and histone modifications in prostate cancer cell line models. The tumours containing TMPRSS2-ERG fusion showed higher gene expression of genes related to proliferation compared to the fusion-negative tumours in untreated cases. Interestingly, endocrine therapy reduced the expression of one-half of these genes and thus diminished the differences between the fusion-positive and -negative samples. This study reports the significantly different effects of an anti-androgen and a GnRH agonist on gene expression in prostate cancer cells. TMPRSS2-ERG fusion seems to bring many proliferation-related genes under androgen regulation.

Transcriptome Sequencing Reveals PCAT5 as a Novel ERG-Regulated Long Noncoding RNA in Prostate Cancer.

Castration-resistant prostate cancers (CRPC) that arise after the failure of androgen-blocking therapies cause most of the deaths from prostate cancer, intensifying the need to fully understand CRPC pathophysiology. In this study, we characterized the transcriptomic differences between untreated prostate cancer and locally recurrent CRPC. Here, we report the identification of 145 previously unannotated intergenic long noncoding RNA transcripts (lncRNA) or isoforms that are associated with prostate cancer or CRPC. Of the one third of these transcripts that were specific for CRPC, we defined a novel lncRNA termed PCAT5 as a regulatory target for the transcription factor ERG, which is activated in approximately 50% of human prostate cancer. Genome-wide expression analysis of a PCAT5-positive prostate cancer after PCAT5 silencing highlighted alterations in cell proliferation pathways. Strikingly, an in vitro validation of these alterations revealed a complex integrated phenotype affecting cell growth, migration, invasion, colony-forming potential, and apoptosis. Our findings reveal a key molecular determinant of differences between prostate cancer and CRPC at the level of the transcriptome. Furthermore, they establish PCAT5 as a novel oncogenic lncRNA in ERG-positive prostate cancers, with implications for defining CRPC biomarkers and new therapeutic interventions.