The peripheral zone of the prostate is more prone to tumor development than the transitional zone: is the ETS family the key?

Predisposition to develop prostate cancer (PCA) varies among the prostate zones, with the peripheral zone (PZ) more prone to tumor development than the transitional zone (TZ). In view of the fact that molecular differences between the zones may explain this difference, combined with the findings that translocations between TMPRSS2 and several ETS members are frequently observed in PCA, we hypothesized that the ETS family may be crucial to explaining this difference. Normal tissues from the PZ and the TZ of 20 PCA patients were laser microdissected to separate glands from stroma. Two oligo microarrays were performed in order to investigate the variation in ETS family gene expression between the glands and the stroma of the two zones. The ETS members, ELF-3, ELF-5, ERG, ETV-1, ETV-4, ETV-5, ETV-7 and FEV, were found to be differentially expressed. A striking observation was that ERG and ETV-1 were found to be up-regulated in the glands of the PZ compared to the TZ, particularly when considering that ERG and ETV-1 fusions account for 50-80% and 20% of PCA occurrences, respectively. These results indicate that the glands and stroma of the two zones display distinct molecular differences and zonal-specific expression of ETS members. Furthermore, ETS members up-regulated in PCA are already overexpressed in the normal PZ, suggesting that these members play a role in the development and progression of PCA.