I found very interesting research here http://www.eusupplements.europeanurology.com/article/S1569-9056(06)00013-3/fulltext
It explains that 5AR inhibitors down-regulate PSA gene expression!
Unlike other 5-α-reductase inhibitors, SR blocks the 5-α-reductase activity of epithelial cells without interfering with their capacity to secrete PSA [[11], [33], [34]]. This contrasts with the synthetic 5-α-reductase inhibitors, which down-regulate PSA gene expression and secretion within the cell by directly inhibiting the binding of the activated α-reductase to the hormone response element (HRE) of the PSA gene promoter [73]. Thus, finasteride and other similar inhibitors have a dual effect on androgen action in the prostate: indirectly through inhibition of 5-α-reductase activity, thereby reducing the availability of the more potent ligand DHT, and directly through interference with DNA binding by the α-reductase.
Then I found other research:
http://cancerres.aacrjournals.org/content/57/4/714.short GENE expression
Maybe it is the reason for long-lasting effects
