5-ARI induces autophagy of prostate epithelial cells through suppressing IGF-1 expression in prostate fibroblasts

5α-reductase inhibitor (5-ARI) is a commonly used medicine in the treatment of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH). Our study mainly focuses on the mechanism of BPH development after 5ARI treatment.

Prostate specimens from patients were collected. Insulin-like growth factor 1 (IGF-1), Beclin-1, LC3 levels, was analysed by immunohistochemistry. The role IGF-1 on autophagic flux in prostate epithelial cells was studied. Additionally, effect of autophagy on recombinant grafts consisting of prostate stromal and epithelial cells in nude mice was investigated.

We demonstrated that IGF-1 expression is down-regulated in prostate fibroblasts after long-term 5-ARI application. A decrease in IGF-1 levels was found to activate autophagic flux through the mTOR pathway in prostate epithelial cells, while the inhibition of IGF-1 receptor function induced autophagy in prostate epithelial cells. In addition, we revealed that blocking autophagic flux initiation can reduce the volume of recombinant grafts in vivo. Finally, our findings suggest that long-term 5-ARI application reduces IGF-1 secretion by prostatic stromal cells, thereby inducing autophagy of prostatic epithelial cells, which is one of the mechanisms underlying BPH pathogenesis and progression.

Focusing on the autophagy induced by low levels of IGF-1 in prostatic epithelial cells, after elucidating AR signalling impairment of prostate stromal cells, might provide a novel strategy for the treatment and prevention of BPH development.