Pigment Epithelium-Derived Factor and Interleukin-6 Control Prostate Neuroendocrine Differentiation via Feed-Forward Mechanism

Abstract

Pigment epithelium-derived factor (PEDF) promotes differentiation and survival of neuronal cells and expands the adult neuronal stem cell niche. In the prostate, PEDF is suppressed by androgen, with unclear physiological consequences. Ectopic and endogenous PEDF cause neuroendocrine differentiation of prostate cancer cells, manifested by neurite-like outgrowths and expression of chromogranin A. The trans-differentiated cells expressed both axonal and dendritic markers, as was ascertained by immunoblotting specific markers. Neuroendocrine cells formed multiple synaptophysin-positive protrusions resembling dendritic spines, and vesicles containing serotonin, pointing to a possibility of synapse formation. Interleukin-6 (IL-6), a known trans-differentiating agent, induced PEDF secretion. Moreover, PEDF neutralizing antibodies abolished trans-differentiation of IL-6 treated cells, suggesting an autocrine loop. Neurogenic events were independent of cyclic AMP. Instead, PEDF activated, in this order, RhoA, NFκB and Stat3. Inhibitors of Rho, NFκB or STAT pathways abolished differentiation and synapse formation. Additionally, NFκB activation caused IL-6 expression. Thus we discovered that NFκB controls formation of neuronal communications in the prostate due to PEDF and defined a feed-forward loop where NFκB induction elicits Stat3 activation and pro-differentiating IL-6 expression causing further expansion of the neuroendocrine communications. Our findings point to the role of NFκB and PEDF in coordinated prostate development.