Advanced prostate cancers frequently manifest aberrant neuroendocrine signaling, such as excessive accumulation of cells with neuroendocrine differentiation and/or overproduction of neuropeptides. That said, little is known about roles of neuroendocrine signaling during the normal prostate development, regeneration and carcinogenesis, thereby complicating the identification and interpretation of mechanisms critical for prostate cancer progression. We have recently generated several mouse strains in which neuroendocrine cells can be depleted specifically in the prostate epithelium. Our preliminary results in these models suggest that the depletion of neuroendocrine cells leads to prostate hypotrophy, likely due to decreased size of the prostate stem cell pool. In another series of preliminary experiments, we have observed that deficiency for the neuropeptide processing enzyme membrane metallo-endopeptidase (MME) may accelerate prostate carcinogenesis in a mouse model, in which Pten gene is specifically inactivated in the prostate epithelium. Interestingly, mice deficient for both MME and Pten preferentially developed neoplasms in the proximal regions of prostatic ducts, the areas highly enriched with prostate stem cells. Our preliminary results show that MME may control gastrin-releasing peptide (GRP)-dependent maintenance of the prostate stem cell niche, and administration of a GRP receptor antagonist may lead to depletion of cancer propagating cells (CPC, aka cancer stem cells). Based on our preliminary results we hypothesize that the neuroendocrine signaling is essential for the maintenance of the prostate epithelium stem cell niche, and that dysregulation of such signaling promotes expansion of androgen withdrawal-resistant cells with stem cell properties. To address this hypothesis we propose to (1) establish the role of neuroendocrine cells during the normal development and regeneration of the prostate, (2) test the role of neuroendocrine cells in autochthonous mouse models of prostate cancer associated with deficiency of Pten, p53/mir-34 and Rb tumor suppressor genes, and (3) study the effects of neuropeptide dysregulation on prostate cancer progression.