Project description:Androgens are required for prostate development, growth and physiology, by activating the androgen receptor (AR) upon activation by testosterone and dihydrotestosterone (DHT), the AR undergoes conformational changes, dimerizes and translocates to the cell nucleus regulation important genes releted to cell survival. Understanding the mechanisms of androgen regulation in the prostate gland is important, because the prostate is affected by several different diseases, in particular prostate cancer (PCa). Several ways exist to treat prostate cancer and promote epithelial cell death. Treatments involving androgen manipulation include surgical castration (bilateral orchiectomy), antiandrogens (usually AR antagonists), or substances that inhibit androgen synthesis (5 alpha-reductase inhibitors, gonadotrophin-releasing hormone blockers). 17 beta-estradiol exerts anti-androgen effects by blocking the hypothalamic production of gonadotropin-releasing hormone and thereby inhibiting the production of testosterone by the testes , but also acts locally via interactions with either of the estrogen receptors found in the gland. It is known that the kinetics of apoptosis are different in the rat ventral prostate (VP) of castrated rats (Cas group) and in rats subjected to 17 beta-estradiol high dose (group E2) or their combination (group Cas+E2), with an evident additive effect in the latter situation (Garcia-Florez et al, 2005). The microarray approach was done to figure out what genes are expressed and how the cells of ventral prostate gland responses when the androgen is not available comparing three diferent androgen deprivation methods (sirurgical castration, high dose of 17-beta estradiol and both treatment combined). Forty-eight 21-day-old male Wistar rats were obtained from the Multidisciplinary Center for Biological Research (CEMIB), University of Campinas. The animals were kept under normal light conditions (12-h light:dark cycle) and received filtered tap water and Purina rodent chow ad libitum. On the 90th day after birth, the rats were divided in four groups (n=3) and assigned to different treatment groups. To cause androgen deprivation, we utilized three different procedures with different effects on epithelial cell apoptosis. Animals in the first group were castrated (Cas) by orchiectomy via scrotal incision under ketamine (150 mg/Kg body weight) and xylazin (10 mg/kg body weight) anesthesia. Animals in the second group received a 25 mg/Kg body weight dose of 17β-estradiol diluted in corn oil (E2 group). The third group received a combination of both treatments (Cas+E2 group) (combined orchiectomy and 17β-estradiol). In the control group (Ct; normal androgen and estrogen), the animals received only the vehicle. Three days after the treatments, the rats were killed by anesthetic overdose, and the ventral prostate was dissected out for the microarray and immunohistochemistry analyses.

Project description:Castration-resistant prostate cancer is a lethal disease. The cell type(s) that survive androgen-deprivation remain poorly described despite global efforts to understand the various mechanisms of therapy resistance. We recently identified in wild type mouse prostates a rare population of luminal progenitor cells that we called LSCmed according to their FACS profile (Lin?/Sca-1+/CD49fmed). Here we investigated the prevalence and castration resistance of LSCmed in various mouse models of prostate tumorigenesis. In intact mice, we show that LSCmed prevalence remains low (5-10% of epithelial cells) when prostatic androgen receptor signaling unaltered (malignant Hi-Myc mice) but significantly increases in models exhibiting reduced prostatic androgen receptor signaling, rising up to 30% in premalignant tumors (Pb-PRL mice) and to >80% in castration-resistant prostate tumors driven by Pten loss (Ptenpc-/- mice). LSCmed tolerance to androgen deprivation was demonstrated by their persistence (Ptenpc-/-) or further enrichment (Pb-PRL) 2-3 weeks after castration as evidenced by FACS analysis. Transcriptomic analysis revealed that LSCmed represent a unique cell entity as their gene-expression profile is different from luminal and basal/stem cells, but shares markers of each. Their intrinsic androgen signaling is markedly decreased, which explains why LSCmed tolerate androgen-deprivation. This also enlightens why Ptenpc-/- tumors are castration-resistant since LSCmed represent the most prevalent cell type in this model. We validated CK4 as a specific marker for LSCmed on sorted cells and prostate tissues by immunostaining, allowing for the detection of LSCmed in various mouse prostate specimens. In castrated Ptenpc-/- prostates, BrdU staining revealed massive proliferation of CK4+ cells, further demonstrating their key role in castration-resistant prostate cancer progression. In all, this study identifies LSCmed as a probable source of prostate cancer relapse after androgen deprivation and as a new therapeutic target for the prevention of castrate-resistant prostate cancer.

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Rattus norvegicus

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