Androgen receptor protein is down-regulated by basic fibroblast growth factor in prostate cancer cells

Interactions between polypeptide growth factors and the androgen receptor (AR) are important for regulation of cellular events in carcinoma of the prostate. Basic fibroblast growth factor (bFGF), the prototype of heparin-binding growth factors, and the AR are commonly expressed in prostate cancer. bFGF diminished prostate-specific antigen protein in the supernatants of androgen-stimulated human prostate cancer cells LNCaP by 80%. In the present study, we asked whether the bFGF effect on prostate-specific antigen is preceded by action on AR expression. LNCaP cells were treated with bFGF and AR protein expression was determined by immunoblotting and ligand binding assay. bFGF down-regulated AR protein in a dose-dependent manner showing a maximal effect at 50 ng ml−1both in the presence or absence of dihydrotestosterone. Down-regulation of AR protein expression occurred already after 8 h of bFGF treatment and a maximal inhibition was observed 24 h after addition of bFGF to culture media. As AR expression can be reduced by an increase in intracellular calcium levels, we investigated whether the bFGF effect on AR protein is mediated by this mechanism. Calcium release from intracellular stores and store-operated calcium influx after treatment with either bFGF or calcium ionophore A 23187 were measured by single cell fluorescence technique. The ionophore A 23187 was able to induce calcium influx and an increase in cytoplasmic calcium concentration in LNCaP cells. In contrast, bFGF was incapable of eliciting a similar effect. In contrast to AR protein, AR mRNA levels were not affected by bFGF as shown by semiquantitative reverse transcription polymerase chain reaction. In summary, these studies show that bFGF is a potent negative regulator of AR protein expression in the human prostate cancer cell line LNCaP. © 2000 Cancer Research Campaig

The androgen receptor can signal through Wnt/β-Catenin in prostate cancer cells as an adaptation mechanism to castration levels of androgens

<p>Abstract</p> <p>Background</p> <p>A crucial event in Prostate Cancer progression is the conversion from a hormone-sensitive to a hormone-refractory disease state. Correlating with this transition, androgen receptor (AR) amplification and mutations are often observed in patients failing hormonal ablation therapies. β-Catenin, an essential component of the canonical Wnt signaling pathway, was shown to be a coactivator of the AR signaling in the presence of androgens. However, it is not yet clear what effect the increased levels of the AR could have on the Wnt signaling pathway in these hormone-refractory prostate cells.</p> <p>Results</p> <p>Transient transfections of several human prostate cancer cell lines with the AR and multiple components of the Wnt signaling pathway demonstrate that the AR overexpression can potentiate the transcriptional activities of Wnt/β-Catenin signaling. In addition, the simultaneous activation of the Wnt signaling pathway and overexpression of the AR promote prostate cancer cell growth and transformation at castration levels of androgens. Interestingly, the presence of physiological levels of androgen or other AR agonists inhibits these effects. These observations are consistent with the nuclear co-localization of the AR and β-Catenin shown by immunohistochemistry in human prostate cancer samples. Furthermore, chromatin immunoprecipitation assays showed that Wnt3A can recruit the AR to the promoter regions of Myc and Cyclin D1, which are well-characterized downstream targets of the Wnt signalling pathway. The same assays demonstrated that the AR and β-Catenin can be recruited to the promoter and enhancer regions of a known AR target gene PSA upon Wnt signaling. These results suggest that the AR is promoting Wnt signaling at the chromatin level.</p> <p>Conclusion</p> <p>Our findings suggest that the AR signaling through the Wnt/β-Catenin pathway should be added to the well established functional interactions between both pathways. Moreover, our data show that via this interaction the AR could promote prostate cell malignancy in a ligand-independent manner.</p

Vascularised Chorioallantoic Membrane (CAM) Culture System for Cryopreserved Human Ovarian Tissue as an Alternative to Xenotransplantation

Purpose: Previously there were only two effective ways to determine the quality of cryopreservation procedures for ovarian tissue after thawing: xenotransplantation and in vitro culture in a big volume of medium with permanent mechanical agitation. The Belgian group of J. Donnez has shown that the chorioallantoic membrane (CAM) culture system offers a new approach to study human ovarian tissue transplantation in its first ischemic stages, yielding information on the timing of tissue changes before neovascularization is established. The aim of this study was to compare the effectiveness after thawing of human ovarian tissue cultured in vitro in a big volume of medium with agitation with a CAM culture system. Material and Methods: Ovarian tissue fragments from 5 patients were transported within 20 min at 32-34 degrees C to the laboratory. The fragments were divided into smaller pieces (1-2 x 0.7-1 mm), frozen, thawed and randomly divided into the following two groups: Group 1: tissue cultured in vitro for 7 days in a big volume of medium with mechanical agitation; Group 2: tissue cultured in a CAM system for 5 days. The viability of the tissue from the respective method of cultivation was evaluated by immunohistochemistry (cytokeratin and Ki-67) and assessed according to the development of follicles and follicular cell proliferation. Results: 85 and 87% of the follicles were morphologically normal in group 1 and group 2, respectively. Immunohistochemical analysis showed that the proliferative characteristics of follicular cells after culture in the CAM system were significantly increased. Conclusion: Both the CAM system and in vitro culturing in a big volume of medium with permanent mechanical agitation are suitable for culturing human ovarian tissue. However, the CAM system provides more information