Glucocorticoid receptor function is modulated by HO-1 in prostate cancer

LEONARDI, DAIANA; PAEZ, ALEJANDRA; SCHUSTER, FEDERICO; ANSELMINO, NICOLAS; BRANDANI, JAVIER; ABBATE, MERCEDES; GUERON, GERALDINE; COTIGNOLA, JAVIER; VAZQUEZ, ELBA

Bariloche

Congreso; Third South American Symposium in Signal and Molecular Medicine ? SISTAM 2015; 2015

Among several treatment options, glucocorticoids are known to produce some benefit for hormone-refractory prostate cancer. Nevertheless, nowadays many authors report that the glucocorticoid receptor (GR) can substitute the androgen receptor and activate a similar but distinguishable set of genes. Our aim is to study GR signaling and the effect of heme oxygenase 1 (HO-1) in prostate cancer cell lines. We tested three dexamethasone (Dex) concentrations (10-7 M, 10-8 M y 10-9 M) for 24 hours on PC3 cells and found out no differences in cell viability. To choose the length of Dex treatment, we performed a time course from 1 to 24 hours with PC3 cells exposed to 10-8 M Dex. The higher GR mRNA induction was measured after 6 hours of treatment. In order to study GR transcriptional activity PC3 cells were transfected with a glucocorticoid response element promoter-driven luciferase expression plasmid, and were treated either with hemin (HO-1 inductor, 80μM, 24h), Dex (10-8 M, 6h) or both drugs. In all the cases the cells were cultured in medium with charcoal-dextran treated serum. Hemin significantly reduced the GR basal activity (p=0.03) as well as the Dex induced activity (p=0.01). These results were confirmed by RTqPCR with a well known GR target, IkB, and a NFkB luciferase reporter assay. Using confocal fluorescence microscopy, we confirmed GR nuclear translocation upon Dex treatment, and showed a lower translocation phenomenon when cells were exposed to the combined effect of hemin and Dex. These results agree with the diminished luciferase activity of the MMTV-luc in the presence of hemin+Dex vs. Dex. By coimmunoprecipitation we showed physical interaction between GR and HO1 in nucleus and cytoplasm with and without Hemin. In conclusion, these results suggest that HO-1 induction modulates GR activity and it subcellular localization in PC3 cell line.