Regina Elena Cancer Institute, 00158 Rome, Italy.
Department of Clinical and Experimental Medicine and Pharmacology, Section of Endocrinology, University of Messina, 98100 Messina, Italy; Institute of Cellular Biology and Neurobiology, National Research Council, 00143 Rome, Italy; Catholic University, F.Pin., P.B., A.P.), 00168 Rome, Italy; Istituto Nazionale di Ricovero e Cura per Anziani, Cardiologic Unit, 60100 Ancona, Italy; Istituto Dermopatico dell'Immacolata, 00167 Rome, Italy; and Department of Biology, University of Rome "Tor Vergata," 00133 Rome, Italy.
We recently identified in prostate tumors (PCa) a transcriptional prognostic signature comprising a significant number of genes differentially regulated in patients with worse clinical outcome. Induction of up-regulated genes was due to chromatin remodeling by a combinatorial complex between estrogen receptor (ER)-β and endothelial nitric oxide synthase (eNOS). Here we show that this complex can also repress transcription of prognostic genes that are down-regulated in PCa, such as the glutathione transferase gene GSTP1. Silencing of GSTP1 is a common early event in prostate carcinogenesis, frequently caused by promoter hypermethylation. We validated loss of glutathione transferase (GST) P1-1 expression in vivo, in tissue microarrays from a retrospective cohort of patients, and correlated it with decreased disease-specific survival. Furthermore, we show that in PCa cultured cells ERβ/eNOS causes GSTP1 repression by being recruited at estrogen responsive elements in the gene promoter with consequential remodeling of local chromatin. Treatment with ERβ antagonist or its natural ligand 5α-androstane-3β,17β-diol, eNOS inhibitors or ERβ small interference RNA abrogated the binding and reversed GSTP1 silencing, demonstrating the direct involvement of the complex. In vitro, GSTP1 silencing by ERβ/eNOS was specific for cells from patients with worse clinical outcome where it appeared the sole mechanism regulating GSTP1 expression because no promoter hypermethylation was present. However, in vivo chromatin immunoprecipitation assays on fresh PCa tissues demonstrated that silencing by ERβ/eNOS can coexist with promoter hypermethylation. Our findings reveal that the ERβ/eNOS complex can exert transcriptional repression and suggest that this may represent an epigenetic event favoring inactivation of the GSTP1 locus by methylation. Moreover, abrogation of ERβ/eNOS function by 3β-adiol emphasizes the significance of circulating or locally produced sex steroid hormones or their metabolites in PCa biology with relevant clinical/therapeutic implications.
Written by:
Re A, Aiello A, Nanni S, Grasselli A, Benvenuti V, Pantisano V, Strigari L, Colussi C, Ciccone S, Mazzetti AP, Pierconti F, Pinto F, Bassi P, Gallucci M, Sentinelli S, Trimarchi F, Bacchetti S, Pontecorvi A, Lo Bello M, Farsetti A. Are you the author?
Reference: Mol Endocrinol. 2011 Nov 3. Epub ahead of print.
doi: 10.1210/me.2011-1024
PubMed Abstract
PMID: 22052999
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