RESUMO
Prostate cancers (PCas) become resistant to hormone withdrawal through increased androgen receptor (AR) signaling. Here we show increased AR-mediated transcription efficiency in PCa cells that have acquired the ability to grow in low concentrations of androgen. Compared to androgen-dependent PCa cells, these cells showed increased activity of transiently transfected reporters and increased mRNA synthesis relative to levels of AR occupancy of the prostate-specific antigen (PSA) gene. The locus also displayed up to 10-fold-higher levels of histone H3-K9/K14 acetylation and H3-K4 methylation across the entire body of the gene. Although similar increased mRNA expression and locus-wide histone acetylation were also observed at another kallikrein locus (KLK2), at a third AR target locus (TMPRSS2) increased gene expression and locus-wide histone acetylation were not seen in the absence of ligand. Androgen-independent PCa cells have thus evolved three distinctive alterations in AR-mediated transcription. First, increased RNA polymerase initiation and processivity contributed to increased gene expression. Second, AR signaling was more sensitive to ligand. Third, locus-wide chromatin remodeling conducive to the increased gene expression in the absence of ligand was apparent and depended on sustained AR activity. Therefore, increased AR ligand sensitivity as well as locus-specific chromatin alterations contribute to basal gene expression of a subpopulation of specific AR target genes in androgen-independent PCa cells. These features contribute to the androgen-independent phenotype of these cells.
Assuntos
Montagem e Desmontagem da Cromatina , Cromatina/genética , Cromatina/metabolismo , Neoplasias da Próstata/genética , Neoplasias da Próstata/patologia , Receptores Androgênicos/metabolismo , Transcrição Gênica , Acetilação/efeitos dos fármacos , Androgênios/metabolismo , Animais , Cromatina/efeitos dos fármacos , Di-Hidrotestosterona/farmacologia , Genes Reporter/genética , Histonas/metabolismo , Humanos , Ligantes , Luciferases/genética , Masculino , Metilação/efeitos dos fármacos , Camundongos , Camundongos Nus , Antígeno Prostático Específico/genética , Elementos de Resposta/efeitos dos fármacos , Elementos de Resposta/genética , Células Tumorais CultivadasRESUMO
BACKGROUND: Mechanisms regulating the transition from hormone responsive to hormone refractory prostate cancer (PCa) have remained unclear. METHODS: We analyzed androgen and anti-androgen treatment on endogenous AR activity in primary human prostate epithelial (HPE) cells cultured directly from patient radical prostatectomy specimens utilizing a transiently infected gene reporter (TIGR) assay. RESULTS: Flutamide treatment exhibited agonist activities in HPE cells derived from tumor and non-tumor specimens which contained wild-type AR. After proteomic comparison of these cells to those where flutamide functioned normally as an antagonist, we identified DJ-1, a positive regulator of AR. DJ-1 expression increased in HPE and LNCaP cells during flutamide treatment as a result of DJ-1 protein stabilization. CONCLUSION: Stabilization of AR and its co-regulators in the absence of androgen may partially account for anti-androgen withdrawal syndrome and potentially contribute to the development of hormone refractory PCa.