Androgen receptor amplification is reflected in the transcriptional responses of Vertebral-Cancer of the Prostate cells.

Androgen receptor (AR) is overexpressed in a majority of castration-resistant prostate cancers, but most of the cell model studies addressing AR function have been conducted in LNCaP prostate cancer cells expressing unamplified AR levels. Here, we have compared the responses of various types of AR ligands towards a pattern of AR target genes and chromatin binding sites in Vertebral-Cancer of the Prostate (VCaP) cells and LNCaP cells. In keeping with the AR gene amplification in VCaP cells, our analyses show that these cells contain ≥10-fold receptor mRNA and protein than LNCaP cells. Loading of the agonist-occupied AR onto chromatin regulatory sites and expression of several AR target genes, including their basal expression, were stronger in VCaP cells than LNCaP cells. Bicalutamide displayed a trend towards agonism in VCaP cells. Bicalutamide also evoked AR-chromatin interaction, whereas diarylthiohydantoin antiandrogen RD162 was inert with this respect both in VCaP and LNCaP cells. These results support the notion that the AR protein level translates into augmented occupancy of AR-regulated enhancers and target gene activity in prostate cancer cells.

Long-range activation of FKBP51 transcription by the androgen receptor via distal intronic enhancers.

Androgen receptor (AR) is a ligand-controlled transcription factor frequently deregulated in prostate carcinomas. Since there is scarce information on the action of AR on the chromatin level, we have elucidated the molecular mechanisms underlying the androgen-dependent regulation of immunophilin FKBP51 in prostate cancer cells. In comparison to the canonical AR target PSA, FKBP51 is more rapidly and strongly induced by androgen, with the regulation occurring merely at the transcriptional level. FKBP51 locus harbors 13 in silico-predicted androgen response elements (AREs), with most of them located downstream from transcription start site (TSS) and capable of binding AR in vitro. Chromatin immunoprecipitation assays in VCaP and LNCaP prostate cancer cells indicate that activation of the locus by the AR relies on four major intronic sites, with the compound ARE-containing sites >or=90 kb downstream from the TSS playing critical roles. Binding of agonist-loaded AR onto these sites in vivo was accompanied with significant recruitment of RNA polymerase II and BRM-containing chromatin remodeling complexes to the FKBP51 locus, which resulted in changes in the histone density of the locus. Our results indicate that very distal AREs act as genuine and robust enhancers, highlighting the importance of long-range regulation of transcription by the AR.

Mannose inhibits hyaluronan synthesis by down-regulation of the cellular pool of UDP-N-acetylhexosamines.

We found that d-mannose dose-dependently decreases hyaluronan synthesis in cultured epidermal keratinocytes to approximately 50%, whereas glucose, galactose, and fructose up to 20 mm concentration had no effect. The full inhibition occurred within 3 h following introduction of mannose and did not involve down-regulation of hyaluronan synthase (Has1-3) mRNA. Following introduction of mannose, there was an approximately 50% reduction in the cellular concentration of UDP-N-acetylhexosamines (UDP-HexNAc, i.e. UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine). On the other hand, 2 mm glucosamine in the culture medium increased UDP-HexNAc content, stimulated hyaluronan secretion, and negated the effect of mannose, supporting the notion that the inhibition by mannose on hyaluronan synthesis was because of down-regulated UDP-HexNAc content. The content of UDP-glucuronic acid, the other building block for hyaluronan synthesis, was not reduced by mannose but declined from 39 to 14% of controls by 0.2-1.0 mm 4-methylumbelliferone, another compound that inhibits hyaluronan synthesis. Applying 4-methylumbelliferone and mannose together produced the expected reductions in both UDP sugars but no additive reduction in hyaluronan production, indicating that the concentration of each substrate alone can limit hyaluronan synthesis. Mannose is a potentially useful tool in studies on hyaluronan-dependent cell functions, as demonstrated by reduced rates of keratinocyte proliferation and migration, functions known to depend on hyaluronan synthesis.