Identification of novel androgen response genes in prostate cancer cells by coupling chromatin immunoprecipitation and genomic microarray analysis.

The androgen receptor (AR) plays a key role as a transcriptional factor in prostate development and carcinogenesis. Identification of androgen-regulated genes is essential to elucidate the AR pathophysiology in prostate cancer. Here, we identified androgen target genes that are directly regulated by AR in LNCaP cells, by combining chromatin immunoprecipitation (ChIP) with tiling microarrays (ChIP-chip). ChIP-enriched or control DNAs from the cells treated with R1881 were hybridized with the ENCODE array, in which a set of regions representing approximately 1% of the whole genome. We chose 10 bona fide AR-binding sites (ARBSs) (P<1e-5) and validated their significant AR recruitment ligand dependently. Eight upregulated genes by R1881 were identified in the vicinity of the ARBSs. Among the upregulated genes, we focused on UGT1A and CDH2 as AR target genes, because the ARBSs close to these genes (in UGT1A distal promoter and CDH2 intron 1) were most significantly associated with acetylated histone H3/H4, RNA polymerase II and p160 family co-activators. Luciferase reporter constructs including those two ARBSs exhibited ligand-dependent transcriptional regulator/enhancer activities. The present study would be powerful to extend our knowledge of the diversity of androgen genetic network and steroid action in prostate cancer cells.