Identification of novel androgen receptor target genes in prostate cancer.
BACKGROUND
The androgen receptor (AR) plays critical roles in both androgen-dependent and castrate-resistant prostate cancer (PCa). However, little is known about AR target genes that mediate the receptor's roles in disease progression.


RESULTS
Using Chromatin Immunoprecipitation (ChIP) Display, we discovered 19 novel loci occupied by the AR in castrate resistant C4-2B PCa cells. Only four of the 19 AR-occupied regions were within 10-kb 5'-flanking regulatory sequences. Three were located up to 4-kb 3' of the nearest gene, eight were intragenic and four were in gene deserts. Whereas the AR occupied the same loci in C4-2B (castrate resistant) and LNCaP (androgen-dependent) PCa cells, differences between the two cell lines were observed in the response of nearby genes to androgens. Among the genes strongly stimulated by DHT in C4-2B cells--D-dopachrome tautomerase (DDT), Protein kinase C delta (PRKCD), Glutathione S- transferase theta 2 (GSTT2), Transient receptor potential cation channel subfamily V member 3 (TRPV3), and Pyrroline-5-carboxylate reductase 1 (PYCR1)--most were less strongly or hardly stimulated in LNCaP cells. Another AR target gene, ornithine aminotransferase (OAT), was AR-stimulated in a ligand-independent manner, since it was repressed by AR siRNA knockdown, but not stimulated by DHT. We also present evidence for in vivo AR-mediated regulation of several genes identified by ChIP Display. For example, PRKCD and PYCR1, which may contribute to PCa cell growth and survival, are expressed in PCa biopsies from primary tumors before and after ablation and in metastatic lesions in a manner consistent with AR-mediated stimulation.


CONCLUSIONS
AR genomic occupancy is similar between LNCaP and C4-2B cells and is not biased towards 5' gene flanking sequences. The AR transcriptionally regulates less than half the genes nearby AR-occupied regions, usually but not always, in a ligand-dependent manner. Most are stimulated and a few are repressed. In general, response is stronger in C4-2B compared to LNCaP cells. Some of the genes near AR-occupied regions appear to be regulated by the AR in vivo as evidenced by their expression levels in prostate cancer tumors of various stages. Several AR target genes discovered in the present study, for example PRKCD and PYCR1, may open avenues in PCa research and aid the development of new approaches for disease management.
Jariwala
Unnati
U
Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, USA. jariwala@usc.edu
Prescott
Jennifer
J
Jia
Li
L
Barski
Artem
A
Pregizer
Steve
S
Cogan
Jon P
JP
Arasheben
Armin
A
Tilley
Wayne D
WD
Scher
Howard I
HI
Gerald
William L
WL
Buchanan
Grant
G
Coetzee
Gerhard A
GA
Frenkel
Baruch
B
D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism; D000728:Androgens; D001665:Binding Sites; D015815:Cell Adhesion Molecules / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D002877:Chromosomes, Human / Q000187:drug effects / Q000378:metabolism; D013196:Dihydrotestosterone / Q000494:pharmacology; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis / Q000235:genetics; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D008297:Male; D055272:Mucin-6; D009077:Mucins / Q000096:biosynthesis / Q000235:genetics; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics*; D009376:Neoplasms, Hormone-Dependent / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D009953:Ornithine-Oxo-Acid Transaminase / Q000096:biosynthesis / Q000235:genetics; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000378:metabolism; D051745:Protein Kinase C-delta / Q000096:biosynthesis / Q000235:genetics; D011762:Pyrroline Carboxylate Reductases / Q000096:biosynthesis / Q000235:genetics; D011944:Receptors, Androgen / Q000235:genetics / Q000502:physiology*; D050916:TRPV Cation Channels / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic; D000097502:delta-1-Pyrroline-5-Carboxylate Reductase
D000728:Androgens; D015815:Cell Adhesion Molecules; D013196:Dihydrotestosterone; D016326:Extracellular Matrix Proteins; D005982:Glutathione Transferase; D047908:Intracellular Signaling Peptides and Proteins; D055272:Mucin-6; D009077:Mucins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D009953:Ornithine-Oxo-Acid Transaminase; D051745:Protein Kinase C-delta; D011762:Pyrroline Carboxylate Reductases; D011944:Receptors, Androgen; D050916:TRPV Cation Channels; D000097502:delta-1-Pyrroline-5-Carboxylate Reductase; C507070:CRELD2 protein, human; C439067:MRFAP1 protein, human; C524734:MUC6 protein, human; C459445:TRPV3 protein, human; C491107:GSTT2 protein, human; C497258:PRKCD protein, human