title: Identification of novel genes that regulate androgen receptor signaling and growth of androgen-deprived prostate cancer cells.
abstract: Prostate cancer progression to castration refractory disease is associated with anomalous transcriptional activity of the androgen receptor (AR) in an androgen-depleted milieu. To identify novel gene products whose downregulation transactivates AR in prostate cancer cells, we performed a screen of enzymatically-generated shRNA lenti-libraries selecting for transduced LNCaP cells with elevated expression of a fluorescent reporter gene under the control of an AR-responsive promoter. The shRNAs present in selected populations were analyzed using high-throughput sequencing to identify target genes. Highly enriched gene targets were then validated with siRNAs against selected genes, testing first for increased expression of luciferase from an AR-responsive promoter and then for altered expression of endogenous androgen-regulated genes in LNCaP cells. We identified 20 human genes whose silencing affected the expression of exogenous and endogenous androgen-responsive genes in prostate cancer cells grown in androgen-depleted medium. Knockdown of four of these genes upregulated the expression of endogenous AR targets and siRNAs targeting two of these genes (IGSF8 and RTN1) enabled androgen-independent proliferation of androgen-dependent cells. The effects of IGSF8 appear to be mediated through its interaction with a tetraspanin protein, CD9, previously implicated in prostate cancer progression. Remarkably, homozygous deletions of IGSF8 are found almost exclusively in prostate cancers but not in other cancer types. Our study shows that androgen independence can be achieved through the inhibition of specific genes and reveals a novel set of genes that regulate AR signaling in prostate cancers.
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA.|Department of Biological Sciences, University of South Carolina, Columbia, SC, USA.
authors.forename: Elina
authors.initials: E
authors.lastname: Levina
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Ji
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA.
authors.forename: Mengqiang
authors.initials: M
authors.lastname: Chen
authors.affiliation: Cancer Center, Ordway Research Institute, Albany, NY, USA.
authors.forename: Mirza
authors.initials: M
authors.lastname: Baig
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA.
authors.forename: David
authors.initials: D
authors.lastname: Oliver
authors.affiliation: Cancer Center, Ordway Research Institute, Albany, NY, USA.
authors.forename: Patrice
authors.initials: P
authors.lastname: Ohouo
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA.
authors.forename: Chang-uk
authors.initials: CU
authors.lastname: Lim
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA.
authors.forename: Garry
authors.initials: G
authors.lastname: Schools
authors.affiliation: Wadsworth Center, NY State Department of Health, Albany, NY, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Carmack
authors.affiliation: Wadsworth Center, NY State Department of Health, Albany, NY, USA.
authors.forename: Ye
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA.
authors.forename: Eugenia V
authors.initials: EV
authors.lastname: Broude
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA.
authors.forename: Igor B
authors.initials: IB
authors.lastname: Roninson
authors.affiliation: The Vancouver Prostate Centre, Vancouver, BC, Canada.
authors.forename: Ralph
authors.initials: R
authors.lastname: Buttyan
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Shtutman
mesh_terms: D000728:Androgens / Q000172:deficiency*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D018450:Disease Progression; D015870:Gene Expression; D006801:Humans; D008297:Male; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D064129:Prostatic Neoplasms, Castration-Resistant / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D011944:Receptors, Androgen / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics
chemical_list: C410798:AR protein, human; D000728:Androgens; D034741:RNA, Small Interfering; D011944:Receptors, Androgen
keywords: IGSF8; androgen receptor; prostate cancer; shRNA; tumor progression