Unknown,Transcriptomics,Genomics,Proteomics

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Identification of an SRF- and androgen-dependent gene signature in prostate cancer

ABSTRACT: The androgen receptor (AR) is the principal target for treatment of non-organ confined prostate cancer (PCa). Systems and bioinformatics approaches suggest that considerable variation exists in the mechanisms by which AR regulates expression of effector genes and point towards a role for secondary transcription factors (TFs) therein. We identified a novel indirect mechanism of androgen action in which effects of androgens on PCa cells are mediated by Serum Response Factor (SRF). To identify and characterize genes and cellular processes that are androgen-regulated in an SRF-dependent manner in PCa, Affymetrix HG-U133 Plus 2.0 GeneChip Array analysis was performed starting from RNA obtained from LNCaP cells in which androgen stimulation was combined with siRNA-mediated SRF silencing. To this end, LNCaP cells were seeded in 60 mm dishes at a density of 550,000 cells per dish in antibiotic-free medium. The next day, cells were transfected with siGenome SmartPool siRNA targeting SRF (Dharmacon, Lafayette, CO) or a custom-made control SmartPool targeting luciferase (LUC condition) using Lipofectamine 2000 (Invitrogen, Carlsbad, CA) following the manufacturer’s instructions. Forty-two hours after transfection, cells were treated with 5nM R1881 or ethanol vehicle. 3 biological triplicates were included per treatment group. Forty-eight hours later, cells were harvested in Trizol reagent (Invitrogen). RNA was isolated, purified on RNeasy columns (Qiagen, Germantown, MD) and checked for integrity by Agilent testing (Affymetrix, Santa Clara, CA). cDNA was generated and hybridized to Human Genome U133 Plus 2.0 arrays (Affymetrix) according to the manufacturer’s instructions at the Mayo Clinic Advanced Genomics Technology Microarray Shared Resource core facility. Two-factor factorial design with three biological replicates (12 total samples) using LNCaP or SRF Silenced cells treated with either R1881 or ethanol vehicle.

ORGANISM(S): Homo sapiens

SUBMITTER: Keith Anderson

PROVIDER: E-GEOD-22606 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Identification of a clinically relevant androgen-dependent gene signature in prostate cancer.

Heemers Hannelore V HV Schmidt Lucy J LJ Sun Zhifu Z Regan Kevin M KM Anderson S Keith SK Duncan Kelly K Wang Dan D Liu Song S Ballman Karla V KV Tindall Donald J DJ

Cancer research 20110215 5

The androgen receptor (AR) is the principal target for treatment of non-organ-confined prostate cancer (PCa). Androgen deprivation therapies (ADT) directed against the AR ligand-binding domain do not fully inhibit androgen-dependent signaling critical for PCa progression. Thus, information that could direct the development of more effective ADTs is desired. Systems and bioinformatics approaches suggest that considerable variation exists in the mechanisms by which AR regulates expression of effec ...[more]

PMID: 21324924

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Project description:Androgens drive the onset and progression of prostate cancer (PCa) by modulating androgen receptor (AR) transcriptional activity. Although several microarray-based studies have identified androgen-regulated genes, here we identify in-parallel global androgen-dependent changes in both gene and alternative mRNA isoform expression by exon-level analyses of the LNCaP transcriptome. While genome-wide gene expression changes correlated well with previously-published studies, we additionally uncovered a subset of 226 novel androgen-regulated genes. Gene expression pathway analysis of this subset revealed gene clusters associated with, and including the tyrosine kinase LYN, as well as components of the mTOR (mammalian target of rapamycin) pathway, which is commonly dysregulated in cancer. We also identified 1279 putative androgen-regulated alternative events, of which 325 (~25%) mapped to known alternative splicing events or alternative first/last exons. We selected 30 androgen-dependent alternative events for RT-PCR validation, including mRNAs derived from genes encoding tumour suppressors and cell cycle regulators. Of seven positively-validating events (~23%), five events involved transcripts derived from known AR gene targets. In particular, we found a novel androgen-dependent mRNA isoform derived from an alternative internal promoter within the TSC2 tumour suppressor gene, which is predicted to encode a protein lacking an interaction domain required for mTOR inhibition. We confirmed that expression of the alternative TSC2 mRNA isoform was directly regulated by androgens. Furthermore, by chromatin immunoprecipitation, we observed recruitment of AR to the alternative promoter region at early timepoints following androgen stimulation, which correlated with expression of alternative transcripts. Together, our data suggest that alternative mRNA isoform expression might mediate the cellular response to androgens, and may have roles in clinical PCa. Total 8 samples were analysed. 4 control (LNCaP cells grown in RPMI-1640 media with charcoal-stripped 10% FBS devoid of steroids) and 4 treatment (LNCaP cells grown in media devoid of steroid, and subsequently treated with 10nM R1881 synthetic androgen analogue for 24 hours).

Dataset Information

Identification of an SRF- and androgen-dependent gene signature in prostate cancer

Publications

Identification of a clinically relevant androgen-dependent gene signature in prostate cancer.

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