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

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 manufacturers 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 manufacturers instructions at the Mayo Clinic Advanced Genomics Technology Microarray Shared Resource core facility.

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Heemers HV, Schmidt LJ, Sun Z, Regan KM, Anderson SK, Duncan K, Wang D, Liu S, Ballman KV, Tindall DJ