Identification of ETS-like transcription factor 4 as a novel androgen receptor target in prostate cancer cells

Abstract

Transcriptional control by androgens via androgen receptor (AR) is strongly involved in prostate cancer development, but the critical target genes have remained elusive. We have characterized E twenty-six-like transcription factor 4 (ELK4) (also known as serum response factor accessory protein 1) as a novel AR target in human prostate cancer cells. In-silico screening identified three putative AR response elements (AREs) within À10 kb from the transcription start site of ELK4. Both ARE1 at À167/À153 and ARE2 at À481/À467 bound AR in vitro and mediated androgen induction as isolated elements in transcription assays in non-prostate cells. However, merely the ARE2 that cooperates with a proximal forkhead box A1-binding site was critical for the ARdependent activation of ELK4 promoter in prostate cancer cells. Preferential loading of holo-AR onto the ARE2 and concomitant recruitment of RNA polymerase II onto the ELK4 promoter was confirmed in prostate cancer cells by chromatin immunoprecipitation. Database searches indicated that the expression of ELK4 is markedly increased in prostate cancers relative to normal prostates. Moreover, prostate cancer tissue immunostainings showed that nuclear ELK4 levels are significantly increased in androgen-refractory prostate cancers compared to untreated tumours. Reduction of the amount of ELK4 in LNCaP cells by RNAi retarded cell growth. In conclusion, ELK4 is a direct AR target in prostate cancer cells. Androgens may thus contribute to the growth of prostate cancer via influencing ELK4 levels.

The controversial role of Sirtuins in tumorigenesis — SIRT7 joins the debate

“…ELK4-mediated stabilization appears to be particularly important for gene repression in the setting of elevated SIRT7 expression, as is seen in cancer. Consistent with these results, lower H3K18Ac levels are associated with overexpression of ELK4 and SIRT7 in prostate cancer [9]. Finally, this study shows that SIRT7 is necessary for maintenance of abnormal growth properties characteristic of cancer cells, including anchorage-independent growth and growth in low serum conditions, and for tumor formation in xenograft assays.…”

ZNF451 Is a Novel PML Body- and SUMO-Associated Transcriptional Coregulator

“…Interestingly, ablation of endogenous ZNF451 in LNCaP cells attenuated expression of several AR target genes, including TMPRSS2 48 and ELK4, 49 without significantly influencing the expression of AR. However, similarly to PML, ZNF451 cannot be considered a classic steroid receptor coactivator as it does not harbor any intrinsic transcription activation function.…”

“…The supernatants of cells lysed in reporter lysis buffer (Promega) were used for measurement of luciferase activity, β-galactosidase activity, and total protein using Luciferase Assay Reagent (Promega) and Protein Assay Dye (Bio-Rad Laboratories), respectively, as previously described. 49 The relative LUC activities are represented as the means ± standard deviations (i.e., luciferase light units divided by β-galactosidase activity). Experiments were done as triplicates and repeated at least three times.…”

Increased Expression of Androgen Receptor Sensitizes Prostate Cancer Cells to Low Levels of Androgens

“…S3). The ELK4 gene is known to be an AR target in human prostate cancer cells with association to cell growth in vitro (27).…”