Kawahara T, etal., Oncotarget. 2015 Oct 6;6(30):29860-76. doi: 10.18632/oncotarget.5007.
Little is known about biological significance of ELK1, a transcriptional factor that activates downstream targets including c-fos proto-oncogene, in bladder cancer. Recent preclinical evidence also suggests the involvement of androgen receptor (AR) signaling in
bladder cancer progression. In this study, we aim to investigate the functions of ELK1 in bladder cancer growth and their regulation by AR signals. Immunohistochemistry in bladder tumor specimens showed that the levels of phospho-ELK1 (p-ELK1) expression were significantly elevated in urothelial neoplasms, compared with non-neoplastic urothelium tissues, and were also correlated with AR positivity. Patients with p-ELK1-positive non-muscle-invasive and muscle-invasive tumors had significantly higher risks for tumor recurrence and progression, respectively. In AR-positive bladder cancer cell lines, dihydrotestosterone treatment increased ELK1 expression (mRNA, protein) and its nuclear translocation, ELK1 transcriptional activity, and c-fos expression, which was restored by an anti-androgen hydroxyflutamide. ELK1 silencing via short hairpin RNA (shRNA) resulted in decreases in cell viability/colony formation, and cell migration/invasion as well as an increase in apoptosis. Importantly, ELK1 appears to require activated AR to regulate bladder cancer cell proliferation, but not cell migration. Androgen also failed to significantly induce AR transactivation in ELK1-knockdown cells. In accordance with our in vitro findings, ELK1-shRNA expression considerably retarded tumor formation as well as its growth in xenograft-bearing male mice. Our results suggest that ELK1 plays an important role in bladder tumorigenesis and cancer progression, which is further induced by AR activation. Accordingly, ELK1 inhibition, together with AR inactivation, has the potential of being a therapeutic approach for bladder cancer.
Human chromosome Xp11.3-Xp11.23 encompasses the map location for a growing number of diseases with a genetic basis or genetic component. These include several eye disorders, syndromic and nonsyndromic forms of X-linked mental retardation (XLMR), X-linked neuromuscular diseases and susceptibility loc
i for schizophrenia, type 1 diabetes, and Graves' disease. We have constructed an approximately 2.7-Mb high-resolution physical map extending from DXS8026 to ELK1, corresponding to a genetic distance of approximately 5.5 cM. A combination of chromosome walking and sequence-tagged site (STS)-content mapping resulted in an integrated framework and transcript map, precisely positioning 10 polymorphic microsatellites (one of which is novel), 16 ESTs, and 12 known genes (RP2, PCTK1, UHX1, UBE1, RBM10, ZNF157, SYN1, ARAF1, TIMP1, PFC, ELK1, UXT). The composite map is currently anchored with 89 STSs to give an average resolution of approximately 1 STS every 30 kb. By a combination of EST database searches and in silico detection of UniGene clusters within genomic sequence generated from this template map, we have mapped several novel genes within this interval: a Na+/H+ exchanger (SLC9A7), at least two zincfinger transcription factors (KIAA0215 and Hs.68318), carbohydrate sulfotransferase-7 (CHST7), regucalcin (RGN), inactivation-escape-1 (INE1), the human ortholog of mouse neuronal protein 15.6, and four putative novel genes. Further genomic analysis enabled annotation of the sequence interval with 20 predicted pseudogenes and 21 UniGene clusters of unknown function. The combined PAC/BAC transcript map and YAC scaffold presented here clarifies previously conflicting data for markers and genes within the Xp11.3-Xp11.23 interval and provides a powerful integrated resource for functional characterization of this clonally unstable, yet gene-rich and clinically significant region of proximal Xp.
Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease with high mortality. Active TGFbeta1 is considered central to the pathogenesis of IPF. A major mechanism of TGFbeta1 activation in the lung involves the epithelially restricted alphavbeta6 integrin. Expression of the alphavbe
ta6 integrin is dramatically increased in IPF. How alphavbeta6 integrin expression is regulated in the pulmonary epithelium is unknown. Here we identify a region in the beta6 subunit gene (ITGB6) promoter acting to markedly repress basal gene transcription, which responds to both the Ets domain-containing protein Elk1 (Elk1) and the glucocorticoid receptor (GR). Both Elk1 and GR can regulate alphavbeta6 integrin expression in vitro We demonstrate Elk1 binding to the ITGB6 promoter basally and that manipulation of Elk1 or Elk1 binding alters ITGB6 promoter activity, gene transcription, and alphavbeta6 integrin expression. Crucially, we find that loss of Elk1 causes enhanced Itgb6 expression and exaggerated lung fibrosis in an in vivo model of fibrosis, whereas the GR agonist dexamethasone inhibits Itgb6 expression. Moreover, Elk1 dysregulation is present in epithelium from patients with IPF. These data reveal a novel role for Elk1 regulating ITGB6 expression and highlight how dysregulation of Elk1 can contribute to human disease.
BACKGROUND: Biological significance of ELK1, a transcriptional factor whose phosphorylation is necessary for c-fos proto-oncogene activation, in prostate cancer remains far from fully understood. In this study, we aim to investigate the role of ELK1
-weight:700;'>ELK1 in tumor growth as well as the efficacy of a selective alpha1A-adrenergic blocker, silodosin, in ELK1 activity in prostate cancer cells. METHODS: We first immunohistochemically determined the levels of phospho-ELK1 (p-ELK1) expression in radical prostatectomy specimens. We then assessed the effects of ELK1 knockdown via short hairpin RNA and silodosin on cell proliferation, migration, and invasion in prostate cancer lines. RESULTS: The levels of p-ELK1 expression were significantly higher in carcinoma than in benign (P < 0.001) or high-grade prostatic intraepithelial neoplasia (HGPIN) (P = 0.002) as well as in HGPIN than in benign (P < 0.001). Kaplan-Meier and log-rank tests revealed that moderate-strong positivity of p-ELK1 in carcinomas tended to correlate with biochemical recurrence after radical prostatectomy (P = 0.098). In PC3 and DU145 expressing ELK1 (mRNA/protein) but no androgen receptor (AR), ELK1 silencing resulted in considerable decreases in the expression of c-fos as well as in cell migration/invasion and matrix metalloproteinase-2 expression, but not in cell viability. Silodosin treatment reduced the expression/activity of ELK1 in these cells as well as the viability of AR-positive LNCaP and C4-2 cells and the migration of both AR-positive and AR-negative cells, but not the viability of AR-negative or ELK1-negative cells. Interestingly, silodosin significantly increased sensitivity to gemcitabine, but not to cisplatin or docetaxel, even in AR-negative cells. CONCLUSIONS: ELK1 is likely to be activated in prostate cancer cells and promote tumor progression. Furthermore, silodosin that inactivates ELK1 in prostate cancer cells not only inhibits their growth but also enhances the cytotoxic activity of gemcitabine. Thus, ELK1 inhibition has the potential of being a therapeutic approach for prostate cancer.
