UMLS:C0376358 - FACTA Search

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Query: UMLS:C0376358 (prostate cancer)
59,338 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Androgen receptor (AR) is essential for the growth and progression of prostate cancer in both hormone-sensitive and hormone-refractory disease. A DNA-binding polyamide that targets the consensus androgen response element binds the prostate-specific antigen (PSA) promoter androgen response element, inhibits androgen-induced expression of PSA and several other AR-regulated genes in cultured prostate cancer cells, and reduces AR occupancy at the PSA promoter and enhancer. Down-regulation of PSA by this polyamide was comparable to that produced by the synthetic antiandrogen bicalutamide (Casodex) at the same concentration. Genome-wide expression analysis reveals that a similar number of transcripts are affected by treatment with the polyamide and with bicalutamide. Direct inhibition of the AR-DNA interface by sequence-specific DNA binding small molecules could offer an alternative approach to antagonizing AR activity.
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PMID:Suppression of androgen receptor-mediated gene expression by a sequence-specific DNA-binding polyamide. 1756 3

Recently, we identified recurrent gene fusions involving the 5' untranslated region of the androgen-regulated gene TMPRSS2 and the ETS (E26 transformation-specific) family genes ERG, ETV1 or ETV4 in most prostate cancers. Whereas TMPRSS2-ERG fusions are predominant, fewer TMPRSS2-ETV1 cases have been identified than expected on the basis of the frequency of high (outlier) expression of ETV1 (refs 3-13). Here we explore the mechanism of ETV1 outlier expression in human prostate tumours and prostate cancer cell lines. We identified previously unknown 5' fusion partners in prostate tumours with ETV1 outlier expression, including untranslated regions from a prostate-specific androgen-induced gene (SLC45A3) and an endogenous retroviral element (HERV-K_22q11.23), a prostate-specific androgen-repressed gene (C15orf21), and a strongly expressed housekeeping gene (HNRPA2B1). To study aberrant activation of ETV1, we identified two prostate cancer cell lines, LNCaP and MDA-PCa 2B, that had ETV1 outlier expression. Through distinct mechanisms, the entire ETV1 locus (7p21) is rearranged to a 1.5-megabase prostate-specific region at 14q13.3-14q21.1 in both LNCaP cells (cryptic insertion) and MDA-PCa 2B cells (balanced translocation). Because the common factor of these rearrangements is aberrant ETV1 overexpression, we recapitulated this event in vitro and in vivo, demonstrating that ETV1 overexpression in benign prostate cells and in the mouse prostate confers neoplastic phenotypes. Identification of distinct classes of ETS gene rearrangements demonstrates that dormant oncogenes can be activated in prostate cancer by juxtaposition to tissue-specific or ubiquitously active genomic loci. Subversion of active genomic regulatory elements may serve as a more generalized mechanism for carcinoma development. Furthermore, the identification of androgen-repressed and insensitive 5' fusion partners may have implications for the anti-androgen treatment of advanced prostate cancer.
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PMID:Distinct classes of chromosomal rearrangements create oncogenic ETS gene fusions in prostate cancer. 1921 47

Fibroblast growth factors (FGFs) are potent mitogens, morphogens, and inducers of angiogenesis, and FGF signaling governs the genesis of diverse tissues and organs from the earliest stages. With such fundamental embryonic and homeostatic roles, it follows that aberrant FGF signaling underlies a variety of diseases. Pathological modifications to FGF expression are known to cause salivary gland aplasia and autosomal dominant hypophosphatemic rickets, while mutations in FGF receptors (FGFRs) result in a range of skeletal dysplasias. Anomalous FGF signaling is also associated with cancer development and progression. Examples include the overexpression of FGF2 and FGF6 in prostate cancer, and FGF8 overexpression in breast and prostate cancers. Alterations in FGF signaling regulators also impact tumorigenesis, which is exemplified by the down-regulation of Sprouty 1, a negative regulator of FGF signaling, in prostate cancer. In addition, several FGFRs are mutated in human cancers (including FGFR2 in gastric cancer and FGFR3 in bladder cancer). We recently identified intriguing alterations in the FGF pathway in a novel model of bladder carcinoma that consists of a parental cell line (TSU-Pr1/T24) and two sublines with increasing metastatic potential (TSU-Pr1-B1 and TSU-Pr1-B2), which were derived successively through in vivo cycling. It was found that the increasingly metastatic sublines (TSU-Pr1-B1 and TSU-Pr1-B2) had undergone a mesenchymal to epithelial transition. FGFR2IIIc expression, which is normally expressed in mesenchymal cells, was increased in the epithelial-like TSU-Pr1-B1 and TSU-Pr1-B2 sublines and FGFR2 knock-down was associated with the reversion of cells from an epithelial to a mesenchymal phenotype. These observations suggest that modified FGF pathway signaling should be considered when studying other cancer types.
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PMID:Aberrant fibroblast growth factor receptor signaling in bladder and other cancers. 1769 26

The androgen-regulated protein androgen-induced bZIP (AIbZIP) is a bZIP transcription factor that localizes to the membrane of the endoplasmic reticulum (ER). The physiological role of AIbZIP is unknown, but other ER-bound transcription factors such as ATF6 and SREBPs play a crucial role in the regulation of protein processing and lipid synthesis, respectively. In response to alterations in the intracellular milieu, ATF6 and SREBPs are processed to their transcriptionally active forms by regulated intramembrane proteolysis. In humans, AIbZIP mRNA is expressed in several organs including the pancreas, liver, and gonads, but it is especially abundant in prostate epithelial cells. We therefore used LNCaP human prostate cancer cells as a model to identify stimuli that lead to AIbZIP activation and define the transcriptional targets of AIbZIP. In LNCaP cells, AIbZIP was processed to its transcriptionally active form by drugs that deplete ER calcium stores (i.e., A23187 and caffeine), but it was unaffected by an inhibitor of protein glycosylation (tunicamycin). To identify AIbZIP-regulated genes, we generated LNCaP cell lines that conditionally express the processed form of AIbZIP and used Affymetrix microarrays to screen for AIbZIP-regulated transcripts. Selected genes (n = 48) were validated by Northern blot hybridization. The results reveal that the downstream targets of AIbZIP include genes that are implicated in protein processing (e.g., BAG3, DNAJC12, KDELR3). Strikingly, a large number of AIbZIP-regulated transcripts encode proteins that are involved in transcriptional regulation, small molecule transport, signal transduction, and metabolism. These results suggest that AIbZIP plays a novel role in cell homeostasis.
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PMID:Transcriptional profiling of genes that are regulated by the endoplasmic reticulum-bound transcription factor AIbZIP/CREB3L4 in prostate cells. 1771 38

CR6-interacting factor 1 (CRIF1) was previously identified as a nuclear protein that interacts with members of the Gadd45 family and plays a role as a negative regulator in cell growth. However, the nuclear function of CRIF1 remains largely unknown. In this study, we demonstrate that CRIF1 acts as a novel corepressor of the androgen receptor (AR) in prostatic cells. Transient transfection studies show that CRIF1 specifically represses AR transcriptional activation of target promoters in a dose-dependent manner. Additionally, CRIF1 is recruited with AR to the endogenous AR target promoters. In vivo and in vitro protein interaction assays reveal that CRIF1 directly interacts with AR via the activation function-1 domain of AR. Interestingly, both the N-terminal and C-terminal half-regions of CRIF1 are independently capable of interacting with and repressing the transactivation of AR. CRIF1 represses AR transactivation through competition with AR coactivators. In addition, the CRIF1-mediated inhibition of AR transactivation involves the recruitment of histone deacetylase 4. Down-regulation of CRIF1 by small interfering RNA increases the transactivation of AR and the mRNA level of the AR target gene prostate-specific antigen, whereas the overexpression of CRIF1 decreases the prostate-specific antigen mRNA level. Finally, the overexpression of CRIF1 inhibits the androgen-induced proliferation and cell cycle progression of prostate cancer cells. Taken together, these results suggest that CRIF1 acts as an AR corepressor and may play an important role in the regulation of AR-positive growth of prostate cancer.
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PMID:CR6-interacting factor 1 represses the transactivation of androgen receptor by direct interaction. 1788 9

Insulin-like growth factor binding protein-3 (IGFBP-3), an antiproliferative and proapoptotic protein, has been shown to be upregulated by growth inhibitory concentrations of androgens in LNCaP human prostate cancer (PCa) cells, but the mechanism of regulation and the role of IGFBP-3 in the modulation of PCa cell proliferation are unknown. In this study, we have examined the effects of a range of concentrations of the synthetic androgen R1881 on IGFBP-3 expression and cell growth in LNCaP cells. We have also investigated the role of androgen-stimulated IGFBP-3 in androgen-induced growth inhibition. We show that low doses of R1881 stimulate LNCaP cell proliferation, but do not induce IGFBP-3 expression, whereas high doses of R1881 that inhibit cell growth, significantly increase expression of IGFBP-3. Importantly, we demonstrate that the combination of calcitriol and androgens not only synergistically upregulates IGFBP-3 expression but also inhibits cell growth better than either hormone alone. siRNA knockdown of IGFBP-3 expression partially reverses the growth inhibition by calcitriol and by androgens. Furthermore, we find that the growth inhibitory dose of R1881 leads to increases in the cyclin dependent kinase inhibitors (CDKIs), p21 and p27 as well as to G1 arrest. These changes can be blocked or partially reversed by IGFBP-3 siRNA, indicating that the induction of CDKIs is downstream of IGFBP-3. Our data suggest, for the first time, that IGFBP-3 is involved in the antiproliferative action of high doses of androgens partly through p21 and p27 pathways and that IGFBP-3 may contribute significantly to androgen-induced changes in LNCaP cell growth.
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PMID:The role of insulin-like growth factor binding protein-3 in the growth inhibitory actions of androgens in LNCaP human prostate cancer cells. 1791 55

Androgen receptor (AR) transactivation is known to enhance prostate cancer cell survival. However, the precise effectors by which the prosurvival effects of androgen and AR drive prostate cancer progression are poorly defined. Here, we identify a novel feed-forward loop involving cooperative interactions between ligand-activated AR and heat-shock protein 27 (Hsp27) phospho-activation that enhance AR stability, shuttling, and transcriptional activity, thereby increasing prostate cancer cell survival. Androgen-bound AR induces rapid Hsp27 phosphorylation on Ser(78) and Ser(82) residues in an AR- and p38 kinase-dependent manner. After this androgen-induced, non-nuclear phospho-activation, Hsp27 displaces Hsp90 from a complex with AR to chaperone AR into the nucleus and interact with its response elements to enhance its genomic activity. Inhibition of Hsp27 phosphorylation, or knockdown using the antisense drug OGX-427, shifted the association of AR with Hsp90 to MDM2, increased proteasome-mediated AR degradation, decreased AR transcriptional activity, and increased prostate cancer LNCaP cell apoptotic rates. OGX-427 treatment of mice bearing LNCaP xenografts transfected with an androgen-regulated, probasin-luciferase reporter construct resulted in decreased bioluminescence and serum PSA levels as pharmacodynamic readouts of AR activity, as well as AR, Hsp27, and Hsp90 protein levels in LNCaP tumor tissue. These data identify novel nongenomic mechanisms involving androgen, AR, and Hsp27 activation that cooperatively interact to regulate the genomic activity of AR and justify further investigation of Hsp27 knockdown as an AR disrupting therapeutic strategy in prostate cancer.
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PMID:Cooperative interactions between androgen receptor (AR) and heat-shock protein 27 facilitate AR transcriptional activity. 1797 89

Prostate cancer (PCa) cell proliferation is dependent on activation of the androgen receptor (AR), a ligand-dependent transcription factor. AR activation controls G1-S phase progression through fostering enhanced translation of the D-type cyclins, which promote cell cycle progression through activation of CDK4/6. However, the D-type cyclins harbor additional, CDK4/6 kinase-independent, functions through manipulation of transcription factors, including AR. It was previously established that cyclins D1 and D3 have the potential to modulate AR, and with regard to cyclin D1, disruption of this function occurs in human tumors. Therefore, it was essential to interrogate cyclin D3 function in this tumor type. Here, we show that cyclin D3 is found in association with AR in PCa cells, as mediated through a conserved motif. Cyclin D3 functions to attenuate AR activity through defined mechanisms that include modulation of ligand-dependent conformational changes and modulation of chromatin binding activity. Accumulated cyclin D3 slows cell proliferation in AR-dependent cells, thus suggesting that androgen-induced D-type cyclin production serves to temper the mitogenic response to androgen. Supporting this hypothesis, it is shown that cyclin D3 expression is reduced in primary PCas as a function of tumor grade, and inversely correlates with the proliferative index. In total, these data identify cyclin D3 as a critical modulator of the androgen response, whose deregulation may foster unchecked AR activity in PCa.
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PMID:Cyclin D3 action in androgen receptor regulation and prostate cancer. 1808 30

The androgen receptor (AR) is involved in the development and progression of prostate cancers. However, the mechanisms by which this occurs remain incompletely understood. In previous reports, hepatocyte nuclear factor-3alpha (HNF-3alpha) has been shown to be expressed in the epithelia of the prostate gland, and has been determined to regulate the transcription of prostate-specific genes. In this study, we report that HNF-3alpha functions as a novel corepressor of AR in prostatic cells. HNF-3alpha represses AR transactivation on target promoters containing the androgen response element (ARE) in a dose-dependent manner. HNF-3alpha interacts physically with AR, and negatively regulates AR transactivation via competition with AR coactivators, including GRIP1. Furthermore, HNF-3alpha overexpression reduces the androgen-induced expression of prostate-specific antigen (PSA) in LNCaP cells. Taken together, our findings indicate that HNF-3alpha is a novel corepressor of AR, and predict its effects on the proliferation of prostate cancer cells.
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PMID:Hepatocyte nuclear factor-3 alpha (HNF-3alpha) negatively regulates androgen receptor transactivation in prostate cancer cells. 1817 53

Prostate cancer is the most common visceral malignancy in men. Androgen deprivation therapy (ADT) is commonly used in patients with nonmetastatic prostate cancer and is associated with significant bone loss and fractures. The greatest bone loss occurs during initiation of ADT. Men should have assessment of skeletal integrity with bone mineral density examination by dual x-ray absorptiometry of the hip and spine. Men with fragility fractures or osteoporosis by bone density should be considered for bisphosphonate therapy. Men with low bone mass may need antiresorptive therapy, depending on other risk factors. Men with a normal bone mineral density should be followed up closely with bone densitometry while on ADT. All men should receive preventive measures with calcium (1200 mg daily in divided doses), vitamin D (800-1000 IU/d), and weight-bearing exercise. Men should be evaluated for additional secondary causes of bone loss including vitamin D insufficiency. Guidelines are needed for androgen-induced bone loss screening and treatment.
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PMID:Approach to the prostate cancer patient with bone disease. 1817 5

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