RESUMO
Advanced prostate cancer (PCa) has emerged as a public health concern due to population aging. Although androgen deprivation has proven efficacy in this condition, most advanced PCa patients will have to face failure of androgen deprivation as a treatment. Mutations in the androgen receptor (AR) from tumor cells have been shown to induce androgen independency both in PCa cell lines and in the clinic. We have investigated the molecular events leading to androgen independency in the 22Rv1 cell line, a commonly used preclinical model of PCa. Besides AR mutants that have been described so far, including nonsense mutations, recent data have focused on AR pre-mRNA aberrant splicing as a new mechanism leading to constitutively active truncated AR variants. In this article, we describe two novel variants arising from aberrant splicing of AR pre-mRNA, characterized by long mRNA transcripts that encode truncated, constitutively active proteins. We also describe several new nonsense mutants that share ligand independency and transcriptional activity. Finally, we show that alongside these mutants, 22Rv1 cells also express a mutant AR lacking exon 3 tandem duplication, a major feature of this cell line. By describing unreported AR mutants in the 22Rv1 cell line, our data emphasize the complexity and heterogeneity of molecular events that occur in preclinical models, and supposedly in the clinic. Future work on the 22Rv1 cell line should take into account the concomitant expression of various AR mutants.
Assuntos
Processamento Alternativo , Mutação , Neoplasias Hormônio-Dependentes/genética , Neoplasias da Próstata/genética , Precursores de RNA , Receptores Androgênicos/genética , Androgênios/metabolismo , Linhagem Celular Tumoral , Éxons , Regulação Neoplásica da Expressão Gênica , Variação Genética , Humanos , Masculino , Precursores de RNA/genética , Precursores de RNA/metabolismo , Receptores Androgênicos/metabolismoRESUMO
Suppressor of cytokine signaling (SOCS) proteins play a pivotal role in the development and progression of various cancers. We have previously shown that SOCS-3 is expressed in prostate cancer, and its expression is inversely correlated with activation of signal transducer and activator of transcription factor 3. We hypothesized that SOCS-1, if expressed in prostate cancer cells, has a growth-regulatory role in this malignancy. The presence of both SOCS-1 mRNA and protein was detected in all tested cell lines. To assess SOCS-1 expression levels in vivo, we analyzed tissue microarrays and found a high percentage of positive cells in both prostate intraepithelial neoplasias and cancers. SOCS-1 expression levels decreased in samples taken from patients undergoing hormonal therapy but increased in specimens from patients who failed therapy. In LNCaP-interleukin-6- prostate cancer cells, SOCS-1 was up-regulated by interleukin-6 and in PC3-AR cells by androgens; such up-regulation was also found to significantly impair cell proliferation. To corroborate these findings, we used a specific small interfering RNA against SOCS-1 and blocked expression of the protein. Down-regulation of SOCS-1 expression caused a potent growth stimulation of PC3, DU-145, and LNCaP-interleukin-6- cells that was associated with the increased expression levels of cyclins D1 and E as well as cyclin-dependent kinases 2 and 4. In summary, we show that SOCS-1 is expressed in prostate cancer both in vitro and in vivo and acts as a negative growth regulator.
Assuntos
Ciclina D1/metabolismo , Ciclina E/metabolismo , Quinases Ciclina-Dependentes/metabolismo , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/patologia , Proteínas Supressoras da Sinalização de Citocina/metabolismo , Idoso , Androgênios/farmacologia , Western Blotting , Regulação para Baixo , Humanos , Técnicas Imunoenzimáticas , Interleucina-6/farmacologia , Masculino , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/genética , Recidiva Local de Neoplasia/metabolismo , Recidiva Local de Neoplasia/patologia , Próstata/metabolismo , Próstata/patologia , Neoplasia Prostática Intraepitelial/genética , Neoplasia Prostática Intraepitelial/metabolismo , Neoplasia Prostática Intraepitelial/patologia , Neoplasias da Próstata/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/farmacologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteína 1 Supressora da Sinalização de Citocina , Proteínas Supressoras da Sinalização de Citocina/antagonistas & inibidores , Proteínas Supressoras da Sinalização de Citocina/genética , Análise Serial de Tecidos , Células Tumorais CultivadasRESUMO
Mutations in the human androgen receptor (AR) gene that lead to C-terminus truncated AR variants are frequently detected in prostate cancer (PC). These AR variants lack both the ligand-binding domain (LBD) and the AF-2 region. The aim of this study was to delineate the alternative mechanisms that lead to the activation of such AR variants as they are unresponsive to hormone stimulation, and to outline consequences of the loss of the LBD/AF-2 region on their functional properties. By using an MMTV-luciferase reporter construct and LY294002, UO126, or ZD1839, inhibitor of PI3K, MEK1/2, and EGFR signaling pathway respectively, we demonstrated that phosphorylation was required for full transcriptional activities of one these AR variants, the Q640X mutant AR. Western-blot analyses confirmed that these inhibitors affect the phosphorylation status of this AR variant. Furthermore, studies of the intranuclear colocalization of the Q640X AR with cofactors, such as CBP, GRIP-1, and c-Jun, reveal that the transcriptional complex that forms around the mutant AR is different to that formed around the wild type AR. We demonstrated that CBP and c-Jun are highly recruited by the mutant AR, and this leads to an unexpected activation of AP-1, NFAT, and NFkappaB transcriptional activities. Similar enhanced activities of these transcription factors were not observed with the wild type AR. The importance of the LBD/AF-2 for the regulation of AR transcriptional activities, the impact of the presence of such AR variants on PC cells proliferation and survival, and on progression to androgen independence are discussed.
Assuntos
Regulação Neoplásica da Expressão Gênica , Variação Genética , Neoplasias Hormônio-Dependentes/genética , Neoplasias da Próstata/genética , Receptores Androgênicos/genética , Receptores ErbB/antagonistas & inibidores , Receptores ErbB/metabolismo , Humanos , MAP Quinase Quinase 1/antagonistas & inibidores , MAP Quinase Quinase 1/metabolismo , MAP Quinase Quinase 2/antagonistas & inibidores , MAP Quinase Quinase 2/metabolismo , Masculino , NF-kappa B/genética , NF-kappa B/metabolismo , Fatores de Transcrição NFATC/genética , Fatores de Transcrição NFATC/metabolismo , Neoplasias Hormônio-Dependentes/metabolismo , Neoplasias Hormônio-Dependentes/patologia , Fosfatidilinositol 3-Quinases/metabolismo , Inibidores de Fosfoinositídeo-3 Quinase , Fosforilação , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/patologia , Receptores Androgênicos/metabolismo , Fator de Transcrição AP-1/genética , Fator de Transcrição AP-1/metabolismo , Transcrição Gênica , Ativação Transcricional , Células Tumorais CultivadasRESUMO
PURPOSE: CITED4 is one member of a family of transcriptional cofactors, several of which are deregulated in a variety of tumors, including colorectal cancer (CRC). We modulated CITED4 expression, in vitro, and analyzed the associated phenotypic and gene expression changes. METHODS: CITED4-overexpressing and shRNA-mediated knockdown cell lines and control cell lines were established in the CRC cell line SW480. The cells were analyzed for changes in proliferation, apoptosis/cell cycle, migration, invasion, colony formation and adhesion. mRNA expression changes were determined by microarray and pathway analysis, and several deregulated genes were validated by qRT-PCR and Western blotting. Based on results obtained from these studies, the status of the actin cytoskeleton was evaluated by phalloidin/vinculin staining. RESULTS: Phenotypically, the CITED4-overexpressing cell line showed only moderate changes in adhesion. Microarray analysis identified several deregulated genes, including several G protein-coupled receptors. Phenotypic analysis of the CITED4 shRNA knockdown cell line demonstrated decreased cell proliferation and G2 cell cycle blockage. Microarray analysis identified many deregulated genes, and pathway analysis discovered genes linked to actin-associated adherens junctions/tight junctions (claudin-4, claudin-7, ezrin, MET, ß-catenin). Phenotypically, no morphological changes of the actin cytoskeleton were seen. CONCLUSIONS: Upregulation of CITED4 in SW480 resulted in no obvious phenotype. CITED4 shRNA-mediated knockdown led to decreased cellular proliferation and modulation of a large number of genes, including the c-MET tyrosine kinase and several actin-associated adherens junctions/tight junction genes.
Assuntos
Junções Aderentes/genética , Biomarcadores Tumorais/genética , Proliferação de Células , Neoplasias Colorretais/metabolismo , Neoplasias Colorretais/patologia , Inativação Gênica , Junções Íntimas/genética , Fatores de Transcrição/metabolismo , Actinas/metabolismo , Apoptose , Biomarcadores Tumorais/metabolismo , Western Blotting , Neoplasias Colorretais/genética , Perfilação da Expressão Gênica , Humanos , RNA Mensageiro/genética , RNA Interferente Pequeno/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/genética , Células Tumorais CultivadasRESUMO
Fibroblast growth factor-2 (FGF-2) is highly expressed in prostate cancer. It promotes tumour progression through multiple pathways including those of signal transducers and activators of transcription factor 3 (STAT3), mitogen-activated protein kinases (MAPKs) and Akt. In previous studies, we have reported that STAT3 phosphorylation inversely correlates with suppressor of cytokine signalling-3 (SOCS-3) expression in prostate cancer cells. Recently, it has become evident that SOCS-3-negative regulation is not only limited to the interleukin-6 (IL-6) receptor. We hypothesised that SOCS-3 interferes with FGF signalling, thus influencing the outcome of its action in prostate cancer cells. For this purpose, we treated DU-145 and LNCaP-IL-6+ cells with increasing concentrations of FGF-2, and verified protein phosphorylation. In the presence of FGF-2, neither STAT3, STAT1, nor Akt could be phosphorylated. Solely the p44/p42 MAPK pathway was activated after FGF-2 stimulation. We show for the first time that SOCS-3 interferes with the FGF-2 signalling pathway by modulating p44 and p42 phosphorylation in prostate cancer cells. Decreased SOCS-3 protein expression results in increased MAPK phosphorylation, whereas SOCS-3 overexpression leads to a decreased cellular proliferation and migration. On the basis of the present results, we propose that SOCS-3 is a novel modulator of FGF-2-regulated cellular events in prostate cancer.
Assuntos
Carcinoma/patologia , Movimento Celular , Proliferação de Células , Fator 2 de Crescimento de Fibroblastos/antagonistas & inibidores , Sistema de Sinalização das MAP Quinases , Neoplasias da Próstata/patologia , Proteínas Supressoras da Sinalização de Citocina/fisiologia , Carcinoma/metabolismo , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Fator 2 de Crescimento de Fibroblastos/farmacologia , Flavonoides/farmacologia , Humanos , Interleucina-6/farmacologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Masculino , Proteína Quinase 1 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Fosforilação/efeitos dos fármacos , Neoplasias da Próstata/metabolismo , Proteína 3 Supressora da Sinalização de Citocinas , Proteínas Supressoras da Sinalização de Citocina/metabolismoRESUMO
The emergence of mutations in the androgen receptor (AR) gene is a recurrent event during progression of prostate cancer (PCa) on androgen ablation therapy. In this study, we show that nonsense mutations that lead to carboxyl-terminal end truncated ARs are found at high frequency in metastatic PCas. Transcriptional activities of the Q640X mutant AR in the androgen-sensitive LNCaP cell line differ to those of the wild-type AR. Indeed, this mutant AR exhibits strong and ligand-independent transcriptional activities from an artificial promoter construct containing two repeats of androgen-responsive elements, but is inactive on the human PSA gene promoter. Nevertheless, the expression of the Q640X mutant AR in LNCaP cells is accompanied by an increase in the level of PSA protein, and by an increase in the expression of the endogenous AR gene. This enhanced expression of the endogenous AR gene is not limited to the sole transfected cells, but is observed in non-transfected neighboring cells. Additionally, in co-cultures of transfected and non-transfected LNCaP cells, the Q640X mutant AR leads to an unpredicted nuclear localization of the endogenous AR protein in the two cellular populations and this, in the absence of androgen. These data indicate that cells expressing the Q640X mutant AR acquire the property to emit a signal that activates the AR in neighboring cells by a paracrine mechanism and in a ligand-independent manner. Our data strongly support the notion of cooperation among tumor cells in PCa and could be of relevance for the understanding of progression on androgen ablation therapy.