RESUMEN
Urothelial cell carcinoma of the bladder (UCCB) is the most common form of bladder cancer and it is estimated that ~15,000 people in the United States succumbed to this disease in 2013. Bladder cancer treatment options are limited and research to understand the molecular mechanisms of this disease is needed to design novel therapeutic strategies. Recent studies have shown that microRNAs play pivotal roles in the progression of cancer. miR-148a has been shown to serve as a tumor suppressor in cancers of the prostate, colon, and liver, but its role in bladder cancer has never been elucidated. Here we show that miR-148a is down-regulated in UCCB cell lines. We demonstrate that overexpression of miR-148a leads to reduced cell viability through an increase in apoptosis rather than an inhibition of proliferation. We additionally show that miR-148a exerts this effect partially by attenuating expression of DNA methyltransferase 1 (DNMT1). Finally, our studies demonstrate that treating cells with both miR-148a and either cisplatin or doxorubicin is either additive or synergistic in causing apoptosis. These data taken together suggest that miR-148a is a tumor suppressor in UCCB and could potentially serve as a novel therapeutic for this malignancy.
Asunto(s)
ADN (Citosina-5-)-Metiltransferasas/genética , MicroARNs/genética , Neoplasias de la Vejiga Urinaria/genética , Urotelio/patología , Apoptosis , Línea Celular Tumoral , Supervivencia Celular , Cisplatino/farmacología , ADN (Citosina-5-)-Metiltransferasa 1 , Regulación hacia Abajo , Doxorrubicina/farmacología , Sinergismo Farmacológico , Epigénesis Genética , Regulación Neoplásica de la Expresión Génica , Humanos , Neoplasias de la Vejiga Urinaria/patologíaRESUMEN
Prostate cancer (PCa) is characterized by a unique dependence on optimal androgen receptor (AR) activity where physiological androgen concentrations induce proliferation but castrate and supraphysiological levels suppress growth. This feature has been exploited in bipolar androgen therapy (BAT) for castrate resistant malignancies. Here, we investigated the role of the tumor suppressor protein p14ARF in maintaining optimal AR activity and the function of the AR itself in regulating p14ARF levels. We used a tumor tissue array of differing stages and grades to define the relationships between these components and identified a strong positive correlation between p14ARF and AR expression. Mechanistic studies utilizing CWR22 xenograft and cell culture models revealed that a decrease in AR reduced p14ARF expression and deregulated E2F factors, which are linked to p14ARF and AR regulation. Chromatin immunoprecipitation studies identified AR binding sites upstream of p14ARF. p14ARF depletion enhanced AR-dependent PSA and TMPRSS2 transcription, hence p14ARF constrains AR activity. However, p14ARF depletion ultimately results in apoptosis. In PCa cells, AR co-ops p14ARF as part of a feedback mechanism to ensure optimal AR activity for maximal prostate cancer cell survival and proliferation.
Asunto(s)
Apoptosis , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , Neoplasias de la Próstata/metabolismo , Receptores Androgénicos/metabolismo , Proteína p14ARF Supresora de Tumor/metabolismo , Adulto , Anciano , Animales , Línea Celular Tumoral , Inhibidor p16 de la Quinasa Dependiente de Ciclina/genética , Factores de Transcripción E2F/genética , Factores de Transcripción E2F/metabolismo , Regulación Neoplásica de la Expresión Génica , Humanos , Calicreínas/genética , Calicreínas/metabolismo , Masculino , Ratones Desnudos , Persona de Mediana Edad , Antígeno Prostático Específico/genética , Antígeno Prostático Específico/metabolismo , Neoplasias de la Próstata/genética , Neoplasias de la Próstata/patología , Receptores Androgénicos/genética , Serina Endopeptidasas/genética , Serina Endopeptidasas/metabolismo , Transducción de Señal , Proteína p14ARF Supresora de Tumor/genéticaRESUMEN
Dicer expression is frequently altered in cancer and affects a wide array of cellular functions acting as an oncogene or tumor suppressor in varying contexts. It has been shown that Dicer expression is also deregulated in urothelial cell carcinoma of the bladder (UCCB) but the nature of this deregulation differs between reports. The aim of the present study was to gain a better understanding of the role of Dicer in bladder cancer to help determine its contribution to the disease. The results showed that Dicer transcript levels were decreased in UCCB tumor tissues as compared to normal tissues, suggesting that Dicer is a tumor suppressor. However, consistent with previous results, we demonstrated that knockdown of Dicer decreases cell viability and increases the induction of apoptosis, suggesting that Dicer is an oncogene. To resolve this discrepancy, we assessed the effects of decreased Dicer expression on epithelial-tomesenchymal transition, migration and invasion. We showed that decreased Dicer levels promoted a mesenchymal phenotype and increased migration. Additionally, the results showed that Dicer protein ablation leads to increased cell invasion, higher levels of matrix metalloproteinase-2, and decreased levels of key miRNAs shown to inhibit invasion. The results of this study suggest that decreased Dicer levels may portend a more malignant phenotype.