RESUMO
MicroRNAs are involved in cancer pathogenesis and act as tumor suppressors or oncogenes. It has been recently reported that miR-148a expression is down-regulated in several types of cancer. The functional roles and target genes of miR-148a in prostate cancer, however, remain unknown. In this report, we showed that miR-148a expression levels were lower in PC3 and DU145 hormone-refractory prostate cancer cells in comparison to PrEC normal human prostate epithelial cells and LNCaP hormone-sensitive prostate cancer cells. Transfection with miR-148a precursor inhibited cell growth, and cell migration and invasion, and increased the sensitivity to anti-cancer drug paclitaxel in PC3 cells. Computer-aided algorithms predicted mitogen- and stress-activated protein kinase, MSK1, as a potential target of miR-148a. Indeed, miR-148a overexpression decreased expression of MSK1. Using luciferase reporter assays, we identified MSK1 as a direct target of miR-148a. Suppression of MSK1 expression by siRNA, however, showed little or no effects on malignant phenotypes of PC3 cells. In PC3PR cells, a paclitaxel-resistant cell line established from PC3 cells, miR-148a inhibited cell growth, and cell migration and invasion, and also attenuated the resistance to paclitaxel. MiR-148a reduced MSK1 expression by directly targeting its 3'-UTR in PC3PR cells. Furthermore, MSK1 knockdown reduced paclitaxel-resistance of PC3PR cells, indicating that miR-148a attenuates paclitaxel-resistance of hormone-refractory, drug-resistant PC3PR cells in part by regulating MSK1 expression. Our findings suggest that miR-148a plays multiple roles as a tumor suppressor and can be a promising therapeutic target for hormone-refractory prostate cancer especially for drug-resistant prostate cancer.
Assuntos
Resistencia a Medicamentos Antineoplásicos , MicroRNAs/química , Paclitaxel/farmacologia , Neoplasias da Próstata/tratamento farmacológico , Proteínas Quinases S6 Ribossômicas 90-kDa/metabolismo , Animais , Sequência de Bases , Linhagem Celular Tumoral , Células Epiteliais/citologia , Hormônios/metabolismo , Humanos , Masculino , MicroRNAs/metabolismo , Dados de Sequência Molecular , Invasividade Neoplásica , Neoplasias da Próstata/metabolismo , Proteínas Quinases S6 Ribossômicas/metabolismo , Homologia de Sequência de AminoácidosRESUMO
Tumor suppressor p53 transcriptionally regulates expression of microRNA-34a, which confers translational inhibition and mRNA degradation of genes involved in cell cycle control and apoptosis. In various cancers, miR-34a expression is lost or reduced. Here, we investigated the role of miR-34a in prostate cancer cell lines. MiR-34a expression was markedly reduced in p53-null PC3 cells and p53-mutated DU145 cells compared with LNCaP cells expressing wild-type p53. In PC3 cell, ectopic expression of miR-34a decreased the SIRT1 mRNA and protein levels as well as protein levels of known direct target genes. Reporter assays revealed that miR-34a-induced SIRT1 inhibition occurred at the transcriptional but not post-transcriptional level despite the presence of a potential miR-34a binding site within its 3'-UTR. Ectopic miR-34a expression resulted in cell cycle arrest and growth inhibition and attenuated chemoresistance to anticancer drug camptothecin by inducing apoptosis, suggesting a potential role of miR-34a for the treatment of p53-defective prostate cancer.
Assuntos
Resistencia a Medicamentos Antineoplásicos/genética , MicroRNAs/metabolismo , Neoplasias da Próstata/metabolismo , Sirtuínas/antagonistas & inibidores , Regiões 3' não Traduzidas/metabolismo , Antineoplásicos Fitogênicos/farmacologia , Sítios de Ligação , Camptotecina/farmacologia , Ciclo Celular , Linhagem Celular Tumoral , Proliferação de Células , Inibidores Enzimáticos/farmacologia , Regulação Neoplásica da Expressão Gênica , Humanos , Masculino , MicroRNAs/genética , Neoplasias da Próstata/genética , Neoplasias da Próstata/patologia , Sirtuína 1 , Sirtuínas/genética , Sirtuínas/metabolismo , Inibidores da Topoisomerase I , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismoRESUMO
SIRT1, which belongs to the family of type III histone deacetylase, is implicated in diverse cellular processes. We have determined the expression levels of SIRT1 in human prostate cancer cell lines and have examined the roles of SIRT1 in cell growth and chemoresistance. SIRT1 expression was markedly up-regulated in androgen-refractory PC3 and DU145 cells compared with androgen-sensitive LNCaP cells and its expression level was correlated with cell growth in PC3 cells. Treatment with a SIRT1 inhibitor, sirtinol, inhibited cell growth and increased sensitivity to camptothecin and cisplatin. Silencing of SIRT1 expression by siRNA also suppressed cell proliferation and reduced camptothecin resistance in PC3 cells, mimicking the chemosensitizing effect caused by sirtinol. Also in DU145 cells, sirtinol treatment enhanced sensitivity to camptothecin and cisplatin. These results suggest that up-regulation of SIRT1 expression may play an important role in promoting cell growth and chemoresistance in androgen-refractory PC3 and DU145 cells.
