RESUMO
Increased retinoic acid receptor beta (RARbeta(2)) gene expression is a hallmark of cancer cell responsiveness to retinoid anticancer effects. Moreover, low basal or induced RARbeta(2) expression is a common feature of many human cancers, suggesting that RARbeta(2) may act as a tumour suppressor gene in the absence of supplemented retinoid. We have previously shown that low RARbeta(2) expression is a feature of advanced neuroblastoma. Here, we demonstrate that the ABC domain of the RARbeta(2) protein alone was sufficient for the growth inhibitory effects of RARbeta(2) on neuroblastoma cells. ATP7A, the copper efflux pump, is a retinoid-responsive gene, was upregulated by ectopic overexpression of RARbeta(2). The ectopic overexpression of the RARbeta(2) ABC domain was sufficient to induce ATP7A expression, whereas, RARbeta(2) siRNA blocked the induction of ATP7A expression in retinoid-treated neuroblastoma cells. Forced downregulation of ATP7A reduced copper efflux and increased viability of retinoid-treated neuroblastoma cells. Copper supplementation enhanced cell growth and reduced retinoid-responsiveness, whereas copper chelation reduced the viability and proliferative capacity. Taken together, our data demonstrates ATP7A expression is regulated by retinoic acid receptor beta and it has effects on intracellular copper levels, revealing a link between the anticancer action of retinoids and copper metabolism.
Assuntos
Adenosina Trifosfatases/fisiologia , Proteínas de Transporte de Cátions/fisiologia , Neuroblastoma/tratamento farmacológico , Receptores do Ácido Retinoico/fisiologia , Adenosina Trifosfatases/genética , Proteínas de Transporte de Cátions/genética , Linhagem Celular Tumoral , Proliferação de Células , Cobre/metabolismo , ATPases Transportadoras de Cobre , Regulação Neoplásica da Expressão Gênica , Humanos , Neuroblastoma/patologia , Retinoides/farmacologia , Retinoides/uso terapêuticoRESUMO
Myc oncoproteins are commonly upregulated in human cancers of different organ origins, stabilized by Aurora A, degraded through ubiquitin-proteasome pathway-mediated proteolysis, and exert oncogenic effects by modulating gene and protein expression. Histone deacetylases are emerging as targets for cancer therapy. Here we demonstrated that the class III histone deacetylase SIRT2 was upregulated by N-Myc in neuroblastoma cells and by c-Myc in pancreatic cancer cells, and that SIRT2 enhanced N-Myc and c-Myc protein stability and promoted cancer cell proliferation. Affymetrix gene array studies revealed that the gene most significantly repressed by SIRT2 was the ubiquitin-protein ligase NEDD4. Consistent with this finding, SIRT2 repressed NEDD4 gene expression by directly binding to the NEDD4 gene core promoter and deacetylating histone H4 lysine 16. Importantly, NEDD4 directly bound to Myc oncoproteins and targeted Myc oncoproteins for ubiquitination and degradation, and small-molecule SIRT2 inhibitors reactivated NEDD4 gene expression, reduced N-Myc and c-Myc protein expression, and suppressed neuroblastoma and pancreatic cancer cell proliferation. Additionally, SIRT2 upregulated and small-molecule SIRT2 inhibitors decreased Aurora A expression. Our data reveal a novel pathway critical for Myc oncoprotein stability, and provide important evidences for potential application of SIRT2 inhibitors for the prevention and therapy of Myc-induced malignancies.
Assuntos
Proteínas Proto-Oncogênicas c-myc/metabolismo , Sirtuína 2/metabolismo , Aurora Quinases , Linhagem Celular Tumoral , Proliferação de Células , Complexos Endossomais de Distribuição Requeridos para Transporte , Expressão Gênica , Humanos , Naftóis/farmacologia , Ubiquitina-Proteína Ligases Nedd4 , Fenilpropionatos/farmacologia , Fosforilação , Ligação Proteica , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Estabilidade Proteica , Proteínas Proto-Oncogênicas c-myc/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-myc/genética , Interferência de RNA , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/metabolismo , Sirtuína 2/antagonistas & inibidores , Sirtuína 2/genética , Ubiquitina-Proteína Ligases , Ubiquitinação , Regulação para Cima/efeitos dos fármacosRESUMO
Embryonal cancer can arise from postnatally persistent embryonal remnant or rest cells, which are uniquely characterized by the absence of p53 mutations. Perinatal overexpression of the MycN oncoprotein in embryonal cancer precursor cells causes postnatal rests, and later tumor formation through unknown mechanisms. However, overexpression of Myc in adult tissues normally activates apoptosis and/or senescence signals as an organismal defense mechanism against cancer. Here, we show that perinatal neuroblastoma precursor cells exhibited a transiently diminished p53 response to MycN oncoprotein stress and resistance to trophic factor withdrawal, compared with their adult counterpart cells from the TH-MYCN(+/+) transgenic mouse model of neuroblastoma. The adult stem cell maintenance factor and Polycomb group protein, Bmi1 (B-cell-specific Moloney murine leukemia virus integration site), had a critical role at neuroblastoma initiation in the model, by repressing p53 responses in precursor cells. We further show in neuroblastoma tumor cells that Bmi1 could directly bind p53 in a complex with other Polycomb complex proteins, Ring1A or Ring1B, leading to increased p53 ubiquitination and degradation. Repressed p53 signal responses were also seen in precursor cells for other embryonal cancer types, medulloblastoma and acute lymphoblastic leukemia. Collectively, these date indicate a general mechanism for p53 inactivation in some embryonal cell types and consequent susceptibility to MycN oncogenesis at the point of embryonal tumor initiation.
Assuntos
Neoplasias Embrionárias de Células Germinativas/patologia , Células-Tronco Neoplásicas/patologia , Proteínas Nucleares/metabolismo , Proteínas Oncogênicas/metabolismo , Complexo Repressor Polycomb 1/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Estresse Fisiológico , Proteína Supressora de Tumor p53/química , Proteína Supressora de Tumor p53/metabolismo , Animais , Apoptose , Linhagem Celular Tumoral , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Humanos , Leucemia/metabolismo , Leucemia/patologia , Meduloblastoma/metabolismo , Meduloblastoma/patologia , Camundongos , Proteína Proto-Oncogênica N-Myc , Neoplasias Embrionárias de Células Germinativas/metabolismo , Células-Tronco Neoplásicas/metabolismo , Neuroblastoma/metabolismo , Neuroblastoma/patologia , Poliubiquitina/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Estabilidade Proteica , Proteólise , Proteínas Proto-Oncogênicas c-mdm2/metabolismo , Transdução de Sinais , UbiquitinaçãoRESUMO
Following the discovery that defective retinoid signaling directly contributes to tumorigenesis, and, that retinoids have an anti-cancer effect in vitro and in vivo, retinoids have become part of the routine care in children with neuroblastoma at the stage of minimal residual disease. However, many patients still relapse following retinoid therapy, demonstrating the need for more effective retinoids and better assays to predict retinoid sensitivity in cancer cells. Recent evidence suggests that the copper metabolism gene, ATP7A, is retinoid-regulated and an important component of the retinoic acid receptor ß (RARß) anticancer effect in neuroblastoma cells. To highlight and further develop the concept of using ATP7A as a target in retinoid therapy, and combination therapy with copper chelators in neuroblastoma, the current literature and abstracts related to the clinical application of retinoids, the function of ATP7A and the clinical application of copper chelators are summarized. We propose that strategies targeting the copper export protein, ATP7A, in combination therapy with retinoids and copper depletion therapy, may have great therapeutic potential in the clinical treatment of neuroblastoma and other malignancies.
Assuntos
Adenosina Trifosfatases/metabolismo , Proteínas de Transporte de Cátions/metabolismo , Neuroblastoma/tratamento farmacológico , Retinoides/uso terapêutico , Adenosina Trifosfatases/antagonistas & inibidores , Proteínas de Transporte de Cátions/antagonistas & inibidores , ATPases Transportadoras de Cobre , HumanosRESUMO
The family of tripartite-motif (TRIM) proteins are involved in diverse cellular processes, but are often characterized by critical protein-protein interactions necessary for their function. TRIM16 is induced in different cancer types, when the cancer cell is forced to proceed down a differentiation pathway. We have identified TRIM16 as a DNA-binding protein with histone acetylase activity, which is required for the retinoic acid receptor ß(2) transcriptional response in retinoid-treated cancer cells. In this study, we show that overexpressed TRIM16 reduced neuroblastoma cell growth, enhanced retinoid-induced differentiation and reduced tumourigenicity in vivo. TRIM16 was only expressed in the differentiated ganglion cell component of primary human neuroblastoma tumour tissues. TRIM16 bound directly to cytoplasmic vimentin and nuclear E2F1 in neuroblastoma cells. TRIM16 reduced cell motility and this required downregulation of vimentin. Retinoid treatment and enforced overexpression caused TRIM16 to translocate to the nucleus, and bind to and downregulate nuclear E2F1, required for cell replication. This study, for the first time, demonstrates that TRIM16 acts as a tumour suppressor, affecting neuritic differentiation, cell migration and replication through interactions with cytoplasmic vimentin and nuclear E2F1 in neuroblastoma cells.