1,721,781 research outputs found
MLL partner genes drive distinct gene expression profiles and genomic alterations in pediatric acute myeloid leukemia: an AIEOP study
No full textICER expression inhibits leukemia phenotype and controls tumor progression.
No full textThe inducible cyclic AMP (cAMP) early repressor (ICER) and cAMP response element-binding protein (CREB) are transcriptional regulators of the cAMP-mediated signaling pathway. CREB has been demonstrated to be upregulated in the majority of childhood leukemias contributing to disease progression, whereas ICER, its endogenous repressor, was found to be downregulated. Our research focus has been the function of restored ICER expression. ICER exogenously expressed in cell lines decreases CREB protein level and induces a lowered clonogenic potential in vitro. It decreases the ability of HL60 to invade the extramedullary sites and to promote bone marrow angiogenesis in nonobese diabetic-severe combined immunodeficient mice, demonstrating its potential effects on tumor progression. ICER represses the majority of 96 target genes upregulated by CREB. It binds CRE promoters and controls gene expression restoring the normal regulation of major cellular pathways. ICER is subjected to degradation through a constitutively active form of the extracellular signal-regulated protein kinase, which drives it to the proteasome. We propose that ICER is downregulated in HL60 to preserve CREB overexpression, which disrupts normal myelopoiesis and promotes blast proliferation. These findings define the function of ICER as a tumor suppressor in leukemia. Unbalanced CREB/ICER expression needs to be considered a pathogenetic feature in leukemogenesis. The molecular characterization of this pathway could be useful for novel therapeutic strategies
MicroRNA-34b promoter hypermethylation induces CREB overexpression and contributes to myeloid transformation.
No full textMicroRNA-34b down-regulation in acute myeloid leukemia was previously shown to induce CREB overexpression, thereby causing leukemia proliferation in vitro and in vivo. The role of microRNA-34b and CREB in patients with myeloid malignancies has never been evaluated. We examined microRNA-34b expression and the methylation status of its promoter in cells from patients diagnosed with myeloid malignancies. We used gene expression profiling to identify signatures of myeloid transformation. We established that microRNA-34b has suppressor ability and that CREB has oncogenic potential in primary bone marrow cell cultures and in vivo. MicroRNA-34b was found to be up-regulated in pediatric patients with juvenile myelomonocytic leukemia (n=17) and myelodysplastic syndromes (n=28), but was down-regulated in acute myeloid leukemia patients at diagnosis (n=112). Our results showed that hypermethylation of the microRNA-34b promoter occurred in 66% of cases of acute myeloid leukemia explaining the low microRNA-34b levels and CREB overexpression, whereas preleukemic myelodysplastic syndromes and juvenile myelomonocytic leukemia were not associated with hypermethylation or CREB overexpression. In paired samples taken from the same patients when they had myelodysplastic syndrome and again during the subsequent acute myeloid leukemia, we confirmed microRNA-34b promoter hypermethylation at leukemia onset, with 103 CREB target genes differentially expressed between the two disease stages. This subset of CREB targets was confirmed to associate with high-risk myelodysplastic syndromes in a separate cohort of patients (n=20). Seventy-eight of these 103 CREB targets were also differentially expressed between healthy samples (n=11) and de novo acute myeloid leukemia (n=72). Further, low microRNA-34b and high CREB expression levels induced aberrant myelopoiesis through CREB-dependent pathways in vitro and in vivo. In conclusion, we suggest that microRNA-34b controls CREB expression and contributes to myeloid transformation from both healthy bone marrow and myelodysplastic syndromes. We identified a subset of CREB target genes that represents a novel transcriptional network that may control myeloid transformation
ICER Evokes Dusp1-p38 Pathway Enhancing Chemotherapy Sensitivity in Myeloid Leukemia
No full textPurpose: The inducible cyclic adenosine monophosphate (cAMP) early repressor (ICER) is found downregulated in acute myeloid leukemia (AML), failing to control cAMP response element binding protein (CREB) transcriptional activity, recently demonstrated to mediate AML progression. We aimed to characterize ICER's role in drug sensitivity by treating myeloid cell lines and primary AML with chemotherapics.
Experimental design: The effects on CREB target genes induced by ICER restoration and drug treatment were studied by quantitative real-time PCR (qRT-PCR) and western blot. Cell cycle and apoptosis analysis were performed. Possible ICER-evoked pathways were investigated in vitro. The mechanism involved in enhanced drug sensitivity was described in primary AML cultures by silencing ICER main target genes.
Results: AML cell lines reduced cell growth and enhanced apoptotic behavior after chemotherapy treatment if ICER was expressed. A significantly lowered expression of CREB target genes involved in cell cycle control (CyA1, B1, D1), and in the mitogen-activated protein kinase signaling pathway (ERK, AKT, DUSP1/4), was found after Etoposide treatment. The dual-specificity phosphatases DUSP1 and DUSP4, directly repressed by ICER, activated the p38 pathway, which triggered enhanced caspase-dependent apoptosis. The silencing of DUSP1/4 in HL60 confirmed the same enhanced drug sensitivity induced by ICER. Primary AML cultures, silenced for DUSP1 as well as restored of ICER expression, showed DUSP1 downregulation and p38 activation.
Conclusion: ICER mediates chemotherapy anticancer activity through DUSP1-p38 pathway activation and drives the cell program from survival to apoptosis. ICER restoration or DUSP1 inhibition might be possible strategies to sensitize AML cancer cells to conventional chemotherapy and to inhibit tumor growth. Clin Cancer Res; 17(4); 742-52. (C) 2011 AACR
BAG-1 IN ACUTE LEUKEMIA: HUNDRED FACES OF A SINGLE PROTEIN
No full textIntroduction. Bcl-2 associated athanogene-1 (Bag-1), a founding member of BAG protein family, is a multifunctional protein which has a role in a wide range of cellular processes including apoptosis, cell survival, transcription, cell motility and proliferation. The involvement of Bag-1 in different cellular pathways can be in part examined by the sub-cellular compartmentalisation of the three major Bag-1 isoforms (Bag-1L, Bag-1M and Bag-1S), generated by alternative translation from a single mRNA, and in part by its interaction with a large number of disparate proteins, including Bcl-2, Raf-1, nuclear hormone receptors, subunits of the ubiquitinylation proteasome complex, Hsc70 and Hsp70. Aims. The elevated level of Bag-1 protein has been confirmed as a considerable index in several malign diseases. To determine significance Bag-1 might have in the processes of leukemogenesis a sequence of human leukemic cell lines and pediatric bone marrow samples with confirmed acute myeloid leukemia were included in our research. Our goal was to clarify the molecular mechanisms potentially in charge for Bag-1 action, in either leukemic cell lines or primary cell cultures. Methods. In vitro studies were based on a small-interfering RNA (siRNA) approach and the results were validated using standard techniques for mRNA and protein expression study. Assays for cell cycle and apoptosis detection were performed. Results. The protein study revealed elevated Bag-1 levels in human leukemic cell lines of both myeloid (ML2, THP1, NOMO1, NB4, MV4;11 and HL60) and lymphoid (REH, RS4;11, 697 and JURKAT) origin. A different expression pattern of Bag-1 protein isoforms was noted for two considered groups of patients, AML or ALL, with changes in protein expression profile at different point of the disease. After Bag-1 was knock-down, a modest effect on cell death or cell cycle profile was observed for the human cell lines while primary cultures showed to be more sensitive to Bag-1 silencing. However, significant decrease was confirmed at the expression level of a wide range of proteins, specially the ones involved in the regulation of apoptosis (Bcl-2, PARP, Caspase-3), cell cycle (p27, CDK2, Cyclin D1) and autophagy (LC3, p62), without affecting the mRNA levels. When double silencing experiments of Bag-1 and Bag-3 (a family co-member) were performed, the effect on cell death and cell cycle arrest were found enforced, suggesting a connection between two proteins to be significant for cells faith in leukemia. Conclusions. Results indicate that the role of Bag-1 in cell death prevention might be more related to lymphoid leukemia, while it might be considered more significant for cell differentiation in myeloid cells. At the same time, elevated Bag-1 protein expression levels in acute leukemia indicates its possible significance for AML and ALL growth. A different expression profile of Bag-1L, Bag-1M and Bag-1S isoforms in myeloid with respect to lymphoid leukemia could lead to the hypothesis that Bag-1 might play a role in leukemia switch, triggering to either ALL or AML phenotype
Diagnosis and genetic subtypes of leucemia combining gene expression and flow cytometry.
No full textAcute leukemia, defined as a genetic disease, is the most common cancer in children representing about one half of all cancers among persons younger than 15 years. Acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) each represents a heterogeneous complex of disorders, with genetic abnormalities presenting in more than 80% of ALLs and more than 90% of AMLs. The diagnostic gold standard and classification of leukaemia involves various methods including morphology, cytochemistry, cytogenetics and molecular genetics, immunophenotyping, and molecular biology. These diagnostic methods are a prerequisite for individual treatment strategies and for the evaluation of treatment response especially considering that many distinct types of acute leukemia are known to carry predictable prognoses and warrant specific therapy. The quantification of gene expression is essential in determination of tailored therapeutic decisions. Microarray technology offers the possibility of quantifying thousands of genes in a single analysis, thus potentially becoming an essential tool for molecular classification to be used in routine leukaemia diagnostics. MLL+ leukaemia is a perfect example as to the exact correspondence between gene expression and protein expression evaluated by flow cytometry. Applying computational analysis to flow cytometry results, it is possible to distinguish the MLL+ acute leukemia from MLL- acute leukemia using as the top ranked antigen some top ranked genes described in the Microarray evaluation. Key markers discriminating different leukemia phenotypes can be identified by univariate hypothesis testing from a data set of immunophenotypic markers described by two variables, one reflecting the intensity of expression (MESF) and the other the pattern of distribution (CV). A current multi center study called Microarray Innovations in Leukemia (MILE Study) uses higher density gene chips providing nearly complete coverage of the human genome. The study which has analyzed thus far 1837 retrospective cases shows that each important leukemia subtype has a specific genetic fingerprint, meaning that different combinations of genes whose expression is linked to each subtype can be identified allowing for patient tailored therapy. Moreover, the study has achieved 97% diagnostic accuracy on samples from tested patients. Statistical analysis has shown a high concordance level between standard diagnostic procedures and those of the microarray technology--globally around 95.6%. Additionally it is possible to correctly classify some subgroups incorrectly identified using gold standard methods. Thus, from a technical viewpoint, gene expression profiling in tandem with flow cytometry should be a viable alternative to standard diagnostic approaches. Whether gene expression profiling will become a practical diagnostic alternative remains to be seen
Apoptosis and phosphatidylserine-mediated recognition during the take-over phase of the colonial life-cycle in the ascidian Botryllus schlosseri
No full textColonies of the ascidian Botryllus schlosseri undergo recurrent generation changes in which adult zooids are gradually resorbed and replaced by new blastogenic generations. During these periods, known as take-over phases, programmed cell death, which, on the basis of morphological analysis is ascribed to apoptosis, occurs widely in zooid tissues. In the present report, we re-investigate cell death during the take-over process. Results confirm the occurrence of diffuse apoptosis, as evidenced by chromatin condensation, positivity to the TUNEL reaction and expression of phosphatidylserine on the outer leaflet of the plasma membrane. Apoptosis also occurs among haemocytes, and senescent blood cells are actively recognised and ingested by circulating professional phagocytes. Both phosphatidylserine and CD36, a component of the thrombospondin receptor, are involved in the recognition of apoptotic haemocytes, which fosters the idea that fundamental recognition mechanisms are well conserved throughout chordate evolution
Leukemia blast cell identification
No full textAcute leukemia is a heterogeneous group of disorders, characterized by different laboratory and prognostic features. An adequate diagnosis of acute leukemia, based on the identification of a leukemic cell population and the hematopoietic lineage assessment, is the first goal toward defining correct risk stratification of patients and tailoring specific therapies to patients. Diagnosis of acute leukemia underwent an important change since the 1970s when the only available diagnostic tools were cytomorphology and cytochemistry. Nowadays, the development of modern techniques and their combined use in a multimodal approach lead to a better identification and sub-classification of acute leukemia. Thus, blast identification in acute leukemia required a comprehensive global approach, by combining cytomorphology, cytochemistry, multiparameter flow cytometry (MFC), cytogenetic, fluorescence in situ hybridization (FISH) and molecular genetic methods. At least, new sequencing technologies, such as gene expression profiling (GEP) and whole-genome sequencing, DNA methylation arrays, and comparative genomic hybridization array, could represent the new frontiers in the characterization of genetic heterogeneity in acute leukemia. WIREs Data Mining Knowl Discov 2015, 5:74-85. doi: 10.1002/widm.1146 For further resources related to this article, please visit the
Can primary cancer of the liver in Western countries be prevented? Pediatric point of view.
No full textThe role of hepatitis B virus (HBV) in the etiology of hepatocellular carcinoma (HCC) in Western countries is uncertain in spite of the large amount of data demonstrating an etiologic relationship between HBV and HCC in endemic areas [1]. This paper will discuss the epidemiology of HBV in HCC and will raise several questions about the conventional wisdom of maintaining a connection between the two
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