MLL rearrangements in pediatric acute lymphoblastic and myeloblastic leukemias: MLL specific and lineage specific signatures

<p>Abstract</p> <p>Background</p> <p>The presence of <it>MLL </it>rearrangements in acute leukemia results in a complex number of biological modifications that still remain largely unexplained. Armstrong et al. proposed <it>MLL </it>rearrangement positive ALL as a distinct subgroup, separated from acute lymphoblastic (ALL) and myeloblastic leukemia (AML), with a specific gene expression profile. Here we show that MLL, from both ALL and AML origin, share a signature identified by a small set of genes suggesting a common genetic disregulation that could be at the basis of mixed lineage leukemia in both phenotypes.</p> <p>Methods</p> <p>Using Affymetrix^®HG-U133 Plus 2.0 platform, gene expression data from 140 (training set) + 78 (test set) ALL and AML patients with (24+13) and without (116+65) <it>MLL </it>rearrangements have been investigated performing class comparison (SAM) and class prediction (PAM) analyses.</p> <p>Results</p> <p>We identified a <it>MLL </it>translocation-specific (379 probes) signature and a phenotype-specific (622 probes) signature which have been tested using unsupervised methods. A final subset of 14 genes grants the characterization of acute leukemia patients with and without <it>MLL </it>rearrangements.</p> <p>Conclusion</p> <p>Our study demonstrated that a small subset of genes identifies <it>MLL</it>-specific rearrangements and clearly separates acute leukemia samples according to lineage origin. The subset included well-known genes and newly discovered markers that identified ALL and AML subgroups, with and without <it>MLL </it>rearrangements.</p

Hepatocyte growth factor receptor c-MET is associated with FAS and when activated enhances drug-induced apoptosis in pediatric B acute lymphoblastic leukemia with TEL-AML1 translocation.

Expression of c-MET, the HGF (hepatocyte growth factor) tyrosine kinase receptor, was investigated in pediatric B-acute lymphoblastic leukemia (ALL) patients. c-MET was found to be expressed in normal B cells and in B-ALL patients with the t(12;21) TEL-AML1 translocation, but it is not expressed in the most part of B-ALL without the t(12;21). We also found that c-MET, related to proliferation and protection from apoptosis, is associated with the pro-apoptotic protein FAS in TEL-AML1 B-ALL cells and in normal B lymphocytes. The possible role of this protein complex in drug-induced apoptosis was thus investigated in REH TEL-AML1 B-ALL cell line. REH cells prestimulated with HGF and treated with doxorubicin had shown a higher apoptotic rate than non-HGF-prestimulated ones (p = 0.03). REH cells stimulated with IL-3 and treated with doxorubicin did not undergo apoptosis more than nonstimulated cells, demonstrating that increased proliferation in itself is not directly related to the higher apoptotic sensitivity observed with HGF stimulation. These results indicate that c-MET activation enhances specifically FAS-mediated apoptosis in TEL-AML1 ALL cells and, considering that the c-MET/FAS complex is present only in normal B lymphocytes and in TEL-AML1 leukemias, this implies that it may have an important contribution in cellular homeostasis and in high sensitivity of TEL-AML1 ALL to chemotherapeutic regimens

Ultrafast molecular motor driven nanoseparation and biosensing

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Molecular Mechanisms of HIF-1α Modulation Induced by Oxygen Tension and BMP2 in Glioblastoma Derived Cells

BACKGROUND: Glioblastoma multiforme (GBM) is one of most common and still poorly treated primary brain tumors. In search for new therapeutic approaches, Bone Morphogenetic Proteins (BMPs) induce astroglial commitment in GBM-derived cells in vitro. However, we recently suggested that hypoxia, which is characteristic of the brain niche where GBM reside, strongly counter-acts BMP effects. It seems apparent that a more complete understanding of the biology of GBM cells is needed, in particular considering the role played by hypoxia as a signaling pathways regulator. HIF-1alpha is controlled at the transcriptional and translational level by mTOR and, alike BMP, also mTOR pathway modulates glial differentiation in central nervous system (CNS) stem cells. METHODOLOGY/PRINCIPAL FINDINGS: Here, we investigate the role of mTOR signaling in the regulation of HIF-1alpha stability in primary GBM-derived cells maintained under hypoxia (2% oxygen). We found that GBM cells, when acutely exposed to high oxygen tension, undergo Akt/mTOR pathway activation and that BMP2 acts in an analogous way. Importantly, repression of Akt/mTOR signaling is maintained by HIF-1alpha through REDD1 upregulation. On the other hand, BMP2 counter-acts HIF-1alpha stability by modulating intracellular succinate and by controlling proline hydroxylase 2 (PHD2) protein through inhibition of FKBP38, a PHD2 protein regulator. CONCLUSIONS/SIGNIFICANCE: In this study we elucidate the molecular mechanisms by which two pro-differentiating stimuli, BMP2 and acute high oxygen exposure, control HIF-1alpha stability. We previously reported that both these stimuli, by inducing astroglial differentiation, affect GBM cells growth. We also found differences in high oxygen and BMP2 sensitivity between GBM cells and normal cells that should be further investigated to better define tumor cell biology

Enforced expression of MLL-AF4 fusion in cord blood CD34+ cells enhances the hematopoietic repopulating cell function and clonogenic potential but is not sufficient to initiate leukemia

AbstractInfant acute lymphoblastic leukemia harboring the fusion mixed-lineage leukemia (MLL)-AF4 is associated with a dismal prognosis and very brief latency. Our limited understanding of transformation by MLL-AF4 is reflected in murine models, which do not accurately recapitulate the human disease. Human models for MLL-AF4 disease do not exist. Hematopoietic stem or progenitor cells (HSPCs) represent probable targets for transformation. Here, we explored in vitro and in vivo the impact of the enforced expression of MLL-AF4 in human cord blood-derived CD34+ HSPCs. Intrabone marrow transplantation into NOD/SCID-IL2Rγ−/− mice revealed an enhanced multilineage hematopoietic engraftment, efficiency, and homing to other hematopoietic sites on enforced expression of MLL-AF4. Lentiviral transduction of MLL-AF4 into CD34+ HSPCs increased the in vitro clonogenic potential of CD34+ progenitors and promoted their proliferation. Consequently, cell cycle and apoptosis analyses suggest that MLL-AF4 conveys a selective proliferation coupled to a survival advantage, which correlates with changes in the expression of genes involved in apoptosis, sensing DNA damage and DNA repair. However, MLL-AF4 expression was insufficient to initiate leukemogenesis on its own, indicating that either additional hits (or reciprocal AF4-MLL product) may be required to initiate ALL or that cord blood-derived CD34+ HSPCs are not the appropriate cellular target for MLL-AF4-mediated ALL

Deciphering KRAS and NRAS mutated clone dynamics in MLL-AF4 paediatric leukaemia by ultra deep sequencing analysis

To induce and sustain the leukaemogenic process, MLL-AF4+ leukaemia seems to require very few genetic alterations in addition to the fusion gene itself. Studies of infant and paediatric patients with MLL-AF4+ B cell precursor acute lymphoblastic leukaemia (BCP-ALL) have reported mutations in KRAS and NRAS with incidences ranging from 25 to 50%. Whereas previous studies employed Sanger sequencing, here we used next generation amplicon deep sequencing for in depth evaluation of RAS mutations in 36 paediatric patients at diagnosis of MLL-AF4+ leukaemia. RAS mutations including those in small sub-clones were detected in 63.9% of patients. Furthermore, the mutational analysis of 17 paired samples at diagnosis and relapse revealed complex RAS clone dynamics and showed that the mutated clones present at relapse were almost all originated from clones that were already detectable at diagnosis and survived to the initial therapy. Finally, we showed that mutated patients were indeed characterized by a RAS related signature at both transcriptional and protein levels and that the targeting of the RAS pathway could be of beneficial for treatment of MLL-AF4+ BCP-ALL clones carrying somatic RAS mutations

Notch3/Jagged1 Circuitry Reinforces Notch Signaling and Sustains T-ALL

AbstractDeregulated Notch signaling has been extensively linked to T-cell acute lymphoblastic leukemia (T-ALL). Here, we show a direct relationship between Notch3 receptor and Jagged1 ligand in human cell lines and in a mouse model of T-ALL. We provide evidence that Notch-specific ligand Jagged1 is a new Notch3 signaling target gene. This essential event justifies an aberrant Notch3/Jagged1 cis-expression inside the same cell. Moreover, we demonstrate in Notch3-IC–overexpressing T lymphoma cells that Jagged1 undergoes a raft-associated constitutive processing. The proteolytic cleavage allows the Jagged1 intracellular domain to empower Notch signaling activity and to increase the transcriptional activation of Jagged1 itself (autocrine effect). On the other hand, the release of the soluble Jagged1 extracellular domain has a positive impact on activating Notch signaling in adjacent cells (paracrine effect), finally giving rise to a Notch3/Jagged1 auto-sustaining loop that supports the survival, proliferation, and invasion of lymphoma cells and contributes to the development and progression of Notch-dependent T-ALL. These observations are also supported by a study conducted on a cohort of patients in which Jagged1 expression is associated to adverse prognosis

Gain-of-function mutations in interleukin-7 receptor-α (IL7R) in childhood acute lymphoblastic leukemias

IL7R-activating mutations identified in B-ALL and T-ALL patient leukemic cells facilitate cytokine-independent growth