Notch3-mediated regulation of MKP-1 levels promotes survival of T acute lymphoblastic leukemia cells

Activation of the Notch pathway occurs commonly in T acute lymphoblastic leukemia (T-ALL) because of mutations in Notch1 or Fbw7 and is involved in the regulation of cell proliferation and survival. Deregulated Notch3 signalling has also been shown to promote leukemogenesis in transgenic mice, but the targets of Notch3 in human T-ALL cells remain poorly characterized. Here, we show that Notch3 controls levels of mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP-1). In a model of T-ALL cell dormancy, both Notch3 activation and MKP-1 expression were upregulated in aggressive compared with dormant tumors, and this inversely correlated with the levels of phosphorylated p38 and extracellular signal-regulated kinase1/2 (ERK1/2) MAPKs, two canonical MKP-1 targets. We demonstrate that MKP-1 protein levels are regulated by Notch3 in T-ALL cell lines because its silencing by RNA interference or treatment with γ-secretase inhibitors induced strong MKP-1 reduction whereas activation of Notch3 signalling had the opposite effect. Furthermore, MKP-1 has an important role in T-ALL cell survival because its attenuation by short hairpin RNA significantly increased cell death under stress conditions. This protective function has a key role in vivo, as MKP-1-deficient cells showed impaired tumorigenicity. These results elucidate a novel mechanism downstream of Notch3 that controls the survival of T-ALL cells.

Long-term results of the Italian Association of Pediatric Hematology and Oncology (AIEOP) Studies 82, 87, 88, 91 and 95 for childhood acute lymphoblastic leukemia

We analyzed the long-term outcome of 4865 patients treated in Studies 82, 87, 88, 91 and 95 for childhood acute lymphoblastic leukemia (ALL) of the Italian Association of Pediatric Hematology and Oncology (AIEOP). Treatment was characterized by progressive intensification of systemic therapy and reduction of cranial radiotherapy. A progressive improvement of results with reduction of isolated central nervous system relapse rate was obtained. Ten-year event-free survival increased from 53% in Study 82 to 72% in Study 95, whereas survival improved from 64 to 82%. Since 1991, all patients were treated according to Berlin-Frankfurt-Muenster (BFM) ALL treatment strategy. In Study 91, reduced treatment intensity (25%) yielded inferior results, but intensification of maintenance with high-dose (HD)-L-asparaginase (randomized) allowed to compensate for this disadvantage; in high-risk patients (HR, 15%), substitution of intensive polychemotherapy blocks for conventional BFM backbone failed to improve results. A marked improvement of results was obtained in HR patients when conventional BFM therapy was intensified with three polychemotherapy blocks and double delayed intensification (Study 95). The introduction of minimal residual disease monitoring and evaluation of common randomized questions by AIEOP and BFM groups in the protocol AIEOP-BFM-ALL 2000 are expected to further ameliorate treatment of children with ALL.

A resting state network in the motor control circuit of the basal ganglia

BACKGROUND

In the absence of overt stimuli, the brain shows correlated fluctuations in functionally related brain regions. Approximately ten largely independent resting state networks (RSNs) showing this behaviour have been documented to date. Recent studies have reported the existence of an RSN in the basal ganglia - albeit inconsistently and without the means to interpret its function. Using two large study groups with different resting state conditions and MR protocols, the reproducibility of the network across subjects, behavioural conditions and acquisition parameters is assessed. Independent Component Analysis (ICA), combined with novel analyses of temporal features, is applied to establish the basis of signal fluctuations in the network and its relation to other RSNs. Reference to prior probabilistic diffusion tractography work is used to identify the basal ganglia circuit to which these fluctuations correspond.

RESULTS

An RSN is identified in the basal ganglia and thalamus, comprising the pallidum, putamen, subthalamic nucleus and substantia nigra, with a projection also to the supplementary motor area. Participating nuclei and thalamo-cortical connection probabilities allow this network to be identified as the motor control circuit of the basal ganglia. The network was reproducibly identified across subjects, behavioural conditions (fixation, eyes closed), field strength and echo-planar imaging parameters. It shows a frequency peak at 0.025 +/- 0.007 Hz and is most similar in spectral composition to the Default Mode (DM), a network of regions that is more active at rest than during task processing. Frequency features allow the network to be classified as an RSN rather than a physiological artefact. Fluctuations in this RSN are correlated with those in the task-positive fronto-parietal network and anticorrelated with those in the DM, whose hemodynamic response it anticipates.

CONCLUSION

Although the basal ganglia RSN has not been reported in most ICA-based studies using a similar methodology, we demonstrate that it is reproducible across subjects, common resting state conditions and imaging parameters, and show that it corresponds with the motor control circuit. This characterisation of the basal ganglia network opens a potential means to investigate the motor-related neuropathologies in which the basal ganglia are involved.

DNA copy-number abnormalities do not occur in infant ALL with t(4;11)/MLL-AF4

The pathogenesis of infant acute lymphoblastic leukemia (ALL) is still not well defined. Short latency to leukemia and very high concordance rate for ALL in Mixed-Lineage Leukemia (MLL)-positive infant twins suggest that the MLL rearrangement itself could be sufficient for overt leukemia. Attempts to generate a suitable mouse model for MLL-AF4-positive ALL did not thoroughly resolve the issue of whether cooperating mutations are required to reduce latency and to generate overt leukemia in vivo. In this study, we applied single-nucleotide polymorphism array technology to perform genomic profiling of 28 infant ALL cases carrying t(4;11) to detect MLL-cooperating aberrations hidden to conventional techniques and to gain new insights into infant ALL pathogenesis. In contrast to pediatric, adolescent and adult ALL cases, the MLL rearrangement in infant ALL is associated with an exceptionally low frequency of copy-number abnormalities, thus confirming the unique nature of this disease. By contrast, additional genetic aberrations are acquired at disease relapse. Small-segmental uniparental disomy traits were frequently detected, mostly constitutional, and widely distributed throughout the genome. It can be argued that the MLL rearrangement as a first hit, rather than inducing the acquisition of additional genetic lesions, has a major role to drive and hasten the onset of leukemia.

Glioblastoma-derived cells exhibit differential responses to glycolysis inhibition under hypoxia

e13031

It has been suggested that oxygen tension is a crucial component of the brain tumor niche, as hypoxia positively correlates with tumor aggressiveness and over-activity of hypoxia inducible factor-1α (HIF-1α) reinforces tumor progression. Furthermore, hypoxia has been implicated in the regulation of several signaling pathways (Notch, BMP), angiogenesis and importantly, glucose metabolism. Here we investigate the effects mediated by in vitro glycolysis inhibition by using 2-deoxyglucose (2-DG) in glioblastoma (GBM) derived cells maintained under two different oxygen tensions, a lowered oxygen tension (2%) versus a higher non-physiological (20%). GBM account for 50% of all gliomas and arise after age 50 in most patients and it has been seen that younger patients tend to have a better prognosis than the elderly. Our results show that adult GBM displaying a highly immature phenotype manifested the highest resistance to glucose deprivation. Furthermore, increase of multi-drug resistant cell fraction, described as side population, occurred following 2-DG treatment, but only under hypoxia. Neuronal committed precursors were selected by 2-DG, but these effects were mitigated by hypoxia. Also, hypoxia inhibits the mitochondria-controlled apoptosis induced by 2-DG, by conferring cell resistance through progressive activation of pro-survival NF-kB and induction of tumor cell autophagy. Importantly, HIF-1α level reduction and proline hydroxylase 2 (PHD2) upregulation occurred following 2-DG treatment even under hypoxia, and this may depend on reactive oxygen species reduction. These results indicate differences in tumor cells behavior that may be predictive of cell response to therapy aiming to limit glucose uptake or glucose metabolism.

No significant financial relationships to disclose.

Association of time to leukemia (TTL) in NOD/SCID mice with expression of apoptosis regulators in pediatric ALL

10042

Background: Acute lymphoblastic leukemia (ALL) is the most frequent malignant disease in childhood. Although advances in therapy have led to improved long term survival, relapse remains a major challenge. In a recent study we transplanted pediatric leukemia samples from newly diagnosed BCP-ALL patients into NOD/SCID mice. Time to leukemia (TTL) was analyzed for each patient sample as time from transplant to overt leukemia in the recipients. Patients whose leukemia cells engrafted rapidly showed a clearly inferior relapse free survival in contrast to patient samples with prolonged in vivo growth. Multivariate analysis showed an almost 45- fold increased risk for relapse in patients with short TTL. Methods: Gene expression profiles of ALL samples (N = 14) with short versus long TTL in the xenograft model were analyzed using a human whole genome array (Affymetrix U133 Plus 2.0) correlating gene expression values (relative expression) to the time from transplant to manifestation of leukemia in the NOD/SCID mice (TTL, in weeks) by quantitative traits analysis (QTA). Results: Among 5 genes significantly correlated (Spearman correlation, P < .0001) XIAP-associated factor 1 (XAF1) was found to be up-regulated in patients with long TTL. XAF1 abrogates the inhibitory effect of XIAP on caspase-3 thereby sensitizing for apoptosis. In accordance to this caspase-3 activation was also found to be up-regulated in patients with long TTL. Patient samples exhibiting a short time to overt leukemia in the xenotransplant model associated with poor relapse free survival showed down-regulated XAF1 and impaired caspase-3 activation leading to decreased apoptosis of the leukemia cells. Conclusions: Taken together, we used a novel approach directly correlating gene expression values to time from transplant to overt leukemia (TTL) identifying the apoptosis regulator XAF1 to be associated with poor outcome of patients. Small XIAP-inhibiting molecules can be used to substitute the lacking inhibitory effect of down-regulated XAF1 in these poor responding pediatric ALL patients.

No significant financial relationships to disclose.

The inducible cyclic adenosine 3’,5’-monophosphate early repressor (ICER) enhances drug sensitivity in acute myeloid leukemia

e22045

Background: The Inducible Cyclic Adenosine 3’,5’-monophosphate early repressor (ICER) is a transcription factor that principally counteracts the cAMP response element binding protein (CREB) activity. CREB was previously demonstrated to be overexpressed in acute leukemia, whereas ICER was found rapidly degradated being unable to control gene transcription. ICER exogenous expression was demonstrated to repress CREB targets preventing leukemia progression. We hypothesized that ICER restoration deserves a special consideration for playing a role in CREB oncogenic feature and in modeling leukemic cell phenotype. Methods: We constructed an expression vector for ICER and induced its exogenous expression in HL60 cells (HL60+ICER). We monitored transcription and translation of a series of genes involved in different pathways by quantitative gene expression and western blot analysis. We investigate ICER's role in cell death after treatment with chemotherapic drugs. Results: We revealed that ICER was able to control gene expression in leukemia, principally of genes involved in cell death and survival. In particular, we focused on DUSP1 and DUSP4 phosphatases which were found significantly repressed. HL60+ICER after being treated with drugs increased apoptosis. Cell cycle analyses revealed a block in G2 phase, a lowered cell proliferation and clonogenic potential with respect to HL60 treated at the same conditions. DUSPs downstream targets (IL6, RB, RAS) were lowered expressed and p38 constitutively phosphorylated confirming their role in mediating cellular stress. ICER driven apoptosis was found to be caspases mediated. An enhanced activity of p38 was observed in treated HL60+ICER, and by the use of specific p38 inhibitors apoptosis decreased. Other possible apoptotic pathways (AKT, ERK, JNK) were excluded because found severely disrupted. Conclusions: Finally, we described an enhanced sensibility to drugs in HL60 induced by ICER exogenous expression and that p38 stress signaling pathway is the direct target of this phenomenon. The ability of ICER to modify leukemic cells phenotype respect to chemotherapeutic treatment gave an important information for targets and therapeutic possibilities.

No significant financial relationships to disclose.

Reproducibility of BOLD signal change induced by breath holding

Blood oxygen level dependent (BOLD) contrast is influenced by some physiological factors such as blood flow and blood volume that can be a source of variability in fMRI analysis. Previous studies proposed to use the cerebrovascular response data to normalize or calibrate BOLD maps in order to reduce variability of fMRI data both among brain areas in single subject analysis and across subjects. Breath holding is one of the most widely used methods to investigate the vascular reactivity. However, little is known about the robustness and reproducibility of this procedure. In this study we investigated three different breath holding periods. Subjects were asked to hold their breath for 9, 15 or 21 s in three separate runs and the fMRI protocol was repeated after 15 to 20 days. Our data show that the BOLD response to breath holding after inspiration results in a complex shape due to physiological factors that influence the signal variation with a timing that is highly reproducible. Nevertheless, the reproducibility of the magnitude of the cerebrovascular response to CO(2), expressed as amplitude of BOLD signal and number of responding voxels, strongly depends on duration of breath holding periods. Breath holding period of 9 s results in high variability of the magnitude of the response while longer breath holding durations produce more robust and reproducible BOLD responses.

Regional apparent metabolite concentrations in young adult brain measured by (1)H MR spectroscopy at 3 Tesla

PURPOSE

To quantify and examine the distribution of brain metabolites in normal young adults using single voxel MR spectroscopy at 3 Tesla (T).

MATERIALS AND METHODS

Short-echo time single-voxel PRESS technique was used to measure the apparent concentration of five metabolites at nine locations in the brains of young adults. Concentrations were estimated by means of an automated fitting method (LCModel) with reference to an unsuppressed water signal and were corrected for T(1) relaxation, T(2) relaxation, and cerebrospinal fluid partial volume. Analysis of variance with Tukey post hoc test was used to evaluate regional variations.

RESULTS

Statistically significant differences in regional concentrations were detected for each of the metabolites. The number of significant differences was greatest for total choline, whereas myo-inositol and the sum of glutamine and glutamate had the fewest. Magnitude of variation was greatest for total choline and least for the sum of N-acetyl aspartate and N-acetylaspartylglutamate.

CONCLUSION

In agreement with previous studies at other field strengths, we found heterogeneous distribution of the major spectroscopically measurable brain metabolites. Although the most distinct differences are between tissue types, there is appreciable variation within a tissue type at different locations. The spectra and metabolite concentrations presented should provide a useful reference for both clinical and research MR spectroscopy studies performed at 3T.

Minimal residual disease-directed risk stratification using real-time quantitative PCR analysis of immunoglobulin and T-cell receptor gene rearrangements in the international multicenter trial AIEOP-BFM ALL 2000 for childhood acute lymphoblastic leukemia

Detection of minimal residual disease (MRD) is the most sensitive method to evaluate treatment response and one of the strongest predictors of outcome in childhood acute lymphoblastic leukemia (ALL). The 10-year update on the I-BFM-SG MRD study 91 demonstrates stable results (event-free survival), that is, standard risk group (MRD-SR) 93%, intermediate risk group (MRD-IR) 74%, and high risk group (MRD-HR) 16%. In multicenter trial AIEOP-BFM ALL 2000, patients were stratified by MRD detection using quantitative PCR after induction (TP1) and consolidation treatment (TP2). From 1 July 2000 to 31 October 2004, PCR target identification was performed in 3341 patients: 2365 (71%) patients had two or more sensitive targets (< or =10(-4)), 671 (20%) patients revealed only one sensitive target, 217 (6%) patients had targets with lower sensitivity, and 88 (3%) patients had no targets. MRD-based risk group assignment was feasible in 2594 (78%) patients: 40% were classified as MRD-SR (two sensitive targets, MRD negativity at both time points), 8% as MRD-HR (MRD > or =10(-3) at TP2), and 52% as MRD-IR. The remaining 823 patients were stratified according to clinical risk features: HR (n=108) and IR (n=715). In conclusion, MRD-PCR-based stratification using stringent criteria is feasible in almost 80% of patients in an international multicenter trial.

Microsurgical treatment of injury to peripheral nerves in upper and lower limbs: a critical review of the last 8 years

Nerve injuries to the upper and inferior limbs represent a common event due both to home and working accidents. Minor traumas can lead to severe disabilities if a wrong treatment is carried out. From 1997 to 2005, 920 patients were observed with a total of 1,200 major or minor nerves injuries operated. In 852 cases acute lesions treated. In 68 patients we reviewed old injuries. In 707 patients direct nerve suture and in 145 patients nerve grafts were carried out. One to 8 years follow up observed. Different protocols were adopted according to the injury: simple cut, complex lesion or surgical revision. Results were evaluated during the follow up period with different models: motor evaluation in six levels (BMRC), sensitive evaluation in five levels (HIGHET), and global evaluation with four grades (from the worst to the best result). Nerve healing is a complex biological phenomenon influenced by many parameters related both to the patient characteristics and nerve lesion. Functional and esthetical outcomes vary also according to: age, cultural and economic condition, health status, and smoking. Post operative rehabilitation is mandatory to obtain an acceptable functional result. Nerve injuries to the upper and inferior limbs represent a challenge for the microsurgeon. Ultimate success in nerve surgery is judged by functional as well as cosmetic parameters. Only patients with the appropriate indication should be operated and always by a skilled surgeon.

Induction of apoptosis in Jurkat cells by photoexcited psoralen derivatives: Implication of mitochondrial dysfunctions and caspases activation

The prevailing form of cell death in lymphocytes exposed to psoralen plus UVA light (PUVA), was investigated. We studied the well known drug 8-methoxypsoralen (8-MOP) and an angular derivatives: angelicin (ANG). We evaluated the induction of apoptosis in a human tumor T-cell line (Jurkat). Both compounds provoke a significant induction of apoptosis at 24h from irradiation as demonstrated by a remarkable percentage of cells Annexin-V positive. We investigated the effects of the psoralen derivatives upon UVA irradiation on the cell cycle. The flow cytometric analysis of propidium labeled cells indicates that treatment induces, in a dose dependent manner, a massive accumulation of cells, for both compounds, in G2-S phase after 24h from the irradiation. We have focused our attention on the mitochondrial functionality after irradiation in the presence of psoralen derivatives. We evaluated, by flow cytometry, (i) the mitochondrial potential (Deltapsi(mt)), (ii) the production of reactive oxygen species (ROS) and (iii) the oxidation of cardiolipin, a phospholipid restricted to the inner mitochondrial membrane. Furthermore the activation of caspases -3, -8 and -9 was also investigated. The obtained data indicated that, upon UVA irradiation, the two compounds induce a strong decrease in mitochondrial functions and activate caspase-3, -8 and -9.

Optimization of PCR-based minimal residual disease diagnostics for childhood acute lymphoblastic leukemia in a multi-center setting

Minimal residual disease (MRD) diagnostics is used for treatment stratification in childhood acute lymphoblastic leukemia. We aimed to identify and solve potential problems in multicenter MRD studies to achieve and maintain consistent results between the AIEOP/BFM ALL-2000 MRD laboratories. As the dot-blot hybridization method was replaced by the real-time quantitative polymerase chain reaction (RQ-PCR) method during the treatment protocol, special attention was given to the comparison of MRD data obtained by both methods and to the reproducibility of RQ-PCR data. Evaluation of all key steps in molecular MRD diagnostics identified several pitfalls that resulted in discordant MRD results. In particular, guidelines for RQ-PCR data interpretation appeared to be crucial for obtaining concordant MRD results. The experimental variation of the RQ-PCR was generally less than three-fold, but logically became larger at low MRD levels below the reproducible sensitivity of the assay (<10(-4)). Finally, MRD data obtained by dot-blot hybridization were comparable to those obtained by RQ-PCR analysis (r(2)=0.74). In conclusion, MRD diagnostics using RQ-PCR analysis of immunoglobulin/T-cell receptor gene rearrangements is feasible in multicenter studies but requires standardization; particularly strict guidelines for interpretation of RQ-PCR data are required. We further recommend regular quality control for laboratories performing MRD diagnostics in international treatment protocols.