Improving survival in recurrent medulloblastoma: earlier detection, better treatment or still an impasse?

Early detection of relapse has been advocated to improve survival in children with recurrent medulloblastoma. However, the prognostic factors and the longer term outcome of these patients remains unclear. Pattern of recurrences were analysed in three consecutive protocols of the Société Française d'Oncologie Pédiatrique (1985-91). A uniform surveillance programme including repeated lumbar puncture combined with computerized tomography (CT) or magnetic resonance imaging (MRI) scan was applied for all registered patients. Forty-six out of 116 patients had progressive or recurrent disease. The median time from diagnosis to recurrence was 10.5 months and 76% relapses occurred during the first 2 years. Seventeen patients had asymptomatic relapses that were detected by the surveillance protocol. Forty-one patients were treated at time of progression. Twenty-three responded to salvage therapy and 11 achieved a second complete remission. The median survival time after progression was 5 months (<1-41 months), and only two patients remained alive at time of follow-up. Length of survival is primarily related to some specific patterns of relapse (time from diagnosis to recurrence, circumstances of relapse, extent of relapse) and to the response to salvage therapy. No evidence of long-term benefit appeared from any form of treatment

Dose finding and O6-alkylguanine-DNA alkyltransferase study of cisplatin combined with temozolomide in paediatric solid malignancies

Cisplatin may have additive activity with temozolomide due to ablation of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (MGMT). This phase I/II study determined recommended combination doses using the Continual Reassessment Method, toxicities and antitumour activity in paediatric patients, and evaluated MGMT in peripheral blood mononuclear cells (PBMCs) in order to correlate with haematological toxicity. In total, 39 patients with refractory or recurrent solid tumours (median age ∼13 years; 14 pretreated with high-dose chemotherapy, craniospinal irradiation, or having bone marrow involvement) were treated with cisplatin, followed the next day by oral temozolomide for 5 days every 4 weeks at dose levels 80 mg m−2/150 mg m−2 day−1, 80/200, and 100/200, respectively. A total of 38 patients receiving 113 cycles (median 2, range 1–7) were evaluable for toxicity. Dose-limiting toxicity was haematological in all but one case. Treatment-related toxicities were thrombocytopenia, neutropenia, nausea-vomiting, asthenia. Hearing loss was experienced in five patients with prior irradiation to the brain stem or posterior fossa. Partial responses were observed in two malignant glioma, one brain stem glioma, and two neuroblastoma. Median MGMT activity in PBMCs decreased after 5 days of temozolomide treatment: low MGMT activity correlated with increased severity of thrombocytopenia. Cisplatin–temozolomide combinations are well tolerated without additional toxicity to single-agent treatments; the recommended phase II dosage is 80 mg m−2 cisplatin and 150 mg m−2 × 5 temozolomide in heavily treated, and 200 mg m−2 × 5 temozolomide in less-heavily pretreated children

Membrane Potential-Dependent Modulation of Recurrent Inhibition in Rat Neocortex

Dynamic balance of excitation and inhibition is crucial for network stability and cortical processing, but it is unclear how this balance is achieved at different membrane potentials (Vm) of cortical neurons, as found during persistent activity or slow Vm oscillation. Here we report that a Vm-dependent modulation of recurrent inhibition between pyramidal cells (PCs) contributes to the excitation-inhibition balance. Whole-cell recording from paired layer-5 PCs in rat somatosensory cortical slices revealed that both the slow and the fast disynaptic IPSPs, presumably mediated by low-threshold spiking and fast spiking interneurons, respectively, were modulated by changes in presynaptic Vm. Somatic depolarization (>5 mV) of the presynaptic PC substantially increased the amplitude and shortened the onset latency of the slow disynaptic IPSPs in neighboring PCs, leading to a narrowed time window for EPSP integration. A similar increase in the amplitude of the fast disynaptic IPSPs in response to presynaptic depolarization was also observed. Further paired recording from PCs and interneurons revealed that PC depolarization increases EPSP amplitude and thus elevates interneuronal firing and inhibition of neighboring PCs, a reflection of the analog mode of excitatory synaptic transmission between PCs and interneurons. Together, these results revealed an immediate Vm-dependent modulation of cortical inhibition, a key strategy through which the cortex dynamically maintains the balance of excitation and inhibition at different states of cortical activity

Off-label use of targeted therapies in osteosarcomas: data from the French registry OUTC'S (Observatoire de l'Utilisation des Thérapies Ciblées dans les Sarcomes):

BACKGROUND: The objective of this study is to explore the off-label use of targeted therapies (TTs) for patients with osteosarcoma registered within the French Sarcoma Group--Bone Tumor Study Group (GSF-GETO) national registry. METHODS: All patients with an osteosarcoma, registered between January 1, 2009 and July 15, 2013 were analyzed. RESULTS: Twenty-nine patients with refractory relapsed osteosarcomas received 33 treatment lines of TTs. The median age at the beginning of treatment was 19 years (range 9-72). The median number of previous lines of chemotherapy was 3 (range 1-8). Before inclusion, 3 patients were in second complete remission, 26 were in progression for metastatic relapse. Twenty-three patients received sirolimus (in combination with cyclophosphamide for 18); 5, sunitinib; 4, sorafenib; and one, pazopanib. Stable disease was observed for 45.5% of patients (95% Confidence Interval (CI) [20-52.8]). The median Progression-Free Survival (PFS) was 3 months (95% CI [2-5.4]) for patients treated by sirolimus and 1.8 months (95% CI [1.3-2.8]) for patients receiving multi-targeted tyrosine kinase inhibitors; 6-month PFS 15%. The median Overall Survival (OS) was 6.8 months (95% CI [4.7-12.1]), and one-year OS was 24%. In a multivariate analysis, PFS was superior for patients receiving sirolimus compared to other TTs (Hazard Ratio (HR) = 2.7, 95% CI [1.05-7.1]). No toxic death was reported. Grade 3 and 4 toxicities were observed in 27 and 6% of cases respectively. CONCLUSION: Off-label TTs, especially sirolimus, reported benefit in the treatment of refractory osteosarcomas with an acceptable toxicity profile, including in pediatric population

Tonic excitation or inhibition is set by GABAA conductance in hippocampal interneurons

Inhibition is a physiological process that decreases the probability of a neuron generating an action potential. The two main mechanisms that have been proposed for inhibition are hyperpolarization and shunting. Shunting results from increased membrane conductance, and it reduces the neuron-firing probability. Here we show that ambient GABA, the main inhibitory neurotransmitter in the brain, can excite adult hippocampal interneurons. In these cells, the GABAA current reversal potential is depolarizing, making baseline tonic GABAA conductance excitatory. Increasing the tonic conductance enhances shunting-mediated inhibition, which eventually overpowers the excitation. Such a biphasic change in interneuron firing leads to corresponding changes in the GABAA-mediated synaptic signalling. The described phenomenon suggests that the excitatory or inhibitory actions of the current are set not only by the reversal potential, but also by the conductance

Biophysical Characteristics Reveal Neural Stem Cell Differentiation Potential

Distinguishing human neural stem/progenitor cell (huNSPC) populations that will predominantly generate neurons from those that produce glia is currently hampered by a lack of sufficient cell type-specific surface markers predictive of fate potential. This limits investigation of lineage-biased progenitors and their potential use as therapeutic agents. A live-cell biophysical and label-free measure of fate potential would solve this problem by obviating the need for specific cell surface markers

Ifosfamide/etoposide alternating with high-dose methotrexate: evaluation of a chemotherapy regimen for poor-risk osteosarcoma

Fifteen patients with relapsed osteosarcoma were treated with an intensive combination chemotherapy schedule. Ifosfamide 2.5 g m−2 daily and etoposide 150 mg m−2 daily coincidentally for 3 days and high-dose methotrexate 8 g m−2 (with folinic acid rescue) on days 10–14 in a planned 21-day cycle. Feasibility, toxicity and response to this alternative combination for the treatment of relapsed osteosarcoma was assessed. There were 98 evaluable cycles for toxicity and tolerability. The majority of cycles were well tolerated. Haematological toxicity of grade 3/4 (common toxicity criteria) was seen in all courses. Renal tubular loss of electrolytes, particularly magnesium, occurred in 71% of cycles. Thirteen per cent of cycles were repeated within 21 days and 61% within 28 days. In the thirteen patients evaluable for response, a partial response rate of 31% was seen after two cycles. However, patients with stable disease continued on therapy, and an overall consequent response rate of 62% was observed. Four patients were alive with no evidence of disease at 8–74 months. Three are alive with disease (at 8–19 months). There were six deaths, all disease related. This regimen exhibits an encouraging response rate in a group of children with poor prognosis disease, with a tolerable toxicity profile. © 1999 Cancer Research Campaig

Models of Neocortical Layer 5b Pyramidal Cells Capturing a Wide Range of Dendritic and Perisomatic Active Properties

The thick-tufted layer 5b pyramidal cell extends its dendritic tree to all six layers of the mammalian neocortex and serves as a major building block for the cortical column. L5b pyramidal cells have been the subject of extensive experimental and modeling studies, yet conductance-based models of these cells that faithfully reproduce both their perisomatic Na+-spiking behavior as well as key dendritic active properties, including Ca2+ spikes and back-propagating action potentials, are still lacking. Based on a large body of experimental recordings from both the soma and dendrites of L5b pyramidal cells in adult rats, we characterized key features of the somatic and dendritic firing and quantified their statistics. We used these features to constrain the density of a set of ion channels over the soma and dendritic surface via multi-objective optimization with an evolutionary algorithm, thus generating a set of detailed conductance-based models that faithfully replicate the back-propagating action potential activated Ca2+ spike firing and the perisomatic firing response to current steps, as well as the experimental variability of the properties. Furthermore, we show a useful way to analyze model parameters with our sets of models, which enabled us to identify some of the mechanisms responsible for the dynamic properties of L5b pyramidal cells as well as mechanisms that are sensitive to morphological changes. This automated framework can be used to develop a database of faithful models for other neuron types. The models we present provide several experimentally-testable predictions and can serve as a powerful tool for theoretical investigations of the contribution of single-cell dynamics to network activity and its computational capabilities