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Fibroblast growth factors (FGFs) and their receptors (FGFRs) initiate diverse cellular responses that contribute to the regulation of oligodendrocyte (OL) function. In order to understand the mechanisms by which FGFRs elicit these cellular responses, we investigated the phosphorylation of signal transduction proteins and the role of cholesterol-glycosphingolipid-enriched “lipid raft” microdomains in differentiated OLs. Surprisingly, we found that the most abundant tyrosine-phosphorylated protein in OLs was the 120-kd isoform of FGFR2 and that it was phosphorylated even in the absence of FGF2, suggesting a potential ligand-independent function for this receptor. Furthermore, FGFR2, but not FGFR1, was associated with lipid raft microdomains in OLs and myelin (but not in astrocytes). This provides the first evidence for the association of FGFR with TX-100-insoluble lipid raft fractions. FGFR2 phosphorylated the key downstream target, FRS2 in OLs. Raft disruption resulted in loss of phosphorylated FRS2 from lipid rafts, coupled with the loss of Akt but not of Mek or Erk phosphorylation. This suggests that FGFR2-FRS2 signaling in lipid rafts operates via the PI3-Kinase/Akt pathway rather than the Ras/Mek/Erk pathway, emphasizing the importance of microenvironments within the cell membrane. Also present in lipid rafts in OLs and myelin, but not in astrocytes, was a novel 52-kd isoform of FGFR2 that lacked the extracellular ligand-binding region. These results demonstrate that FGFR2 in OLs and myelin possess unique characteristics that are specific both to receptor type and to OLs and provide a novel mechanism to elicit distinct cellular responses that mediate both FGF-dependent and -independent functions.

Axon–glial interactions are critical for normal functioning of peripheral nerves, and their disruption leads to peripheral neuropathies. Fibroblast growth factors (FGFs) are key players in peripheral nerve regeneration after injury. We investigated the role of FGF receptor (Fgfr) signaling in Schwann cells and the consequent regulation of normal Schwann cell–axon interactions. Fgfr1 and Fgfr2 were conditionally inactivated, either singly or in combination, in myelinating and nonmyelinating Schwann cells (NMSCs) of transgenic mice. The double mutant mice displayed significant loss of thermal sensitivity accompanied by marked neuropathy of unmyelinated nociceptive sensory axons terminating in the dorsal horn of spinal cords, the primary site for integrating pain and temperature inputs. Neuropathy, although to a lesser extent, was also observed in the nociceptive C-fibers in the Remak bundles of sciatic nerves; however, there was no loss of NMSCs that ensheathe these axons. Furthermore, axons wrapped by myelinating Schwann cells and associated myelin sheaths appeared to be unaffected. Relative to the double mutants, axonal neuropathy developed much later in the Fgfr1 but not Fgfr2 single mutant, indicating a difference in signaling potential of the two receptors, with Fgfr1 being more robust than Fgfr2. These findings emphasize the importance of Fgfr1 and Fgfr2 signaling as potential mediators of axon–glial interaction in the peripheral sensory pain pathway primarily via influencing NMSC function, which in turn modulates the structure and function of unmyelinated sensory axons. This study provides a novel molecular mechanism for nociception with possible implications for pain sensitivity in peripheral sensory neuropathies.

© Impact Journals, LLC. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited., Advances in the molecular biology of medulloblastoma revealed four genetically and clinically distinct subgroups. Group 3 medulloblastomas are characterized by frequent amplifications of the oncogene MYC, a high incidence of metastasis, and poor prognosis despite aggressive therapy. We investigated several potential small molecule inhibitors to target Group 3 medulloblastomas based on gene expression data using an in silico drug screen. The Connectivity Map (C-MAP) analysis identified piperlongumine as the top candidate drug for non-WNT medulloblastomas and the cyclin-dependent kinase (CDK) inhibitor alsterpaullone as the compound predicted to have specific antitumor activity against Group 3 medulloblastomas. To validate our findings we used these inhibitors against established Group 3 medulloblastoma cell lines. The C-MAP predicted drugs reduced cell proliferation in vitro and increased survival in Group 3 medulloblastoma xenografts. Alsterpaullone had the highest efficacy in Group 3 medulloblastoma cells. Genomic profiling of Group 3 medulloblastoma cells treated with alsterpaullone confirmed inhibition of cell cycle-related genes, and down-regulation of MYC. Our results demonstrate the preclinical efficacy of using a targeted therapy approach for Group 3 medulloblastomas. Specifically, we provide rationale for advancing alsterpaullone as a targeted therapy in Group 3 medulloblastoma., This study was supported by the Canadian Cancer Society (Grant #2011-70051), the Pediatric Brain Tumor Foundation of the United States, the Brain Tumour Foundation of Canada, Meagan’s Walk, b.r.a.i.n.child and the Wiley Fund at the Hospital for Sick Children.

Fibroblast growth factor receptors (Fgfr) comprise a widely expressed family of developmental regulators implicated in oligodendrocyte (OL) maturation of the CNS. Fgfr2 is expressed by OLs in myelinated fiber tracks.In vitro, Fgfr2 is highly upregulated during OL terminal differentiation, and its activation leads to enhanced growth of OL processes and the formation of myelin-like membranes. To investigate thein vivofunction of Fgfr2 signaling by myelinating glial cells, we inactivated the floxed Fgfr2 gene in mice that coexpress Cre recombinase (cre) as a knock-in gene into the OL-specific 2′,3′-cyclic nucleotide phosphodiesterase (Cnp1) locus. Surprisingly, no obvious defects were detected in brain development of these conditional mutants, including the number of OLs, the onset and extent of myelination, the ultrastructure of myelin, and the expression level of myelin proteins. However, unexpectedly, a subset of these conditional Fgfr2 knock-out mice that are homozygous forcreand therefore are also Cnp1 null, displayed a dramatic hyperactive behavior starting at ∼2 weeks of age. This hyperactivity was abolished by treatment with dopamine receptor antagonists or catecholamine biosynthesis inhibitors, suggesting that the symptoms involve a dysregulation of the dopaminergic system. Although the molecular mechanisms are presently unknown, this novel mouse model of hyperactivity demonstrates the potential involvement of OLs in neuropsychiatric disorders, as well as the nonpredictable role of genetic interactions in the behavioral phenotype of mice.

The mechanisms regulating the number of myelinating cells in the central nervous system are crucial for both normal development and repair in pathological conditions. Among relevant growth factors involved in this process, fibroblast growth factor-2 (FGF2) induces oligodendrocyte progenitors (OLPs) to proliferate and stimulates mature oligodendrocytes (OLs) to reenter the S-phase of the cell cycle. S-phase entry is modulated by the formation of complexes between cyclins and cyclin-dependent kinases (CDKs), on one hand, and by their interactions with cell cycle inhibitors (e.g., p18INK, p27Kip1, p21Cip1), on the other. Although the roles of cyclin E/CDK2 complexes and the inhibitor p27Kip1 have been extensively investigated relative to proliferation and differentiation in the OL lineage, less is known about the regulation of the formation of cyclin D1/CDK4 complexes and the role of p21Cip1 in these events. In this study, we show that the FGF2-mediated increase in bromodeoxyuridine (BrdU) incorporation into OL progenitors and mature OLs occurs concomitantly with increase in the levels of p21Cip1 and the formation of p21Cip1/cyclin D1/CDK4 ternary complexes. These complexes are functionally active is indicated by the ensuing FGF2-dependent hyperphosphorylation of the downstream target Rb. In untreated mature OLs that do not incorporate BrdU, the levels of p21Cip1 are low, and the level of the inhibitor p18INK is high. Furthermore, p18INK sequesters CDK2 into binary complexes, precluding the formation of p21Cip1/cyclin D1/CDK4 ternary complexes in these cells. Therefore, we propose that p21Cip1 is acting as a positive regulator, rather than an inhibitor, of cell cycle entry by favoring the assembly of active cyclin D1/CDK4 complexes.

This study investigated the accuracy of the proprioceptive system in swallowing as compared with fist clenching. The role of surface electromyography (SEMG) biofeedback in replicating motor strength was also evaluated. The study was completed in two phase. Phase 1 participants (n = 50) were aged 20–30 years; phase 2 involved participants(n= 50) aged over 50 years. SEMG activity was measured during performance of maximal and graded (half) strength swallowing and fist-clenching tasks. Subjects performed each task eight consecutive times, under three conditions: (1) with biofeedback; (2) without biofeedback; and (3) without feedback following a delay. A portable SEMG biofeedback device recorded the strength and timing of muscular activity and represented the information in analogue waveform on a computer screen. Under biofeedback conditions, subjects were instructed to observe the SEMG waveform to determine their maximal peak SEMG amplitudes. Data were collected from the final five of eight consecuti...

// Roberto Jose Diaz 1,2,3,* , Brian Golbourn 1,* , Claudia Faria 1 , Daniel Picard 1 , David Shih 1 , Denis Raynaud 4 , Michael Leadly 4 , Danielle MacKenzie 1 , Melissa Bryant 1 , Matthew Bebenek 1 , Christian A. Smith 1 , Michael D. Taylor 1,2,3 , Annie Huang 1 and James T. Rutka 1,2,3 1 The Hospital for Sick Children. Arthur and Sonia Labatt Brain Tumour Research Centre, Toronto, Ontario, Canada 2 Department of Laboratory Medicine & Pathobiology, University of Toronto, Toronto, Ontario, Canada 3 Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Ontario, Canada 4 Analytical Facility for Bioactive Molecules, The Hospital for Sick Children, Toronto, Ontario, Canada * These authors contributed equally to this work Correspondence: James T. Rutka, email: // Keywords: Aurora kinase, medulloblastoma, tumor biology, molecular therapy,cell-cycle Received : June 29, 2014 Accepted : December 24, 2014 Published : December 31, 2014 Abstract Medulloblastoma comprises four molecular subgroups of which Group 3 medulloblastoma is characterized by MYC amplification and MYC overexpression. Lymphoma cells expressing high levels of MYC are susceptible to apoptosis following treatment with inhibitors of mitosis. One of the key regulatory kinases involved in multiple stages of mitosis is Aurora kinase B. We hypothesized that medulloblastoma cells that overexpress MYC would be uniquely sensitized to the apoptotic effects of Aurora B inhibition. The specific inhibition of Aurora kinase B was achieved in MYC- overexpressing medulloblastoma cells with AZD1152-HQPA. MYC overexpression sensitized medulloblastoma cells to cell death upon Aurora B inhibition. This process was found to be independent of endoreplication. Using both flank and intracranial cerebellar xenografts we demonstrate that tumors formed from MYC-overexpressing medulloblastoma cells show a response to Aurora B inhibition including growth impairment and apoptosis induction. Lastly, we show the distribution of AZD1152-HQPA within the mouse brain and the ability to inhibit intracranial tumor growth and prolong survival in mice bearing tumors formed from MYC-overexpressing medulloblastoma cells. Our results suggest the potential for therapeutic application of Aurora kinase B inhibitors in the treatment of Group 3 medulloblastoma.

BACKGROUND The current study evaluated factors influencing survival in patients diagnosed with human immunodeficiency virus (HIV)-related primary central nervous system lymphoma (PCNSL), with a focus on the effects of therapeutic radiotherapy (RT) and highly active antiretroviral therapy (HAART). METHODS A retrospective chart review of patients with a diagnosis of HIV-related PCNSL at one of five university hospitals between 1987 and 1998 was performed. Clinical details including antiretroviral agent use, brain imaging scan results, RT use, and survival outcomes were recorded. RESULTS One hundred eleven patients with HIV-related PCNSL were identified. The annual incidence decreased significantly between 1992 and 1995 and between 1996 and 1998 (P = 0.04). The median survival period was 50 days (mean, 109 days; range, 4–991 days), with improved survival for patients diagnosed after 1993. Patients treated with two or more antiretroviral agents had improved survival (P = 0.01), as did patients who received RT (P < 0.0001). For patients who received RT, completion of the prescribed course and treatment to ≥ 30 Gray (Gy) independently predicted a more favorable outcome. RT used in conjunction with antiretroviral therapy involving two or more agents had an additive positive effect on survival. For patients who did not receive RT, poor performance status and encephalopathy predicted a shorter survival duration. CONCLUSIONS The results of the current study suggest that HAART and treatment with RT to ≥ 30 Gy improve survival for patients with HIV-related PCNSL. This combination of therapies may provide a standard of care as the basis for further trials of chemotherapy, novel adjunctive treatment, and quality of life assessment. Cancer 2004. © 2004 American Cancer Society.

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