PRMT5-PTEN molecular pathway regulates senescence and self-renewal of primary glioblastoma neurosphere cells.

Glioblastoma (GBM) represents the most common and aggressive histologic subtype among malignant astrocytoma and is associated with poor outcomes because of heterogeneous tumour cell population including mature non-stem-like cell and immature stem-like cells within the tumour. Thus, it is critical to find new target-specific therapeutic modalities. Protein arginine methyltransferase enzyme 5 (PRMT5) regulates many cellular processes through its methylation activity and its overexpression in GBM is associated with more aggressive disease. Previously, we have shown that silencing of PRMT5 expression in differentiated GBM cell lines results in apoptosis and reduced tumour growth in mice. Here, we report the critical role of PRMT5 in GBM differentiated cells (GBMDC) grown in serum and GBM neurospheres (GBMNS) grown as neurospheres in vitro. Our results uncover a very significant role for PRMT5 in GBMNS self-renewal capacity and proliferation. PRMT5 knockdown in GBMDC led to apoptosis, knockdown in GBMNS led to G1 cell cycle arrest through upregulation of p27 and hypophoshorylation of retinoblastoma protein, leading to senescence. Comparison of impact of PRMT5 on cellular signalling by the Human Phospho-Kinase Array and chromatin immunoprecipitation-PCR revealed that unlike GBMDC, PRMT5 regulates PTEN expression and controls Akt and ERk activity in GBMNS. In vivo transient depletion of PRMT5 decreased intracranial tumour size and growth rate in mice implanted with both primary tumour-derived GBMNS and GBMDC. This is the first study to identify PTEN as a potential downstream target of PRMT5 and PRMT5 is vital to support both mature and immature GBM tumour cell populations.

At the interface of the immune system and the nervous system: how neuroinflammation modulates the fate of neural progenitors in vivo.

Neural stem and progenitor cells express a variety of receptors that enable them to sense and react to signals emanating from physiological and pathophysiological conditions in the brain as well as elsewhere in the body. Many of these receptors and were first described in investigations of the immune system, particularly with respect to hematopoietic stem cells. This emerging view of neurobiology has two major implications. First, many phenomena known from the hematopoietic system may actually be generalizable to stem cells from many organ systems, reflecting the cells' progenitor-mediated regenerative potential. Second, regenerative interfaces may exist between diverse organ systems; populations of cells of neuroectodermal and hematopoietic origin may interact to play a crucial role in normal brain physiology, pathology, and repair. An understanding of the origins of signals and the neural progenitors' responses might lead to the development of effective therapeutic strategies to counterbalance acute and chronic neurodegenerative processes. Such strategies may include modifying and modulating cells with regenerative potential in subtle ways. For example, stem cells might be able to detect pathology-associated signals and be used as "interpreters" to mediate drug and other therapeutic interventions. This review has focused on the role of inflammation in brain repair. We propose that resident astroglia and blood-born cells both contribute to an inflammatory signature that is unique to each kind of neuronal degeneration or injury. These cells play a key role in coordinating the neural progenitor cell response to brain injury by exerting direct and indirect environmentally mediated influence on neural progenitor cells. We suggest that investigations of the neural progenitor-immunologic interface will provide valuable data related to the mechanisms by which endogenous and exogenous neural progenitor cells react to brain pathology, ultimately aiding in the design of more effective therapeutic applications of stem cell biology. Such improvements will include: (1) ascertaining the proper timing for implanting exogenous neural progenitor cells in relation to the administration of anti-inflammatory agents; (2) identifying what types of molecules might be administered during injury to enhance the mobilization and differentiation of endogenous and exogenous neural progenitor cells while also inhibiting the detrimental aspects of the inflammatory reaction; (3) divining clues as to which molecules may be required to change the lesioned environment in order to invite the homing of reparative neural progenitor cells.

Therapeutic strategies to prevent neurodegeneration and promote regeneration in multiple sclerosis.

Multiple sclerosis (MS) is an immune-mediated demyelinating and degenerative disease of the central nervous system (CNS), with lesions predominantly occurring in the CNS white matter. The current treatment for MS relies on therapies that primarily target the peripheral immune response. However, it is clear that these strategies alone are insufficient for treating the chronic progressive disability that is the ultimate outcome of the disease. Axonal degeneration may be the primary determinant of fixed neurological deficits in MS. Here, we will discuss the contribution of axonal damage to MS pathogenesis, and potential cellular and molecular targets in the prevention of neurodegeneration. In addition, we will discuss potential molecular approaches to promote repair of CNS components in multiple sclerosis.

Oral salbutamol decreases IL-12 in patients with secondary progressive multiple sclerosis.

IL-12 is a key cytokine for Th1 cell development and may be important in the pathogenesis of multiple sclerosis (MS). The beta2-agonist salbutamol is known to decrease IL-12 production in monocytes of normal individuals through increased intracellular cAMP. In a prospective open-label study, we investigated by flow cytometry the effect of a 2-week long oral salbutamol treatment on monocyte IL-12 production in 21 secondary progressive MS patients. Baseline IL-12 production was higher in patients than in healthy controls. The treatment induced a significant decrease in the percentage of IL-12-producing monocytes and dendritic cells that lasted up to 1 week after treatment interruption. This first report on the use of salbutamol in MS shows that this drug has immunomodulatory properties both in vivo and in vitro, and may be beneficial in the treatment of MS.

Molecular analysis of alterations of the p18INK4c gene in human meningiomas.

Meningiomas are common primary brain tumours frequently presenting with deleted and/or mutated NF2 gene located on 22q.1p has been reported as the second most commonly deleted chromosomal region in these neoplasms. A new member of the INK4 family of CDK inhibitors, the p18INK4c gene, has recently been mapped to this chromosomal arm. By virtue of its structural and functional similarities with the p16 gene, p18 has been implicated as a tumour suppressor gene in a variety of cancers. In this paper 40 human meningiomas were analysed for loss of heterozygosity (LOH) at the p18 locus, mutations and inactivating methylation of the p18 gene. LOH at D1S193, D1S463 and D1S211 microsatellite marker loci mapped to 1p32 was detected in 13 of 35 (37%), four of 20 (20%), and six of 24 (25%) tumour samples, respectively. One sample presented with homozygous deletion at D1S193. Mutational analysis using single stranded conformational polymorphism (SSCP) and direct sequencing did not detect any missense mutation but revealed a novel silent mutation, G to T, at coding nucleotide 435. Analysis of HgaI, BsaHI, ScrFI and Eco0109I restriction sites of p18 exon 1 revealed absence of inactivating methylation. Immunohistochemistry with p18 monoclonal antibody detected presence of cytoplasmic p18 staining in 21 of 22 examined samples. One sample did not stain and was shown to carry homozygous deletion at D1S193. Despite the high frequency of LOH at 1p32 microsatellite markers, the lack of genetic and epigenetic aberrations in the p18 gene together with the presence of p18 protein in all but one meningioma samples argues against the role of p18 as a tumour suppressor gene important for meningioma development.