Neurofibromatosis type 1 (NF1) gene mutations or alterations occur within neurofibromatosis type 1 as well as in many different malignant tumours on the somatic level. In glioblastoma, NF1 loss of function plays a major role in inducing the mesenchymal (MES) subtype and, therefore defining the most aggressive glioblastoma. This is associated with an immune signature and mediated via the NF1–MAPK–FOSL1 axis. Specifically, increased invasion seems to be regulated via mutations in the leucine-rich domain (LRD) of the NF1 gene product neurofibromin. Novel targets for therapy may arise from neurofibromin deficiency-associated cellular mechanisms that are summarised in this review.

The cyclic (c)AMP responsive element binding protein (CREB) plays a key role in many cellular processes, including differentiation, proliferation, and signal transduction. Furthermore, CREB overexpression was found in tumors of distinct origin and evidence suggests an association with tumorigenicity. To establish a mechanistic link between HER-2/neu–mediated transformation and CREB protein expression and function, in vitro models of HER-2/neu–overexpressing and HER-2/neu–negative/silenced counterparts as well as human mammary carcinoma lesions with defined HER-2/neu status were used. HER-2/neu overexpression resulted in the induction and activation of CREB protein in vitro and in vivo, whereas short hairpin RNA (shRNA)–mediated inhibition of HER-2/neu correlated with downregulated CREB activity. CREB activation in HER-2/neu–transformed cells enhanced distinct signal transduction pathways, whereas their inhibition negatively interfered with CREB expression and/or activation. CREB downregulation in HER-2/neu–transformed cells by shRNA and by the inhibitors KG-501 and lapatinib caused morphologic changes, reduced cell proliferation with G₀–G₁ cell-cycle arrest, which was rescued by CREB expression. This was accompanied by reduced cell migration, wound healing, an increased fibronectin adherence, invasion, and matrix metalloproteinase expression. In vivo shCREB-HER-2/neu⁺ cells, but not control cells, exerted a significantly decreased tumorgenicity that was associated with decreased proliferative capacity, enhanced apoptosis, and increased frequency of T lymphocytes in peripheral blood mononuclear cells. Thus, CREB plays an important role in the HER-2/neu–mediated transformation by altering in vitro and in vivo growth characteristics.

Clinical and experimental data assumed a neuroprotective effect of the calcium channel blocker nimodipine. However, it has not been proven which neuronal or glial cell types are affected by nimodipine and which mechanisms underlie these neuroprotective effects. Therefore, the aim of this study was to investigate the influence of nimodipine treatment on the in vitro neurotoxicity of different cell types in various stress models and to identify the associated molecular mechanisms. Therefore, cell lines from Schwann cells, neuronal cells and astrocytes were pretreated for 24 h with nimodipine and incubated under stress conditions such as osmotic, oxidative and heat stress. The cytotoxicity was measured via the lactate dehydrogenase (LDH) activity of cell culture supernatant. As a result, the nimodipine treatment led to a statistically significantly reduced cytotoxicity in Schwann cells and neurons during osmotic (p ≤ 0.01), oxidative (p ≤ 0.001) and heat stress (p ≤ 0.05), when compared to the vehicle. The cytotoxicity of astrocytes was nimodipine-dependently reduced during osmotic (p ≤ 0.01), oxidative (p ≤ 0.001) and heat stress (not significant). Moreover, a decreased caspase activity as well as an increased proteinkinase B (AKT) and cyclic adenosine monophosphate response element-binding protein (CREB) phosphorylation could be observed after the nimodipine treatment under different stress conditions. These results demonstrate a cell type-independent neuroprotective effect of the prophylactic nimodipine treatment, which is associated with the prevention of stress-dependent apoptosis through the activation of CREB and AKT signaling pathways and the reduction of caspase 3 activity.

The extracellular matrix protein biglycan (Bgn) is a leucine-rich proteoglycan that is involved in the matrix assembly, cellular migration and adhesion, cell growth, and apoptosis. Although a distinct expression of Bgn was found in a number of human tumors, the role of this protein in the initiation and/or maintenance of neoplastic transformation has not been studied in detail. Using an in vitro model of oncogenic transformation, a down-regulation of Bgn expression as well as an altered secretion of different Bgn isoforms was found both in murine and human HER-2/neu oncogene-transformed cells when compared with HER-2/neu⁻ cells. This was associated with a reduced growth, wound closure, and migration capacity. Vice versa, silencing of Bgn in HER-2/neu⁻ fibroblasts increased the growth rate and migration capacity of these cells. Bgn expression was neither modulated in HER-2/neu⁺ cells by transforming growth factor-β₁ nor by inhibition of the phosphoinositol 3-kinase and MAP kinase pathways. In contrast, inhibition of the protein kinase C (PKC) pathway led to the reconstitution of Bgn expression. In particular, the PKC target protein cAMP response element binding protein (CREB) is a major regulator of Bgn expression as the silencing of CREB by RNA interference was accompanied by ∼5000-fold increase in Bgn-mRNA expression in HER-2/neu⁺ cells. Thus, Bgn inhibits the major properties of HER-2/neu-transformed cells, which is inversely modulated by the PKC signaling cascade.

// <![CDATA[ $('.header-date').hide();$('#titleAuthors').hide();$('#abstractHeader').hide(); // ]]> Sandra Leisz1, Kristin Schulz1, Susanne Erb1, Peter Oefner2, Katja Dettmer2, Dimitrios Mougiakakos3, Ena Wang4, Francesco M. Marincola4, Franziska Stehle1, Barbara Seliger1 1Institute of Medical Immunology, Martin Luther University Halle-Wittenberg, 06112 Halle (Saale), Germany 2Institute of Functional Genomics, University of Regensburg, 93053 Regensburg, Germany 3Department of Internal Medicine 5, University of Erlangen, 91054 Erlangen, Germany 4Sidra Medical and Research Center, PO Box 26999, Doha, Qatar Correspondence to: Barbara Seliger, e-mail: Barbara.Seliger@uk-halle.de Keywords: hypoxia, von Hippel Lindau gene, renal cell carcinoma, cell metabolism, aerobic glycolysis Received: February 03, 2015 Accepted: February 25, 2015 Published: March 27, 2015