Bone morphogenetic protein-7 release from endogenous neural precursor cells suppresses the tumourigenicity of stem-like glioblastoma cells

Glioblastoma cells with stem-like properties control brain tumour growth and recurrence. Here, we show that endogenous neural precursor cells perform an anti-tumour response by specifically targeting stem-like brain tumour cells. In vitro, neural precursor cells predominantly express bone morphogenetic protein-7; bone morphogenetic protein-7 is constitutively released from neurospheres and induces canonical bone morphogenetic protein signalling in stem-like glioblastoma cells. Exposure of human and murine stem-like brain tumour cells to neurosphere-derived bone morphogenetic protein-7 induces tumour stem cell differentiation, attenuates stem-like marker expression and reduces self-renewal and the ability for tumour initiation. Neurosphere-derived or recombinant bone morphogenetic protein-7 reduces glioblastoma expansion from stem-like cells by down-regulating the transcription factor Olig2. In vivo, large numbers of bone morphogenetic protein-7-expressing neural precursors encircle brain tumours in young mice, induce canonical bone morphogenetic protein signalling in stem-like glioblastoma cells and can thereby attenuate tumour formation. This anti-tumour response is strongly reduced in older mice. Our results indicate that endogenous neural precursor cells protect the young brain from glioblastoma by releasing bone morphogenetic protein-7, which acts as a paracrine tumour suppressor that represses proliferation, self-renewal and tumour-initiation of stem-like glioblastoma cell

Cellular and molecular mechanisms of glioma growth control

Im ersten Teil meiner Arbeit habe ich den molekularen Mechanismus beschrieben, mit dem endogene neuronale Vorläuferzellen antitumorigen gegen Gliomstammzellen wirken. Unsere Forschungsgruppe hat in bereits veröffentlichten Arbeiten gezeigt, dass neuronale Vorläuferzellen zu experimentellen Gehirntumoren migrieren und Tumorzelltod induzieren können. In der nun vorliegenden Arbeit zeige ich, dass die neuronalen Vorläuferzellen nicht nur benefiziell gegen die Hauptpopulation der Tumorzellen wirken, sondern darüber hinaus auch die kleinere Population der sehr aggressiven Tumorstammzellen – mittels Sekretion von BMP7 – supprimieren. Insgesamt zeigt meine Arbeit, dass neuronale Vorläuferzellen die Pathogenität der Gliomstammzellen unterdrücken. Im zweiten Teil meiner Arbeit habe ich einen zellautonomen Mechanismus untersucht, der Gliomzellen in vitro und in vivo vermehrt expandieren lässt. Meine Ergebnisse zeigen, dass die Familie der ets-Transkriptionsfaktoren Gliomzellen zur Proliferation anregen, indem sie die Expresion eines Eisentransporters (dem Transferrin-Rezeptor-1) induzieren und damit die intrazelluläre Akkumulation von Eisenionen begünstigen. Die Veränderung des Redox-Gleichgewichts in den Gliomzellen regt die Tumore zu verstärkter Sekretion von Glutamat an. Dadurch werden die Gliome sehr zytotoxisch und induzieren Zelltod in den Zellen des tumorumgebenden Parenchyms. Das untergegangene Nervengewebe schafft damit den Platz, den der Tumor zur Expansion braucht. Insgesamt zeigt meine Arbeit, dass die ets1-induzierte CD71 Expression nicht nur das Tumorwachstum befördert, sondern auch den Platz zum Tumorwachstum schafft.In my first part,Gliomas cells with stem-like properties (GSCs) control tumor growth and recurrence. Here, I showed that endogenous neural precursor cells (NPCs) perform an anti-tumor response by specifically targeting GSCs: In vitro, NPCs predominantly expressed BMP7; BMP7 was constitutively released from neurospheres and induced canonical BMP-signaling in GSCs. Exposure of human and murine GSCs to neurosphere-derived BMP7 increased GSC differentiation, attenuated GSC-marker expression, GSC self-renewal and the ability for tumor initiation.This anti-tumor response of NPCs protect the brain from gliomas by releasing BMP7, which acts as a paracrine tumor suppressor that represses proliferation, self-renewal and tumor-initiation of GSCs. In the 2nd part, Transferrin receptors (TfR) are overexpressed in brain tumors, but the pathological relevance has not been fully explored. Here, I showed that TfR is an important downstream effector of ets transcription factors that promotes glioma proliferation and increases glioma-evoked neuronal death. TfR mediates iron accumulation and reactive oxygen formation and thereby enhanced proliferation in clonal human glioma lines. TfR-induced oxidant accumulation modified cellular signaling by inactivating a protein tyrosine phosphatase (low-molecular-weight protein tyrosine phosphatase), activating mitogen-activated protein kinase and Akt and by inactivating p21/cdkn1a and pRB. Inactivation of these cell cycle regulators facilitated S-phase entry. Besides its effect on proliferation, TfR also boosted glutamate release, which caused NMDA mediated reduction of neuron cell mass. Overall my results indicate that TfR promotes glioma progression by two mechanisms, an increase in proliferation rate and glutamate production, the latter mechanism providing space for the progressing tumor mass

Expression and Immunological Characterization of the Carboxy-Terminal Region of the P1 Adhesin Protein of Mycoplasma pneumoniae

Mycoplasma pneumoniae is the causative agent of primary atypical pneumonia in humans. Adherence of M. pneumoniae to host cells requires several adhesin proteins, such as P1, P30, and P116. A major limitation in developing a specific diagnostic test for M. pneumoniae is the inability to express adhesin proteins in heterologous expression systems due to unusual usage of the UGA stop codon, leading to premature termination of these proteins in Escherichia coli. In the present study, we successfully expressed the C-terminal (P1-C1) and N-terminal (P1-N1) regions of the P1 protein in E. coli. On screening these recombinant proteins with sera from M. pneumoniae-infected patients, only the P1-C1 protein was found to be immunogenic. This protein can be used as an antigen for immunodiagnosis of M. pneumoniae infection, as well as in adherence inhibition studies to understand the pathophysiology of the disease

Smad7 Regulates the Adult Neural Stem/Progenitor Cell Pool in a Transforming Growth Factor β- and Bone Morphogenetic Protein-Independent Manner▿

Members of the transforming growth factor β (TGF-β) family of proteins modulate the proliferation, differentiation, and survival of many different cell types. Neural stem and progenitor cells (NPCs) in the adult brain are inhibited in their proliferation by TGF-β and by bone morphogenetic proteins (BMPs). Here, we investigated neurogenesis in a hypomorphic mouse model for the TGF-β and BMP inhibitor Smad7, with the hypothesis that NPC proliferation might be reduced due to increased TGF-β and BMP signaling. Unexpectedly, we found enhanced NPC proliferation as well as an increased number of label-retaining cells in vivo. The enhanced proliferation potential of mutant cells was retained in vitro in neurosphere cultures. We observed a higher sphere-forming capacity as well as faster growth and cell cycle progression. Use of specific inhibitors revealed that these effects were independent of TGF-β and BMP signaling. The enhanced proliferation might be at least partially mediated by elevated signaling via epidermal growth factor (EGF) receptor, as mutant cells showed higher expression and activation levels of the EGF receptor. Conversely, an EGF receptor inhibitor reduced the proliferation of these cells. Our data indicate that endogenous Smad7 regulates neural stem/progenitor cell proliferation in a TGF-β- and BMP-independent manner

Bone morphogenetic protein-7 release from endogenous neural precursor cells suppresses the tumourigenicity of stem-like glioblastoma cells

Glioblastoma cells with stem-like properties control brain tumour growth and recurrence. Here, we show that endogenous neural precursor cells perform an anti-tumour response by specifically targeting stem-like brain tumour cells. In vitro, neural precursor cells predominantly express bone morphogenetic protein-7; bone morphogenetic protein-7 is constitutively released from neurospheres and induces canonical bone morphogenetic protein signalling in stem-like glioblastoma cells. Exposure of human and murine stem-like brain tumour cells to neurosphere-derived bone morphogenetic protein-7 induces tumour stem cell differentiation, attenuates stem-like marker expression and reduces self-renewal and the ability for tumour initiation. Neurosphere-derived or recombinant bone morphogenetic protein-7 reduces glioblastoma expansion from stem-like cells by down-regulating the transcription factor Olig2. In vivo, large numbers of bone morphogenetic protein-7-expressing neural precursors encircle brain tumours in young mice, induce canonical bone morphogenetic protein signalling in stem-like glioblastoma cells and can thereby attenuate tumour formation. This anti-tumour response is strongly reduced in older mice. Our results indicate that endogenous neural precursor cells protect the young brain from glioblastoma by releasing bone morphogenetic protein-7, which acts as a paracrine tumour suppressor that represses proliferation, self-renewal and tumour-initiation of stem-like glioblastoma cells