Glioma-Research

Synowitz© 2014 Kontaktieren Sie mich
Microglia cells - glioma interaction

Scientific focus
Gliomas are the most frequent primary tumours of the central nervous system (CNS). The majority of glioma patients suffers from glioblastoma multiforme, which is the most aggressive form of a glioma, consituting an average survival of only 14 months after diagnosis. A major clinical problem is the diffuse infiltration of the tumour cells into the adjacent brain which makes complete surgical removal impossible. Invasion of glioma cells into the brain parenchyma is facilitated by metalloprotease-mediated degradation of the extracellular matrix. Matrix Metallo-Proteinases (MMP) are released as inactive pro-forms and get activated upon cleavage e.g. by membrane-bound metalloproteases. We have recently shown, that membrane type 1 metalloprotease (MT1-MMP) is upregulated in glioma-associated microglia (the intrinsic immune cells of the brain), but not in the glioma cells proper. Our data indicate that glioma depend on tumour-associated microglia to facilitate tumour-cell invasion (1-5).

Current state of the field
Microglia are the intrinsic immune cells of the brain, they control the innate and the adaptive immune response in the CNS and are activated by inflammatory or other pathological stimuli (6). Activation of microglial toll-like receptors (TLR) triggers the innate immune response and can initiate host-defence and tissue repair mechanisms, but also CNS inflammation, neurodegeneration and trauma (6), (7). Since microglial cells are attracted towards glioma in large numbers - glioma tissue consists up to 30% of microglial cells - and since microglia density in gliomas positively correlates with malignancy, invasiveness and grading of the tumours (8-10), we are investigating if microglia may actively contribute to glioma expansion. We have previously demonstrated that soluble factors released from glioma stimulate microglial TLRs, resulting in microglial MT1-MMP expression via the TLR downstream signalling molecules MyD88 and p38 MAPK. In turn, MT1-MMP expression and activity in these immune cells promotes glioma cell invasion and tumour expansion.

Own contributions
Invasion of glioma cells into the brain parenchyma is induced by metalloprotease-mediated degradation of the extracellular matrix. Matrix metalloproteases (MMP) are released as inactive pro-forms and get activated upon cleavage e.g. by membrane-bound metalloproteases. Recently, we could show that glioma depend on membrane type 1 metalloprotease (MT1-MMP) expression in glioma-associated microglia to facilitate tumor invasion. Our studies suggested that a soluble factor from glioma stimulates microglial TLRs (toll like receptor), triggers MyD88 and p38MAPK signalling and thereby induces microglial MT1-MMP expression. Increased parenchymal MT1-MMP in turn promoted accelerated glioma expansion, presumably also by activation of glioma-derived MMP2. Interfering with microglial TLR-signalling or experimental depletion of microglia in our in vivo glioma models resulted in more than an 70% reduction in glioma volume. Overall, our data indicate that microglia significantly contribute to glioma progression in mouseand rat-glioma models. Furthermore, our data from primary patient material show that our observation is of relevance for human brain tumors (11-15).

Stacks Image 76
Figure 1

(A) GFP-expressing glioma cells 5days after injection into a cultivated brain slices shows that MT1-MMP (blue) is expressed on microglia and endothelia (labelled by Isolectin-B4;ILB4; red). (B) A microglia depleted brain slice preparation shows MT1-MMP only on endothelial cells (insert in B). The size bars are 35µm

Stacks Image 71
Figure 2
Glioma exploits microglial MT1-MMP expression

Membrane type 1 metalloprotease (MT1-MMP) is up-regulated in glioma-associated microglia, but not in the glioma cells. Overexpression of MT1-MMP is even lethal for glioma cells. Glioma-released factors trigger the expression and activity of MT1-MMP via microglial toll-like receptors and the p38 MAPK pathway, as deletion of the toll-like receptor adapter protein MyD88 or p38 inhibition prevented MT1-MMP expression and activity.

References
1. Markovic DV, K; Chirasani, S; Synowitz, M; Raguet, H; Stock, K; Sliwa, M ; Lehmann, S ; Kälin, R; van Rooijen, N; Holmbeck, K; Heppner, FL; Kiwit, J; Matyash, V; Lehnardt, S; Kaminska, B; Glass, R * and Kettenmann, H*. (2009) Glioma induce and exploit microglial MT1-MMP expression for tumour expansion. . Proc Natl Acad Sci U S A (2009) vol. 106 (30) pp. 12530-5.
2. Osenkowski P, Toth M, & Fridman R (2004) Processing, shedding, and endocytosis of membrane type 1-matrix metalloproteinase (MT1-MMP). J Cell Physiol 200(1):2-10.
3. Mayes DA, Hu Y, Teng Y, Siegel E, Wu X, Panda K, Tan F, Yung WK, & Zhou YH (2006) PAX6 suppresses the invasiveness of glioblastoma cells and the expression of the matrix metalloproteinase-2 gene. Cancer Res 66(20):9809-9817.
4. Guo P, Imanishi Y, Cackowski FC, Jarzynka MJ, Tao HQ, Nishikawa R, Hirose T, Hu B, & Cheng SY (2005) Up-regulation of angiopoietin-2, matrix metalloprotease-2, membrane type 1 metalloprotease, and laminin 5 gamma 2 correlates with the invasiveness of human glioma. Am J Pathol 166(3):877-890.
5. Rao JS (2003) Molecular mechanisms of glioma invasiveness: the role of proteases. Nat Rev Cancer 3(7):489-501.
6. Olson JK & Miller SD (2004) Microglia initiate central nervous system innate and adaptive immune responses through multiple TLRs. (Translated from eng) J Immunol 173(6):3916-3924 (in eng).
7. Crack PJ & Bray PJ (2007) Toll-like receptors in the brain and their potential roles in neuropathology. (Translated from eng) Immunol Cell Biol 85(6):476-480 (in eng).
8. Watters JJ, Schartner JM, & Badie B (2005) Microglia function in brain tumors. J Neurosci Res 81(3):447-455.
9. Markovic DS, Glass R, Synowitz M, Rooijen N, & Kettenmann H (2005) Microglia stimulate the invasiveness of glioma cells by increasing the activity of metalloprotease-2. J Neuropathol Exp Neurol 64(9):754-762.
10. Glass R, Synowitz M, Kronenberg G, Walzlein JH, Markovic DS, Wang LP, Gast D, Kiwit J, Kempermann G, & Kettenmann H (2005) Glioblastoma-induced attraction of endogenous neural precursor cells is associated with improved survival. J Neurosci 25(10):2637-2646.
11. Watters TM, Kenny EF, & O'Neill LA (2007) Structure, function and regulation of the Toll/IL-1 receptor adaptor proteins. (Translated from eng) Immunol Cell Biol 85(6):411-419 (in eng).
12. Boyd PJ, Doyle J, Gee E, Pallan S, & Haas TL (2005) MAPK signaling regulates endothelial cell assembly into networks and expression of MT1-MMP and MMP-2. Am J Physiol Cell Physiol 288(3):C659-668.
13. Munshi HG, Wu YI, Mukhopadhyay S, Ottaviano AJ, Sassano A, Koblinski JE, Platanias LC, & Stack MS (2004) Differential regulation of membrane type 1-matrix metalloproteinase activity by ERK 1/2- and p38 MAPK-modulated tissue inhibitor of metalloproteinases 2 expression controls transforming growth factor-beta1-induced pericellular collagenolysis. J Biol Chem 279(37):39042-39050.
14. Belkaid A, Fortier S, Cao J, & Annabi B (2007) Necrosis induction in glioblastoma cells reveals a new "bioswitch" function for the MT1-MMP/G6PT signaling axis in proMMP-2 activation versus cell death decision. Neoplasia 9(4):332-340.
15. Synowitz M, Glass R, Farber K, Markovic D, Kronenberg G, Herrmann K, Schnermann J, Nolte C, van Rooijen N, Kiwit J, & Kettenmann H (2006) A1 adenosine receptors in microglia control glioblastoma-host interaction. Cancer Res 66(17):8550-8557.