TGF-ß2 and it's role in the invasion of high-grade glioma into parenchyma

Introduction: Invasion of high-grade gliomas into parenchyma is one of the hallmarks of these tumors preventing curative resections. TGF-ß2 plays a role in invasion and is able to modulate molecules of the ECM (extracellular matrix) which are known to modulate invasion. However, this complex mechanism is not detailed yet. Goal of this project is to define the role of TGF-ß2 in the invasion of high-grade glioma cells into healthy parenchyma.

Methods: A set of published or possibly relevant factors of the ECM like Tenascin-C, Fibronectin, Vitronektin, Collagens, Versican, Laminin, Nestin and Vimentin were evaluated for their regualtory role in invasion. First, expression was evaluated in as set of high-grade gliomas. Second, a set of tumors were treated with TGF-ß2 to induce these factors. Induction was measured by quantitative PCR (CybrGreen) and protein assays (ELISA, Western Blot). The biological relevance of induced factors was revealed by functional analysis like attachment, migration and invasion assays.

Results: In a set of high-grade gliomas, about 90% showed expression of TGF-ß2, and ECM molecules were expressed in most tumors in a nonsystematic manner. Low producers of TGF-ß2 were chosen for the induction assays. Cells from different cell lines (U87, A172) and primary cultures were treated with TGF-ß2. After harvesting of cells and supernatant, RNA was prepared and RNA and protein were measured quantitatively. A dose- and time dependent induction was observed for Versican, MMP-2 and Collagen1 alpha 1 after treatment with TGF-ß2. In a first set of functional experiments, TGF-ß2 inhibited attachment and migration (spheroid assay) in the cell line U87.

Conclusion: TGF-ß2 may play a crucial role in the regualtion of molecules of the extracellular matrix which influence the invasion of high-grade gliomas into parenchyma. In a next step, we will evaluate if the observed functional effects are due to the regulation of one of the induced molecules. Furthermore, we will downregulate TGF-ß2 in TGF-ß2 expressing cell lines to verify the observed effects. In summary, we hope to add knowledge to the complex field of the interactions of ECM molecules with other factors involved in invasion in high-grade glioma, and to further elucidate the role of TGF-ß2 in this process.