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The role of the gap junction protein connexin43 in glioma migration and invasion

University of British Columbia

Glioblastoma Multiforme (GBM), an aggressive form of adult brain tumor, is difficult to treat due to its invasive nature. A molecular change frequently observed in GBM is a decrease in the expression of the gap junction protein Connexin43 (Cx43); however, how a reduction in Cx43 expression contributes to glioma malignancy is still unclear. The first objective of this thesis was to establish an in vitro human GBM cell model to clearly delineate the role of Cx43 in the migration and invasion phenotype. Characterization of a panel of immortalized high grade human GBM cell lines showed variability in Cx43 protein expression, subcellular localization, gap junctional coupling and migration. For the second objective of my thesis I selected the human GBM cell line U118 from the aforementioned panel and developed a 3D spheroid migration model that mimics the in vivo architecture of tumor cells to quantify migration changes. Down-regulation of Cx43 expression increased migration by reducing cell-ECM adhesion. Using live imaging my findings are the first to show that glioma cells change their migration pattern from collective to single cell when Cx43 is reduced. In addition, reducing Cx43 expression enhanced relative migration by increasing the cell speed and affecting the direction of migration. Subsequently, gap junction intercellular communication (GJIC) played a more prominent role in mediating migration than the cytoplasmic interactions of the C-terminal tail. Taken together my findings reveal an unexplored role of Cx43 in facilitating collective glioma migration. The third objective of this thesis was to assess the role of homocellular and heterocellular gap junctions in glioma invasion using a syngeneic in vivo mouse model. A reduction in invasion was observed when we reduced Cx43 in mouse GL261 glioma cells and deleted it in host astrocytes. Interestingly, blocking the channel in GL261 did not decrease invasion. In summary, a reduction in homocellular gap junction communication increases migration of glioma cells in vitro however when they encounter astrocytes in the brain a lack of heterocellular gap junction communication reduced invasion. This suggests that gap junctions may have opposing roles when formed between glioma cells versus when formed between glioma and astrocytes.

Text

2015-04-15

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/52774

Cell and Developmental Biology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/