Purpose: Glioblastoma multiforme (GBM) are aggressive astrocytomas typified by progressive diffuse infiltration and surgical complications. The urgency to discover factors promoting GBM tumour progression remains. The expression of CD147 (a matrix metalloproteinase (MMP) inducer and the receptor for cyclophilin A (CypA) mediated signalling) is correlated with GBM severity. Interestingly, CypA is a potent chemokine and cytoprotectant associated with GBM tumour severity through CD147 mediated MMP9 expression. Macrophages secrete CypA in response to LPS, as do neurons and endothelial cells in response to hypoxia. Thus, we aim to firstly determine if microglia (the brain’s resident macrophage) and/or GBM’s can secrete CypA and secondly, determine if extracellular CypA can support GBM pathogenesis through its interaction with CD147.
Methods: BV2 microglia (n=3) were treated with LPS (1uM) and oxidative stress inducer LY83583 (1ug/ml) at a range of time points, and their supernatants subjected to WB analysis to determine the presence of secreted CypA protein. BV2 microglia (n=3) were treated with CypA protein (1nM-1000nM) in a transwell boyden chamber to assess changes in cell migration after 24h. U251 glioma cells (n=3) were treated with CypA protein (100nM) and their cell lysates subjected to WB analysis to determine the Akt phosphorylation status.
Results: We found that microglia (BV2), like macrophages, secreted CypA in response to LPS and LY83583. Furthermore, CypA protein (100nM) increased cell migration of BV2 cells. In addition, CypA protein (10nM and 100nM) reduced basal cell death after 72h (p<0.006) in BV2 microglia (n=3). For the first time, we also demonstrated that CypA protein induces Akt phosphorylation (p<0.05) in U251 glioma cells (n=3).
Conclusion: Our preliminary findings support our hypothesis that CypA secretion by microglia could potentiate tumour-enhancing CD147 mediated signalling in GBM.