P10.05.B Platelet-derived growth factor signalling pathways in patient-derived glioblastoma cells

Abstract

Abstract Background Platelet-derived growth factor (PDGF) signalling is essential in the development and maintenance of the neurovasculature. Of particular importance is PDGFRβ signalling for the recruitment and maintenance of the mural cell type pericytes, which occupy an important position in coordinating blood-brain barrier functions. The PDGF pathway is also implicated in glioblastoma, where overexpression of PDGFRα is a signature of the proneural subtype of the highly malignant and invasive tumour. The expression and signalling of both PDGFRα and β by tumour cells have been implicated in tumorigenesis and progression. Therefore, we sought to study PDGF receptor signalling in primary human-derived glioblastoma tumour cells to gain a better understanding of the signalling mechanisms driven by these receptors. Material and Methods Primary human epilepsy pericytes and glioblastoma tumour cells were isolated from surgical resections obtained from consenting patients at Auckland City Hospital. PDGF signalling pathways were investigated through treatment with exogenous PDGF ligands. Pathway activation was quantified using immunocytochemistry, human cytokine XL Proteome Profiler and cytometric bead arrays. Results PDGF-BB and PDGF-DD treatment led to the activation of PDGFRβ in pericyte cultures, which mediated the activation of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/Akt cascades, ultimately increasing pericyte proliferation and cytokine secretion. PDGF-AA treatment resulted in transient MAPK activation, but was not followed by increased proliferation in pericytes. In contrast, although PDGF-AA, -BB and -DD induced PDGFRα internalisation (and PDGF-BB and -DD induced PDGFRβ internalisation) in GBM tumour cells, this did not result in MAPK or PI3K/Akt activation or cell proliferation. Conclusion Despite PDGF receptor expression, the GBM tumour cells, in contrast to pericytes, surprisingly displayed a lack of responses to ligand stimulation through either PDGFRα or PDGFRβ. This warrants further investigation into the signalling mechanisms behind tumour cells to better understand tumour biology.