The Effect of Epidermal Growth Factor (EGF) on EGF receptor expression and the MMP-2 activation pathway in U87 and T98 human glioma cell lines
Abstract: Glioblastoma multiforme (GBM ) is a highly invasive brain tumor with an extremely high death rate. The invasive properties of GBM stem from the tumor cells' ability to produce proteases that degrade the extracellular matrix, allowing invasion of surrounding tissue. Matrix metalloproteinases (MMPs), in particular, degrade the extracellular matrix. Cells secrete them as proenzymes, and with the assistance of membrane-type MMPs (MT-MMP) and other enzymes, MMPs convert to their active form. One of the main perpetrators implicated in GBM invasion is MMP-2. In order to study the MMP-2 activation pathway, U87 and T98 human glioma cells were treated with epidermal growth factor (EGF), and its effects on proteins implicated in the MMP-2 activation pathway were assessed via immunoblotting and immunofluorescence assays. MMP-2 activation was monitored using zymography. Glioma cells, like several types of cancer cells, are known to overexpress the EGF receptor (EGFR); the effects of EGF on EGFR were considered to detect a link between the inherent EGFR overexpression and high levels of MMP-2 activation. Preliminary data suggests that treatment of U87 cells with EGF causes downregulation of EGFR. Recent zymography results indicate no trend in MMP-2 activation following EGF treatment, though previous data suggests that EGF downregulates MMP-2 activation. Additionally, experiments indicate that EGF treatment causes phosphorylation of MT1-MMP. Together, this data suggests that EGF treatment causes phosphorylation of MT1-MMP, impairing its ability to convert MMP-2 from its pro to active form in U87 cells. Most data collected on T98 cells is inconclusive.
