DOI
https://doi.org/10.25772/MY57-KX07
Defense Date
2010
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Biochemistry
First Advisor
Helen Fillmore
Abstract
Glioblastoma Multiforme (GBM) is an aggressive and fatal cancer of the brain. It is characterized with augmented morbidity and elusion to therapies due in part to the incessant infiltration and spread of tumor cells in normal brain. We investigated the function of Matrix metalloproteinase-1, an important enzyme noted to be responsible for invasion in other cancers, in GBM and its regulation by epidermal growth factor receptor (EGFR) signaling. Previous studies from our laboratory demonstrated elevated levels of MMP-1 in GBM. Further studies indicated the involvement of MMP-1 in GBM invasion. The GBM cell lines T98G, U251MG and U87MG were used for this study. In T98G cell lines, inhibition of MMP-1 by siRNA significantly suppressed basal in vitro invasion without impacting cell viability. The over-expression of MMP-1 was accomplished in U251MG and U87MG using the mammalian expression vector, pIRES, encoding full length MMP-1 cDNA. The MMP-1 over-expressing U251MG and U87MG cells exhibited significantly enhanced invasion in vitro with no modification in the cell proliferation rates. A majority of GBM patients present defective EGFR signaling due to over-expression, amplification or mutation in the receptor. MMP-1 is known to be up-regulated by various stimulatory agents including growth factors. We examined the regulation of MMP-1 by EGFR activation and observed the induction of MMP-1 after EGF treatment. Inhibition of the receptor by pharmaceutic inhibitor treatment and genetic approaches led to reduction in MMP-1 levels. We also observed that this regulation is primarily mediated by the downstream MAPK pathway. Inhibition of MAPK and not PI3K pathway resulted in diminished MMP-1 protein levels even in the presence of EGF. These studies demonstrate the importance of the EGFR-MAPK signaling pathway in the induction of MMP-1 in glioma cell lines. In addition, MMP-1 plays a role in glioma cell invasion in vitro. These results along with the reports of MMP-1 over-expression in GBM warrant future studies examining the function of MMP-1 in vivo.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
August 2010