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Basic and Translational Investigations |
The Arthur and Sonia Labatt Brain Tumour Research Center and Division of Neurosurgery, The Hospital for Sick Children, Toronto, ON, Canada (H.O., C.A.S., P.K., J.T.R.); Department of Neurosurgery, Nagoya University Graduate School of Medicine, Nagoya, Japan (H.O.); Department of Neurosurgery, Asian Medical Center, Seoul, Korea (Y.S.R.); Department of Surgery, University of Toronto, Toronto, ON, Canada (J.T.R.)
Address correspondence to James T. Rutka, Division of Neurosurgery, Suite 1503, The Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada (james.rutka{at}sickkids.ca.).
Medulloblastoma is a highly malignant brain tumor that occurs predominantly in children. The molecular pathogenesis of medulloblastoma is under investigation. Previously, we used complementary DNA microarray analysis to compare patterns of gene expression in medulloblastoma samples versus normal cerebellum. The cytoskeletal protein ezrin was found to be overexpressed in medulloblastoma compared with normal cerebellum, an observation that was further validated by immunohistochemistry and real-time PCR analysis. To assess the role of ezrin in medulloblastoma, we studied ezrin's role in medulloblastoma migration, invasion, and adhesion. Western blotting and immunofluorescence showed high expression of ezrin in four medulloblastoma cell lines, and ezrin was primarily localized to filopodia. Ezrin-specific small interfering RNA suppressed the formation of filopodia and in vitro migration, invasion, and adhesion. We also used a stably transfected medulloblastoma cell line to study the effect of ezrin overexpression. We showed that high expression of ezrin promotes filopodia formation and in vitro invasion. Finally, athymic mice implanted with ezrin-overexpressing DAOY medullo-blastoma cell clones in the cerebellum showed shortened survival compared with controls. These findings suggest that, in addition to other cytoskeletal proteins, ezrin plays an important role in medulloblastoma adhesion, migration, and invasion.
Key Words: cytoskeleton ezrin invasion medulloblastoma siRNA
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