Functional role of phosphoinositide-3 kinase delta subunit in glioblastoma cell migration

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Functional role of phosphoinositide-3 kinase delta subunit in glioblastoma cell migration

 

Author: Chan, Wai-mui Ellis
Title: Functional role of phosphoinositide-3 kinase delta subunit in glioblastoma cell migration
Degree: M.Sc.
Year: 2008
Subject: Hong Kong Polytechnic University -- Dissertations.
Glioblastoma multiforme.
Cell migration.
Phosphoinositides.
Department: Dept. of Health Technology and Informatics
Pages: x, 60 leaves : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2305608
URI: http://theses.lib.polyu.edu.hk/handle/200/4876
Abstract: Glioblastoma (GBM) is the most common primary brain cancer and a very typical aggressive tumor. It is also the deadliest of brain cancers and notorious for its treatment refractoriness. Even with the current combination therapy (consisting of surgery, radiation and temozolomide), the median survival time is only around 15 months. However, with the advances in cellular; molecular and genetic technology, some of its molecular lesions have been unveiled. Such information has provided a new dimension for drug intervention and made GBM a suitable target for molecular therapy. Phosphoinositide-3 kinase (PI3K) is a large familiar of enzymes, crucial for intracellular signaling transduction and which in turn regulate various cellular processes. Accumulated evidence suggested a close correlation of PI3K pathway deregulation and cancer progression, thus making it a focus of current cancer research. Besides, the successful cloning of individual isoforms and development of isoform-specific inhibitors, allows the biological role(s) of individual PI3K. family member to be studied intensively. Recently, it is found that PI3K delta subunit (p110d), a class IA member of PI3K family, plays an important role in the epidermal growth factor (EGF)-driven in vitro migration of breast cancer cells and in a macrophage cell line. In this project, a protocol for migration study has been set up using the Dunn chemotaxis chamber and a newly installed microscope with built-in digital camera. This new experimental tool enables real-time, direct observation of cell behavior under ideal optical condition and can be adjusted for studying other cell types. Using this set-up, two GBM cell lines U343 and U87 were chosen to compare their relative p110d expression level (as reported in a previous study) and migration response. A control study was performed using cells pretreated with wortmannin (a well known PI3K inhibitor) and fluorescent dye viability assay was also performed using flow cytometry. Besides, western blot analysis with antibodies against total and phosphorylated P21-activated kinase 1 (PAKl) was carried out, to check if PAKl pathway was being activated. Results showed that U87 cells with a relatively high p110d expression exhibited a significant directional movement when compared with U343 cells and the displacement was reduced with wortmannin treatment. A similar pattern was observed in western blot analysis, in which U87 cells have a higher phosphorylated PAKl expression than U343 cells and the level was reduced with wortmannin treatment. In conclusion, the results provide some clues as to the possible functional role of p110d in cell migration and activation of the PAKl pathway which warrants further investigation.

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