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The effect of polysialyltransferase modulation on tumour cell migration

About This PhD Project

Project Description

One of the main reasons for failure of cancer therapy today is an inability to control tumour dissemination, with secondary tumour deposits the cause of morbidity. Thus there is much interest in developing therapeutic strategies that can intervene in the dissemination process and overcome the issues with secondary deposits.

The glycoprotein polysialic acid (PolySia) is aberrantly expressed in many tumours of mainly neural crest origin, where it decorates the surface of NCAM (neuronal cell adhesion molecule) and modulates cell-cell and cell-matrix adhesion. PolySia-NCAM expression is strongly associated with poor clinical prognosis and correlates with aggressive and invasive disease. The synthesis of polySia is mediated by two polysialyltransferase enzymes (polySTs), ST8SiaIV (PST) and particularly ST8SiaII (STX) in cancer cells and polySia is essentially absent from normal cells after embryonic development. Selective inhibition of polySTs therefore presents a much-needed and unique therapeutic opportunity to stem tumour dissemination.

Cell migration is one of the key steps of tumour dissemination, and the in vitro scratch assay is a commonly used method for evaluating cell migration. We have developed and validated the scratch assay in-house, and demonstrated that first-generation polyST inhibitors have an inhibitory effect on tumour cell migration, with a decrease in scratch wound healing seen in cells expressing PolySTs, whilst there is no effect on wound healing in cells not expressing the enzymes.

Whilst these results show an effect on migration of the cell population, what is unclear is what is happening at the cellular level, i.e. what signals are being switched on/off to make a cell migrate into the scratch. Therefore this project will investigate how expression of a range of proteins thought to be associated with control of migration differs in migrating cells in comparison with non-migrating cells at different distances from the wound edge over time. The migratory capacity of cells that have a range of polyST and polySia expression, in the presence/absence of polyST inhibitors, will be studied.

In addition to extensive protein and DNA investigations (immunocytochemistry, immunoblotting, flow cytometry, RT-PCR), we will also, in collaboration with Centre for Advanced Materials Engineering, investigate using Atomic Force Microscopy how the cell surface changes during the migratory process in terms of its elasticity and charge.

Cells within the body undergo constant changes of force in their environment, where the biomechanical properties of cells define a different physical and physiological response to such external stresses.

Recent literature shows that a measure of the elasticity of cells is an indication to the state of health of the cells. It is widely recognised that diseases like cancer induces a reduction in the elastic properties of cells as compared with ‘normal’ cell counterparts. These changes in properties are associated to changes of the architecture within the cell.

The atomic force microscope (AFM) is a highly versatile research instrument that allows cell surface imaging and high-accuracy measurement of force and deformation under physiological conditions. Further investigations of cell mechanics of cancer cells may help further understanding of the physical mechanisms for cancer metastasis, which may lead to development of novel strategies for prevention and diagnosis. As well as expanding on our understanding of what is happening at the cellular level during the migratory
process within this assay, the knowledge gained regarding protein expression and cell mechanics will have application when studying the effects of polysia modulation of migration in the preclinical in vivo situation, and ultimately in the clinic.


Entry requirements

At least 2:1 honours degree or equivalent.
For full details of our entry requirements, please visit our website.

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