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Title: Characterising the effect of S100P overexpression in cell adhesion
Author: Smith, R.
ISNI:       0000 0004 6058 7878
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2016
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S100P is overexpressed in a number of different cancers and this overexpression has been shown to be associated with a significant decrease in patient survival. This decrease in survival is thought to be due to unregulated high levels of S100P within the cells of the primary tumour resulting in an increased risk of metastasis. In this thesis it is demonstrated, in an S100P-inducible cancer cell system, that overexpression of S100P decreases cell-extracellular matrix adhesion and increases cell migration and invasion. These effects caused by overexpression of S100P are shown to be dependent on the breakdown of NMIIA-containing cytoskeletal filaments and are coupled with a reduction in the abundance and alteration in the distribution of immunofluorescently-stained focal adhesions. In order to determine whether there were any alterations in the abundance of proteins within S100P-overexpressing cells, whole cell mass spectrometry was utilized which yielded several proteins although none that would directly account for the observed reduction in cell adhesion. A novel adhesome isolation technique is presented using both non-ionic detergents and hydrodynamic shearing which was used to study the effect of overexpression of S100P on the cell adhesome fraction. Western blotting of this cell fraction showed that S100P-overexpression did not cause any changes in the abundance of core focal adhesion proteins. However, mass spectrometry of the cell adhesome did identify several key proteins, the cellular level of which was significantly altered due to S100P-overexpression. In particular, the scaffold protein IQGAP1 was identified using this method, the redistribution of which can have substantial effects on cell dynamics. Finally it was determined that there was an alteration in the rate of focal adhesion maturation possibly due to a loss of NMIIA-mediated tension caused by S100P overexpression, as demonstrated by a reduction in the phosphorylation state of focal adhesion signalling proteins, linked to adhesion maturation. It is concluded that overexpression of S100P results in a breakdown of NMIIA filaments, which reduces cellular tension leading to a reduction in focal adhesion maturation which, in turn, leads to a reduction in the rate and strength of cell-extracellular matrix adhesion within this system. With a greater understanding of the way in which overexpression of S100P mechanistically affects the adhesive properties of carcinogenic cells, it may be possible to develop therapeutic drugs targeting these pathways, thus inhibiting the harmful effects of S100P overexpression in cancers.
Supervisor: Rudland, P. S. ; Barraclough, R. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral