Title:
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The regulation of cell migration and invasion by Eph-ephrin
signalling
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Cell migration and invasion are essential aspects of normal cellular behaviour, however
abnormal cell migration can lead to defects in essential cell processes, such as wound
healing, or can also promote diseases such as cancer. Cell migration can be regulated by
many factors and, importantly, can depend upon a cells interaction with its surrounding
cellular microenvironment. Eph receptors are the largest family of receptor tyrosine
kinases and are essential in transmitting signals between cells as, uniquely to this family,
the ephrin ligands are cell surface bound, therefore signalling is cell-cell contact
dependent.
Although Eph and ephrin functions have been studied for many years, much of the
mechanisms by which they signal are still unclear. In this thesis, I have investigated the
role of Eph-ephrin signalling in regulating different aspects of cell migration and invasion
in prostate cancer cells and during keratinocyte cell wound healing. I find that the activity
of EphB4 is regulated by the expression of PTEN phosphatase both in DU145 and PC-3
prostate cancer cells. This regulation leads to altered heterotypic cell contact inhibition of
locomotion, in a co-culture assay between DU145 cells and fibroblasts. I also find that
PTEN expression regulates the number of DU145 cells invading from a tumour cell
spheroid, towards fibroblasts, in a 3D collagen gel. I suggest these cell behaviours may be
as a consequence of altered Rac activity, downstream of EphB4 and PTEN signalling. I also
use SILAC based phosphoproteomics to investigate some of the proteins regulated
downstream of PTEN expression ilnd EphB4 activity. Furthermore I find that Ephrin-Bs
are essential in regulating keratinocyte cell reepithelialisation during tissue culture
wound healing, by regulating the actin cytoskeleton structure and E-cadherin processing.
Finally, I have attempted to investigate the role of EphB2 in regulating prostate cancer cell
migration and invasion, and find that EphB2 depletion does not alter PC-3 cell migration
velocity in two dimensions.
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