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dc.contributor.authorCullingworth, Janen
dc.date.accessioned2019-02-15T14:15:17Z
dc.date.available2019-02-15T14:15:17Z
dc.date.issued2002
dc.identifier.urihttp://hdl.handle.net/1842/33407
dc.description.abstracten
dc.description.abstractMutations in the tumour suppressor genes SMAD4 (or DPC4, deleted in pancreatic cancer locus 4), APC (adenomatous polyposis coli) and p53 have been implicated in pancreatic cancer in humans. This thesis firstly documents the in vivo effects of mutations in these genes singly and in combination through spontaneous and carcinogen- induced murine models of pancreatic tumourigenesis. Second, it examines the in vitro effects of TGF -ß signalling, of which SMAD4 is the central mediator, on murine primary cultured pancreatic acinar cells. Previously p53 ApcM "i+ mice have been shown to develop pancreatic tumours. To examine the effect of Smad4 heterozygous mutation on the development of these tumours, Smad4 +i mutation was introduced into p534- and p531- ApcM "v+ mice. No pancreatic phenotype was found in p534- Smad4 +i - animals. p53 4-ApcM1 Smad4 +i animals did not exhibit promotion of tumourigenesis in any tissues compared to the p53í- ApcM"+ mice. Immunohistochemical studies revealed loss of SMAD4 protein within the majority of the lesions arising in p53 - ApcM "i+Smad4 + / animals. Furthermore, microdissection and mutational analysis revealed LOH for Apc and Smad4. Treatment of wild -type (WT) Smad4 +i, ApcM "l+ or ApcM "i+Smade- mice with NNitroso- N- Methyl Urea (NMU) resulted in abnormal foci in pancreatic acinar cells, characterised by (3- catenin stabilisation. Previously these foci have been shown to be the precursors of pancreatic neoplasia. Only NMU- treated ApcM "i+Smad4 + / mice exhibited a significant increase in abnormal pancreas, which was found to be due to an increased number of abnormal foci rather than increased focus size. A range of foci sizes were analysed, but only smaller abnormal foci were characterised by morphological nuclear atypia. These studies suggest functional co- operation between TGF -(3 and Wnt signalling pathways in the suppression of pancreatic tumourigenesis in the mouse. In order to investigate TGF -ß signalling in WT murine primary pancreatic acinar cells TGF -3 was given to these cells under different conditions. Two main conclusions were drawn from these experiments. First that TGF -13 in conjunction with EGF could accentuate acinar cell attachment and motility in the presence of serum. This effect was not associated with changes in cell proliferation. Others working on primary culture of rat hepatocytes have also reported synergy between EGF and TGF -13 resulting in increased motility suggesting this interaction may be common among different cell types. Second, in serum free conditions, TGF -13 caused reduced BrdU incorporation and increased apoptosis. Immunofluorescent studies, analysed by confocal microscopy, revealed that these cellular behaviours were associated with changes in the cyclin dependent kinase inhibitor, p27, but not p21. Whether these effects are mediated by SMAD4 remains unconfirmed as immunoblotting revealed SMAD4 to be present in the nucleus of these cells in the absence and presence of TGF -ß. This investigation into the effect of TGF -ß on primary pancreatic acinar cells reflects the multi -functional nature of TGF -13 signalling, highlighting interaction between TGF -13 and EGF signalling pathways and suggesting a mechanism of TGF -ß- induced growth suppression via p27 in these cells. These studies provide insight into the combined effects of mutation in p53, Apc and Smad4 in the development of pancreatic cancer and suggest possible cellular mechanisms through which Smad4 mutation and disrupted TGF -ß signalling could promote pancreatic cancer in humans.en
dc.publisherThe University of Edinburghen
dc.relation.ispartofAnnexe Thesis Digitisation Project 2019 Block 22en
dc.relation.isreferencedbyAlready catalogueden
dc.titleTumour suppression mediated through DPC4, p53 and APCen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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