Epithelial ovarian cancer frequently metastasizes to the omentum, a process that requires pro-angiogenic activation of local microvascular endothelial cells (ECs) by tumour-secreted factors. We have previously shown that ovarian cancer cells secrete factors, other than vascular endothelial growth factor (VEGF), with possible roles in metastatic angiogenesis including the lysosomal proteases cathepsin L (CathL) and cathepsin D (CathD), and insulin-like growth factor binding protein 7 (IGFBP7). However, the mechanisms by which these factors may contribute to omental endothelial angiogenic changes are unknown. Therefore the aims of this thesis were a) to examine disease relevant human omental microvascular endothelial cell (HOMEC) proliferation, migration and angiogenesis tube-formation induced by CathL, CathD and IGFBP7; b) to investigate whether CathL and CathD act via a proteolytic or non-proteolytic mechanism; c) to identify activated downstream intracellular signalling cascades in HOMECs and their activation in proliferation and migration; and finally d) to identify activated cell surface receptors by these factors. CathL, CathD and IGFBP7 significantly induced proliferation and migration in HOMECs, with CathL and CathD acting in a non-proteolytic manner. Proteome-profiler and ELISA data identified increased phosphorylation of the ERK1/2 and AKT (protein kinase B) pathways in HOMECs in response to these factors. CathL induced HOMEC proliferation and migration via the ERK1/2 pathway, whereas, although CathD-induced proliferation was mediated by activation of ERK1/2, its migratory effect was dependent on both ERK1/2 and AKT pathways. Interestingly, CathL induced secretion of galectin-1 (Gal1) from HOMECs which in turn significantly induced HOMEC proliferation via ERK1/2. However, none of the ERK1/2 or AKT pathways was observed to be active in Gal1-induced HOMEC migration. Interestingly, Gal1-induced proliferation and migration were significantly inhibited by L-glucose, suggesting a role for a receptor with extracellular sugar moieties. IGFBP7-induced migration was shown to be mediated via activation of the ERK1/2 pathway only. CathL, Gal1 and IGFBP7 significantly induced angiogenesis tube-formation in HOMECs which was not observed in CathD-treated cells. Receptor tyrosine kinase array revealed activation of Tie-1 and VEGF receptor type 2 (VEGFR2) in CathL and IGFBP7-treated HOMECs respectively. In conclusion, all CathL, CathD, Gal1 and IGFBP7 have the potential to act as proangiogenic factors in the metastasis of ovarian cancer to the omentum. These in vitro data suggest all four factors activate intracellular pathways which are involved in well-known angiogenesis models.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:761694 |
| Date | January 2017 |
| Creators | Pranjol, Md Zahidul Islam |
| Contributors | Whatmore, Jacqueline ; Gutowski, Nicholas ; Hannemann, Michael |
| Publisher | University of Exeter |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10871/29914 |
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