Nitrogen-containing bisphosphonates (N-BPs) are the standard treatment in cancerassociated bone disease due to their ability to inhibit osteoclast-mediated resorption. However, beyond their anti-resorpitive activity there is increasing evidence from preclinical studies to demonstrate that N-BPs can also have an anti-tumour effect, although the mechanism is still unclear. In vitro studies suggest that anti-tumour effects may be due to direct effects on tumour cells (by inhibiting protein prenylation) or via indirect effects on other cell types. The studies described in this thesis sought to answer this question by developing novel approaches and molecular tools. N-BP resistant tumour cell lines were created by over-expressing FPP synthase (the molecular target of N- BPs) by lentiviral transduction of B16 melanoma cells. Although these cells were only modestly resistant to N-BP, such an approach might be a novel strategy for determining whether NBPs directly affect tumour cells in vivo. However, further studies carried out with mice bearing 4T1 mammary fat pad tumours demonstrated that macrophages and myeloid derived suppressor cells (MDSC) internalised a fluorescently-labelled N-BP. Since macrophages and MDSC are important for tumour growth and metastasis, these studies indicate that these myeloid cells may actually be responsible for the anti-tumour effects of N-BPs. The functional effects of N- BPs on MDSC and macrophages remain to be determined. However, an in vitro prenylation assay was developed as a novel and sensitive tool to study subtle changes in protein prenylation and should prove vital in future studies to determine conclusively whether N-BPs inhibit protein prenylation in these myeloid cell types in vivo. Finally, proteomic techniques were used to examine the levels of small GTPases in MDA-MB-231 breast cancer cells and showed that Rab7 appears to be elevated in a clone that preferentially metastasises to the skeleton. This highlights the need for further investigation of the role of Rab7 in skeletal metastasis and as a potential new therapeutic target.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:558594 |
| Date | January 2011 |
| Creators | Shay, Gemma |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=186676 |
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