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The purpose of the present thesis was to better understand the effect of targeting key biological mechanisms in order to improve radiotherapy response. Two important and distinct pathways were targeted using novel agents: (1) the phosphoinoside-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway; (2) the ataxia telangiectasia-mutated-Rad3-related (ATR)/Chkl pathway. The role of the PI3K1mTOR signalling pathway in tumour radiosensitivity and tumour microerivlronment (TME) was examined using three, recently-developed signalling inhibitors obtained from Novartis Pharma: NVP-BEZ235 (dual PI3K1mTOR inhibitor), NVP-BGT226 (dual PI3K1mTOR inhibitor) and NVP-BKM120 (single PI3K inhibitor). The radiosensitising potential of NVP-BEZ235 and NVP-BGT226 was demonstrated in tumour and endothelial cells. Additionally, a thorough research into the effects ofNVP-BKM120 and NVP-BEZ235 on TME showed that oncogenic signalling inhibitors can improve vascular morphology and increase tumour oxygenation and perfusion in tumour xenograft models, resulting in improved radiation response. Furthermore, a highly potent and selective A TR inhibitor, VE-822, that was obtained from Vertex Pharmaceuticals (Europe) Ltd, was tested in pancreatic ductal adenocarcinoma (PDAC) cells and tumour xenograft models. A TR inhibition by VE-822 resulted in sensitisation of tumour cells but not normal cells to radiation and gemcitabine. Similarly, VE-822 strongly enhanced radiation- and chemoradiation-induced tumour growth delay in tumour xenograft models. Importantly, VE-822 did not potentiate radiation-induced gastrointestinal tract epithelial damage. To summarize, the impact of targeting two distinct pathways in combination with radiation and chemoradiation was explored. Inhibition of the PI3K1mTOR and ATRlChkl signalling pathways increases response of tumours to radiotherapy they and might be promising targeting strategies for cancer treatment. Our findings have considerable translational implications and future clinical trials should aim to validate these observations.

The 37kDa/67kDa laminin receptor (LRP/LR) is thought to play a major role in the adhesion to laminin and consequently invasion resulting in the metastasis of tumor cells. This receptor is reported to be over-expressed in several neoplastic cell lines and is believed to increase tumor aggressiveness. This research aims at determining whether the application of anti-LRP/LR specific antibody (IgG1-iS18) on neoplastic cell lines would result in a decrease in invasion and adhesion. All neoplastic cell lines had significantly increased cell surface LRP/LR levels compared to NIH/3T3 cells, with the most notable increase seen in SW480 cells (10.98%). Due to a positive correlation between the cell surface LRP/LR levels and invasion potential we propose that an increased LRP/LR level correlates to an increased ability to invade. A significantly decreased adhesion potential was noted in all neoplastic cell lines except the non-invasive MCF-7 cell line, upon application of IgG1-iS18, 21% decrease in HT-1080 cells, 14% in HeLa, 20% in LNCaP, 48% and 74% in A549 and SW480 cells, respectively. Incubation with the anti-LRP/LR antibody IgG1-iS18 resulted in a significant reduction of the invasive potential of HT-1080 (44%), A549 (33%), HeLa (69%), SW480 (91%) and LNCaP cells (38%). Furthermore, a high Pearson’s correlation coefficient between adhesion potential and invasive potential was seen, confirming that adhesion is indeed a pre-requisite for invasion. The significant reduction in invasion and adhesion of HT-1080, A549, HeLa, SW480 and LNCaP cells upon application of the IgG1-iS18 antibody suggests that this macromolecule might act as a promising therapeutic tool for the treatment of various metastatic cancer types.

University of Macau / Faculty of Health Sciences