Tumours contain heterogeneous cell populations. A population enriched in tumour-initiating potential has been identified in soft-tissue sarcoma (STS) by the isolation of "side population" (SP) cells. In this study, we compared the gene expression profiles of SP and non-SP cells in STS and identified Hedgehog (Hh) and Notch pathways as potential candidates for the targeting of SP cells. Upon verification of the activation of these pathways in SP cells, using primary tumor xenografts in NOD-SCID mice as our experimental model, we used the Hh blocker Triparanol and the Notch blocker DAPT to demonstrate that the suppression of these pathways effectively depleted the abundance of SP cells, reduced tumour growth, and inhibited the tumour-initiating potential of the treated sarcoma cells upon secondary transplantation. The data provide additional evidence that SP cells act as tumour initiating cells and points to Hh and Notch pathways as enticing targets for developing potential cancer therapies.

The FMS-like tyrosine kinase 3- internal tandem duplication (FLT3/ITD) aberration is common in acute myeloid leukemia (AML) and associated with poor patient outcome. Inhibitors targeting FLT3/ITD are in development, but clinical responses are transient. This project focussed on elucidating molecular signalling consequences of FLT3/ITD inhibition, to identify rational drug combinations for future development. A Multicolour Phospho Flow Cytometry (MPFC) assay was developed to assess signalling events downstream of FLT3/ITD in primary patient samples, focusing on alterations in ERK, STAT5, Akt, and S6. STAT5 signalling appeared to be important exclusively in FLT3/ITD samples. MPFC accurately predicted the presence of FLT3/ITD, inhibitor sensitivity and the initial positive clinical response of a trial patient receiving a FLT3/ITD inhibitor. PI3K pathway upregulation was observed in a Sorafenib-resistant FLT3/ITD cell line established to study resistance mechanisms of FLT3 inhibition. Further, combination FLT3 and PI3K inhibition demonstrated synergy, suggesting potential clinical relevance to this therapeutic strategy.

Objective: Evaluate a patient-reported-oral mucositis scale (PROMS) on its own and in relation to existing measures of mucositis. Methods: 50 patients with head and neck cancer receiving radiotherapy were examined before cancer treatment, twice weekly during 6-7 weeks of therapy and post-therapy. Oral mucositis (OM) signs were evaluated clinically using NCI-CTCAE v.3, OMAS criteria and Total VAS-OMAS score. OM symptoms were recorded on PROMS-VAS questionnaires. Albumin and polymorphonuclear neutrophils were measured in saline rinses. The PROMS data were subjected to Spearman rank correlations versus the other clinical and biomarker data. Results: 33 participants completed the study. Significant correlations (p<.001) were seen between PROMS scores and other clinical and biomarker indicators of OM at a group level. Significant variations were seen between individuals. Conclusion: The PROMS tool demonstrates good correlation with other clinical indicators of OM and adds novel dimensions to currently available methods of assessments used for quantification of OM.

Radioresistance is a major cause of treatment failure and relapse in head and neck squamous cell carcinoma (HNSCC). Novel molecular targets need to be identified to increase cure rates and radiosensitivity in HNSCC. The MET receptor tyrosine kinase is highly dysregulated in cancer and plays a role in tumourigenesis, chemoresistance, and radioresistance. However, the role of MET in HNSCC radioresistance has not yet been investigated and may potentially be a radiosensitizing target. We discovered MET expression and intact ligand-induced signalling in HNSCC cell lines. Small molecule MET kinase inhibitors inhibited ligand-induced MET activation and downstream signalling. These inhibitors decreased HNSCC cell proliferation and clonogenic survival. Similarly, short-interfering RNAs targeting MET also decreased cell proliferation. The combination of radiation with the MET kinase inhibitors decreased clonogenic survival in an additive manner. Cell cycle analyses demonstrated that MET inhibitors alone or in combination with radiation induced small increases in sub-G1 cell populations.

Clear cell renal cell carcinoma (ccRCC) is an aggressive malignancy characterized by inactivation of the von Hippel-Lindau tumour suppressor gene, the protein product of which mediates degradation of the transcription factor hypoxia-inducible factor (HIF). GAL3ST1 is a sulfotransferase which catalyzes the production of sulfatide, a plasma membrane sulfolipid previously implicated in metastasis. We observed GAL3ST1 overexpression in primary ccRCC tumours relative to matched-normal tissue and subsequently asked if GAL3ST1 was a HIF-responsive gene that facilitates ccRCC metastasis. GAL3ST1 expression was suppressed in ccRCC cells by stable reconstitution of wild-type VHL and also siRNA-mediated knockdown of HIF1alpha and HIF2alpha. Dual luciferase assays and chromatin immunoprecipitation revealed a hypoxia-response element in the GAL3ST1 5’-UTR that appeared to be crucial for HIF-mediated upregulation. Finally, stable knockdown of GAL3ST1 significantly impeded ccRCC cell invasion through an in vitro basement membrane mimic. These results suggest GAL3ST1 is a HIF-responsive gene that promotes tumour cell invasion.

Non-Small-Cell-Lung Cancer (NSCLC) patients with mutations in EGFR have greater response rates and survival when treated with the tyrosine kinase inhibitor erlotinib. To elucidate how erlotinib inhibits EGFR, this study included: 1) inhibiting an EGFR mutant cell line to reveal EGFR regulated phosphotyrosine (pY) sites; 2) comparing erlotinib sensitive and insensitive cell lines to reveal functionally important pY sites; 3) revealing novel pY sites. Observations were collected using the LTQ-Orbitrap mass spectrometer. This study identified five new EGFR regulated pY sites and five pY sites that correlated with erlotinib sensitivity; the majority of them are related to cell-cell interactions. By comparing all observed pY sites to the Phosphosite and PhosphoELM database, our results included 67 unregistered sites. This study has identified novel biomarkers and potential therapeutic targets, many of which were associated with cell migration and adhesion function. Further functional validation is necessary.

In an attempt to identify agents that specifically target neuroblastoma (NB) tumour-initiating cells (TIC) we performed drug screens using libraries of bioactive compounds. Cardiac glycosides (CGs) were the largest class of drugs identified with antitumour activity. At high CG doses inhibitory effects on the Na+/K+-ATPase induce cardiotoxicity; therefore, CG analogues were designed in an attempt to separate the effects on NB cells from cardiotoxicity. We identified RIDK34 as our lead compound from a structure-activity-relationship analysis (IC50 8 nM). RIDK34 contains a unique oxime group and shows increasing potency against NB TICs. The Na+/K+-ATPase is a target for the apoptotic activity of digoxin and RIDK34, whereby a signaling cascade involving Src and ERK may induce apoptosis. Furthermore, we predict that signaling activation does not require inactivation of the Na+/K+-ATPase and subsequent deregulation of [Na+]i and [K+]I gradients. Thus CGs and particularly RIDK34 may be expected to display diminished cardiotoxicity and greater therapeutic potential.

Dynamic nuclear polarization and dissolution of 13C-labeled metabolite allows dynamic imaging of metabolism in-vivo. However, the spatial and temporal resolutions of magnetic resonance spectroscopic imaging are limited by the duration of free-induction decay acquisitions and the T1-based, non-recoverable polarization decay. This thesis describes the implementation of a spectral-spatial radiofrequency excitation pulse with a `flyback' echo-planar readout trajectory to dynamically image [1-13C]-pyruvate and [1-13C]-lactate in an interleaved manner. This technique excites a single resonance of either [1-13C]-pyruvate or [1-13C]-lactate and generates dynamic images with 5mm in-plane resolution. Metabolite dynamics extracted from the images and the corresponding non-localized spectroscopic data reveal similar kinetic rates upon fitting to a kinetic model. This demonstrates the feasibility of probing metabolism in heterogeneous tissues in-vivo with dynamic interleaved 13C MR imaging.

Tumours contain heterogeneous cell populations. A population enriched in tumour-initiating potential has been identified in soft-tissue sarcoma (STS) by the isolation of "side population" (SP) cells. In this study, we compared the gene expression profiles of SP and non-SP cells in STS and identified Hedgehog (Hh) and Notch pathways as potential candidates for the targeting of SP cells. Upon verification of the activation of these pathways in SP cells, using primary tumor xenografts in NOD-SCID mice as our experimental model, we used the Hh blocker Triparanol and the Notch blocker DAPT to demonstrate that the suppression of these pathways effectively depleted the abundance of SP cells, reduced tumour growth, and inhibited the tumour-initiating potential of the treated sarcoma cells upon secondary transplantation. The data provide additional evidence that SP cells act as tumour initiating cells and points to Hh and Notch pathways as enticing targets for developing potential cancer therapies.

The FMS-like tyrosine kinase 3- internal tandem duplication (FLT3/ITD) aberration is common in acute myeloid leukemia (AML) and associated with poor patient outcome. Inhibitors targeting FLT3/ITD are in development, but clinical responses are transient. This project focussed on elucidating molecular signalling consequences of FLT3/ITD inhibition, to identify rational drug combinations for future development. A Multicolour Phospho Flow Cytometry (MPFC) assay was developed to assess signalling events downstream of FLT3/ITD in primary patient samples, focusing on alterations in ERK, STAT5, Akt, and S6. STAT5 signalling appeared to be important exclusively in FLT3/ITD samples. MPFC accurately predicted the presence of FLT3/ITD, inhibitor sensitivity and the initial positive clinical response of a trial patient receiving a FLT3/ITD inhibitor. PI3K pathway upregulation was observed in a Sorafenib-resistant FLT3/ITD cell line established to study resistance mechanisms of FLT3 inhibition. Further, combination FLT3 and PI3K inhibition demonstrated synergy, suggesting potential clinical relevance to this therapeutic strategy.