ABSTRACT MUC1, a mucin-like transmembrane glycoprotein, is highly overexpressed and aberrantly localized in several invasive carcinomas. MUC1 is proposed to play numerous roles in the transformed behaviour of cells in which it is expressed. A number of these roles are facilitated by the interaction of MUC1 with β-catenin, a protein that is central to both cellular adhesion as well as Wnt-responsive gene transcription. The aim of this study was to investigate MUC1 expression, localization, and interaction with β-catenin, as a means of providing insight into the behaviour of human oesophageal squamous cell carcinoma. This cancer-type is exceptionally aggressive and is a major cause of cancer-related morbidity and mortality in South Africa. MUC1 is expressed and aberrantly localized in oesophageal squamous cell carcinoma cell lines, as demonstrated by RT-PCR, western blotting and indirect immunofluorescence. Moreover, evidence from coimmunoprecipitation assays shows that the MUC1 cytoplasmic tail and β-catenin form a complex both at the cell membrane and importantly, within the nucleus of these cell lines. This is the first demonstration of such a complex in the nucleus of a carcinoma derived from stratified, as opposed to simple, epithelia. Data presented here further indicates that activation of the epidermal growth factor receptor results in modulation of the association between MUC1 and β-catenin at the cell membrane. MUC1 membrane-localization, and interaction with β-catenin, may modulate cellular adhesion through steric interference of cell surface adhesion molecules as well as through sequestration of β-catenin away from adherens junctions. On the other hand, MUC1 association with β-catenin may enhance β- catenin signalling either through the stabilization of β-catenin, or as an essential functional component of the β-catenin/LEF/TCF transcription factor complex. Furthermore, results presented in this study identify oesophageal squamous cell carcinoma as a prime candidate for MUC1-specific immunotherapy. This finding is of substantial importance considering the ineffectual nature of existing therapies used in the treatment of oesophageal carcinoma.

Abstract Integrin-linked Kinase (ILK) is an integrin-associated protein kinase, which regulates growth factor-signalling pathways and cell-ECM adhesion events. Abrogated ILK expression or activity has been implicated in contributing to oncogenic transformation. We examined the role played by ILK in growth factor-stimulated and integrin signalling events in five human oesophageal squamous cell carcinoma cell lines (HOSCCs), known to overexpress the EGF receptor. Western blot analysis revealed the presence of ILK (59kDa) in all the moderately differentiated HOSCC lines. ILK1 was confirmed as being the predominant isoform. Densitometrically analysed Western blots showed that, per unit of protein, ILK is expressed uniformly across the cell lines under standard culture conditions. Following EGF (10 ng/ml) and TGFβ1 (1 ng/ml) treatment, ILK expression increased in all five HOSCCs. Indirect immunofluorescence microscopy showed the majority of ILK to localise at a cytoplasmic/nuclear level, with a proportion of ILK localising at the membrane, which resembled the distribution pattern of the β3 integrin subunit. This membranal distribution most likely follows that of the adhesion plaques although lesser, and variable, amounts were also identified throughout the cytoplasm. The functionality of the ILK1 kinase domain was demonstrated using myelin basic protein (MBP)-based kinase assays. EGF and TGFβ1 treatment produced an increase in ILK activity in the WHCO3 cell line of 3.5 fold, but a decrease in activity in the other cell lines, which are suggested to involve the actions of PTEN. The identification of nuclear ILK was surprising, and the mechanism for nuclear ILK localisation was suggested to involve a caveolae-associated protein, caveolin-1. Cell adhesion assays revealed that KP-392-mediated inhibition of ILK resulted in a nonsignificant reduction in cell adhesion to collagen and fibronectin. These data provide distinctive evidence for the influence of growth factors on ILK expression, but a duality in the effect on ILK activity. This apparent dichotomy is noteworthy and may be of particular relevance in HOSCC. It is further suggested that KP-392-induced ILK inhibition destabilises the αβ integrin heterodimer and that PI3K acts upstream of ILK-mediated cell adhesion events in HOSCCs. This suggests that ILK mediates integrin associated processes in human oesophageal SCC cell lines.

A naphthoquinone, 7-methyljuglone and some of its 5-hydroxy, 5-acetoxy-, 5-alkoxy- and 1,2,4,5-tetra-O-acetate derivatives were tested for their activity in four human cancer cell lines: breast adenocarcinoma, cervical epithelial carcinoma, oesophageal carcinoma and prostate epithelial carcinoma. Compound 2,5-dihydroxy-7-methyl-1,4-naphthoquinone was found to be the most effective one (exhibited a fifty percent inhibitory concentration (IC50) in the range of 5.3 to 14.7 μM), while the parent compound 7-methyljuglone was less active than several of these derivatives. The IC50 values of 5-hydroxy-6-methyl-1,4-naphthoquinone were found to be between 19.1 and 15.4 μM on the four cell lines. However this compound showed toxicity on peripheral blood mononuclear cells. Six derivatives were selected for mechanistic studies. Considering the findings from cell cycle analysis, caspase 3/7 activation and annexinV-FITC dual labelling, 5-hydroxy-6-methyl-1,4-naphthoquinone was found to have antitumour effect by inducing apoptosis. Two derivatives namely, ‘8-fluoro-5-hydroxy-7- methyl-1,4-naphthoquinone’ and ‘2,5-dihydroxy-7-methyl-1,4-naphthoquinone’ were found to be not toxic on peripheral blood mononuclear cells suggesting their action is specific for tumour cells. Compound 2,5-dihydroxy-7-methyl-1,4-naphthoquinone was found to induce apoptosis through caspase 3/7 activation. In view of the enhanced potencies associated with these derivatives, these analogues may hold considerable therapeutic potential for the treatment of leukaemia cancers. The ethanol extracts of seven plant species (ethnobotanically selected) were also tested for their cytotoxicity, assayed by the XTT assay, against four human cancer cell lines at concentrations ranging from 0.78 to 100 μg/ml. Of all the ethanol extracts, Foeniculum vulgare was found to have the best activity on HeLa cells, which exhibited an IC50 value of 19.97± 0.048 μg/ml. Therefore, it was selected for isolation of the bioactive principles. The extract of Foeniculum vulgare was fractionated using column chromatography with hexane and ethyl acetate at different ratios as eluent. Two known compounds, ‘4-methoxycinnamyl alcohol’ and ‘syringin’ were isolated. The IC50 values of ‘4-methoxycinnamyl alcohol’ and ‘syringin’ were found to be 7.82 ± 0.28 μg/ml and 10.26 ± 0.18 μg/ml respectively on HeLa cells. Both compounds were tested for their cytotoxicity against U937 cells and also on peripheral blood mononuclear cells. At the concentrations of 10 and 100 μg/ml ‘4- methoxycinnamyl alcohol’ showed similar cell proliferation as that of the positive control ‘cisplatin’. ‘Syringin’ however, had much lower cytotoxicity on the U937 cells than ‘4- methoxycinnamyl alcohol’. IC50 was found to be 91.14 ± 0.63 μg/ml. Both ‘syringin’ and ‘4- methoxycinnamyl alcohol’ were not cytotoxic at concentrations of 1 and 10 μg/ml on the PBMCs as compared to cisplatin. ‘4-Methoxycinnamyl alcohol’ was selected based on its activity on the cancer cells, for further investigation with regard to its mechanism of action. On gel electrophoresis it did not show a typical ladder pattern, instead a characteristic smear resulted which indicated necrosis. Two best derivatives of 7-methyljuglone (‘8-fluoro-5-hydroxy-7-methyl-1,4-naphthoquinone’ and ‘2,5-dihydroxy-7-methyl-1,4-naphthoquinone’) and the ethanol extract of F. vulgare warrant further investigation to be considered for their potential as anticancer agents. / Dissertation (MSc)--University of Pretoria, 2011. / Plant Science / unrestricted

Radiation therapy is afflicted by a multitude of geometric uncertainties, which must be compensated to ensure treatment success. Such mitigation is currently achieved by enlarging the apparent target volume by various safety margins. This thesis investigated uncertainty sources relating to target position and extent in oesophageal carcinoma, both static and dynamic, and evaluated their impact in a combined model. The first were errors inherent to delineation of the gross tumour volume (GTV), where computed tomography (CT) imaging, the overall modality of choice for target volume delineation (TVD), has a tendency to overestimate target extent. Two rival modalities, [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) and endoscopic ultrasound (EUS), are generally expected to yield more accurate assessments. EUS has previously suffered from a difficulty in transferring its findings to the spatial domain in which TVD is undertaken. This limitation was overcome here through the use of endoscopically implanted fiducial markers visible on the planning CT. This has enabled their inclusion in TVD and allowed a direct comparison of FDG-PET and EUS based target extents, which were found to agree quite well on average, but showed occasional discrepancies on the order of a few cm. Recently published reports on inter-observer variability (IOV) in TVD of oesophageal carcinoma were summarised with a particular focus on its reduction afforded by the use of fiducial markers. The influence of IOV was investigated more widely in other tumour entities, where it was shown to increase during the course of treatment, mostly due to differing adaptation practices. Microscopic disease extension (MDE), undetectable prior to treatment with current imaging techniques, constituted the second uncertainty source. Reports on histopathological measurements of MDE incidence and its distance from the main tumour were reviewed and spatial measurements extracted to derive a combined estimate of the distribution of extension distances. The overall incidence was estimated as 14.6%, with individual studies reporting widely differing values. Conventional margin widths to compensate for MDE were extracted from the pooled distribution and found to largely agree with the common clinical choice of 3–5 cm, but associated with broad confidence intervals. The addition of such margins to the GTV defines the clinical target volume (CTV). Most studies acknowledged tissue deformations as a major problem, but not all implemented means to prevent or correct it. Preliminary measurements on oesophageal resection specimens were presented, wherein fiducial markers were used to measure tissue deformations, and might ultimately be used to correct spatial measurements of MDE. Fiducial markers also facilitated the study of inter-fractional target mobility in a cohort (n=23) receiving daily orthogonal X-ray imaging for target positioning verification. Markers were found capable of detecting target misalignments, which were a common occurrence with 54% and 15% of analysed markers and treatment fractions showing displacements from their planned position in excess of 5 and 10mm, respectively. Mobility amplitudes were highest in the longitudinal direction and a dependence on tumour location was hinted at, with motion more restricted for proximally located lesions. Measures of systematic and random mobility components were extracted to derive safety margins, which are added to the CTV to form the planning target volume (PTV). A radiobiological model of tumour control probability (TCP) was then evaluated under different uncertainty scenarios. It simplified the tumour system to its longitudinal dimension, which is most affected by the aforementioned phenomena, and simulated positional uncertainties, as well as MDE. The differential impact of systematic and random mobility components on TCP was demonstrated and margin widths sufficient to limit TCP reduction to 1% could best be described by a quadratic combination of their magnitudes. This composition was still applicable when MDE was introduced and mitigated by a conventional margin, but the relative impact of both components shifted. The addition of a PTV margin to the CTV afforded the MDE-positive subpopulation similar protection against positional uncertainties as the same margin achieved without consideration of MDE. The MDE-negative subpopulation attained a much improved tolerance to positional uncertainties through the CTV margin, which also propagated to the overall population. An alternative mitigation of MDE was attempted by optimising the applied dose distribution to an assumed tumour cell density distribution motivated by the literature, which decreases towards the target edge. The optimisation maximised TCP while preserving the integral dose delivered with a conventional margin, under the assumption that this translates into a similar likelihood of normal tissue toxicity. Reduced doses could be delivered to lower cell density regions without sacrificing overall TCP, but this reduction was modest despite vastly diminished cell densities. When this spared dose was redistributed so as to enlarge the treated area, negligible TCP change was observed, but redistribution to the central target did result in appreciably improved TCP in both subpopulations. These effects persisted when positional uncertainties were added and when MDE incidence was increased to the most extreme value reported in the literature.