Cervical cancer is one of the most common female cancers in Africa, both in terms of incidence and mortality, and is disproportionately prevalent in developing nations due to a lack of adequate access to healthcare. While new vaccine technologies are rapidly reducing the incidence of Human Papilloma Virus (HPV) infection, the primary causative agent of cervical cancer, new cases continue to accumulate in the developing world. Beyond the role of HPV in the early stages of cancer development, the molecular aetiology of this disease is poorly understood. Frequent exposure to seminal fluid (SF), the liquid component of semen, has been proposed as a potential driver of oncogenesis in cervical cancers and has been shown to exacerbate some aspects of cervical cancers. While some of the cellular signaling pathways responsible for these phenomena have been identified, much remains to be elucidated. We hypothesized that TBX2 and TBX3, two highly homologous transcription factors frequently implicated in other cancers, may be responsible for mediating some of the effects of SF on cervical cancer cells. We established that TBX3 protein is significantly overexpressed in both primary cervical adenocarcinomas and squamous cell carcinomas compared to normal tissue. SF was shown to increase expression of both TBX2 and TBX3 mRNA in HeLa and CaSki, but not C-33 A, cervical cancer cell lines. Furthermore, SF upregulated TBX3 protein expression in both of these cell lines. In contrast, TBX2 protein was undetectable in these cell lines. In addition, our results showed that SF treatment of HeLa cells increases the expression of the known TBX3 target gene, p21CIP1/WAF1 (p21), while having no effect on PTEN expression. Transient knockdown of TBX3 resulted in decreased p21 expression in SF-treated cells suggesting that SF upregulation of p21 is dependent on TBX3. This is the first study to investigate TBX3 protein expression in primary cervical tissues and SF regulation of TBX3. However, further research is required in order to elucidate the role of SF-induced TBX3 in cervical cancer development. The identification of the role of TBX3 in cervical cancer development could aid in the development of more effective treatments for cervical cancers and could potentially impact sexual health policy recommendations for women with cervical cancer.

The molecular basis of alpha thalassaemia in the so-called 'Cape Coloured' population of the Western Cape was investigated. Restriction endonuclease digestion, Southern blotting and hybridisation with alpha and zeta globin-specific probes were used to investigate the incidence of the the various alpha thalassaemia determinants and their disorders. Results indicate that one determinant in this population results from the deletion of a single alpha globin gene on the short arm of chromosome 16. In individuals homozygous or heterozygous for this deletion, digestion with restriction endonuclease Bam H1 shows the presence of a shorter 10,5kb alpha globin-specific fragment as opposed to the 14kb fragment found in normal individuals. Individuals with both alpha globin genes deleted on the same chromosome i.e. the genotype --/aa, were detected and their alpha thalassaemia determinant characterised by: 1. a family study 2. quantification of the alpha/gamma glob in gene ratio, and 3. mapping with the zeta globin probe since the deletion extends into the zeta locus. The --/ alpha thalassaemia determinant was found to be of Southeast-Asian origin. A non-deletion form of alpha thalassaemia was also detected in which the alpha globin restriction map appeared to be normal. This condition may have resulted from a point mutation within the alpha ilobin gene region which affects transcription or RNA processing. The DNA of infants born with detectable levels of Hb Bart's in their cord blood was investigated in order to estimate the frequency of the single and double gene deletions in this population. The results indicate that infants with Hb Bart's in the 4 - 8% range predominantly have the genotype -a/-a. Using the data obtained the incidence of the heterozygote was calculated according to the Hardy-Weinberg equation. The calculated incidence of the heterozygote (-a/aa) was found to be 16,9%.

In an attempt to understand the roles played by the ubiquitin-dependent and calpain pathways in protein degradation in chicken skeletal muscles, biochemical studies were conducted on components of these two systems as well as their potential endogenous and exogenous substrates. ATP- and ubiquitin-dependent breakdown of endogenous proteins (measured by tyrosine release) or exogenous proteins (measured by the appearance of trichloroacetic acid-soluble radiolabel after incubation with 125I-lysozyme) took place in muscle extracts; the specific activities of these processes were significantly lower than those detected in rabbit reticulocytes. Conjugation of ubiquitin to a subset of endogenous proteins was detected by incubating muscle extracts (fraction II: depleted of ubiquitin by DEAE-cellulose chromatography) with 125I-ubiquitin and Mg2+-ATP, followed by analysis of the radiolabelled conjugates by one-dimensional polyacrylamide gel electrophoresis in the presence of SOS, and autoradiography. Discrete conjugates were formed with apparent molecular weights between 30 -100 000, as well as a large number of undifferentiated entities of higher molecular weights. Conjugation of ubiquitin to the exogenous protein lysozyme was detected only when fresh, as opposed to previously frozen fraction II preparations were assayed: three bands were obtained, as opposed to the six ubiquitin conjugates formed by reticulocyte extracts. The muscle system catalyzed the ubiquitination of partially purified myofibrillar proteins, principally myosin and possibly actin. Fractionation of the ubiquitin-activating enzymes into El and E2 on the one hand, and E3 on the other, permitted mixing experiments to be conducted by means of conjugation assays, and confirmed the low content of E3 in muscle as opposed to reticulocytes. Fraction II from muscle displayed ubiquitin conjugate-degrading activity but again this was less active than in reticulocytes. A number of other proteolytic activities, independent of ubiquitin, were also present. Isopeptidases, active on 125I-ubiquitin conjugates were strongly inhibited by sulphydryl alkylating agents such as N-ethylmaleimide. The overall picture of the ubiquitin pathway in muscle is one where many proteins may be converted into long-lived conjugates but not in all cases requiring the action of E3: some E3-dependent protein degradation undoubtably does occur in this physiologically basal system. Formation of a ubiquitin conjugate of the ubiquitinactivating enzyme (E1) and some of the ubiquitin carrier proteins (E2 's) was detected during incubations of 125Iubiquitin and ATP lasting 2 hr or longer. Because treatment of such systems with NaOH, even at early times during the incubations, greatly enhanced the appearance of the same entities, the phenomenon appeared to be one of auto-, rather than E3-mediated ubiquitination. The bonds involved had properties compatible with their being peptidic in nature, and their formation occurred from ubiquitin thiolesters bound to E1 and E2. The protease inhibitor and alkylating agent, TLCK, when pre-incubated with fraction II for 2 hr before the addition of 125I-ubiquitin and ATP, greatly enhanced the subsequent auto-ubiquitination of E1 in the absence of NaOH treatment, and caused the inhibition of its adenylate-forming and thiolester-transferring activities: thus ubiquitin transfer to E2's and further to other acceptors was markedly impaired. such an inactivation of El by TLCK may, in a manner analogous to that described in the thermolabile ts85 mutants (Finley et al., 1984), be the basis of the action of this agent to block the cell cycle in late G2 or early M phase (Schnebli & Haemmerli, 1974). TLCK-induced inactivating auto-ubiquitination of El may be an important tool for the study of ubiquit-independent processes which (apart from possible intrinsic protease activity), all appear to require the activity of this enzyme. The number of calpain species existing in chicken skeletal muscle is controversial with only one (Ishiura et al., 1978) or three (Wolfe et al., 1985) species having been reported. When extracts of chicken skeletal muscle were applied to a DEAE-cellulose column and the bound protein eluted in a linear salt gradient, two calpain activities, separated from their endogenous inhibitors (calpastatins), were detected. The first eluting activity, "calpain I", was active at low ca2+ concentrations, was heat-labile and had a lower apparent molecular weight on gel filtration when compared with the later eluting activity which appeared to be a typical calpain II species. "Calpain I". was not an autolytic product of calpain II but appeared to be derived from a more heat-stable calpain I species. A proportion (up to 14%) of the calpains in crude muscle extracts was bound to membrane fractions in the presence of ca2+; this could be removed by EGTA treatment. In addition, membrane-bound fractions examined by 9el filtration contained calpain· forms of an apparent molecular · weight lower than that of calpain which had not been membrane-associated. Membrane binding of the calpains (especially of calpain II), may be important in physiological activation.

Two manuscripts based on the work reported in this thesis were submitted and accepted for publication, the abstracts of which follow: SOLUBLE AND PARTICULATE FORMS OF MUSCLE ALKALINE PROTEINASE SHOW DIFFERENTIAL SENSITIVITY TO ENDOGENOUS INHIBITOR(S): Firhaad Ismail and Wieland Gevers, (Biochemistry International, In Press). Membrane-free washed myofibrils derived from rat skeletal muscle homogenates contained a chymostatin-sensitive protease(s) which acted on associated myofibrillar proteins, at an optimum pH of 8.5, much less rapidly at low ionic strength (insoluble myofilaments) than at high salt concentrations (solubilized proteins). When the myofibrillar fraction was added to the particle-free cytosol prepared from the muscle extracts, proteins of the cytosol were also degraded, but the activity in this case was much more pronounced at low ionic strength. This was because inhibitor(s) of the proteinase present in the cytosol fraction were only effective at high ionic strength when all the myofibrillar (and associated) proteins were in solution. The protease was separated from the bulk of the myofibrillar proteins by gel chromatography at high ionic strength. On dialysis against a low-salt buffer, part of the enzyme was precipitated. The putative cytosolic inhibitor(s) were again only effective on the soluble enzyme at high ionic strength. A HIGH MOLECULAR WEIGHT CYSTEINE ENDOPEPTIDASE FROM RAT SKELETAL MUSCLE: Firhaad Ismail and Wieland Gevers, (Biochim. Biophys. Acta, In Press). A cytosolic enzyme of high molecular weight (about 500000), which attacks native or denatured proteins (inter alia casein, globin and hexokinase) was purified about 1000-fold from mixed rat skeletal muscles, including muscles freed of mast cells by prior treatment of the animals with the degranulator, compound 48/80. Peptides of varying size were generated from radio-actively labelled globin, but no free amino acids were formed; free tyrosine was also not released from azocasein. The pH optimum was 7.5 and the presence of an essential cysteine group was suggested because dithiothreitol (1 mM) stimulated the activity and N-ethylmaleimide (5 mM) and p-chloromercuriphenylsulphonic acid (1 mM) were inhibitors. The activity was markedly inhibited by Zn²⁺ but not by leupeptin, chymostatin or pepstatin. The enzyme was stabilized by ATP, at concentrations as low as 0.1 mM, against inactivation at 42°C. The endopeptidase was clearly separated on gel chromatography from another large protease, also sensitive to Zn²⁺, but with marked aminopeptidase activity and the properties of Hydrolase H. The activity levels of the protease, assayed after chromatography on Sepharose 68 of high-speed supernatant fractions, did not vary significantly in skeletal muscle samples which were derived from denervated, starved, diabetic or hyperthyroid animals, in all of which the abnormal physiological states expressed themselves as enhanced rates of tyrosine release by incubated soleus and extensor digitorum longus muscles. Nevertheless, the enzyme described here may be part of an ATP-dependent, multi-component proteolytic system similar to that already known to be present in reticulocytes.

Status epilepticus (SE) describes a state of persistent seizures which are unrelenting. First- line treatment for status epilepticus uses a group of drugs, the benzodiazepines, that promote the action of the major inhibitory neurotransmitter within the brain, gamma (γ)-aminobutyric acid (GABA). In a subset of patients however, benzodiazepines prove to be ineffective in terminating SE. Previous data from in vitro models has demonstrated that during single seizures, instead of being inhibitory, activation of the GABAA receptor can have an excitatory effect on neurons. To date, it is unknown whether this shift in GABAergic function contributes to SE, nor how it may modulate the anticonvulsant properties of benzodiazepines. In this thesis I explore the role of excitatory GABAergic signaling in an in vitro model of SE and how this may affect the anticonvulsant efficacy of the benzodiazepine, diazepam. Firstly, I confirm that benzodiazepine-resistant SE is prevalent in a South African paediatric population. Secondly, consistent with its established mechanism of action, I show that diazepam enhances GABAAR synaptic currents. Thirdly, using the in vitro 0 Mg²⁺ model of status epilepticus I show that whilst early application of diazepam has anticonvulsant properties, this is lost when the drug is applied during prolonged epileptiform activity. Fourthly, to investigate this phenomenon I use optogenetic activation of GABAergic interneurons to show that interneurons can drive epileptiform discharges during SE-like activity in vitro. Finally, I confirm that during seizure-like events there is a transient shift in GABAergic signaling that is caused by activity driven changes in the transmembrane Cl⁻ gradient. This thesis provides insight into how excitatory GABAergic signaling during prolonged seizures may contribute towards benzodiazepine resistance in SE. I believe that these results are relevant for understanding of the pathophysiology of SE and may help inform optimal treatment protocols for this condition.

The Karyopherin superfamily is a group of soluble transport proteins which are involved in nuclear-cytoplasmic trafficking. Studies have shown the involvement of Karyopherin proteins in nuclear pore assembly, nuclear membrane assembly and DNA replication. Since all these cell regulatory functions are critical for normal cell function, dysregulation of Karyopherin proteins may have an impact on cancer cell survival. Previous research in our laboratory and in that of others has shown that Karyopherin Beta 1 (KPNB1) is elevated in and necessary for the survival of cervical cancer cells as inhibiting its expression with siRNAs interfered with the proliferation of cancer cells. KPNB1 has thus been proposed as an anticancer target. In addition to inhibition by siRNA, an in silico screen for small molecules with potential to bind KPNB1 identified a number of compounds that are currently under investigation for their cancer cell killing effects. In this study, we investigated the ability of a novel small molecule 1-benzyl-4[(4-methoxy-1-naphyl) methylamino]-N-methyl pyrrolidine-2-carboxamide (Compound 53) to kill cancer cells and inhibit the activity of KPNB1 cargo proteins. In addition, the in vitro pharmacokinetic properties and in vivo toxicology of Compound 53 (C53) were investigated. Cervical (HeLa and CaSki) and oesophageal (WHCO6 and Kyse30) cancer cell lines were found to be more sensitive to C53 treatment compared to non-cancer cells (FG₀), with EC₅₀ values of ~20 μM for the cancer cell lines and ~30-40 μM for the non-cancer cells. C53 treatment significantly inhibited proliferation in cancer cell lines. The reduction in proliferation in cancer cells was associated with a block in the G1 phase of the cell cycle and a change in the expression of cell cycle related proteins such as CyclinD1 and CDK4. C53 treatment resulted in cell death via apoptosis as observed using Annexin V staining and PARP cleavage. To assess whether C53 interferes with KPNB1 associated nuclear import, we investigated the effect of C53 on the activity of KPNB1 cargo proteins, NFAT and NF-ĸB as well as investigate its effect on KPNB1 localisation. The results show that C53 has no effect on the localisation of KPNB1 but it does however block the nuclear activity of the KPNB1 cargoes, NFAT and NF-ĸB. In order to predict the behaviour of C53 in a living system, in vitro ADME pharmacokinetic studies showed that C53 has moderate solubility, permeability and protein binding however, rapid clearance was shown by liver microsome assay. In vivo repeated dose toxicology studies showed that C53 is tolerable in nude mice. Taken together, the data presented in this study shows that a novel small molecule, C53 has a negative effect on the proliferation of cancer cells, inhibits the nuclear import of KPNB1 cargoes, displays tolerable in vitro ADME pharmacokinetic properties and showed no toxic side effects in vivo. These results suggest that C53 targets KPNB1 and shows potential as an anticancer molecule.

Squamous cell carcinoma of the oesophagus is a formidable disease which poses a significant health risk in developing countries where the incidence is frequently high and access to health care facilities is often limited. The identification of genes involved in oesophageal tumourigenesis may provide new targets for therapy and improved diagnostics techniques, thereby improving the prognosis of this pernicious disease. In this study, real-time RT-PCR and immunohistochemistry described the overexpression of N-Myc Downstream-Regulated Gene 1 (NDRG1) in oesophageal squamous cell carcinoma (OSCC) tissue compared to normal tissue in a cohort of South African cancer patients. Despite more than ten years of research into the role of NDRG1 in cancer, the precise function of this protein remains enigmatic. Reports have been contentious, suggesting both tumour suppressor and tumour promoter functions for NDRG1, implicating it in tumourigenic processes such as metastasis and angiogenesis. Our immunohistochemical analysis if NDRG1 expression in OSCC tissue and matched normal epithelium (n=83) showed that NDRG1 expression is elevated by 2.6-fold in cancer tissue compared to normal tissue. Moreover, the expression and localisation of NDRG1 appeared to track with epithelial cell maturation where basal cells of normal oesophageal epithelium displayed plasma membrane-associated NDRG1 while maturing cells were mostly positive for NDRG1 in the cytoplasm and nucleus. Likewise, NDRG1 displayed interesting patterns of localisation in tumour tissue of the xiii oesophagus. Dysplastic tissue and poorly differentiated tumour tissue stained positively for NDRG1 in the plasma membrane, while moderately and well differentiated tumours displayed mixed staining for NDRG1 in the plasma membrane, cytoplasm and nucleus. Analysis of NDRG1 expression in cell lines cultured under anchorage-independent conditions revealed that NDRG1 expression is strongly induced when cells are prevented from adhering to the surface of culture dishes. Induced NDRG1 expression correlated inversely with mRNA expression of invasion genes, MMP-2 and MMP-9, as well as the mRNA expression of angiogenic factors Ang- 1, PDGF-B and VEGF-C but, in contrast, showed positive correlation with the angiogenesis cytokine, VEGF-A. Knock-down of NDRG1 expression with siRNA had no effect on anchorage-independent cell proliferation or apoptosis but did inhibit VEGF-A expression. Moreover, VEGF-A promoter activity, induced by culturing cells under anchorage-independent conditions was shown to be NDRG1-dependent. In order to identify factors that may drive NDRG1 transcription in cultured OSCC cell lines we cloned and partly characterised the NDRG1 promoter. Through the generation of promoter deletion constructs, site-directed mutagenesis and Chromatin Immunoprecipitation (ChIP) assays, we showed that both EGR-1 and cJun/AP-1 are capable of driving transcription of NDRG1 in response to 12-o-tetradecanoylphorbol- 13-acetate (TPA) through activation of PKC/MEK/ERK1/2 and JNK MAPK pathways. Taken together, we describe the regulation of NDRG1 expression by EGR-1 and AP-1 and we show that NDRG1 is overexpressed in squamous cell carcinoma of the oesophagus compared to normal oesophageal tissue. We associate NDRG1 with an xiv oncogenic function in OSCC through its potential role in angiogenesis via modulation of VEGF-A expression.

Oesophageal squamous cell carcinoma (OSCC) ranks as one of the deadliest tumours with a high incidence in developing countries in the areas of Southern Africa, Middle East and Far East. Moreover, its unfavourable prognosis is further complicated by the lack of knowledge about the molecular biology of this disease. In this thesis, we describe our work analysing the function of N-myc downstream regulated gene 1 (NDRG1, also known as Cap43 or Drg-1) in the neoplastic progression and maintenance of OSCC. Although NDRG1 has previously been implicated in breast, prostate, colon and liver carcinoma, the exact role of NDRG1 in OSCC still remains unclear. According to the immunohistochemical analysis of clinical OSCC tissue samples (n=52), NDRG1 expression was gradually increased in tumour tissue versus normal, indicating the potential involvement of NDRG1 in the neoplastic progression of OSCC. We next performed ectopic NDRG1 gain-of-function and loss-of-function studies using transfectants established from transduced OSCC cell lines (KYSE30 and KYSE150) by lentiviral vector mediated gene delivery. In KYSE30 cells, although no substantial effects on in vitro cell proliferation and differentiation were observed with altered NDRG1 expression, the ectopic overexpression of NDRG1 was found to be positively linked to metastasis, angiogenesis and apoptotic evasion as measured in cell culture. Accordingly, in the nude mouse xenograft model system, NDRG1 overexpression promoted the in vivo growth and metastasis of KYSE30 derived xenografts, which could be attributed to the reduced apoptotic and enhanced angiogenic activities promoted by this gene. Nevertheless, no significant phenotypic changes were observed in response to NDRG1 knock-down, suggesting that this gene was not essential for the neoplastic progression of OSCC. Moreover, null effect of either ectopic NDRG1 overexpression or knock-down were observed in KYSE150 cells, indicating ix that the function of NDRG1 may be largely dependent on the cellular context (Chapter 2). In addition to direct functional assays, evidence from analysing the regulation pattern of NDRG1 in OSCC cells was also presented to provide clues to indirectly predict the function of NDRG1 in OSCC. In Chapter 3, we demonstrated that NDRG1 could be actively regulated by various oncogenic stimuli such as cellular stress (genotoxicity and hypoxia) and mitogenic factors (EGF and IGF). Although these oncogenic regulatory effects on NDRG1 expression in OSCC cells may be dichotomous, the functional significance of NDRG1 upregulation, especially by hypoxia and EGF signalling, is highlighted. In our studies, the regulatory pattern of NDRG1 in OSCC is highly consistent with its oncogenic function revealed in ectopic studies (Chapter 2), further suggesting that phenotypic changes observed in the functional studies may not be artifactual, but may reflect the role of NDRG1 in the neoplastic progression of OSCC in physiological conditions. Taken together, our current data implicate NDRG1 as an effective but non-essential promoter in the neoplastic progression of oesophageal squamous cell carcinoma. Although the mechanism still needed to be further explored, our study suggests important clues regarding these mechanistic roles considering the impact of this gene on apoptosis, metastasis and angiogenesis.

Includes bibliographical references (leaves 149-163). / Oesophageal cancer is the most common cause of cancer related deaths among black males in South Africa. Currently there are very limited treatment options, and patients have a very poor prognosis, due in part to the late stage at which this cancer is usually detected. In this thesis we describe the establishment of a screening assay using an oesophageal cancer cell line as a model. It was our hope that this screen would allow us to identify compounds which have activity against oesophageal cancer, that could be used as lead agents for further development of chemotherapeutic agents. Once our screen was established, we tested a wide range of extracts from southern African marine organisms, supplied by our collaborators from Rhodes University, South Africa. The marine environment represents a rich, untapped repository of novel and interesting compounds, and through our collaboration we had access to a wide range of marine-derived extracts and compounds. During the course of this project we provided screening data to assist in activity-directed fractionation from five active marine extracts, giving rise to 15 compounds of varying activity. These included several groups of novel active compounds such as the makaluvic acids from the sponge Strongylodesma aliwaliensis and the malonganenones from the octocoral Leptogorgia gi/christii. The identification of a number of novel, active compounds through our screening program highlights the potential of marine organisms from the southern African coast as a source of novel drug leads.

Angiotensin-converting enzyme (ACE) is a zinc metallopeptidase that plays an important role in vascular function; with ACE inhibitors being clinically utilised in the treatment of cardiovascular disease and diabetic nephropathy. Somatic ACE consists of two homologous catalytically active domains (designated N- and C-domains) that share high overall sequence identity and structural topology. Despite the high degree of similarity between domains, each domain displays differences in substrate processing and inhibitor binding abilities. This suggests that active site residues differing between the two domains could provide unique interactions within the N-domain that allow for N-selective binding and processing. Literature reports of ACE crystal structures and studies with substrate and inhibitor analogues have implicated unique residues present in the S2 and S2' subsites in providing important interactions for N-selectivity.