Browsing by Author "Hendricks, Denver T"

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    Differentially expressed genes in oesophageal cancer
    (2002) Wamunyokoli, Fred Alexander Wafula; Parker, Iqbal; Hendricks, Denver T
    Oesophageal cancer (OC) is a leading cause of cancer death in the black population in South Africa. The lifetime risk of the disease amongst black males is 1 in 59. High incidence areas are the Transkei, Ciskei and KwaZulu-Natal where it is responsible for over 45 of all malignancies. Cancer develops through a multistep process of genomic instability of clonal evolution. Several oncogenes, tumour suppressor genes and transcription factors have been shown to be altered in oesophageal cancer. Their role however, in the development and/or susceptibility to the development of oesophageal cancer is poorly understood. The aim if this project is to identify candidate genes that are differentially expressed in oesophageal cancer patients with a view to understanding the development of oesophageal cancer. The ultimate objective of the project is to use this data to develop possible biomarkers for the disease.
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    Investigating a novel small molecule inhibitor of nuclear import as an anti-cancer approach
    (2016) Chi, Ru-pin Alicia; Leaner, Virna D; Hendricks, Denver T
    The identification of novel cancer-associated biomarkers against which drugs can be developed is anticipated to be beneficial in multiple ways; including their use as monotherapies and in combination with current chemotherapeutic agents for improved anti-cancer treatment outcome. Recently, research in our own laboratory and others have reported elevated expression of the nuclear transporter Kpnβ1 in multiple cancers. Using the cervical cancer model, we showed that its inhibition using small-interfering RNA (siRNA) resulted in cancer cell death via apoptosis while sparing normal cells, suggesting it has potential as a target for anti-cancer therapy. An in silico screen for Kpnβ1 inhibitors identified several small molecules that showed inhibitory effects on nuclear import as well as cancer killing activity. In this study, we aimed to examine the potential of one such small molecule, the Inhibitor of Nuclear Import-43 (INI-43) as a lead compound with anti-cancer activities using multiple cancer models. Through culture-based in vitro assays, we demonstrated that INI-43 inhibited the proliferation of cancer cells grown anchorage-dependently and independently. These effects were similarly observed in Kpnβ1 knock-down cells, and Kpnβ1 over-expression was able to partially reverse these effects, suggesting that the anti-cancer effects of INI-43 is mediated through interference of the Kpnβ1 function. Toxicology studies and liver microsomal assay showed that INI-43 has an acceptable toxicity profile in nude mice and is metabolically stable, allowing its use in in vivo testing. Intraperitoneal administration of INI-43 significantly reduced the growth of subcutaneously xenografted cervical and oesophageal tumour cells in nude mice, supporting its anti-cancer activity in vivo. To examine the potential of using INI-43 in combination therapy, we examined the effects of the combined treatment of INI-43 and Cisplatin (CDDP), a first-line chemotherapeutic agent used in the treatment of many cancers. INI-43 treatment at sub-lethal concentrations enhanced cancer cells' sensitivity to CDDP, which was similarly observed in Kpnβ1 knock-down cells. Using an ovarian cancer model, we demonstrated that CDDP treatment led to elevated expression and nuclear localization of Kpnβ1, suggesting that Kpnβ1 is involved in CDDP-induced stress response. INI-43 treatment impeded the CDDP-induced nuclear accumulation of Kpnβ1 which correlated with increased cell death, suggesting that nuclear localization of Kpnβ1 may be important for ovarian cancer cell survival when challenged with genotoxins such as CDDP. Using the cervical cancer model, we demonstrated that INI-43 enhanced CDDP-induced cell death synergistically, and that the enhanced cell death is mediated through stabilizing p53 protein. This associated with decreased levels of Myeloid Cell Leukemia 1 (Mcl-1), an anti-apoptotic factor negatively regulated by p53. Furthermore, INI-43 treatment reduced the nuclear import of NFκB, a stress-regulated response known to promote cancer cell survival. Decreased levels of various downstream pro-survival and DNA-repair targets of NFκB were observed, including cyclinD1, c-Myc and X-Linked Inhibitor of Apoptosis Protein (XIAP), which correlated with increased DNA damage and apoptosis. Taken together, we show that nuclear import inhibition using small molecules could have therapeutic benefits in the treatment of cancer, and that INI-43 is a promising candidate for further development to be used in anti-cancer monotherapy or combination chemotherapy.
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    Modulating ADAM-10 activity and expression in cervical and oesophageal cancer cells
    (2016) Wagiet, Mateen; Leaner, Virna D; Hendricks, Denver T
    The ADAMs (A Disintegrin And Metalloproteinase) is a family of transmembrane and secreted proteins essential in cellular fate determination, wound healing, cell migration, proliferation and angiogenesis. Previous studies have linked a range of ADAMs, which include ADAM10 to cancer development and progression. Research in our laboratory found endogenous ADAM10 levels to be higher in both oesophageal and cervical cancer cell lines. Reports in the literature have highlighted a correlation between high levels of ADAM10 expression with that of cancer cell biology; hence ADAM10 shows promise as an anti-cancer target. The aim of this study was to modulate ADAM10 activity in oesophageal and cervical cancer cell lines using the small molecule inhibitor GI254023X as well as previously undescribed two molecules generated en route to synthesizing GI254023X, namely SN-254 and SN-311. A CX₃CL1 ELISA functional assay as an indicator of ADAM10 activity showed a decrease in CX₃CL1 cleavage after treatment with GI254023X, SN-311 and SN-254 suggesting that all three compounds substantially inhibited ADAM10 activity. The effects of these compounds on the cell biology of WHCO5 oesophageal and HeLa cervical cancer cells were monitored. Our data shows that GI254023X, SN-254 and SN-311 inhibit oesophageal and cervical cancer cell proliferation, and cause cell death via apoptosis as observed by PARP cleavage, and elevated Caspase 3/7 activity. Drug treatment also resulted in an increase in cellular adhesion as well as a significant decrease in the invasion and migration of WHC05 and HeLa cells. The effect of ADAM10 inhibition on typical markers of the epithelial to mesenchymal transition state was also examined. An increase in epithelial cell markers (E-Cadherin, B-Catenin) and a decrease in mesenchymal marker expression (Vimentin) post treatment with the compounds tested strongly suggested that ADAM10 plays a role in mesenchymal cell transition. These results suggest that ADAM10 activity is necessary for the biological phenotypes that associate with cervical and oesophageal cancer cells and that targeting ADAM10 with inhibitors have potential as anticancer therapies.
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    South African marine compounds as anticancer agents
    (2006) Whibley, Catherine Evelyn; Hendricks, Denver T; Davies-Coleman, Michael T
    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.
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    Use of NQO1 status as a selective biomarker for oesophageal squamous cell carcinomas with greater sensitivity to 17-AAG
    (2014-05-15) Hadley, Katie E; Hendricks, Denver T
    Abstract Background Oesophageal squamous cell carcinoma (OSCC) is a major health burden in Sub-Saharan Africa, and novel chemotherapies are urgently required to combat this disease. The heat shock protein 90 (HSP90) inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) has previously been proposed as a possible candidate drug. NADPH quinone oxidoreductase 1 (NQO1) is known to increase the potency of 17-AAG, therefore we investigated the effects of 17-AAG in OSCC cell lines in the context of their NQO1 status. Methods We used MTT assays to compare the sensitivity of a panel of OSCC cell lines to 17-AAG. Western blotting, and RT-PCR were used to investigate NQO1 protein and mRNA levels, while an RFLP approach was used to investigate the NQO1 C609T SNP. Results Expression of NQO1 markedly increased sensitivity to 17-AAG in the OSCC cell lines, while normal fibroblasts, which expressed HSP90 at much lower levels, were more resistant to 17-AAG. In isolation, neither the C609T SNP, nor NQO1 mRNA levels was an accurate predictor of NQO1 protein levels. Conclusions Since NQO1 greatly enhances the anti-cancer effects of 17-AAG, this could be used as a selective marker for patients that would benefit most from 17-AAG chemotherapy at low doses. Testing for the presence of the C609T SNP in both alleles could be used as a screen to exclude potentially poor responders to 17-AAG treatment at low dosages.