An in vitro assessment of pharmacodynamic interactions between selected herbal extracts and anticancer chemotherapeutic agents
- Authors: Hwehwe, Nyashadzashe , Swanepoel, Bresler
- Date: 2024-04
- Subjects: Chemotherapy , Herbs -- Therapeutic use , Antineoplastic agents
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63506 , vital:73383
- Description: Cancer is a disease caused by uncontrolled growth and spreading of abnormal cells to distant body parts. Approximately 19.3 million and 10 million new cancer cases and cancer deaths, respectively were recorded in 2020. Despite advancements in prevention and therapeutic strategies, cancer remains a global health problem. Cancer patients are increasingly seeking complementary and alternative medicines, of which herbal medicines are the most common form of CAM used by patients. Numerous in vitro and in vivo studies of herbal medicines in cancer have shown that they have antioxidant and anticancer (antitumor and anti-proliferative) properties. While concurrent use with conventional cancer treatments may improve treatment efficacy, alleviate chemotherapy-related side effects, boost the immune system, or impede drug resistance, it can also prompt drug-herbal interactions, and this may affect the pharmacodynamics and pharmacokinetics of the chemotherapeutic drug. This study aimed to determine relevant pharmacodynamic interactions with chemotherapeutic drugs and investigate such interactions' mechanisms. The objectives of the study were to screen the cytotoxicity effects of drug compounds, herbal extracts, and drug-herb combinations, to determine the ability of treatments to induce apoptosis, and to determine the most beneficial treatment. The cytotoxic effects of cisplatin in HeLa cells, tamoxifen in MCF7 cells, 5-fluorouracil in Caco-2 cells, and grapeseed, green tea, fermented rooibos, and green rooibos in all the listed cell lines were evaluated individually and in combination using the bis-Benzamide H 33342 trihydrochloride/propidium iodide (Hoechst 33342/PI) dual staining method. CompuSyn 1.0 Software was used to quantify synergism and antagonism. The mechanism of apoptosis induction of the different synergetic combinations, drug compounds, and herbal extracts was illustrated by quantitative fluorescence image analysis, specifically cell cycle analysis, phosphatidylserine translocation, mitochondrial membrane potential analysis, caspase 3 activation, and reactive oxygen species production using the relevant contrast dyes. Grapeseed displayed cytotoxicity towards MCF7 and HeLa cells (IC50 57.98 and 83.28 μg/mL, respectively). Green tea was only cytotoxic against HeLa cells at an IC50 of 91,92 μg/mL. None of the extracts displayed cytotoxicity against Caco-2 cells (IC50 values > 200μg/mL). If the herbal extracts had inconclusive IC50 values in the three cell lines subsequent experiments were conducted using 100 μg/mL. The results showed that most of the combinations were antagonistic but, some combinations had synergistic or enhancement effects(1:3 for cisplatin with grape seed or green tea and tamoxifen with grapeseed or green tea, and 3:1 for cisplatin with green tea as well as for tamoxifen with fermented rooibos or green rooibos, and all the 1:1 combinations of 5- fluorouracil with all herbal extracts) with a combination index (CI) < 1. Grape seed and green tea were found to induce apoptosis in the three cell lines. Assays that were conducted to detect apoptosis induction showed positive staining for phosphatidylserine (PS), activated caspase 3, and reactive oxygen species (ROS), mitochondrial membrane depolarization. Analysis of the cell cycle showed two things; 1) that grape seed and green tea were apoptotic in HeLa and MCF7 cells only, and 2) the extracts of green tea and green rooibos, and the combinations of grape seed with all drug compounds arrested the cell in more than one phase of the cell cycle. The combinations of grapeseed and green tea potentially induced apoptosis in various manners but those with both rooibos extracts were unclear in all the cell lines. The results for combinations with grapeseed and green tea are promising and provide a basis for further research as combinations of chemotherapeutic drugs and herbal extracts may be effective therapeutic strategies. , Thesis (MPharm) -- Faculty of Health Sciences, School of Clinical Care & Medicinal Sciences, 2024
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- Date Issued: 2024-04
Mathematical modelling of the tumour treatment with chemotherapy
- Authors: Nyaweni, Fundile Sindy
- Date: 2024-04
- Subjects: Mathematical models , Mathematics , Chemotherapy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64289 , vital:73672
- Description: In this study, a cancer disease model incorporating predator-prey dynamics between immune cells and tumor cells, as well as competition between tumor cells and normal cells, is formulated in an attempt to understand the interaction dynamics that govern the complex interplay within the tumor microenvironment. Mathematical analysis is employed to derive conditions for the boundedness of solutions and to discuss disease thresholds such as the basic reproduction number, R0. Equilibrium points are identified, and stability conditions for the system are derived. Sensitivity analysis is used to assess uncertainties in the parameters of the model, specifically their impact on R0. Numerical simulations are conducted, utilizing the Runge-Kutta scheme to solve the model. Furthermore, optimal control (OC) techniques are applied to examine the role of chemotherapy in enhancing tumor cell elimination and minimizing adverse effects on immune cells and normal cells. The improved model, incorporating normal cells, anticancer drugs, and immune cells, allows for a more comprehensive analysis of the dynamic interactions within the biological system. The optimal control is determined using the forward-backward sweep numerical method. The numerical simulation is carried out in MATLAB to validate and complement the analytical findings. The results indicate that a low concentration of the drug leads to a prolonged period for tumor clearance. Conversely, a higher drug concentration results in quicker tumor clearance, albeit with adverse effects on normal and effector cells. The OC identifies when to stop the treatment once the tumor clears. Furthermore, OC facilitates the regeneration of normal and immune cells beyond treatment, in contrast to a control scenario without optimization. The findings highlight the importance of early detection and careful chemotherapy dosage selection for effective and personalized cancer treatment strategies. , Thesis (MSc) -- Faculty of Science, School Computer Science, Mathematics, Physics and Statistics, 2024
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- Date Issued: 2024-04
In silico analysis of human Hsp90 for the identification of novel anti-cancer drug target sites and natural compound inhibitors
- Authors: Penkler, David Lawrence
- Date: 2015
- Subjects: Heat shock proteins , Cancer -- Treatment , Molecular chaperones , Homeostasis , Carcinogenesis , Chemotherapy , Ligand binding (Biochemistry) , Protein-protein interactions
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4162 , http://hdl.handle.net/10962/d1018938
- Description: The 90-KDa heat shock protein (Hsp90) is part of the molecular chaperone family, and as such it is involved in the regulation of protein homeostasis within cells. Specifically, Hsp90 aids in the folding of nascent proteins and re-folding of denatured proteins. It also plays an important role in the prevention of protein aggregation. Hsp90’s functionality is attributed to its several staged, multi-conformational ATPase cycle, in which associated client proteins are bound and released. Hsp90 is known to be associated with a wide array of client proteins, some of which are thought to be involved in multiple oncogenic processes. Indeed Hsp90 is known to be directly involved in perpetuating the stability and function of multiple mutated, chimeric and over-expressed signalling proteins that are known to promote the growth and survival of cancer cells. Hsp90 inhibitors are thus thought to be promising therapeutic agents for cancer treatment. A lack of a 3D structure of human Hsp90 however has restricted Hsp90 inhibitor development in large to in vivo investigations. This study, aims to investigate and calculate hypothetical homology models of the full human Hsp90 protein, and to probe these structural models for novel drug target sites using several in silico techniques. A multi-template homology modelling methodology was developed and in conjunction with protein-protein docking techniques, two functionally important human Hsp90 structural models were calculated; the nucleotide free “v-like” open and nucleotide bound closed conformations. Based on the conservation of ligand binding, virtual screening experiments conducted on both models using 316 natural compounds indigenous to South Africa, revealed three novel putative target sites. Two binding pockets in close association with important Hsp90-Hop interaction residues and a single binding pocket on the dimerization interface in the C-terminal domain. Targeted molecular docking experiments at these sites revealed two compounds (721395-11-5 and 264624-39-7) as putative inhibitors, both showing strong binding affinities for at least one of the three investigated target sites. Furthermore both compounds were found to only violate one Lipinski’s rules, suggesting their potential as candidates for further drug development. The combined work described here provides a putative platform for the development of next generation inhibitors of human Hsp90.
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- Date Issued: 2015
Identification of novel marine algal compounds with differential anti-cancer activity: towards a cancer stem-cell specific chemotherapy
- Authors: De la Mare, Jo-Anne
- Date: 2012
- Subjects: Breast -- Cancer , Stem cells -- Research , Chemotherapy , Algae -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4143 , http://hdl.handle.net/10962/d1016250
- Description: Breast cancer remains the leading cause of cancer-related death in women worldwide. Furthermore, it has been demonstrated that the treatment-resistant ER-PR-HER2/neu- sub-type is more common among women of African descent, necessitating the search for novel chemotherapies for this form of the disease. The secondary metabolites produced by marine algae represent a rich source of structurally unique compounds with chemotherapeutic potential, particularly in South Africa, whose oceans allegedly host 15 % of the total number of species in the world. Indeed, a recent study reported the isolation of a range of novel compounds from South African red and brown algae of the Plocamium, Portiera and Sargassum genera which displayed cytotoxicity against oesophageal cancer cells in vitro. The molecular mechanisms mediating this toxicity were unknown, as was the effect of these and similar compounds on metastatic ER-PR-HER2/neu- breast cancer cell lines or breast cancer stem cells. The current study aimed to address these questions by screening a library of twenty-two novel marine algal compounds for the ability to inhibit MDA-MB-231 and Hs578T breast cancer cells, while having no adverse effects on non-cancerous MCF12A breast epithelial cells. While twelve of these were toxic in the micromolar range against breast cancer cells, only the polyhalogenated monoterpenes RU004 and RU007, and the tetraprenylated quinone sargaquinoic acid (SQA) were identified as hit compounds based on the criteria that their cytotoxicity was specific to breast cancer and not healthy breast cells in vitro. On the other hand, the halogenated monoterpene RU015 was found to be highly toxic to both breast cancer and non-cancerous breast cell lines, while the halogenated monoterpene stereoisomers RU017 and RU018 were non-toxic to either of these cell lines. The mode of action of RU004, RU007, RU015 and SQA, together with the previously characterized carotenoid fucoxanthin (FXN), was assessed in terms of the type of cell death induced and the effect on cell cycle distribution of these compounds. Flow cytometric analysis of the extent of Hoescht 33342 and propidium iodide staining along with PARP cleavage studies suggested that SQA induced apoptosis in MDA-MB-231 cells. On the other hand, the highly toxic compound RU015 appeared to induce necrosis as evidenced by 50 kDa PARP cleavage product in MDA-MB-231 cells. The flow cytometry profiles of MDA-MB-231 and Hst578T cells treated with the hit compounds RU004 and RU007 were suggestive of the induction of apoptosis by these compounds. Cell cycle analysis by flow cytometry with propidium iodide staining revealed that both SQA and FXN induced G0-G1 arrest together with an increase in the apoptotic sub-G0 population, which agreed with previous reports in the literature. The molecular mechanism of action of SQA and FXN were further investigated by the identification of specific signal transducer molecules involved in mediating their anti-cancer activities. SQA was found to require the activity of numerous caspases, including caspase-3, -6, -8, -9, -10 and -13, for its cytotoxicity and was demonstrated to decrease the level of the antiapoptotic protein Bcl-2. On the other hand, FXN was shown to require caspase-1, -2, -3, -9 and - 10 for its toxicity. This, together with the ability to decrease the levels of Bcl-2, pointed to the involvement of the intrinsic pathway in particular in mediating the activity of FXN. The screening of algal compounds against non-cancerous breast epithelial cells carried out in this study, together with the investigation into their mechanisms of action, represent one of the few reports in which characterization of algal metabolites goes beyond the initial cytotoxicity assays. Finally, in order to assess the potential anti-cancer stem cell activity of the marine algal compounds, a subset of these was screened using a mammosphere assay technique developed in this study. The cancer stem cell (CSC) theory proposes that cancers arise from and are maintained by a specific subpopulation of cells able to undergo asymmetric cell division and termed CSCs. These CSCs are capable of anchorage-independent growth in serum-free culture conditions, such as those in the mammosphere assay. Using this assay, the novel halogenated monoterpene stereoisomers RU017 and RU018 were demonstrated to possess putative anti- CSC activity as evidenced by their ability to completely eliminate mammosphere formation in vitro. Furthermore, since RU017 and RU018 were non-toxic to both breast cancer and healthy breast cells, it appeared that the activity of the compounds was potentially specific to the CSCs. The results require further validation, but represent the first report of selective anti-CSC activity.
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- Date Issued: 2012