4. Electronic Theses and Dissertations (ETDs) - Faculties submissions
Permanent URI for this communityhttps://hdl.handle.net/10539/37773
Browse
2 results
Search Results
Item Insights into silver(I) phosphine complexes in targeting cell death and metastatic mechanisms in malignant cell lines(University of the Witwatersrand, Johannesburg, 2023-09) Roberts, Kim Elli; Engelbrecht, Zelinda; Cronjé, Marianne J.Cancer is the leading cause of death worldwide, with 18.1 million new cases and 9.6 million deaths reported annually. Cisplatin, a popular chemotherapeutic drug, exhibits certain limitations in terms of selectivity and efficacy. This emphasizes the necessity for novel therapeutic approaches in addressing a variety of cancer types. Multiple studies have shown that silver-based compounds suppress cancer cell proliferation and induce apoptosis. Thirteen novel silver(I) mono-dentate phosphine complexes were investigated for their anticancer effects on seven different human malignant cell lines; A375 non-pigmented melanoma, A549 lung adenocarcinoma, HEP-G2 hepatocellular carcinoma, HT-29 colorectal adenocarcinoma, MCF-7 and MDA-MB-231 breast adenocarcinoma, and SNO oesophageal squamous cell carcinoma. Two non-malignant human cell lines, HEK-293 embryonic kidney cells and MRHF foreskin fibroblast cells, were used to assess the selectivity of the complexes. Cisplatin and the efficient silver(I) phosphine complexes were selected for dose-response experiments to determine IC50 concentrations for the respective cell lines. On the basis of these screening results (chapter two), five difficult-to-treat cancer cell lines, and their most efficient complexes were selected for further investigation. Various cellular characteristics were investigated in chapter three (A549, HEP-G2, HT-29); these included morphological changes, ATP levels, GAPDH levels, Ptd-L-Ser externalization, mitochondrial membrane potential, oxidative stress levels, and the activity of a metabolic enzyme, cytochrome P450 isoform CYP1B1. The antimetastatic activity of the selected complexes was assessed by evaluating their ability to impede the migration of A549 cells. The fourth chapter examines the anticancer effect of selected complexes on hormone-dependent (MCF-7) versus triple-negative (MDA-MB-231) breast cells. Changes in morphology, Ptd-L-Ser externalization, alterations in mitochondrial membrane potential, oxidative stress levels, cytochrome c release, and DNA damage were studied. Furthermore, in chapter five, molecular docking simulations were used to determine whether the most potent silver(I) phosphine complex across all cell lines bonds to estrogen receptor alpha (ER-α) and estrogen receptor beta (ER-β). Seven of the thirteen silver(I) phosphine complexes significantly reduced cell viability in malignant cell lines while being less toxic to non-malignant cells. Complex 4 best targeted all cancer types, with IC50 values ranging from 5.75 to 10.80 µM across malignant cell lines. In the malignant treated cells, morphological changes, reactive oxygen species production, mitochondrial membrane depolarization, and Ptd-L-Ser externalization were observed. Complexes 1 and 4 repressed cell migration in the A549 cells. The presence of damaged nuclei, metabolically inactive mitochondria and cytochrome c translocation from the mitochondria’ intermembrane to the cytosol in MCF-7 cells were observed. These findings suggest that complexes 2, 4 and 7 induced apoptotic cell death. Furthermore, in silico computational predictions suggested a promising interaction between complex 4, and ER-α and ER-β. Overall, this study demonstrates the potential of silver(I) phosphine complexes as anticancer agents, with promising effects on various cancer cell lines.Item Synthesis, characterization and investigation of the mode of action in the anticancer activity of novel platinum complexes(University of the Witwatersrand, Johannesburg, 2024) Peega, Tebogo; Harmse, Leonie; Kotzé, Izak. A.Cancer remains a global health concern, causing approximately 10 million deaths in 2020. Lung cancer, accounting for 18% of cancer-related deaths, and colorectal cancer, contributing 9.4%, are major contributors to this alarming statistic, emphasizing the urgent need for innovative and effective treatment options. Despite the success of platinum-based drugs such as cisplatin, carboplatin, and oxaliplatin, their limitations and severe adverse effects necessitate the exploration of alternative chemotherapeutic agents. This research project focused on synthesizing and characterizing square planar platinum(II) complexes bearing variations of two bidentate coordinating ligands; disubstituted acylthiourea and diimine ligands, each possessing unique physical and chemical properties. A series of cationic [Pt(diimine)(Ln-κO,S)]Cl complexes were successfully synthesized and characterized using nuclear magnetic resonance spectroscopy, infrared spectroscopy, mass spectrometry, and elemental analysis. The anticancer activity of these complexes was evaluated against two lung cancer cell lines, A549 and H1975, and a colorectal cancer cell line, HT-29. In vitro cytotoxicity studies included the determination of IC50 values of active complexes and assessing their cell death mechanisms through multiple biochemical marker assays. These included annexin-V binding, caspase-3/7 and caspase-8 activity, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and immunofluorescence for the expression of key proteins involved in the DNA damage response and oxidative stress response, such as p21 and haemoxygenase-1 (HO-1). A proteome array was employed to investigate the effects on apoptosis-associated proteins. The results indicated that these platinum complexes were more cytotoxic than cisplatin with IC50 values ranging between 0.68 μM and 2.28 μM. Further investigation showed that the platinum complexes induced cell stress, chromatin condensation, nuclear fragmentation, increased phosphatidylserine (PS) on the outer cell membranes and activated caspase-3/7. Platinum complexes induced intrinsic apoptosis in cancer cells, as evidenced by the loss of mitochondrial membrane potential and the absence of caspase-8 activity. Elevated ROS levels, increased HO-1 expression and increased expression of p21 suggested oxidative stress and DNA damage as the trigger source for intrinsic apoptotic cell death. The active complexes downregulated pro-survival proteins (IGFs) in lung cancer cells and anti-apoptotic proteins (survivin and HSP70) and upregulated pro-apoptotic proteins (p21, TRAIL R2), across the three cancer cell lines, indicating potential dual activation of apoptotic pathways. DNA binding studies indicated groove binding and intercalation as the mode of interaction with DNA. The findings highlight the potential of these platinum complexes as promising candidates for further development as cancer therapeutics.