| dc.description.abstract | One of the novel treatments of cancer is to use USPIONs to create reactive oxidative stress on the cancer cells. However, there was no research of this nanoparticle on Glioblastoma Multiforme (GBM), which is the most common and lethal brain tumour. The key feature of these nanoparticles is their high stability and relaxivity, so that we can visualize the distribution of nanoparticles in high contrast using magnetic resonance imaging (MRI) (Eamegdool et al., 2014). Thus, we can track the distribution of the anti-neoplastic drugs tagged USPIONs in the GBM of the brain. This could also be applicable for tracking human neural precursor cells (hNPCs) for stem cell therapy. Therefore, my PhD study has focused on how USPIONs will affect the biological functions of hNPCs and GBM cells in vitro. To assess this, we have measured the cell viability, heat shock protein (HSP) protective mechanism, cytotoxicity, migration, proliferation, mitochondrial potentials, and various biological functions of hNPCs and GBM cells exposed to USPIONs. This project has also provided insights into the mechanism of entry and the cellular interaction of USPIONs on hNPCs and GBM cells.
With the ubiquitous presence of nanoparticles (NPs) in the environment and the extensive application of iron oxide nanoparticles in industry and medical applications, hNPCs were utilized to represent a normal, healthy neuronal cell model to examine potential cytotoxicity induced by USPIONs. While the cytotoxic effect of USPIONs on GBM cells could provide valuable insights into cancer treatments by targeting the heat shock protein (HSP) protective pathways.
In Chapter 2, we have observed that USPIONs entered the hNPCs through clathrin-mediated endocytosis using transmission electron microscopy (TEM) and dynasore which is an inhibitor of clathrin-dependent endocytosis. This data has shown that USPIONs localized within vesicles of the cytoplasm, and some USPIONs were proximal to the mitochondria. It was also found that continuous exposure to a high dosage (20 μg/mL) of USPIONs could induce a Fenton-like reaction, which potentially induced reactive oxygen species (ROS) and protein misfolding. Following, mitochondrial dysfunctions including mitochondrial membrane depolarization, mitochondrial permeability transition pore (mPTP) opening, cytochrome c (Cyt c) release and calcium dysfunction were detected. Although HSP protective mechanism was shown to be involved to compact the toxicity of USPIONs, this protective mechanism was overwhelmed at a later stage of exposure as evident by the increase in nitric oxide (NO) and disruption of the bioenergetic profile from 16 hr. Following, Caspase 3/7 activation and a reduction in cell viability were detected at 24 hr. Taken together, these findings have provided valuable insights to assess possible cytotoxicity and safe dosage of USPIONs before the application of tracking hNPCs using MRI.
In Chapter 3, we have shown the potential cytotoxicity of USPIONs on CNS-1 cells, a rat GBM model with infiltrative and growth patterns similar to human gliomas. This study has demonstrated that exposure to 20 μg/mL USPIONs could induce oxidative stress in CNS-1 cells, activating the HSP protective response mechanism, which was later overwhelmed, causing a reduction in cell viability at 12 hr. In due course, HSPs were then upregulated, re-activating the HSP protective mechanisms and eventually cell viability similar to control was detected. Therefore, by targeting this HSP protective mechanism in CNS-1 cells and the cytotoxicity induced by high dosage of USPIONs exposure, this could provide insights into novel cancer therapeutics for GBM.
In Chapter 4, we have investigated the cellular interaction of the co-administration of 20 μg/mL USPIONs, HSP inhibitors, deferoxamine (DFO), ironomycin (AM5) and Bafilomycin A1 in B30, primary GBM cells. The results have shown that the co-administration of Bafilomycin, HSP70 inhibitor and USPIONs could cause lysosomal dysfunction. In addition, HSP90 inhibitor along with USPIONs, DFO, AM5 and Bafilomycin induce the greatest reduction in autophagy. Taken together, the findings from this chapter have contributed to new understandings of the usage of USPIONs, HSP inhibitors, DFO, AM5 and Bafilomycin for magnetic hyperthermia therapy, autophagic pathways-targeted toxicity and other therapeutic interventions for GBM treatments.
This thesis has compared the cytotoxic effects of high dosage (20 μg/mL) exposure of USPIONs to hNPCs, CNS-1 cells and primary B30 cells. In addition, the results have shown that the amount of USPIONs uptake is the least in hNPCs, followed by CNS-1 cells and then primary B30 cells. While cytotoxicity affecting the mitochondrial functions are seen across all three models, HSP protective mechanisms were involved in protecting the cells from further cellular insults induced by USPIONs. Thus, targeting the HSP protective mechanisms along with the multiple cellular stress and cytotoxicity induced by USPIONs could provide insights into novel anti-cancer therapy. | en_AU |
