| Summary: | Thesis (M.Sc.)--Memorial University of Newfoundland, 2001. Medicine Bibliography: leaves 123-154 The possible role of endonuclease and protein synthesis inhibition by aurin tricarboxylic acid (ATA) and by cycloheximide (CHX) respectively was investigated in sanguinarine induced apoptosis (PCD) and blister cell death (BCD) in K562 erythroleukemia cells. -- Studies in our laboratory have consistently shown that when K562 cells are treated with sanguinarine - a quaternary benzophenanthridine alkaloid which is reported to inhibit protein kinase C and nuclear factor NF-κB, at concentrations of 1.5 μg/ml for 2hrs induced the morphology of PCD, and at concentrations of 12.5 μg/ml for 2 hrs the morphology of BCD (blister formation). This phenomenon of dual cell death modality was termed "bimodal cell death" or BMCD (Liepins et al., 1996). -- The role of endonuclease activity and protein synthesis in PCD and BCD was assessed by the capacity of ATA and CHX respectively, to inhibit these processes. This was investigated by pretreating cells with ATA and CHX prior to sanguinarine treatment and subsequently measuring their effects on bimodal cell death using a host of standard methods: light microscopy and quantitative morphology; electron microscopy; terminal dUTP mediated nick end labelling (TUNEL) assay; annexin V binding assay (fluorescence microscopic and flow cytometric analysis); 51Cr release assay; DNA content analysis by flowcytometry; oxygen consumption studies; trypan blue assay. Results show that, while ATA pretreatment of cells inhibited PCD almost completely and BCD by 30-40%, CHX pretreatment failed to inhibit PCD and BCD. This may indicate the importance of endonuclease in sanguinarine induced PCD and to some extent in BCD. This may also signify the importance of post-translational modification of proteins rather than their de novo synthesis in both these forms of cell death. -- Discovering new drugs and understanding their mechanisms of action may lead to more effective administration of these agents with other more established therapeutics in the treatment of cancer. To this end, better understanding the mechanism of PCD and identifying novel forms of cell death like BCD, would contribute in no small measure.
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