AuthorLawson, Kathryn René
Health Sciences, Pharmacology.
Health Sciences, Pathology.
AdvisorGerner, Eugene W.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractMaintenance of optimal polyamine pool levels is critical for cell survival. Intracellular polyamine depletion is usually cytostatic, whereas unregulated polyamine accumulation can result in cytotoxicity. The purpose of this work was to examine the importance of polyamine depletion in cell survival, either through increased polyamine catabolism or decreased polyamine synthesis. The polyamine analogue CHENSpm, which induces apoptosis in several cell lines, was used to examine the role of polyamine catabolism in cell survival. The susceptibility of Chinese hamster ovary cells and HCT 116 human colon cells to CHENSpm-mediated toxicity was inversely correlated with the level of polyamine oxidase (PAO) activity present in each cell type. Chinese hamster ovary cells (CHO), which contained high levels of PAO, were not growth inhibited by CBENSpm, however concomitant PAO inhibition led to a moderate growth suppression. The inhibition of the diamine exporter (DAX) in addition to PAO led to a CHENSpm-mediated cytotoxic response that was manifested as apoptosis induction. HPLC analysis of CHENSpm- treated CHO cell extracts revealed the presence of an unidentified amine that was not present when PAO was inhibited. This suggests that PAO is able to utilize CHENSpm as a substrate, and that this metabolism protects cells from CHENSpm-mediated cytotoxicity. The effect of polyamine depletion in apoptosis induced by the non-steroidal anti-inflammatory drug (NSAID) sulindac was examined in cells harboring an activated Ki-ras. Cells overexpressing Ki-ras underwent an accelerated apoptosis induction with either metabolite of sulindac, however overall toxicity was unaffected in long-term survival assays. DFMO did not affect apoptosis induction by sulindac sulfone, nor did it increase sulindac sulfone toxicity in long-term survival studies. DFMO alone was selectively cytotoxic to Ki-ras transfected clones in a dose-dependent manner. Ki-ras transfection increased c-myc expression, but had no effect on ODC steady-state mRNA levels. The downregulation of N1-spermidine/spermine acetyltransferase (SSAT) seen in Ki-ras transfected cells suggests polyamine, catabolism may protect cells from DFMO-induced cytotoxicity. These studies demonstrate that polyamine, catabolism may play an important role in cell survival under conditions of suboptimal polyamine levels.
Degree ProgramGraduate College