No description available.

The principal goal of this work was to synthesise and fully characterise a range of platinum group metal chelates of bis(pyridine-imine) ligands. These four-nitrogen donor Schiff base ligands are underdeveloped relative to their salen (ONNO donor) counterparts. The purified metal complexes were to be tested for their cytotoxicity against cancer cell lines and their mode of interaction (expected to be intercalation) studied. The syntheses, spectroscopic and structural properties of some novel and some already known bis(pyridine-imine) ligands are described. Furthermore, UV-Vis, IR and NMR spectroscopy, as well as electrospray ionisation mass spectrometry, have been used to characterize the ligands and comparisons were made with relevant literature. Fifteen Schiff base ligands were successfully condensed from a 2-formyl or 2-ketopyridine starting material and a diamine bridging group, while the attempted syntheses of a further three are described. Literature methods or variations thereof were employed in the syntheses of these derivatives, which generally resulted in good yields. X-ray quality crystals were obtained and X-ray structures were determined for four novel ligands and five unexpected cyclised hexahydropyrimidine- and imidazole-containing bidentate ligands, of which three were novel structures. The series of bicationic palladium and platinum complexes synthesised here were analysed by NMR, IR and UV-Vis techniques, as well as X-ray crystallography when possible. The complexes were prepared by reacting the free ligands with platinum group metal salts in refluxing acetonitrile. The complexes exhibit infrared bands for the imine C=N stretch between 1604–1670 cm-1; around 15–40 cm-1 lower than the free ligands. The 1H NMR spectra in the CH=N chemical shift region also display shifts (0.1 to 0.8 ppm for the palladium complexes or 0.4 to 0.9 ppm for the platinum complexes) which are consistent with metallation. X-ray crystal structures were obtained for eight novel metal complexes, which all crystallised in the monoclinic crystal system. The solid state analysis shows changes in the free ligands upon introduction of the metal ions, caused by the coordination process. Metallation of the free ligands led to twisting of the ligands due to size effects and the spatial restrictions of the coordination geometry of the central metal ions. The structures were generally solved by direct methods and refined to R1 = 0.0729 or less. Singlecrystal X-ray diffraction analysis confirmed that the mononuclear complexes exhibit a distorted square planar coordination sphere composed of the four donor nitrogen atoms (two imine and two pyridyl nitrogen atoms) from the Schiff base ligands. The complexes were generally very stable and differed by the type of metal ion (platinum(II) or palladium(II)) and the diamine bridging group (2-carbon or 3-carbon linking chain with various substituted groups). A range of unconventional F···H−C contacts is revealed to play an important role in the overall bonding and crystal packing of many complexes. To better understand our measured data and to separate the intrinsic properties of our molecules from intermolecular interactions, theoretical calculations at the DFT (B3LYP) level were carried out. These calculations predict the structural and spectroscopic properties for the free ligands and their metallated counterparts. DFT simulations were performed for the fifteen synthesised ligands (B3LYP functional, 6-31G** basis set), as well as three projected ligands that could not be synthesised, and for all proposed thirtysix metal complexes (B3LYP functional, SDD basis set). DFT simulations were used to obtain theoretical IR frequency data which was compared to the literature and used to prove the location of a local minimum energy structure in the geometry optimisation rather than a transition state. Our results collectively showed the B3LYP level of theory to be useful in the prediction of IR frequencies for these Schiff base ligands as well as the platinum(II) and palladium(II) complexes. Geometry optimisations performed using density functional theory for the free ligands and metal complexes were compared, where possible, with X-ray data. For the free ligands the main structural differences were observed for the position of the pyridyl-imine "arms" of the ligands with relatively good agreement between the two structures for the bridging groups. On the other hand, the metal complexes showed greater discrepancies for the bridging groups rather than for the pyridine rings. These differences were also affected by the length of the carbon bridge; the longer the carbon bridge, the less variation was observed. The trends in the variation of bond distances and angles with the metal ion identity and ligand structure delineated by DFT simulations were matched by similar trends in the X-ray data. Differences between the gas phase calculated geometries and those determined by Xray diffraction were attributed to packing effects in the solid state and intermolecular interactions not being accounted for during DFT computations. The impressive similarity observed between the structures obtained from X-ray crystallography and computed by DFT shows the applicability of these computations at the B3LYP level of theory. They were able to accurately predict structural and spectroscopic properties for the ligands and complexes presented in this work. The in vitro cytotoxicities of some of the metal complexes were evaluated against two mouse cancer cell lines. The compounds tested had lower than expected cytotoxicity towards the cell lines studied with IC50 values > 100 μM. The interaction of the complexes with calf thymus DNA has been explored by using absorption studies. From the observed changes in absorption possible modes of binding to DNA have been proposed for the metal complexes. Significant changes were observed in the absorption spectra upon interaction of the complexes with DNA, from which large binding constants were determined. The changes were, however, not as intense as expected nor were the spectral variations typical of intercalating drugs. There were also no bathochromic shifts nor any isobestic points observed for most of the metal complexes, except one. For the cationic PGM chelates studied, the lack of shift in the wavelength of the visible range MLCT band maximum and small changes in the band intensity were more indicative of weak electrostatic interactions. Our spectral data were thus interpreted as being consistent with non-intercalative binding; either simple electrostatic adduct formation or major/minor groove binding. The binding constant values (Kb) of the metal complexes estimated from the titration with calf thymus DNA monitored by absorption spectroscopy were all in the range of 105 M-1. This is within the range of those reported for other platinum(II) and palladium(II) metal complexes that have shown intercalation and/or groove binding. With the lack of inhibition of growth of the selected cancer cell lines it is possible that the compounds do not reach nuclear DNA in living cells or that such compounds are possibly substrates for efflux transporters. All the metal complexes in this work were determined to not be pure DNA intercalators as had been expected; however, in some cases partial intercalation cannot be ruled out from the spectral data. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

No description available.

No description available.

No description available.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1976. / Bibliography: leaves 203-208. / Microfiche. / xv, 208 leaves ill

Iron (Fe) is a fundamental requirement for life since it is involved in many cellular processes critical for growth and proliferation. Indeed, studies which deplete Fe from neoplastic cells using specific chelating agents result in G1/S arrest and apoptosis. However, the precise role of Fe in the control of the cell cycle remains unclear. Chapter one of this thesis, discusses the potential mechanism(s) by which Fe chelators cause cell cycle arrest and apoptosis. Recent studies have shown that this process involves multiple molecules and is highly complex. Thus, the studies presented in this thesis assess the effects of specific high affinity Fe chelators on the expression of molecules that may play important roles in cellular arrest and apoptosis. The general methodology used in these studies is summarized in chapter 2. In previous investigations Fe chelators such as 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311) were shown to be far more potent anti-tumor agents than the clinically used ligand, desferrioxamine (DFO). Studies detailed in chapter 3, examined the expression of the tumor suppressor protein p53 and the universal cyclindependent kinase inhibitor p21CIP1/WAF1 following Fe-deprivation. To further characterize the effects of chelators on cell cycle arrest, experiments compared their activity to the DNA-damaging agents, actinomycin D (Act D) and cisplatin (CP). The latter two compounds increase the expression of p53 and its target gene p21CIP1/WAF1. Incubation of normal and neoplastic cells with all agents resulted in increased accumulation of nuclear p53, with the effect being more pronounced for Act D and CP. As expected, both Act D and CP markedly increased nuclear p21CIP1/WAF1 protein levels, while DFO and 311 caused a significant (p &lt 0.0004) decrease. This result was surprising, since the WAF1 gene which encodes the universal cyclin dependent kinase inhibitor p21CIP1/WAF1 was markedly up-regulated at the mRNA level following Fe chelation. Proteasomal inhibition studies demonstrated the partial involvement of proteasomes in decreasing nuclear p21CIP1/WAF1 levels following DFO treatment. In contrast, the incubation of 311-treated cells with proteasomal inhibitors did not reverse the down-regulation of p21CIP1/WAF1 when compared to the control. Immunofluorescence experiments showed that only DNA-damaging agents and not Fe chelators increased the nuclear translocation of p21CIP1/WAF1. Collectively, this suggests that the chelators prevented translation of WAF1. Moreover, this decrease in nuclear p21CIP1/WAF1 protein expression did not appear to be due to a general effect in which Fe chelators inhibited mRNA translation since the transferrin receptor 1 was markedly up-regulated (15-21- fold) by DFO or 311. The combination of 311 with Act D or CP prevented the marked p21CIP1/WAF1 nuclear accumulation normally observed in response to these DNAdamaging agents. Significantly, the effect of chelation on reducing nuclear p21CIP1/WAF1 expression was reversed by the Fe-donor, ferric ammonium citrate (FAC), indicating that WAF1 translation was dependent on intracellular Fe levels. This study is the first to demonstrate that Fe chelators markedly up-regulate the mRNA expression of WAF1 but paradoxically inhibit its translation. The down-regulation of p21CIP1/WAF1 protein by chelators may be a novel mechanism by which these ligands cause G1/S arrest through cell cycle dysregulation. In chapter 4, gene arrays were used to assess the expression of molecules associated with cell cycle control and the p53 pathway following the incubation of cells with DFO, 311 or Act D. The N-myc downstream regulated gene 1 (Ndrg1) was the only molecule identified that was specifically up-regulated by Fe chelation and not DNA-damage. Although the exact function of the Ndrg1 protein is unclear, previous studies have shown that this molecule markedly slows down tumor growth (Kurdistani et al. Cancer Res. 1998:58;4439-44) and acts as a potent metastasis suppressor protein (Bandyopadhyay et al. Cancer Res. 2003:63;1731-6). Subsequent experiments examined the mRNA and protein expression of Ndrg1 using reverse-transcriptase PCR (RT-PCR) and Western blot analysis, respectively. Incubation of cells with DFO or 311 resulted in a marked increase in the expression of Ndrg1 mRNA and protein within 3 h and 6 h, respectively. This increase in Ndrg1 after incubation with chelators was not found with their Fe complexes nor when the Fe-binding site had been synthetically inactivated. In addition, the induction of Ndrg1 following Fe chelation was correlated with the ligands??? permeability and anti-proliferative activity. Indeed, the up-regulation of Ndrg1 by Fe chelators can be readily reversed by Fe-repletion. Collectively, this indicates that the induction of Ndrg1 was dependent on intracellular Fe levels. Previous studies demonstrated for the first time that the transactivation of Ndrg1 was dependent on HIF-1?? and p53 stabilization. In contrast, investigations using fibroblasts derived from a HIF-1?? knockout (HIF-1??-KO) mouse demonstrated that the transcriptional upregulation of Ndrg1 following Fe chelation was mediated by a HIF-1??-dependent and - independent mechanism. In addition, subsequent experiments using the p53-deficient H1299 lung carcinoma cell line revealed that the transactivation of Ndrg1 was not dependent on p53 status after Fe-depletion. Collectively, the presented studies suggest that Ndrg1 may be a novel link between Fe metabolism and the control of proliferation. The up-regulation of Ndrg1 by potent Fe chelators is significant and may be beneficial in the prevention of tumor metastasis. In conclusion, this thesis demonstrates that the molecular mechanisms behind the G1/S arrest and apoptosis involved multiple molecules following Fe chelation. Indeed, this study shows a potential mechanism by which Fe chelators may cause cell cycle dysregulation through the down-regulation of nuclear p21CIP1/WAF1 protein levels. In addition, the work presented identifies the up-regulation of the metastasis suppressor protein, Ndrg1, following Fe-deprivation. Collectively, the results indicate that potent Fe chelators can not only be used as anti-proliferative agents, but may also be beneficial at inhibiting tumor cell metastasis.

Iron (Fe) is a fundamental requirement for life since it is involved in many cellular processes critical for growth and proliferation. Indeed, studies which deplete Fe from neoplastic cells using specific chelating agents result in G1/S arrest and apoptosis. However, the precise role of Fe in the control of the cell cycle remains unclear. Chapter one of this thesis, discusses the potential mechanism(s) by which Fe chelators cause cell cycle arrest and apoptosis. Recent studies have shown that this process involves multiple molecules and is highly complex. Thus, the studies presented in this thesis assess the effects of specific high affinity Fe chelators on the expression of molecules that may play important roles in cellular arrest and apoptosis. The general methodology used in these studies is summarized in chapter 2. In previous investigations Fe chelators such as 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311) were shown to be far more potent anti-tumor agents than the clinically used ligand, desferrioxamine (DFO). Studies detailed in chapter 3, examined the expression of the tumor suppressor protein p53 and the universal cyclindependent kinase inhibitor p21CIP1/WAF1 following Fe-deprivation. To further characterize the effects of chelators on cell cycle arrest, experiments compared their activity to the DNA-damaging agents, actinomycin D (Act D) and cisplatin (CP). The latter two compounds increase the expression of p53 and its target gene p21CIP1/WAF1. Incubation of normal and neoplastic cells with all agents resulted in increased accumulation of nuclear p53, with the effect being more pronounced for Act D and CP. As expected, both Act D and CP markedly increased nuclear p21CIP1/WAF1 protein levels, while DFO and 311 caused a significant (p &lt 0.0004) decrease. This result was surprising, since the WAF1 gene which encodes the universal cyclin dependent kinase inhibitor p21CIP1/WAF1 was markedly up-regulated at the mRNA level following Fe chelation. Proteasomal inhibition studies demonstrated the partial involvement of proteasomes in decreasing nuclear p21CIP1/WAF1 levels following DFO treatment. In contrast, the incubation of 311-treated cells with proteasomal inhibitors did not reverse the down-regulation of p21CIP1/WAF1 when compared to the control. Immunofluorescence experiments showed that only DNA-damaging agents and not Fe chelators increased the nuclear translocation of p21CIP1/WAF1. Collectively, this suggests that the chelators prevented translation of WAF1. Moreover, this decrease in nuclear p21CIP1/WAF1 protein expression did not appear to be due to a general effect in which Fe chelators inhibited mRNA translation since the transferrin receptor 1 was markedly up-regulated (15-21- fold) by DFO or 311. The combination of 311 with Act D or CP prevented the marked p21CIP1/WAF1 nuclear accumulation normally observed in response to these DNAdamaging agents. Significantly, the effect of chelation on reducing nuclear p21CIP1/WAF1 expression was reversed by the Fe-donor, ferric ammonium citrate (FAC), indicating that WAF1 translation was dependent on intracellular Fe levels. This study is the first to demonstrate that Fe chelators markedly up-regulate the mRNA expression of WAF1 but paradoxically inhibit its translation. The down-regulation of p21CIP1/WAF1 protein by chelators may be a novel mechanism by which these ligands cause G1/S arrest through cell cycle dysregulation. In chapter 4, gene arrays were used to assess the expression of molecules associated with cell cycle control and the p53 pathway following the incubation of cells with DFO, 311 or Act D. The N-myc downstream regulated gene 1 (Ndrg1) was the only molecule identified that was specifically up-regulated by Fe chelation and not DNA-damage. Although the exact function of the Ndrg1 protein is unclear, previous studies have shown that this molecule markedly slows down tumor growth (Kurdistani et al. Cancer Res. 1998:58;4439-44) and acts as a potent metastasis suppressor protein (Bandyopadhyay et al. Cancer Res. 2003:63;1731-6). Subsequent experiments examined the mRNA and protein expression of Ndrg1 using reverse-transcriptase PCR (RT-PCR) and Western blot analysis, respectively. Incubation of cells with DFO or 311 resulted in a marked increase in the expression of Ndrg1 mRNA and protein within 3 h and 6 h, respectively. This increase in Ndrg1 after incubation with chelators was not found with their Fe complexes nor when the Fe-binding site had been synthetically inactivated. In addition, the induction of Ndrg1 following Fe chelation was correlated with the ligands??? permeability and anti-proliferative activity. Indeed, the up-regulation of Ndrg1 by Fe chelators can be readily reversed by Fe-repletion. Collectively, this indicates that the induction of Ndrg1 was dependent on intracellular Fe levels. Previous studies demonstrated for the first time that the transactivation of Ndrg1 was dependent on HIF-1?? and p53 stabilization. In contrast, investigations using fibroblasts derived from a HIF-1?? knockout (HIF-1??-KO) mouse demonstrated that the transcriptional upregulation of Ndrg1 following Fe chelation was mediated by a HIF-1??-dependent and - independent mechanism. In addition, subsequent experiments using the p53-deficient H1299 lung carcinoma cell line revealed that the transactivation of Ndrg1 was not dependent on p53 status after Fe-depletion. Collectively, the presented studies suggest that Ndrg1 may be a novel link between Fe metabolism and the control of proliferation. The up-regulation of Ndrg1 by potent Fe chelators is significant and may be beneficial in the prevention of tumor metastasis. In conclusion, this thesis demonstrates that the molecular mechanisms behind the G1/S arrest and apoptosis involved multiple molecules following Fe chelation. Indeed, this study shows a potential mechanism by which Fe chelators may cause cell cycle dysregulation through the down-regulation of nuclear p21CIP1/WAF1 protein levels. In addition, the work presented identifies the up-regulation of the metastasis suppressor protein, Ndrg1, following Fe-deprivation. Collectively, the results indicate that potent Fe chelators can not only be used as anti-proliferative agents, but may also be beneficial at inhibiting tumor cell metastasis.

Iron (Fe) is a fundamental requirement for life since it is involved in many cellular processes critical for growth and proliferation. Indeed, studies which deplete Fe from neoplastic cells using specific chelating agents result in G1/S arrest and apoptosis. However, the precise role of Fe in the control of the cell cycle remains unclear. Chapter one of this thesis, discusses the potential mechanism(s) by which Fe chelators cause cell cycle arrest and apoptosis. Recent studies have shown that this process involves multiple molecules and is highly complex. Thus, the studies presented in this thesis assess the effects of specific high affinity Fe chelators on the expression of molecules that may play important roles in cellular arrest and apoptosis. The general methodology used in these studies is summarized in chapter 2. In previous investigations Fe chelators such as 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311) were shown to be far more potent anti-tumor agents than the clinically used ligand, desferrioxamine (DFO). Studies detailed in chapter 3, examined the expression of the tumor suppressor protein p53 and the universal cyclindependent kinase inhibitor p21CIP1/WAF1 following Fe-deprivation. To further characterize the effects of chelators on cell cycle arrest, experiments compared their activity to the DNA-damaging agents, actinomycin D (Act D) and cisplatin (CP). The latter two compounds increase the expression of p53 and its target gene p21CIP1/WAF1. Incubation of normal and neoplastic cells with all agents resulted in increased accumulation of nuclear p53, with the effect being more pronounced for Act D and CP. As expected, both Act D and CP markedly increased nuclear p21CIP1/WAF1 protein levels, while DFO and 311 caused a significant (p &lt 0.0004) decrease. This result was surprising, since the WAF1 gene which encodes the universal cyclin dependent kinase inhibitor p21CIP1/WAF1 was markedly up-regulated at the mRNA level following Fe chelation. Proteasomal inhibition studies demonstrated the partial involvement of proteasomes in decreasing nuclear p21CIP1/WAF1 levels following DFO treatment. In contrast, the incubation of 311-treated cells with proteasomal inhibitors did not reverse the down-regulation of p21CIP1/WAF1 when compared to the control. Immunofluorescence experiments showed that only DNA-damaging agents and not Fe chelators increased the nuclear translocation of p21CIP1/WAF1. Collectively, this suggests that the chelators prevented translation of WAF1. Moreover, this decrease in nuclear p21CIP1/WAF1 protein expression did not appear to be due to a general effect in which Fe chelators inhibited mRNA translation since the transferrin receptor 1 was markedly up-regulated (15-21- fold) by DFO or 311. The combination of 311 with Act D or CP prevented the marked p21CIP1/WAF1 nuclear accumulation normally observed in response to these DNAdamaging agents. Significantly, the effect of chelation on reducing nuclear p21CIP1/WAF1 expression was reversed by the Fe-donor, ferric ammonium citrate (FAC), indicating that WAF1 translation was dependent on intracellular Fe levels. This study is the first to demonstrate that Fe chelators markedly up-regulate the mRNA expression of WAF1 but paradoxically inhibit its translation. The down-regulation of p21CIP1/WAF1 protein by chelators may be a novel mechanism by which these ligands cause G1/S arrest through cell cycle dysregulation. In chapter 4, gene arrays were used to assess the expression of molecules associated with cell cycle control and the p53 pathway following the incubation of cells with DFO, 311 or Act D. The N-myc downstream regulated gene 1 (Ndrg1) was the only molecule identified that was specifically up-regulated by Fe chelation and not DNA-damage. Although the exact function of the Ndrg1 protein is unclear, previous studies have shown that this molecule markedly slows down tumor growth (Kurdistani et al. Cancer Res. 1998:58;4439-44) and acts as a potent metastasis suppressor protein (Bandyopadhyay et al. Cancer Res. 2003:63;1731-6). Subsequent experiments examined the mRNA and protein expression of Ndrg1 using reverse-transcriptase PCR (RT-PCR) and Western blot analysis, respectively. Incubation of cells with DFO or 311 resulted in a marked increase in the expression of Ndrg1 mRNA and protein within 3 h and 6 h, respectively. This increase in Ndrg1 after incubation with chelators was not found with their Fe complexes nor when the Fe-binding site had been synthetically inactivated. In addition, the induction of Ndrg1 following Fe chelation was correlated with the ligands??? permeability and anti-proliferative activity. Indeed, the up-regulation of Ndrg1 by Fe chelators can be readily reversed by Fe-repletion. Collectively, this indicates that the induction of Ndrg1 was dependent on intracellular Fe levels. Previous studies demonstrated for the first time that the transactivation of Ndrg1 was dependent on HIF-1?? and p53 stabilization. In contrast, investigations using fibroblasts derived from a HIF-1?? knockout (HIF-1??-KO) mouse demonstrated that the transcriptional upregulation of Ndrg1 following Fe chelation was mediated by a HIF-1??-dependent and - independent mechanism. In addition, subsequent experiments using the p53-deficient H1299 lung carcinoma cell line revealed that the transactivation of Ndrg1 was not dependent on p53 status after Fe-depletion. Collectively, the presented studies suggest that Ndrg1 may be a novel link between Fe metabolism and the control of proliferation. The up-regulation of Ndrg1 by potent Fe chelators is significant and may be beneficial in the prevention of tumor metastasis. In conclusion, this thesis demonstrates that the molecular mechanisms behind the G1/S arrest and apoptosis involved multiple molecules following Fe chelation. Indeed, this study shows a potential mechanism by which Fe chelators may cause cell cycle dysregulation through the down-regulation of nuclear p21CIP1/WAF1 protein levels. In addition, the work presented identifies the up-regulation of the metastasis suppressor protein, Ndrg1, following Fe-deprivation. Collectively, the results indicate that potent Fe chelators can not only be used as anti-proliferative agents, but may also be beneficial at inhibiting tumor cell metastasis.

Thesis (Ph. D.)--University of New South Wales, 2004. / Also available online.