Platinum-based anticancer drugs such as cisplatin, carboplatin and nedaplatin have been widely used in the chemotherapy of a variety of solid tumours for several decades. However, the development of both inherent and acquired resistance has greatly limited the efficacy of all of these drugs. Several mechanisms were proposed to explain the cellular resistance to these platinum drugs, including decreased drug accumulation. Previously, it was suggested that cisplatin enters cells via passive diffusion, followed by intracellular hydrolysis and activation prior to targeting DNA. However, recent in vivo and in vitro studies confirmed that transporters and carriers involved in copper homeostasis play important roles on the transport as well as cellular resistance to the platinum drugs. CTR1, a major plasma-membrane transporter involved in intracellular copper(I) homeostasis, was found to facilitate the uptake of several platinum drugs although the molecular mechanism remains unclear. The extracellular N-terminal domain of human CTR1 (hCTR1) with two methionine(Met)-rich and two histidine(His)-rich motifs has been proved to be essential for the uptake of both copper and platinum drugs by the transporter. In this thesis, the extracellular domain of hCTR1 (hCTR1_N, residues 1-55) was overexpressed and the role of the Met- and His-rich motifs on cisplatin binding was examined by either mutagenesis or chemical modification. Cisplatin was found to directly and rapidly bind to the Met residues of hCTR1_N by the formation of monofunctional cisplatin-thioether adducts. The kinetics of the binding process was found to correlate with the number of Met residues, indicating that all Met residues are exposed to solvents and capable for cisplatin binding. Such a non-sequence-specific binding may increase the likelihood of capturing the anticancer drug in extracellular fluid by the N-terminus of hCTR1. The effect of hCTR_N on the binding and activation of second-generation platinum anticancer drugs, e.g. carboplatin and nedaplatin, were subsequently investigated. hCTR1_N was found to significantly facilitate the activation of these platinum drugs by the formation of ring-opened monofunctional Pt-thioether species through Met residues. Although the activities of platinum drugs against hCTR1_N are significantly different, their monofunctional protein-bound species demonstrated great similarity in both structure and kinetic aspects, suggesting the uptake of these platinum drugs by hCTR1 might follow the same mechanism. The formation of active ring-opened species of carboplatin and nedaplatin by chloride/bicarbonate was observed, indicating these nucleophiles may play a critical role in the pre-activation of the drugs prior to their reaching cellular targets. Pt-thioether species were proposed as intermediates for the platination of other biomolecules. The monofunctional cisplatin adduct of hCTR1_N was proved to further transfer its active platinum species to either cysteine- or guaninecontaining biomolecules which mimic the C-ternimus of hCTR1 and DNA. Methionine residues of hCTR1 may therefore serve as key residues for the activation and transport of platinum anticancer drugs in the form of monofunctional Pt-thioether species through the pole of trimeric hCTR1 and eventually to their final target – DNA. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

The structural elucidations of nine new natural products from Thevetia ahouia, Eremocarpus setigerus, Trichilia hispida, Chrysothamus paniculatus, Uvaria acuminata, Wikstroemia monticola, and Uvaria zelanica are discussed in detail. Also included are some known compounds that were found in these plants. Of the new compounds discussed, two are diterpenes (eremone, chrysothame), two are relatively simple triterpenes (hispidols A, B), two are highly oxidized triterpenes (hispidins A, B), one is a fatty acid derivative (uvaricin), one is a shikimate-derived metabolite (1-epizeylenol), and one has both steroidal and carbohydrate features (3'-OMe-evomonoside). ¹H and ¹³C NMR spectral data are given for all the new compounds. Assignments were made by analogy with model compounds, computer simulation, and ¹H-¹H and ¹H-¹³C decoupling where indicated. High resolution mass spectral fragmentations are given for most of the new compounds, and individual structural assignments made for intense peaks. An X-ray analysis (eremone) was done with all pertinent information included. Most of the compounds have been tested for anti-tumor activity, and several exhibit strong cytotoxicity (hispidins A and B, 3'-OMe-evomonoside, huratoxin, uvaricin).

No description available.

No description available.

No description available.

The most promising therapy for cytomegalovirus (CMV) disease focuses on enhancing the patient’s immunity to viral pathogens. In this investigation, the therapeutic efficacy of bulk-cultured cytotoxic T lymphocytes was examined in primary murine cytomegalovirus infection. Virus-specific cytotoxic T cells (CTL( were generasted using immune spleen cells stimulated with irradiated murine CMV-infected cells. These CTL demonstrated significant cytolytic activity in a chromium-release assay. They were administered to mice infected with a lethal dose of murine CMV. The group receiving 107 CTL had a 50% reduction of mortality and lost 10% less weight. Virus titer of mice who received 107 CTL decreased 10 fold in the lungs and spleen and decreased 100 fold in the salivary gland. However, the therapy failed to decrease serum aminotransferase levels or restore lymphocyte blastogenic responsiveness. Although the mechanism is unclear, this therapy was effective in reducing mortality, morbidity, and virus titer in select organs. / Center for Medical Education

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.