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Several chemically-modified analogues of α-melanotropin (α-MSH, Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH₂) were prepared by solid-phase peptide synthesis, including [Nle⁴]-α-MSH, Ac-[Nle⁴]-α-MSH₄₋₁₃-NH₂, Ac-[Nle⁴]-α-MSH₁₋₆-NH₂, Ac-α-MSH₇₋₁₀-NH₂, Ac-α-MSH₁₁₋₁₃-NH₂, Ac-[Nle⁴]-α-MSH(,4-10)-NH₂, Ac-[Nle⁴, D-Phe⁷]-α-MSH₄₋₁₀-NH₂, [Nle⁴, D-Phe⁷]-α-MSH, Ac-α-MSH₄₋₁₀-NH₂, Ac-[Tyr⁴]-α-MSH₄₋₁₀-NH₂ and [half-Cys⁴, half-Cys¹⁰]-α-MSH. The synthetic strategy involved: (1) p-methylbenzhydrylamine resin as a solid support, (2) N,N'-dicyclohexylcarbodiimide as a coupling reagent, (3) acetylation of the N-terminus and HF cleavage and deprotection (except for Nⁱ-For-Trp) of the fully assembled peptide-resin and (4) alkaline hydrolysis to deformylate Nⁱ-For-Trp. In the preparation of [half-Cys⁴, half-Cys¹⁰]-α-MSH, oxidative-cyclization provided formation of an intramolecular disulfide bridge. A comparative biological analysis in vitro of these above structural, stereoisomeric and conformationally-restricted analogues of α-MSH on several different vertebrate pigment cell systems provided the following results: (1) The [Nle⁴, D-Phe⁷]-α-MSH effected high melanotropic potency (> 60 times relative to α-MSH), ultralong biological activity and unprecedented metabolic stability. (2) Utilizing [Nle⁴, D-Phe⁷]-α-MSH as a molecular probe, two melanotropic receptor types were demonstrated which were mechanistically different in terms of calcium dependency and apparent hormone-receptor complex reversibility. (3) The Ac-[Nle⁴, D-Phe⁷]-α-MSH₄₋₁₀-NH₂ was a highly potent active site (Met-Glu-His-Phe-Arg-Trp-Gly) analogue of α-MSH (ranging from 0.2- to 10-times relative to α-MSH) without the ultralong melanotropic activity possessed by the parent stereostructural tridecapeptide. (4) The [half-Cys4, half-Cys10]-α-MSH exhibited superpotency on frog (Rana pipiens) melanophores (≥ 10,000 times relative to α-MSH), and provided experimental evidence that a pseudocyclic conformation of the native hormone containing a β-turn structural requirement at His-Phe-Arg-Trp might be related to its biological activity at the pigment cell receptor. The [Nle⁴, D-Phe⁷]-α-MSH may be suitable for use as a radio-labeled tracer or drug-delivery agent for the localization or treatment of human melanoma in vivo.

Yeung Chung Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 83-97). / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (Chinese) --- p.iv / Acknowledgements --- p.vii / Table of contents --- p.ix / List of figures --- p.xii / List of tables --- p.xiv / List of abbreviations --- p.xv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- General Introduction --- p.1 / Chapter 1.2 --- Literature Review --- p.5 / Chapter 1.2.1 --- Cancer and melanoma --- p.5 / Chapter 1.2.2 --- Anticancer drugs from natural products --- p.6 / Chapter 1.2.3 --- Challenges in treatment of melanoma --- p.9 / Chapter 1.2.4 --- TCM - New source of natural products for cancer therapy --- p.10 / Chapter 1.2.6 --- The genus Schefflera --- p.11 / Chapter 1.2.7 --- Anticancer activities of triterpenoids --- p.16 / Chapter 1.2.8 --- Cancer and apoptosis --- p.17 / Chapter 1.2.8.1 --- The Apoptosis Pathways --- p.20 / Chapter 1.2.9 --- Studies of anticancer molecules against melanoma --- p.26 / Chapter 1.2.9.1 --- In vitro models for studying anticancer molecules --- p.26 / Chapter 1.2.9.2 --- In vivo models for studying anticancer molecules --- p.30 / Chapter Chapter 2 --- Materials and Methods --- p.34 / Chapter 2.1 --- Phytochemicals --- p.34 / Chapter 2.2 --- "Chemicals, Cell Lines and Culture Conditions" --- p.34 / Chapter 2.3 --- Determination of in vitro antiproliferative effects of HLDA and the ethyl acetate fraction from S. heptaphylla on human cancer cells --- p.36 / Chapter 2.3.1 --- MTT assay --- p.36 / Chapter 2.4 --- Determination of the in vitro antiproliferative mechanisms of HLDA and the ethyl acetate fraction from S. heptaphylla in human melanoma A375 cells --- p.37 / Chapter 2.4.1 --- Flow cytometric analysis --- p.37 / Chapter 2.4.2 --- Western blot analysis --- p.38 / Chapter 2.5 --- Determination of the in vivo anticancer effects of the ethyl acetate fraction from S. heptaphylla --- p.41 / Chapter 2.5.1 --- Determination of cancer chemopreventive effect of the ethyl acetate fraction with DMBA/TPA-induced skin carcinogenesis model --- p.41 / Chapter 2.5.2 --- Determination of cancer therapeutic effect of the ethyl acetate fraction with athymic BALB/c nude mice model --- p.42 / Chapter 2.6 --- Statistical Analysis --- p.44 / Chapter Chapter 3 --- Results --- p.45 / Chapter 3.1 --- Effects of HLDA and the ethyl acetate fraction on viability and proliferation of different cancer cell lines by MTT assay --- p.45 / Chapter 3.2 --- Effects of HLDA and the ethyl acetate fraction on cell cycle and apoptosis in A375 cells determined by DNA flow cytometry --- p.46 / Chapter 3.3 --- Effects of HLD A and the ethyl acetate fraction on apoptosis induction in A375 cells determined by Western blotting --- p.53 / Chapter 3.4 --- Effects of HLD A and ethyl acetate fraction on caspases in A375 cells --- p.55 / Chapter 3.5 --- Effects of caspase inhibitors on the HLDA- and the ethyl acetate fraction-induced apoptosis in A375 cells --- p.57 / Chapter 3.6 --- Effects of HLD A and the ethyl acetate fraction on the expression of Bcl-2 family proteins in A375 cells --- p.62 / Chapter 3.7 --- Chemopreventive effect of the ethyl acetate fraction from S. heptaphylla on the DMBA/TPA-induced skin carcinogenesis model --- p.65 / Chapter 3.8 --- Chemotherapeutic effect of the ethyl acetate fraction from S. heptaphylla on A375 xenograft in athymic nude mice --- p.70 / Chapter Chapter 4 --- Discussion --- p.73 / References --- p.83

Li, Wing Yan Kate. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 130-154). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.iii / Abstract (Chinese Version) --- p.vi / Table of Contents --- p.viii / List of Figures --- p.xiii / List of Abbreviations --- p.xv / Chapter Chapter 1 --- General Introduction / Chapter 1.1. --- Overview of cancer --- p.1 / Chapter 1.2. --- Apoptosis and cancer --- p.4 / Chapter 1.3. --- Roles and regulation of caspase-dependent apoptosis --- p.7 / Chapter 1.3.1. --- Extrinsic death receptor pathway --- p.8 / Chapter i. --- TNFR1 and TNFa --- p.13 / Chapter ii. --- CD95/Fas and CD95 Ligand/FasL --- p.14 / Chapter iii. --- "TRAIL-R1(DR4), TRAIL-R2 (DR5) and TRAIL" --- p.14 / Chapter 1.3.2. --- Intrinsic mitochondrial pathway --- p.16 / Chapter i. --- Bcl-2 family of proteins --- p.17 / Chapter ii. --- Reactive Oxygen Species (ROS) --- p.19 / Chapter 1.4. --- Phytochemicals from Traditional Chinese Medicine (TCM) as a source of new therapeutics --- p.22 / Chapter 1.5. --- Biological effects of baicalein --- p.25 / Chapter 1.5.1 --- Roles of baicalein as a lipoxygenase inhibitor --- p.28 / Chapter 1.5.2 --- Dual roles of baicalein as an antioxidant and prooxidant --- p.28 / Chapter 1.5.3 --- "Roles of baicalein as an anti-carcinogenic, anti-proliferative and anti-metastatic agent" --- p.29 / Chapter 1.6. --- Aims of current study --- p.30 / Chapter Chapter 2 --- Effects of Baicalein on Growth and Survival of Human Cancer Cells / Chapter 2.1 --- Introduction --- p.33 / Chapter 2.2 --- Materials and Methods / Chapter 2.2.1 --- Cell culture --- p.35 / Chapter 2.2.2 --- Measurement of growth and survival of various cell lines --- p.36 / Chapter 2.2.3 --- Statistical analysis --- p.37 / Chapter 2.3 --- Results / Chapter 2.3.1 --- Baicalein retards the growth and survival of human melanoma A375 and colorectal carcinoma Caco-2 --- p.37 / Chapter 2.3.2 --- Baicalein reduces the growth and survival of melanoma A375 but not in normal skin fibroblast Hs68 cells --- p.40 / Chapter 2.4 --- Discussion --- p.42 / Chapter Chapter 3 --- Effects of Baicalein on Cell Cycle and the Apoptosis in Human Melanoma A375 Cells / Chapter 3.1 --- Introduction --- p.44 / Chapter 3.2 --- Materials and Methods / Chapter 3.2.1 --- Determination of cell cycle changes and quantification of apoptosis --- p.51 / Chapter 3.2.2 --- Immunoblotting --- p.52 / Chapter 3.2.3 --- Inhibition of caspase-8 by caspase-8 inhibitor --- p.54 / Chapter 3.2.4 --- Fluorometric measurement of caspase-3 activity --- p.54 / Chapter 3.2.5 --- Statistical analysis --- p.55 / Chapter 3.3 --- Results / Chapter 3.3.1 --- Baicalein induces S-phase arrest in cell cycle and triggers apoptosis --- p.55 / Chapter 3.3.2 --- Baicalein induces proteolytic inactivation of PARP and activation of caspases --- p.59 / Chapter 3.3.3 --- Caspase-8 is the major initiator caspase eliciting the baicalein-induced apoptosis --- p.62 / Chapter 3.4 --- Discussion --- p.67 / Chapter Chapter 4 --- Effects of Baicalein on the Extrinsic Apoptotic Pathways in Human Melanoma A375 Cells / Chapter 4.1 --- Introduction --- p.72 / Chapter 4.2 --- Materials and Methods / Chapter 4.2.1 --- Immunoblotting --- p.75 / Chapter 4.2.2 --- Determination of sub-lethal dose of exogenous TRAIL --- p.76 / Chapter 4.2.3 --- Determination of the combinatory effect of exogenous TRAIL and baicalein --- p.76 / Chapter 4.2.4 --- Statistical analysis --- p.77 / Chapter 4.3 --- Results / Chapter 4.3.1 --- Baicalein upregulates the expressions of death receptor 4 (DR4) and death receptor 5 (DR5) --- p.77 / Chapter 4.3.2 --- Baicalein sensitizes the melanoma cells to sub-lethal dose of exogenous TRAIL --- p.80 / Chapter 4.4 --- Discussion --- p.84 / Chapter Chapter 5 --- Effects of Baicalein on the Extrinsic Apoptotic Pathways in Human Melanoma A375 Cells Cancer Cells / Chapter 5.1 --- Introduction --- p.88 / Chapter 5.2 --- Materials and Methods / Chapter 5.2.1 --- Analysis of mitochondrial membrane potential --- p.94 / Chapter 5.2.2 --- Fractionation of cell lysates into cytosolic and mitochondrial fractions for immunoblotting --- p.95 / Chapter 5.2.3 --- Immunoblotting --- p.95 / Chapter 5.2.4 --- Determination of cellular reactive oxygen species (ROS) production --- p.96 / Chapter 5.2.5 --- Verification of ROS generation via the addition of Trolox´ёØ --- p.96 / Chapter 5.2.6 --- Statistical analysis --- p.97 / Chapter 5.3 --- Results / Chapter 5.3.1 --- Baicalein induces mitochondrial membrane depolarization --- p.97 / Chapter 5.3.2 --- Cytochrome c is released in the baicalein-induced mitochondrial membrane depolarization --- p.100 / Chapter 5.3.3 --- Baicalein does not elicit the intrinsic apoptotic pathway via modulation of some better-characterized Bcl-2 family proteins in A375 cells --- p.102 / Chapter 5.3.4 --- Baicalein induces ROS production --- p.105 / Chapter 5.3.5 --- Baicalein induces mitochondrial permeabilization via ROS-mediated mechanisms --- p.108 / Chapter 5.4 --- Discussion --- p.112 / Chapter Chapter 6 --- General Discussion --- p.119 / References --- p.130

Tong, Kit Fong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 91-104). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.vi / Table of Contents --- p.vii / List of Figures --- p.x / List of Tables --- p.xii / List of Abbreviations --- p.xiii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Cancer --- p.2 / Chapter 1.1.1 --- Tumor development --- p.2 / Chapter 1.1.2 --- Cell cycle --- p.4 / Chapter 1.1.3 --- Apoptosis --- p.9 / Chapter 1.1.3.1 --- The extrinsic pathway --- p.14 / Chapter 1.1.3.2 --- The intrinsic pathway --- p.16 / Chapter 1.1.3.3 --- The Bcl-2 family proteins --- p.17 / Chapter 1.1.3.4 --- Execution of apoptosis --- p.20 / Chapter 1.1.4 --- Melanoma --- p.22 / Chapter 1.2 --- Polyunsaturated fatty acids (PUFAs) --- p.24 / Chapter 1.2.1 --- "Chemistry, classification, metabolic conversion and sources …" --- p.24 / Chapter 1.2.2 --- Epidemiology studies --- p.27 / Chapter 1.2.3 --- Docosahexaenoic acid (DHA) --- p.28 / Chapter 1.2.3.1 --- Sources --- p.28 / Chapter 1.2.3.2 --- DHA and cancer --- p.29 / Chapter 1.3 --- Objectives --- p.33 / Chapter Chapter 2 --- Materials and Methods --- p.34 / Chapter 2.1 --- In vitro studies of DHA on growth and survival of human cancer cells --- p.34 / Chapter 2.1.1 --- Cell cultures --- p.34 / Chapter 2.1.2 --- Studies of growth inhibition of DHA on human cancer cells --- p.35 / Chapter 2.1.2.1 --- MTT assay --- p.35 / Chapter 2.1.2.2 --- Chemiluminescent-bromodeoxyuridine (Chemi-BrdU) immunoassay --- p.36 / Chapter 2.1.3 --- Studies of growth inhibitory mechanism of DHA on A375 cells. --- p.38 / Chapter 2.1.3.1 --- DNA -flow cytometry analysis --- p.38 / Chapter 2.1.3.2 --- Western blot analysis --- p.39 / Chapter 2.1.3.3 --- Caspase inhibitor studies --- p.42 / Chapter 2.1.3.4 --- Mitochondrial membrane potential analysis --- p.42 / Chapter 2.2 --- In vivo study of the anticancer effect of DHA on A375 cells --- p.44 / Chapter 2.2.1 --- Animals --- p.44 / Chapter 2.2.2 --- Cell inoculation and treatments --- p.44 / Chapter 2.2.3 --- Western blot analysis --- p.45 / Chapter 2.3 --- Statistical analysis --- p.46 / Chapter Chapter 3 --- Results --- p.47 / Chapter 3.1 --- In vitro studies of DHA on growth and survival of human canccr cells --- p.47 / Chapter 3.1.1 --- DHA reduced proliferation and survival of human cancer cells --- p.47 / Chapter 3.1.2 --- DHA modulated cell cycle of A375 cells --- p.52 / Chapter 3.1.3 --- DHA induced apoptosis in A375 cells --- p.55 / Chapter 3.1.4 --- Caspase activations were involved in the DHA-induced apoptosis in A375 cells --- p.59 / Chapter 3.1.5 --- "Caspase 3´ة 6, 8 and 9 were activated in DHA-induced apoptosis of A375 cells" --- p.62 / Chapter 3.1.6 --- DHA dissipated mitochondrial membrane potential in A375 cells --- p.66 / Chapter 3.1.7 --- DHA triggered the mitochondrial pathway of apoptosis --- p.68 / Chapter 3.1.8 --- DHA triggered the death receptor pathway of apoptosis --- p.71 / Chapter 3.2 --- In vivo study of the anticancer effect of DHA on A375 cells --- p.74 / Chapter 3.2.1 --- Effect of DHA on the growth ofA375 xenograft in athymic Bαlb/c mice --- p.74 / Chapter 3.2.2 --- DR4 and TRAIL were upregulated by DHA treatment in A375 solid tumor --- p.77 / Chapter Chapter 4 --- Discussion --- p.79 / References --- p.91

Additionally, we showed that SeC induced S-phase arrest in MCF-7 cells associated with a marked decrease in the protein expression of cyclin A, D1 and D3 and cyclin-dependent kinases (CDK) 4 and 6, with concomitant induction of p21waf1/Cip1, p27Kip1 and p53. Expose of MCF-7 cells to SeC resulted in delayed onset of apoptosis as evidenced by caspase activation, PARP cleavage and DNA fragmentation. SeC treatment also triggered the activation of JNK, p38 MAPK, ERK and Akt phosphorylation. Inhibitors of ERK (U0126) or Akt (LY294002), but not JNK (SP600125) and p38 MAPK (SB203580), significantly suppressed SeC-induced S-phase arrest and apoptosis in MCF-7 cells. In conclusion, our findings establish a mechanistic link between the PI3K/Akt pathway, MAPK pathway and SeC-induced cell cycle arrest and apoptosis in human breast cancer cells. (Abstract shortened by UMI.) / The role of selenium as potential cancer chemopreventive and chemotherapeutic agents has been supported by epidemiological, preclinical and clinical studies. Although cell apoptosis has been evidenced as a critical mechanism mediating the anticancer activity of selenium, the underlying molecular mechanisms remain elusive. In the present study, selenocystine (SeC), a novel organic selenocompound, is identified as a novel antiproliferative agent with a broad spectrum of inhibition against eight human cancer cell lines with the IC50 values ranged from 3.6 to 37.0 muM. Despite this potency, SeC was relatively nontoxic toward HS68 human fibroblasts with an IC 50 value exceeded 400 muM. Further investigation on the molecular mechanisms indicated that SeC induced caspase-independent apoptosis in MCF-7 breast carcinoma cells, which was accompanied by poly(ADP-ribose) polymerase (PARP) cleavage, caspase activation, DNA fragmentation, phosphatidylserine exposure and nuclear condensation. Moreover, SeC induced the loss of mitochondrial membrane potential (DeltaPsim) by regulating the expression and phosphorylation of pro-surivival and pro-apoptotic Bcl-2 family members. Loss of DeltaPsim led to the mitochondrial release of cytochrome c and apoptosis-inducing factor (AIF) which subsequently translocated into the nucleus and induced chromatin condensation and DNA fragmentation. MCF-7 cells exposed to SeC shown increase in total p53 and phosphorylated p53 on serine residues of Ser15, Ser20, and Ser392 prior to mitochondrial dysfunction. Silencing and attenuation of p53 expression with RNA interference and pifithrin-alpha treatment respectively, partially suppressed SeC-induced cell apoptosis. Furthermore, generation of reactive oxygen species (ROS) and subsequent induction of DNA strand breaks were found to be upstream cellular events induced by SeC. The thiol-reducing antioxidants, N-acetylcysteine and glutathione, completely blocked the initiation and execution of cell apoptosis. Taken together, these results suggest that SeC, as a promising anticancer selenocompound, induces caspase-independent apoptosis in MCF-7 cells mediated by ROS generation and p53 phosphorylation through regulating the mitochondrial membrane permeability. / Chen, Tianfeng. / Adviser: Yun-Shing Wong. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3260. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 124-136). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

New Zealand has the second highest incidence of melanoma skin cancer in the world. Chemotherapy is the standard treatment for melanoma derived tumours which have undergone metastasis and current therapies have limited benefit. There is a great need for new therapies and to increase the efficacy of current therapies. Temozolomide (TMZ) is a chemotherapy agent effective in the treatment of both metastatic melanoma and glioblastoma (brain cancer), although TMZ resistance has been observed in many tumours. The activity of the DNA repair enzyme O6 methyl-guanine methyltransferase (MGMT) is thought to be largely responsible for TMZ resistance. MGMT protects the cell from the effects of TMZ by removing cytotoxic lesions placed on the DNA. Mechanisms of regulation of MGMT expression remain unclear in melanoma. DNA methylation at the MGMT promoter has been linked to MGMT silencing in some cancers and has been associated with specific chromatin modifications. The present study was aimed at investigating the promoter methylation status of MGMT in primary melanoma cell lines using a new technique named methyl DNA immuno-precipitation (MeDIP). Next, the chromatin immuno-precipitation (ChIP) method was used to examine post translational modifications on the surrounding chromatin. The data obtained was correlated with both MGMT transcription levels and TMZ sensitivity. The promoter methylation status of MGMT has been used to predict the clinical responsiveness of glioblastoma patients to TMZ. Establishing the regulatory mechanisms of MGMT expression in melanoma patients would validate a means to predict clinical responsiveness to TMZ. Furthermore, establishing mechanisms of MGMT silencing may provide the basis for future clinical trials of novel therapies for melanoma and glioblastoma.