Liu, Yanan. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 87-98). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

Wong, Wing Yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 90-105). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.iii / Abstract (Chinese Version) --- p.v / Table of Contents --- p.vi / List of Figures --- p.ix / List of Abbreviations --- p.xi / Chapter Chapter 1 --- General Introduction / Chapter 1.1 --- Overview of cancer --- p.1 / Chapter 1.2 --- Acute lymphoblastic leukemia --- p.3 / Chapter 1.2.1 --- T-cell acute lymphoblastic leukemia --- p.5 / Chapter 1.2.1.1 --- Chemotherapy / Chapter 1.2.1.2 --- Induction therapy / Chapter 1.2.1.3 --- Intensification therapy / Chapter 1.2.1.4 --- Maintenance therapy --- p.6 / Chapter 1.2.2 --- Chemoresistance in T-ALL / Chapter 1.3 --- Apoptosis and cancer --- p.7 / Chapter 1.3.1 --- Chemoresistance --- p.9 / Chapter 1.4 --- Caspase-dependent apoptosis --- p.10 / Chapter 1.4.1 --- Regulation of caspase-dependent apoptosis / Chapter 1.4.2 --- Initiation of apoptosis --- p.11 / Chapter 1.4.3 --- Exrtinsic pathway / Chapter 1.4.4 --- Intrinsic mitochondrial pathway --- p.15 / Chapter 1.4.4.1 --- Regulation of apoptosis by Bcl-2 family proteins --- p.16 / Chapter 1.4.4.2 --- Reactive Oxygen Species --- p.19 / Chapter 1.5 --- Selenium --- p.23 / Chapter 1.5.1 --- Importance of Se to human health --- p.25 / Chapter 1.5.2 --- Cancer chemoprevention by Se --- p.27 / Chapter 1.5.3 --- Preclinical studies --- p.28 / Chapter 1.5.4 --- Clinical investigations / Chapter 1.5.5 --- Mechanisms of action by selenocompounds --- p.29 / Chapter 1.6 --- Aims of current study --- p.31 / Chapter Chapter 2 --- Materials and Methods / Chapter 2.1 --- Cell culture --- p.32 / Chapter 2.2 --- Measurement of growth and survival of T-ALL cell lines / Chapter 2.3 --- Induction and quantification of apoptosis --- p.34 / Chapter 2.4 --- Western blotting / Chapter 2.4.1 --- Protein extraction and determination of protein concentration / Chapter 2.4.2 --- SDS-PAGE and immunodetection --- p.35 / Chapter 2.5 --- Analysis of mitochondrial membrane potential --- p.36 / Chapter 2.6 --- Measurement of ROS generation --- p.37 / Chapter 2.7 --- Verification of ROS generation via the addition of N-Acetyl-L-cysteine and glutathione / Chapter 2.8 --- Statistical analysis --- p.38 / Chapter Chapter 3 --- Results / Chapter 3.1 --- SeC induces prominent growth inhibition on Sup-T1 --- p.39 / Chapter 3.2 --- SeC induces S-phase arrest in cell cycle and triggers apoptosis in Sup-T1 --- p.44 / Chapter 3.3 --- SeC triggers DNA fragmentation in Sup-T1 --- p.48 / Chapter 3.4 --- SeC induces PARP cleavage in Sup-T1 --- p.52 / Chapter 3.5 --- SeC activates caspases in Sup-T1 --- p.53 / Chapter 3.6 --- SeC abrogates mitochondrial membrane potential in Sup-T1 cells --- p.56 / Chapter 3.7 --- SeC modulates expressions of Bcl-2 members and activates Bim and Bid in Sup-T1 --- p.61 / Chapter 3.8 --- SeC induces ROS production in Sup-T1 --- p.64 / Chapter 3.9 --- Antioxidants protect Sup-T1 cells from SeC-induced growth inhibition --- p.66 / Chapter 3.10 --- Antioxidants protect Sup-T1 cells from SeC-induced apoptosis --- p.69 / Chapter 3.11 --- Antioxidants effectively block SeC-induced ROS generation in Sup-T1 cells --- p.72 / Chapter 3.12 --- SeC induces mitochondrial membrane permeabilization via ROS-mediated mechanisms Sup-T1 cells --- p.75 / Chapter Chapter 4 --- Discussion --- p.79 / Conclusion --- p.87 / References --- p.90

Male weanling inbred, mice were inoculated with fibrosarcoma cells (hindquarter) originally produced by 2-methylcholanthrene. Before inoculation, mice were randomly divided into three groups of 24 and one of 12 (control). After a one week acclimation period, each group was fed a diet containing either suboptimal vitamin B-6, 0.5 mg/kg diet; adequate, 7.0 mg/kg diet; or excess, 100 mg/kg diet. Controls were fed the adequate vitamin. B-6 diet. Twenty-four hours after tumor cell inoculation, a series of sodium selenite injections (0.5 μg/.10 mL) were given to half of each treatment group and all controls. Mice were sacrificed two wk after tumor inoculation. Tumors were excised and weighed. Selenium-treated mice had significantly smaller tumors as compared to untreated mice regardless of vitamin B-6 treatment. The smallest tumors were found in the selenium-treated group maintained on adequate B-6, while the largest tumors were developed by mice on the excess B-6 diet without selenium treatments. All groups had similar blood selenium levels as measured by gas chromatography. Tumor selenium levels, analyzed by atomic absorption, were significantly higher for untreated groups than selenium-treated groups (larger tumor size). The excess and adequate vitamin B-6 selenium-treated groups had significantly lower tumor selenium levels than the adequate vitamin B-6 untreated group. Plasma pyridoxal phosphate (concentrations) determined radiometrically and tumor vitamin B-6 levels determined microbiologically, related directly to dietary treatments. Sodium selenite injections and adequate vitamin B-6 diets reduced the size of fibrosarcomas in BALB/c inbred mice. / Master of Science

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.