Cheung, Ka Yan. / "Aug 2010." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 157-167). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgments --- p.v / Table of Contents --- p.vi / List of Figures --- p.x / List of Tables --- p.xi / Abbreviations --- p.xii / Chapter Chapter1 --- General Introduction --- p.1 / Chapter 1.1 --- Cancer epidemiology and managements --- p.2 / Chapter 1.2 --- Photodynamic therapy (PDT) as cancer treatment --- p.7 / Chapter 1.3 --- Pheophorbide a (Pa) as a photosensitizer for PDT --- p.13 / Chapter 1.4 --- Aim of study --- p.15 / Chapter Chapter2 --- The anti-proliferative effect of pheophorbide a- mediated photodynamic therapy on human breast adenocarcinoma cell line MCF-7 --- p.17 / Chapter 2.1 --- Introduction / Chapter 2.1.1 --- Cell cycle regulation --- p.18 / Chapter 2.1.2 --- Growth arrest and DNA damage inducible (GADD) genes as cell cycle regulators --- p.22 / Chapter 2.2 --- Materials and Methods / Chapter 2.2.1 --- Materials / Chapter 2.2.1.1 --- Cell line --- p.29 / Chapter 2.2.1.2 --- "Cell culture medium, supplements and other reagents" --- p.29 / Chapter 2.2.1.3 --- Gene expression assay reagents --- p.30 / Chapter 2.2.1.4 --- Reagents and buffers for Western blotting --- p.32 / Chapter 2.2.1.5 --- Cell cycle analysis reagents --- p.35 / Chapter 2.2.2 --- Methods / Chapter 2.2.2.1 --- Cell line propagation and subculture --- p.36 / Chapter 2.2.2.2 --- Whole-transcript expression micro array analysis --- p.37 / Chapter 2.2.2.3 --- GADD genes expression assay- RT-PCR --- p.37 / Chapter 2.2.2.4 --- Cell cycle analysis --- p.40 / Chapter 2.2.2.5 --- Western Blotting --- p.41 / Chapter 2.2.2.6 --- Statistical analysis --- p.43 / Chapter 2.3 --- Results / Chapter 2.3.1 --- Effect of Pa-PDT on GADD genes expression by whole-transcript expression microarray analysis --- p.44 / Chapter 2.3.2 --- Effect of Pa-PDT on GADD genes expression by RT-PCR --- p.46 / Chapter 2.3.3 --- Temporal change in the cell cycle profile after Pa-PDT --- p.48 / Chapter 2.3.4 --- Effect of Pa-PDT on cell cycle associated proteins --- p.65 / Chapter 2.4 --- Discussion --- p.67 / Chapter Chapter3 --- Development of drug resistance in human breast adenocarcinoma cell line MDA and the circumvention by pheophorbide a-mediated photodynamic therapy --- p.77 / Chapter 3.1 --- Introduction / Chapter 3.1.1 --- Clinical Importance of multidrug resistance (MDR) --- p.78 / Chapter 3.1.2 --- Mechanisms of MDR --- p.78 / Chapter 3.1.3 --- Development of MDR cell lines --- p.82 / Chapter 3.1.4 --- Reversal of MDR by P-glycoprotein modulators --- p.83 / Chapter 3.1.5 --- Therapeutic potential of Pa-PDT in treating MDR cancers --- p.83 / Chapter 3.2 --- Materials and Methods / Chapter 3.2.1 --- Materials / Chapter 3.2.1.1 --- Cell line --- p.85 / Chapter 3.2.1.2 --- "Cell culture medium, supplements and other reagents" --- p.85 / Chapter 3.2.1.3 --- Cell viability assay reagents --- p.85 / Chapter 3.2.1.4 --- Gene expression assay reagents --- p.86 / Chapter 3.2.2 --- Methods / Chapter 3.2.2.1 --- Cell line propagation and subculture --- p.87 / Chapter 3.2.2.2 --- Drug-resistance development --- p.88 / Chapter 3.2.2.3 --- Measurement of cell viability - MTT reduction assay --- p.88 / Chapter 3.2.2.4 --- ABCB1 expression assay- RT-PCR --- p.89 / Chapter 3.2.2.5 --- Doxorubicin uptake assay --- p.91 / Chapter 3.2.2.6 --- Pheophorbide a uptake assay --- p.91 / Chapter 3.2.2.7 --- Statistical analysis --- p.92 / Chapter 3.3 --- Results / Chapter 3.3.1 --- Cytotoxicity of doxorubicin on MDA and MDA-R cells --- p.93 / Chapter 3.3.2 --- mRNA expression of ABCB1 (P-glycoprotein) in MDA and MDA-R cells --- p.96 / Chapter 3.3.3 --- Doxorubicin uptake by MDA and MDA-R cells --- p.98 / Chapter 3.3.4 --- Circumvention of drug resistance in MDA-R cells by Pa-PDT --- p.102 / Chapter 3.3.5 --- Pheophorbide a uptake by MDA and MDA-R cells --- p.104 / Chapter 3.4 --- Discussion --- p.106 / Chapter Chapter4 --- Synergistic anti-proliferation of pheophorbide a-mediated photodynamic therapy and doxorubicin on multidrug resistant uterine sarcoma cell line Dx5 --- p.113 / Chapter 4.1 --- Introduction / Chapter 4.1.1 --- Clinical limitations of doxorubicin as chemotherapeutic drug --- p.114 / Chapter 4.1.2 --- Clinical limitations of photodynamic therapy --- p.115 / Chapter 4.1.3 --- Combination therapy with Dox and Pa-PDT --- p.117 / Chapter 4.1.4 --- Uterine sarcoma cell line Dx5 as in vitro model for combination therapy --- p.118 / Chapter 4.2 --- Materials and Methods / Chapter 4.2.1 --- Materials / Chapter 4.2.1.1 --- Cell line --- p.120 / Chapter 4.2.1.2 --- "Cell culture medium, supplements and other reagents" --- p.120 / Chapter 4.2.1.3 --- Anti-cancer drugs --- p.121 / Chapter 4.2.1.4 --- "ROS inhibitor, α-tocopherol" --- p.121 / Chapter 4.2.1.5 --- Cell viability assay reagents --- p.122 / Chapter 4.2.1.6 --- P-glycoprotein activity assay reagents --- p.122 / Chapter 4.2.2 --- Methods - / Chapter 4.2.2.1 --- Cell line propagation and subculture --- p.123 / Chapter 4.2.2.2 --- Cell viability assay --- p.123 / Chapter 4.2.2.3 --- P-glycoprotein activity assay --- p.124 / Chapter 4.2.2.4 --- Statistical analysis --- p.125 / Chapter 4.3 --- Results / Chapter 4.3.1 --- Combination therapy of Pa-PDT and doxorubicin in Dx5 cells --- p.126 / Chapter 4.3.2 --- Effect of α-tocopherol on the synergism between Pa-PDT and doxorubicin in Dx5 cells --- p.129 / Chapter 4.3.3 --- Effect of Pa-PDT on P-glycoprotein activity in Dx5 cells --- p.132 / Chapter 4.3.4 --- Combination therapy of Pa-PDT and doxorubicin in SA cells --- p.138 / Chapter 4.4 --- Discussion --- p.141 / Chapter Chapter5 --- General Discussion --- p.148 / Chapter 5.1 --- Pa-PDT induced growth arrest and DNA fragmentation in breast cancer MCF-7 cells --- p.149 / Chapter 5.2 --- Circumvention of doxorubicin resistance by Pa-PDT in breast cancer MDA cells --- p.151 / Chapter 5.3 --- Synergistic anti-proliferation of Pa-PDT and doxorubicin on uterine sarcoma cell line Dx5 --- p.151 / Chapter 5.4 --- Clinical implication --- p.153 / Chapter 5.5 --- Conclusions and future perspectives --- p.153 / References --- p.157

Interactions between the retinoic acid receptor alpha (RARalpha) and coregulators play a key role in coordinating gene transcription and myeloid differentiation. In acute promyelocytic leukemia (APL), RARalpha is fused with the promyelocytic leukemia (PML) gene, resulting in the expression of the fusion protein PML/RARalpha. Here, I report that topoisomerase II beta (topoIIbeta) associates with and negatively modulates PML/RARalpha and RARalpha transcriptional activity, and increased levels and association of topoIIbeta cause resistance to retinoic acid (RA) in APL cell lines. Knock down of topoIIbeta was able to overcome resistance by permitting RA-induced differentiation and increased RA-gene expression. Overexpression of topoIIbeta, in clones from an RA-sensitive cell line, conferred resistance by a reduction in RA-induced expression of target genes and differentiation. Chromatin immunoprecipitation assays indicate that topoIIbeta is bound to an RA-response element, and inhibition of topoIIbeta causes hyper-acetylation of histone 3 at lysine 9 and activation of transcription. These results identify a novel mechanism of resistance in APL and provide further insights to the role of topoIIbeta in gene regulation and differentiation. / Studies to determine the mechanism by which topoIIbeta protein is regulated found that levels of protein kinase C delta (PKCdelta) correlated with topoIIbeta protein expression. Moreover, activation of PKCdelta, by RA or PMA, led to an increase of topoIIbeta protein levels. Most notably, in NB4-MR2 cells, we observed increased phosphorylation levels of threonine 505 on PKCdelta, a marker of activation. Inhibition of PKCdelta was able to overcome the topoIIbeta repressive effects on RA-target genes. In addition, the combination of RA and PKCdelta inhibition led to increased expression of the granulocytic marker, CD11c, in NB4 and NB4-MR2 cells. These results suggest that PKCdelta regulates topoIIbeta expression, and a constitutively active PKCdelta in the NB4-MR2 cell line leads to overexpression of topoIIbeta. / In conclusion, these studies demonstrate that topoIIbeta associates with RARalpha, binds to RAREs and plays a critical role in RA dependent transcriptional regulation and granulocytic differentiation. In addition, I show that topoIIbeta overexpression leads to RA resistance and provide evidence that topoIIbeta protein levels are regulated via a mechanism involving the PKCdelta pathway. This work has contributed to an enhanced understanding of the role of topoIIbeta in gene regulation and brings novel perspectives in the treatment of RA-resistance in APL.

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