abstract / toc / Physiology / Master / Master of Philosophy

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 193-205).

Thesis (Ph. D.)--University of Virginia, 1997. / Spine title: [alpha]₂-M & LRP in atherosclerosis. Includes bibliographical references (180-195). Also available online through Digital Dissertations.

Thesis (Ph.D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 140-172) Also available in print.

Thesis (M. Med. Sc.)--University of Hong Kong, 2005.

Thesis (M.C.E.)--University of Delaware, 2007. / Principal faculty advisor: Dionisios G. Vlachos, Dept. of Chemical Engineering. Includes bibliographical references.

Improved corneal epithelial cell growth over artificial cornea materials is required to improve device retention within the eye. In this work, varying concentrations of epidermal growth factor (EGF), a potent mitogen for epithelial cells, were immobilized to polydimethylsiloxane (PDMS) substrates, and the cellular response was analyzed. Three methods were developed to bind EGF to PDMS via polyethylene glycol (PEG) tethers. 1) Plasma Modification: EGF was first reacted with homobifunctional NHS2PEG and then bound to allylamine plasma-modified PDMS. 2) Hydrosilylation: PDMS was modified with heterobifunctional allyl-PEG-NBS and then EGF was attached to the surface-bound PEG. 3) Thiol Modification: EGF was first reacted with heterobifunctional NHS-PEG-maleimide and then bound to thiol-modified PDMS. Using Method 1 (Plasma Modification), 40 to 90 ng/cm2 of EGF was bound, however 70% of this was adsorbed even under optimized EGF-PEG reaction conditions. Cells rapidly grew to confluence on these surfaces, and cell counts increased significantly compared to control surfaces. Extracellular matrix protein production was also increased on the EGF-modified surfaces, corresponding to significantly higher levels of cell adhesion observed under a detachment force. Modification by Method 2 (Hydrosilylation) resulted in 10 to 300 ng/cm2 of bound EGF, of which 20% was adsorbed. However, despite increased EGF binding homogeneity, the cell growth was slower on these surfaces than on those prepared by Method 1, and coverage was non-uniform at all EGF concentrations. This is likely due to a higher underlying PEG density, and binding of the PEG and EGF in clusters on the surface. Simultaneous tethering of the cell adhesion peptide YIGSR had no further effect on cell coverage. Using Method 3 (Thiol Modification), 24 to 65 ng/cm2 of EGF was bound, of which 22% was adsorbed. This method enables more homogeneous EGF surface binding than Method 1, with a lower PEG density than Method 2. However, free thiol groups were inhibitory to corneal epithelial cell growth, even in the presence of bound EGF. Defunctionalization of free thiols by reaction with 3-maleimidopropionic acid restored cell growth and morphology on the PDMS, and may hence allow for retention of the proliferative effect of the EGF. These results indicate that while tethering of EGF to PDMS can improve the coverage by corneal epithelial cells, and presents a promising strategy for modification of polymeric artificial cornea materials, the effects are highly dependent on the underlying surface chemistry. / Thesis / Doctor of Philosophy (PhD)

The dynamics of cell signalling are critical to cell fate decisions. Human Epidermal growth factor Receptors (HERs)-mediated Ras/Raf/MEK/ERK and PI3K/Akt signalling cascades relay extracellular signals from the plasma membrane to targets in the nucleus and cytoplasm and play pivotal roles in cell fate determination including proliferation, differentiation and cell survival. Both pathways, once activated, are further regulated by complex feedback loops which may exert either positive or negative effects on cascade components and can result in signalling oscillation. In this study, heregulin (HRG) - and epidermal growth factor (EGF)- stimulated oscillation of both p-ERK1/2 and p-Akt expression in breast cancer cell lines was demonstrated. The oscillation was cell line dependent and was observed in MCF-7 and MCF-7/HER2-18 cells but not in BT474 cells. The oscillation was augmented by cycloheximide implicating transcriptional involvement. Gene expression analysis identified 29 genes as possible candidates involved in the transcriptional feedback regulation. Apart from the feedback regulation, feedforward regulation was also observed. To expedite the analyses In-cell Western and Reverse Phase Protein Array (RPPA) assays were developed. A scheme of transcriptional feedback loops regulating the oscillation in the ERK1/2 pathway is proposed, including negative feedback loops to ERK1/2 from DUSPs, early positive and late negative feedback loops to MEK1/2 and positive feedback loops to HER-3 from AREG, HB-EGF, CYR61 and CTGF. Two HER-2-targeted inhibitory monoclonal antibodies were investigated – trastuzumab and pertuzumab. Trastuzumab not only inhibited the growth of HER-2 over-expressing MCF-7/HER2- 18 cells and BT474 cells but also that of EGF-driven MCF-7 cells which expressed low/moderate HER-2 levels. Pertuzumab blocked the growth of both MCF-7 and MCF-7/HER2-18 driven by either EGF or HRG. When used in combination with trastuzumab, pertuzumab had much more potent activity in inhibiting cell growth and signalling than either single drug. Trastuzumab and pertuzumab had opposing effects on immediate p-ERK1/2 signalling and trastuzumab’s effects on signalling could be mimicked by the PI3K inhibitor LY294002. PTPN13, a non-receptor type tyrosine protein phosphatase, is a proposed tumour suppressor in breast cancer. This was investigated as a candidate regulator of the signalling oscillation and although not observed as a transcriptional modulator of the oscillation, its high expression level was observed to be associated with cell growth inhibition in MCF-7/HER2-18 cells by trastuzumab. Moreover, immunohistochemical analysis of 121 clinical tumours which had received trastuzumab treatment revealed the correlation between the expression level of PTPN13 and the mutation status of PIK3CA. In conclusion, the observed oscillation may contribute to the elucidation of the complex regulation of signalling pathways, which is vital to the different cell fate decision made through the same core pathway. The synergy between trastuzumab and pertuzumab supports the clinical use of the combination treatment and suggested PI3K/Akt pathway as the major pathway in controlling tumour growth.

Yung, Kam Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 107-129). / Abstracts in English and Chinese. / ABSTRACT --- p.ii / 摘要 --- p.iv / ACKNOWLEDGEMENTS --- p.vi / TABLE OF CONTENTS --- p.vii / PUBLICATION --- p.ix / LIST OF TABLES --- p.x / LIST OF FIGURES --- p.xi / LIST OF ABBREVIATIONS --- p.xii / Chapter SECTION I: --- BACKGROUND --- p.1 / Chapter CHAPTER 1: --- "The biology, diagnostics and management of lung cancer" --- p.2 / Chapter 1.1 --- "Basic biology, classification and diagnostics" --- p.2 / Chapter 1.1.1 --- Epidemiology and etiology of lung cancer --- p.2 / Chapter 1.1.2 --- Clinical Presentation and Diagnostics of Lung Cancer --- p.3 / Chapter 1.2 --- Treatment of lung cancer --- p.9 / Chapter 1.2.2 --- Radiotherapy --- p.10 / Chapter 1.2.3 --- Chemotherapy --- p.11 / Chapter CHAPTER 2: --- Epidermal Growth Factor Receptor Mutations in Lung Cancer --- p.13 / Chapter 2.1 --- The Epidermal Growth Factor Receptor --- p.13 / Chapter 2.2 --- Overexpression of EGFR in NSCLC --- p.14 / Chapter 2.3 --- The development of EGFR inhibitors --- p.15 / Chapter 2.3.1 --- Monoclonal Antibodies --- p.16 / Chapter 2.3.2 --- Small-molecule inhibitors --- p.17 / Chapter 2.3.2.1 --- Gefitinib --- p.17 / Chapter 2.3.2.2 --- Erlotinib --- p.19 / Chapter 2.3.2.3 --- Other small-molecule inhibitors --- p.20 / Chapter 2.4 --- Mutations of EGFR in NSCLC --- p.21 / Chapter 2.4.1 --- Activating Mutations conferring sensitivity to tyrosine kinase inhibitors --- p.21 / Chapter 2.4.2 --- Secondary mutations associated with resistance to tyrosine kinase inhibitors --- p.23 / Chapter 2.5 --- EGFR gene amplification --- p.24 / Chapter 2.6 --- Detection of EGFR mutations --- p.25 / Chapter 2.7 --- Aim of the thesis --- p.31 / Chapter SECTION II: --- DETECTION OF EGFR MUTATIONS IN TUMOR AND PLASMA SAMPLES BY MASS SPECTROMETRY AND DIGITAL PCR --- p.33 / Chapter CHAPTER 3: --- Detection of EGFR mutations by mass spectrometric methods --- p.34 / Chapter 3.1 --- Introduction --- p.34 / Chapter 3.1.1 --- Principles of Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) --- p.34 / Chapter 3.1.2 --- The MassARRAY Homogenous MassEXTEND (hME) assay --- p.35 / Chapter 3.1.3 --- The Single-Allele Base Extension Reaction (SABER) and the Allele-Specific Base Extension Reaction (ASBER) --- p.36 / Chapter 3.2 --- Materials and Methods --- p.36 / Chapter 3.2.1 --- The protocol for the detection of EGFR exon 21 point mutation by Mass Spectrometric Methods --- p.37 / Chapter 3.3 --- Results --- p.42 / Chapter 3.4 --- Discussion --- p.49 / Chapter CHAPTER 4: --- Evaluation of the detection limit and sensitivity of the digital PCR assays --- p.51 / Chapter 4.1 --- Introduction --- p.51 / Chapter 4.1.1 --- The theoretical basis of digital PCR quantification and the relationship with the Poisson distribution --- p.51 / Chapter 4.1.2 --- Assessment of Assay Detection Limit --- p.54 / Chapter 4.1.3 --- Comparing Digital PCR with sequencing after conformation sensitive gel electrophoresis (CSGE) --- p.59 / Chapter 4.2 --- Materials and Methods --- p.59 / Chapter 4.2.1 --- Design of digital PCR assay for the detection of EGFR exon21 L858R point mutation --- p.59 / Chapter 4.2.2 --- Design of digital PCR assay for the detection of EGFR exon19 deletion --- p.60 / Chapter 4.2.3 --- The protocols of digital PCR assays for EGFR mutation detection --- p.64 / Chapter 4.2.4 --- Single molecule detection test --- p.65 / Chapter 4.2.5 --- Artificial mixtures of mutant and wild-type DNA --- p.66 / Chapter 4.2.6 --- Sequencing after CSGE --- p.66 / Chapter 4.3 --- Results --- p.67 / Chapter 4.3.1 --- Results of the single molecule detection test and artificial mixture analysis --- p.67 / Chapter 4.3.2 --- Results of CSGE and sequencing compared with digital PCR --- p.73 / Chapter 4.4 --- Discussion --- p.75 / Chapter CHAPTER 5: --- Detection of EGFR mutations in prospectively collected tumor samples of NSCLC patients --- p.77 / Chapter 5.1 --- Introduction --- p.77 / Chapter 5.2 --- Materials and Methods --- p.78 / Chapter 5.2.1 --- Sample preparation and DNA extraction of tumor tissues --- p.78 / Chapter 5.3 --- Results --- p.79 / Chapter 5.4 --- Discussion --- p.82 / Chapter CHAPTER 6: --- Detection of EGFR mutations in prospectively collected plasma samples of NSCLC patients --- p.85 / Chapter 6.1 --- Introduction --- p.85 / Chapter 6.2 --- Materials and Methods --- p.87 / Chapter 6.2.1 --- Sample preparation and DNA extraction of plasma samples --- p.87 / Chapter 6.3 --- Results --- p.88 / Chapter 6.3.1 --- Digital PCR analysis of EGFR mutations in plasma samples of NSCLC patient --- p.88 / Chapter 6.3.2 --- Variations in plasma EGFR mutation concentration after TKI treatment --- p.93 / Chapter 6.4 --- Discussion --- p.96 / Chapter SECTION III: --- CONCLUDING REMARKS --- p.100 / Chapter CHAPTER 7: --- Conclusion and future perspectives --- p.101 / Chapter 7.1 --- Mass spectrometric analysis --- p.101 / Chapter 7.2 --- Microfluidics Digital PCR --- p.102 / Chapter 7.3 --- Future perspectives --- p.105 / References --- p.107