published_or_final_version / abstract / toc / Surgery / Master / Master of Philosophy

Metastasis is one of the critical hallmarks of malignancy tumor and the principal cause of death in patients with cancer. Cell migration is the basic and essential step in cancer metastasis process. To systematically investigate functional genes regulating cell migration and cancer metastasis on large scale, we developed a novel on-chip method, SAMcell (self-assembled cell microarray). This method was demonstrated to be particularly suitable for loss-of-function high-throughput screening because of its unique advantages. The first application of SAMcell was to screen human genome miRNAs, considering that more and more miRNAs had been proved to govern cancer metastasis. We found that over 20 % of miRNAs have migratory regulation activity in diverse cell types, indicating a general involvement of miRNAs in migratory regulation. Through triple-round screenings, we discovered miR-23b, which is down-regulated in human colon cancer samples, potently mediates the multiple steps of metastasis, including cell motility, cell growth and cell survival. In parallel, the second application of SAMcell was to screen human genome kinase genes, considering that more and more kinase genes had become successful diagnostic marker or drug targets. We found over 11% migratory kinase genes, suggesting the important role of kinase group in metastasis regulation. Through both functional screening and bioinformatics analysis, we discovered and validated 6 prospective metastasis-related kinase genes, which can be new potential targets in cancer therapy. These findings allow the understanding of regulation mechanism in human cancer progression, especially metastasis and provide the new insight into the biological and therapeutical importance of miRNAs or kinases in cancer.

Cancer has been a disease, which has generated intense research interest for many years. Misexpression of two oncoproteins, TAL 1 and LMO 1, has been found to help induce a particular type of leukemia, called T-cell acute lymphoblastic leukemia (T-ALL). Presently, it is not completely understood how these proteins induce leukemogenesis or what other cellular proteins they interact with to drive this progression. In this study, a series of experiments were conducted to identify downstream targets of TALI and LMO1. Using retroviral gene transfer, both genes were introduced, either singly or in combination, into a murine T-cell line called AKR-DP-603. Empty vectors were introduced as controls. In order to assay the effects of TALI and LMO I expression on expression of other proteins, a series of Western blots were completed on all populations of engineered cells. It was determined that there were differences in expression of Bcl-2 and p16 as indicated by differences in band intensities on the blots. This is important because it implies an effect on protein levels by TAL 1 and LMO 1. However, there were no differences in protein expression levels for Bax or cyclin D1. This suggests that TAL1 and LMOI do not have any regulatory effects on these proteins. In addition, apoptotic assays were completed on all populations of cells. The results of both a TUNEL assay and ethidium bromide/acridine orange staining protocol showed TAL1- and LMO1expressing cells to have an increase in cell survival under starvation conditions and a lower frequency of apoptosis. Statistical analysis verified significant difference in the apoptosis assays. The data suggests an up-regulation of anti-apoptotic proteins. The finding of this research allow a clearer understanding of the process of leukemogenesis and may lead to a development of better cancer treatments. / Department of Biology

An intact cellular response to DNA damage is important for the maintenance of genomic stability and tumour prevention. EDD, the human orthologue of Drosophila melanogaster ???hyperplastic discs???, is over-expressed or mutated in a number of common human cancers. EDD is a progestin regulated gene that encodes an E3 ubiquitin ligase involved in cell communication and cell adhesion, and although it has also been implicated in the DNA damage response through its association with DNA damage proteins, a definitive role has yet to be demonstrated. The work presented herein shows that EDD is necessary for an adequate cellular response to double-strand DNA breaks. Cells depleted of EDD exhibit reduced survival, radio-resistant DNA synthesis and failure to maintain G2/M arrest following DNA damage induced by phleomycin exposure. Furthermore, EDD-depleted cells display impaired activating phosphorylation and kinase activity of the checkpoint kinase CHK2 after DNA damage. These effects appear to be largely modulated through a phospho-dependent interaction involving the CHK2 FHA domain and a region of EDD spanning a number of putative FHA-binding threonines. These results identify EDD as a novel mediator in DNA damage signal transduction via CHK2 and emphasise the potential importance of EDD in cancer.

[Truncated abstract] Introduction: Breast cancer is a heterogeneous disease, resulting in very different outcomes for women with apparently similar tumour characteristics. In order for patients to have optimal treatment, a better understanding of the molecular nature of their disease is required. Aims: The aims of this thesis were: 1) To determine whether methylation of RARβ2, ER, CDH1, BRCA1, CCND2, p16 and TWIST genes are associated with phenotypic features of breast cancer and the prognostic significance of methylation of these genes. 2) To investigate for possible associations between the frequency of methylation at RARβ2, CDH1, ER, BRCA1, CCND2, p16 and TWIST genes and the presence of germ-line variants in the TS, MTHFR, MS, CBS, MTHFD1 and DNMT3B genes, as well as for possible correlations between these polymorphisms and clincopathological features of breast cancer including patient outcome. 3) To determine whether PIK3CA mutations determined clinical phenotype and the prognostic significance of PIK3CA mutations in a large and well characterized cohort of breast cancer patients. Methods: A large and well characterized series of primary breast tumours were selected for methylation of RARβ2, ER, CDH1, BRCA1, CCND2, p16 and TWIST genes using MSP, and for polymorphisms in TS, MTHFR, MS, CBS, MTHFD1 and DNMT3B genes using PCR, PCR-RFLP and PCR-SSCP. Mutations to PIK3CA were detected using F-SSCP. Results and Conclusions: Methylation frequencies ranged from 11% for CCND2 to 84% for ER. More frequent hypermethylation was observed in tumours with poor histological differentiation compared to those with well/moderate differentiation, as well as trends for association with larger tumour size and mutant TP53. Tumours with ER and CDH1 methylation were associated with significantly lower hormone receptor levels, younger age at diagnosis and the presence of mutant p53. TWIST methylation is firstly reported to be associated with significantly older patient age at diagnosis and larger tumour size. Our data suggests that gene methylation may be linked to various pathological features of breast cancer. However, there appears to be little support for a distinctive CpG island methylator phenotype in breast cancer.

Made available in DSpace on 2014-06-11T19:26:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-22Bitstream added on 2014-06-13T20:54:03Z : No. of bitstreams: 1 lopes_jr_me_sjrp.pdf: 325435 bytes, checksum: 90136719a8eb0c15c4ae524dada45238 (MD5) / Câncer de mama representa a mais comum das neoplasias no sexo feminino, respondendo por 22% dos novos casos de câncer a cada ano. As neoplasias mamárias são ainda mais freqüentes na espécie canina, representando aproximadamente 52% de todas as neoplasias nas cadelas. A identificação de agentes terapêuticos que possam ser utilizados no tratamento alternativo para este tipo tumoral têm se revelado extremamente útil. A melatonina, um hormônio natural, parece exercer efeito oncostático em diferentes tipos de neoplasias. Considera-se como provável mecanismo de ação, sua interação com receptores estrogênicos e com os receptores MT1 e MT2 das células epiteliais, inibindo a proliferação das células neoplásicas. Dessa forma, o objetivo deste estudo foi avaliar o potencial valor terapêutico da melatonina em linhagens de câncer de mama e em tumores mamários caninos estrógeno-positivo e estrógeno-negativo, além de relacionar sua ação com a expressão dos receptores MT1 e MT2. A identificação de tumores mamários estrógeno-positivo e negativo foi realizada por meio de imuno-histoquímica e a expressão dos genes MT1 e MT2 nas amostras foi analisada por PCR em tempo real. As células cultivadas, provenientes dos tumores e das linhagens MCF-7 e MDA-MB-231 foram tratadas com melatonina e a viabilidade celular foi analisada pelo ensaio MTT. Observou-se 40% de redução na viabilidade celular nos tumores RE+ e RE- quando tratados, respectivamente, com 1mM e 10mM de melatonina (p<0,05). Além disso, os tumores RE+ apresentaram alta expressão dos receptores de melatonina MT1 e MT2 quando comparados aos tumores RE-. Com relação às linhagens, a linhagem MCF-7 (RE+) reduziu em 63% a viabilidade celular quando tratada com 10mM de melatonina (p<0,05) e para a linhagem MDA-MB-23 (RE-), esta mesma... / Breast cancer is the most common cancer in women, accounting for 22% of new cancer cases each year. The mammary neoplasias are also common in canine species, representing about 52% of all cancers in female dogs. The identification of therapeutic agents that can be used as an alternative treatment for this tumor type has proven to be extremely useful. Melatonin, a natural hormone, can exercise oncostatic effects in several types of neoplasias. It is considered as a probable mechanism of action, their interaction with estrogenic receptors and with MT1 and MT2 receptors of the epithelial cells by inhibiting the proliferation of neoplastic cells. In this context, the objective of this study was to evaluate the potential therapeutic value of melatonin in breast cancer cell lines and canine mammary tumors estrogen-positive and estrogen-negative, also establishing relationship of its action to the MT1 and MT2 receptor. Identification of canine mammary tumors ER+ and negative was performed by immunohistochemistry and gene expression MT1 and MT2 in the samples was analyzed by real-time PCR. Cells cultured from the tumors and cell lines MCF-7 and MDA-MB-231 were treated with melatonin and cell viability was analyzed by MTT assay. We observed 40% reduction in cell viability in ER+ tumors and ER- when treated, respectively, with 1mM and 10mM melatonin (p <0.05). Furthermore, the ER+ tumors showed high expression of melatonin receptors MT1 and MT2 when compared to ER- tumors. Regarding cell lines, the cell line MCF-7 (ER+) showed 63% reduction in cell viability when treated with 10mM of melatonin (p <0.05) for the cell line MDA-MB-23 (ER-), this same concentration reduced 50% cell viability (p <0.05). The results suggest that melatonin decreases the viability of neoplastic cells, being more effective for RE-positive tumors... (Complete abstract click electronic access below)

\ / Doctorat en sciences, Spécialisation biologie moléculaire / info:eu-repo/semantics/nonPublished

Submitted in the fulfillment of the requirement for the Degree of Master's in Chemistry, Durban University of Technology, 2017. / P53 is a tumour suppressor protein that is dysfunctional in most human cancer cells. Mutations in the p53 genes result in the expression of mutant proteins which accumulate to high levels in tumour cells. Several studies have shown that majority of the mutations are concentrated in the DNA-binding domain where they destabilize its conformation and eliminate the sequence- specific DNA-binding to abolish p53 transcription activities. Accordingly, this study involved an investigation of the effects of mutations associated with cancer, based on the framework of sequences and structures of p53 DNA-binding domains, analysed by SIFT, Pmut, I-mutant, MuStab, CUPSAT, EASY-MM and SDM servers. These analyses suggest that 156 mutations may be associated with cancer, and may result in protein malfunction, including the experimentally validated mutations. Thereafter, 54 mutations were further classified as disease- causing mutations and probably have a significant impact on the stability of the structure. The detailed stability analyses revealed that Val143Asp, Ala159Pro, Val197Pro, Tyr234Pro, Cys238Pro, Gly262Pro and Cys275Pro mutations caused the highest destabilization of the structure thus leading to malfunctioning of the protein. Additionally, the structural and functional consequences of the resulting highly destabilizing mutations were explored further using molecular docking and molecular dynamics simulations. Molecular docking results revealed that the p53 DNA-binding domain loses its stability and abrogates the specific DNA-binding as shown by a decrease in binding affinity characterized by the ZRANK scores. This result was confirmed by the residues Val143Asp, Ala159Pro, Val197Pro, Tyr234Pro and Cys238Pro p53-DNA mutant complexes inducing the loss of important hydrogen bonds, and introduced non-native hydrogen bonds between the two biomolecules. Furthermore, Molecular dynamics (MD) simulations of the experimental mutant forms showed that the structures of the p53 DNA-binding domains were more rigid comparing to the wild-type structure. The MD trajectories of Val134Ala, Arg213Gly and Gly245Ser DNA-binding domain mutants clearly revealed a loss of the flexibility and stability by the structures. This might affect the structural conformation and interfere with the interaction to DNA. Understanding the effects of mutations associated with cancer at a molecular level will be helpful in designing new therapeutics for cancer diseases. / M

DNA damage is a constant threat to our genomes which drives genome instability and contributes to cancer progression. DNA damage interferes with important DNA transactions such as transcription and replication. DNA lesions are removed by repair pathways that ensure genome stability during transcription and replication. Here, we identify and characterize distinct roles for the ultra violet stimulated scaffold protein A (UVSSA) in the maintenance of genome stability during transcription in human cells. First, we unravel a novel function for UVSSA in transcription-coupled repair of DNA interstrand crosslinks (ICLs), genotoxic adducts that covalently bind opposing strands of the DNA and block transcription and replication. UVSSA knockout cells are sensitive to ICL inducing drugs, and UVSSA is specifically required for transcription-coupled repair of ICLs in a fluorescence-based reporter assay. Based on analysis of the UVSSA protein interactome in crosslinker treated cells we propose a model for transcription-coupled ICL repair (TC-ICR) that is initiated by stalling of transcribing RNA polymerase II (Pol II) at an ICL. Stalled Pol II is first bound by CSA and CSB, followed by UVSSA which recruits TFIIH to initiate downstream lesion removal steps. Second, we establish that UVSSA counteracts MYC dependent transcription stress to promote genome stability in cells aberrantly expressing the cMYC oncogene. UVSSA knockdown sensitizes cells to MYC expression, resulting in synthetic sickness and increased doubling time. UVSSA knockdown impacts Pol II dynamics in MYC activated cells. We conclude that UVSSA is required for regulation of Pol II during MYC induced transcription to prevent transcription stress. Together, these studies expand our understanding of UVSSA’s role in genome stability during transcription and elucidates the poorly understood transcription-coupled ICL repair pathway.

Cancer is the leading cause of death in Hong Kong (21,300 new cases and 11,500 deaths in 2003), with nasopharyngeal carcinoma (NPC), esophageal cancer (ESCC), and colorectal cancer (CRC) among the common ones. For these tumors, most patients present with advanced stage disease and poor treatment outcome, with an urge of early detection. Epigenetic inactivation of tumor suppressor genes (TSG) by CpG methylation represents an important mechanism of tumorigenesis, in addition to genetic abnormalities. Tumor-specific methylation can also be used as biomarkers for the identification of novel TSGs and for cancer early diagnosis and prognosis prediction. / Finally, for the purpose of development of epigenetic biomarker for cancer molecular diagnosis, I screened gene methylation in the serum samples. Aberrant methylation of PCDH10 and DLC1 was detected in serum samples (2/14 (14%) and 4/14 (29%) respectively) from tumor patients but not in normal controls. It suggests that screening for PCDH10 and DLC1 methylation in sera could be a tumor-specific and non-invasive epigenetic biomarker for molecular diagnosis and prognostics. (Abstract shortened by UMI.) / In the second approach, 1-Mb array-based comparative genomic hybridization (aCGH) was carried out to detect DNA copy number aberrations, which contain potential TSG loci, in a panel of NPC and ESCC cell lines. Frequent deletions include: 1p36.3, 3p14-11, 4p16-15, 5p13-q12, 6p21-12, 8p22-cent, 9p, 9q22-31, 10p, 13q12, 14q32, 16q23-24, 17q11.2, 18q in NPC, and 1p21, 4q21, 7p21, 7q35, 8p22-23, 8q11, 10p11, 11q22, 13q31, 14q32, 18q11-23 in ESCC. Several deletions (3p14-11 and 16q23) were further investigated in detail in this study. More than 12 genes were identified to be frequently silenced by methylation in tumors, including FHIT (3p14), WNT5A (3p14), ADAMTS9 (3p14), FEZF2 (3p14), ROBO (3p12), CADM2 (3p12), EPHA3 (3p11), RAB (11q22), ADAMTS18 (16q23), and TUSC8 (16q23), while homozygous deletion of these genes was infrequently detected. Aberrant methylation of these genes was also frequently detected in primary tumors in a tumor-specific manner. The tumor suppressor functions of TUSC8, WNT5A, CADM2 and ROBO were further investigated and validated. Further experiment indicated that induction of tumor cell apoptosis may contribute to the tumor suppressor function of TUSC8. / Modified genomic methylation subtractive approaches using uracil-DNA glycosylase or combined with pharmacological demethylation were developed. GADD45G, PCDH10, ROR2, DLC1L1 were among a series of novel methylated targets identified by these approaches. Methylation-associated silencing of these genes was frequently detected in various types of tumor cell lines and primary tumors including NPC, ESCC and CRC, in a tumor-specific manner. Ectopic expression of these genes strongly suppressed tumor cell growth and colony formation of silenced tumor cells. Epigenetic inactivation of GADD45G is the major mechanism for the loss of its response to environmental stresses. Reintroduction of PCDH10 strongly suppressed tumor cell migration and invasion. Ectopic expression of DLC1L1 in silenced tumor cells resulted in a remarkable suppression of tumor cell clonogenicity, which depends on its GAP activity. Furthermore, DLC1L1, but not its inactivating mutants, inhibited Ras mediated oncogenic transformation. Thus, these identified genes are functional TSGs. / Ying Jianming. / "July 2007." / Adviser: Qian Tao. / Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0083. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 147-173). / 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. / Abstract in English and Chinese. / School code: 1307.