Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 122-140).

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 164-183). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 164-183). Also available on the Internet.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 119-155).

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Clinical Oncology / Master / Master of Philosophy

NK-cell malignancies (NKLL) consist of two separate entities: Extranodal NK-cell lymphoma, nasal type (ENKL) and aggressive NK-cell leukemia (ANKL). ENKL is the second most common group of extranodal lymphomas in Hong Kong. Deletions in the 6q21 region in ENKL have been consistently reported in the literature and differential expression data indicated that the transcription factor PRDM1 (PR domain containing 1, with ZNF domain) located at 6q21-q22.1 is a candidate TSG in NK-cell neoplasms. PRDM1 exists as 2 isoforms generated from the same gene by alternative transcription promoter. PRDM1- differs from PRDM1-βin that it lacks the amino-terminal 101 amino acids with a disrupted PR domain. As the PRDM1- is functionally impaired, with a loss of repressive function on multiple target genes while maintaining normal DNA-binding activity, we hypothesize that the  -isoform, which is overexpressed in NKLLs, may act as a negative regulator of the tumor suppressive α-isoform in NKLLs. In this study, we investigated the possible role of PRDM1- as a negative regulator of tumor suppressor PRDM1-α in NK-cell lymphoma by using a gene silencing technique. Short hairpin-RNA (sh-RNA) construct with sequence targeting to PRDM1- purchasing from biotechnology company was used to knockdown of the gene expression. Series of functional assays were then performed to evaluate the effect of the PRDM1-  knockdown in two NK cell line, YT and NKYS, which xpress endogenous PRDM1-. Comparison was made between the 1) shRNA targeting to nt65-nt94 of PRDM1- sequence, sh-PRDM1 -pGFP-V-RS (shV2), and 2) scrambled-pGFPV-RS (scrambled shRNA), negative control with a non-effective shRNA cassette in pGFP-VRS plasmid. Western blot analysis was performed to examine the efficiency of shRNA in knockdown the expression of PRDM1-  in 293T cells (normal human embryonic kidney cells). The protein expression level for ectopic PRMD1- was reduced in cells expressing shV2 when compared with the negative control. NKYS cell line expressed with shV2 showed a significant reduction in the number of colonies. Percentage of dead cells was found higher in these cells. The proliferation rate of shV2 expressing cells started to retarded significantly on the third day of measurement in the MTS proliferation assay. The cell also underwent G1 cell cycle arrest and had lower proliferation rate, as indicated by cell cycle analysis. For YT cell line expressed with shV2, significant reduction in both colony number and size in methylcellulose colony formation assay was observed. Base on the results obtained from the two NK-cell lines, we suggest that the shV2 inhibit the tumor cell growth. The knockdown of the PRDM1-  lead to an increase level of PRDM1- α. PRDM1- α is a tumor suppressor gene with suppressive function by preventing damaged cells from proliferation or inhibiting the clonogenecity of the tumor cells. An imbalance expression of PRDM1- and PRDM1-αplay an important role in tumor growth and formation, and PRDM1 could possibly be the new tumor suppressor gene in NK-cells lymphoma. / published_or_final_version / Pathology / Master / Master of Medical Sciences

Acute promyelocytic leukemia (APL) is one of the subtypes of acute myeloid leukemia carrying t(15;17), and constitutes 10 to 15% of adult AMLs. One of the mechanisms of gene inactivation is hypermethylation of promoter-associated CpG islands. Cancers are characterized by global hypomethylation with locus-specific hypermethylation and hence silencing of tumor suppressor genes. Apart from tumor suppressor genes, microRNA, a class of non-coding RNA measuring 19-25 nucleotides, with tumor suppressive function is also found to be inactivated by DNA methylation in hematological malignancies. microRNAs repress target gene translation and hence expression by binding to 3'-untranslated region of corresponding mRNA. Because TP53 mutation is frequently involved in solid cancer carcinogenesis but is rarely found in APL, TP53 network may be dysregulated through epigenetic inactivation of tumor suppressor gene/miRNAs engaged in TP53 tumor suppressor network. This thesis aimed to study DNA methylation of tumor suppressor genes and miRNAs engaged in TP53 tumor suppressor network in APL. Overall survival (OS) and event free survival (EFS) of patients with or without candidate gene/miRNA hypermethylation were compared to examine their prognostic significances. Promoter methylation of DAPK1, p14ARF, miR-34a, miR-34b/c and miR-605 were studied in 10 normal bone marrow samples, NB4 cell line and 60 APL primary samples at diagnosis by methylation-specific PCR (MSP). DAPK1, miR-34a, miR-34b/c and miR-605 were completely unmethylated in normal bone marrow samples but completely methylated in NB4. Treatment of NB4 by 5'-Aza-2'-deoxyctidine (5-azadC) resulted in promoter demethylation together with re-expression of DAPK1, miR-34a, miR-34b/c and miR-605. Promoter methylation of DAPK1, p14ARF, miR-34a were absent while miR-34b/c and miR-605 methylation were detected in 43% and 10% APL samples respectively. However, methylation of miR-34b/c and miR-605 bore no prognostic significance. Overexpression of miR-34b in NB4 resulted in inhibition of proliferation. In short, methylation of DAPK1, miR-34a, miR-34b/c and miR-605 is associated with gene/miRNAs silencing. miR-34b/c is frequently methylated whereas miR-605 is methylated in small number of APL patients. miR-34b/c is a tumor suppressive miRNA in APL. Methylation of miR-34b/c may contribute to APL leukemogenesis. / published_or_final_version / Medicine / Master / Master of Philosophy