Date of Award

2010

Document type

Thesis

Degree Name

PhD (Doctor of Philosophy)

First Supervisor

Professor Raymond Stallings

Second Supervisor

Dr. Isabella Bray

Funder/Sponsor

The work carried out in this thesis was kindly supported by The Children's Medical and Research Foundation Our Lady's Children's Hospital, Crumlin.

Keywords

MicroRNAs

Abstract

MicroRNA dysregulation has been widely reported in many cancers, including neuroblastoma, an often fatal paediatric cancer originating from precursor cells of the sympathetic nervous system. MiRNAs function as negative regulators of post-transcriptional gene expression, and can have oncogenic or tumour suppressor functions.

Here, we describe a large number of miRNAs that have altered expression in All-Trans Retinoic Acid (ATRA) induced differentiation of neuroblastoma cell lines. Differentiation status is associated with good prognosis in neuroblastoma, suggesting these ATRA-sensitive miRNAs play an essential mechanistic role in neuroblastoma pathogenesis. The aim of our study was to elucidate the functional role of ATRA-sensitive miRNAs, and their contribution to neuroblastoma outcome and disease. Forced over or under-expression of miR- 184, miR- 1 Oa, miR- 1 Ob, miR- 152 and miR-196a was accomplished in a variety of neuroblastoma cell lines, allowing us to determine the biological effects of each individual miRNA. The phenotypic effects included mo~-phological differentiation, increased apoptosis, decreased cell proliferation, invasiveness, anchorage-independent cell growth, along with alterations in DNA methylation patterns and profound changes in rnRNA transcript levels. mRNA targets were identified for miR-184 (AKT2), miR-10 (NCOR2) and miR-152 (DNMTI), allowing us to further define the mechanism by which each miRNA alters the cellular phenotype.

In conclusion, this study describes a detailed functional analysis of five ATRA-induced miRNAs. We identified rniRNAs that play functional roles in apoptosis, DNA methylation and differentiation in neuroblastoma cancer cells and demonstrated the relevance of these miRNAs to clinical parameters in neuroblastoma primary tumours. It is also proposed that these miRNAs could be of some value in potential rniRNA-mediated therapeutics given their anti-proliferative effects on cells in vitro.

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Comments

A thesis submitted to the Royal College of Surgeons in Ireland for the degree of Doctor of Philosophy from the National University of Ireland in 2010