RARβ genetic and epigenetic alterations in aero-respiratory tract cancers

Warrak, Suemyya. (2004) RARβ genetic and epigenetic alterations in aero-respiratory tract cancers. PhD thesis, University of Liverpool.

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Abstract

Early detection of lung and head and neck cancer would potentially improve diagnosis and prognosis. For such an approach to be successful, specific and novel markers at a pre-clinical stage of the disease must be identified. There is growing evidence that hypermethylation of CpG-rich sequences in the promoter regions of tumour suppressor genes such as RARJ3, may lead to long-term transcriptional silencing of such genes and thus contribute to tumour development. Many previous studies have implicated RARJ3 promoter methylation in the transcriptional silencing of the RARJ3 gene in a variety of cancers. Since carcinogenesis is a multi-step process that arises as a result of combinations of genetic and epigenetic events, it was the purpose of this study to investigate both genetic changes such as mutations and allelic imbalance, as well as epigenetic changes such as aberrant methylation and establish whether the presence of such changes was influencing transcription of isoforms one and two of the RARJ3 gene in non-small cell lung cancer and head and neck squamous cell carcinoma. Mutational analysis revealed a lack of mutations within all the coding exons of the RAR~ gene sequence, whilst allelic imbalance studies on five microsatellite markers within and surrounding the gene demonstrated relatively high levels of allelic imbalance. Methylation analysis of the RARJ3 promoter was carried out using the much utilized MSP method and the results obtained displayed a significant level of aberrant hypermethylation in non-small cell lung cancer and head and neck squamous cell carcinoma tumour samples compared to their corresponding normal samples. Sensitivity and specificity of the MSP method was also studied and results suggested that more stringent controls are needed as well as exceptionally specific conditions so as to achieve analysis-analysis reproducibility. Expression analysis of RARJ3 isoform one displayed significance levels of expression in a variety of normal tissues including lung and head and neck tissue, furthermore, analysis of both isoforms in non-small cell lung cancer and head and neck squamous cell carcinoma samples revealed no statistically significant differences in expression levels between normal and tumour paired samples, which implies that RARJ3 differential expression may not be as significant a marker of carcinogenesis as previously considered. The study demonstrated that whilst differential expression was not found as being a feature of non-small cell lung cancer or head and neck squamous cell carcinoma, allelic imbalance as well as aberrant promoter methylation of the RARJ3 gene were found to be frequent features of both these diseases, although the number of clinical samples investigated did not allow statistically significant correlations to be made.

Item Type:	Thesis (PhD)
Depositing User:	Symplectic Admin
Date Deposited:	20 Oct 2023 14:38
Last Modified:	20 Oct 2023 14:49
DOI:	10.17638/03174884
Copyright Statement:	Copyright © and Moral Rights for this thesis and any accompanying data (where applicable) are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge.
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3174884