A siRNA screen to identify molecular determinants of tumour radiosensitivity
<p>The effectiveness of radiotherapy treatment could be significantly improved if tumour cells could be rendered more sensitive to ionising radiation without altering the sensitivity of normal tissues. However, many of the key mechanisms that determine intrinsic tumour radiosensitivity are lar...
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| Format: | Thesis |
| Language: | English |
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2010
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| _version_ | 1826300336616243200 |
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| author | Higgins, G Geoffrey Higgins |
| author2 | McKenna, G |
| author_facet | McKenna, G Higgins, G Geoffrey Higgins |
| author_sort | Higgins, G |
| collection | OXFORD |
| description | <p>The effectiveness of radiotherapy treatment could be significantly improved if tumour cells could be rendered more sensitive to ionising radiation without altering the sensitivity of normal tissues. However, many of the key mechanisms that determine intrinsic tumour radiosensitivity are largely unknown. This thesis is concerned with the identification of novel determinants of tumour radiosensitivity. A siRNA screen of 200 genes involved in DNA damage repair was conducted using γH2AX foci post-irradiation as a marker of cell damage. This screen identified POLQ as a potential tumour-specific contributor to radioresistance. Subsequent investigations demonstrated that POLQ knockdown resulted in radiosensitisation of a panel of tumour cell lines, whilst having little or no effect on normal tissue cell lines.</p> <p>It was subsequently shown that POLQ depletion rendered tumour cells significantly more sensitive to several classes of cytotoxic agents. Following exposure to etoposide, it was found that tumour cells depleted of POLQ had reduced RAD51 foci formation, suggesting that POLQ is involved in homologous recombination. A homologous recombination assay was used to confirm that POLQ depletion does indeed result in reduced homologous recombination efficiency.</p> <p>These findings led to the investigation of the clinical significance of tumour overexpression of <em>POLQ</em>. The clinical outcomes of patients with early breast cancer were correlated with tumour expression levels of <em>POLQ</em>. It was found that <em>POLQ</em> overexpression was correlated with ER negative disease and high tumour grade, both of which are associated with poor clinical outcomes. <em>POLQ</em> overexpression was associated with extremely poor relapse free survival rates, independently of any other clinical or pathological feature. The mechanism that causes this adverse outcome may in part arise from resistance to adjuvant chemotherapy and radiotherapy treatment. These findings, combined with the limited normal tissue expression of <em>POLQ</em>, make it an appealing target for possible clinical exploitation.</p> |
| first_indexed | 2024-03-07T05:15:35Z |
| format | Thesis |
| id | oxford-uuid:dd1472c2-225c-47df-80a6-67adf2fdaae7 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T05:15:35Z |
| publishDate | 2010 |
| record_format | dspace |
| spelling | oxford-uuid:dd1472c2-225c-47df-80a6-67adf2fdaae72022-03-27T09:22:21ZA siRNA screen to identify molecular determinants of tumour radiosensitivityThesishttp://purl.org/coar/resource_type/c_db06uuid:dd1472c2-225c-47df-80a6-67adf2fdaae7TumoursRadiationEnglishOxford University Research Archive - Valet2010Higgins, GGeoffrey HigginsMcKenna, G<p>The effectiveness of radiotherapy treatment could be significantly improved if tumour cells could be rendered more sensitive to ionising radiation without altering the sensitivity of normal tissues. However, many of the key mechanisms that determine intrinsic tumour radiosensitivity are largely unknown. This thesis is concerned with the identification of novel determinants of tumour radiosensitivity. A siRNA screen of 200 genes involved in DNA damage repair was conducted using γH2AX foci post-irradiation as a marker of cell damage. This screen identified POLQ as a potential tumour-specific contributor to radioresistance. Subsequent investigations demonstrated that POLQ knockdown resulted in radiosensitisation of a panel of tumour cell lines, whilst having little or no effect on normal tissue cell lines.</p> <p>It was subsequently shown that POLQ depletion rendered tumour cells significantly more sensitive to several classes of cytotoxic agents. Following exposure to etoposide, it was found that tumour cells depleted of POLQ had reduced RAD51 foci formation, suggesting that POLQ is involved in homologous recombination. A homologous recombination assay was used to confirm that POLQ depletion does indeed result in reduced homologous recombination efficiency.</p> <p>These findings led to the investigation of the clinical significance of tumour overexpression of <em>POLQ</em>. The clinical outcomes of patients with early breast cancer were correlated with tumour expression levels of <em>POLQ</em>. It was found that <em>POLQ</em> overexpression was correlated with ER negative disease and high tumour grade, both of which are associated with poor clinical outcomes. <em>POLQ</em> overexpression was associated with extremely poor relapse free survival rates, independently of any other clinical or pathological feature. The mechanism that causes this adverse outcome may in part arise from resistance to adjuvant chemotherapy and radiotherapy treatment. These findings, combined with the limited normal tissue expression of <em>POLQ</em>, make it an appealing target for possible clinical exploitation.</p> |
| spellingShingle | Tumours Radiation Higgins, G Geoffrey Higgins A siRNA screen to identify molecular determinants of tumour radiosensitivity |
| title | A siRNA screen to identify molecular determinants of tumour radiosensitivity |
| title_full | A siRNA screen to identify molecular determinants of tumour radiosensitivity |
| title_fullStr | A siRNA screen to identify molecular determinants of tumour radiosensitivity |
| title_full_unstemmed | A siRNA screen to identify molecular determinants of tumour radiosensitivity |
| title_short | A siRNA screen to identify molecular determinants of tumour radiosensitivity |
| title_sort | sirna screen to identify molecular determinants of tumour radiosensitivity |
| topic | Tumours Radiation |
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