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X chromosome studies and breast and ovarian carcinoma

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dc.contributor.author Harbord, Sara Helen Alison
dc.date.accessioned 2007-12-06T20:02:36Z
dc.date.available 2007-12-06T20:02:36Z
dc.date.copyright 2007 en
dc.date.issued 2007-12-06T20:02:36Z
dc.identifier.uri http://hdl.handle.net/2429/212
dc.description.abstract Skewed somatic X inactivation (XCI), X-linked gene overexpression and abnormal X content have been associated with breast and ovarian cancer. Partial or complete reactivation of the inactive X in females may be a step in breast and ovarian cancer progression, leading to overexpression of some tumour enhancing gene. Markers of an X reactivation event were examined: X gene dosage, expression, and methylation in 8 ovarian cancer cell lines. Another marker of an X reactivation event, skewed XCI, was assayed in peripheral blood DNA from 106 breast and/or ovarian cancer patients (52 BRCA1 mutation carriers, 24 BRCA2 mutation carriers, 30 non-mutation carriers), 147 age-matched population controls. Combined RNA/DNA FISH was used to quantify the number of inactive Xs compared to total number of Xs. Five cell lines had increased X content. Three cell lines localized XIST to the presumptive inactive X; however the numbers of inactive Xs were variable. Expression levels of 8 X-linked genes were assessed by real-time PCR. Expression was inconsistent between different genes and among cell lines, ranging from a 2 to 300-fold increase compared to a control. Overall, expression was greatly increased for genes subject to inactivation but not increased in genes that escape inactivation for most ovarian cancer cell lines. Methylation at AR and FMR1 was quantified by a real-time PCR based assay and SNuPE respectively. Methylation was lower than expected for 7 of 8 ovarian cancer cell lines at AR or FMR1, while three cell lines had low or no methylation for both genes. Skewed XCI was evaluated using a methylation-based PCR assay at AR. There was no significant increase in skewing above 90% for any cancer group assayed. In addition, two markers of X reactivation were assayed in two low passage cultures of normal ovarian surface epithelium from BRCA1 mutation positive breast cancer patients. One sample did not localize XIST to the inactive X and three of five genes subject to inactivation were overexpressed. In summary, there is evidence for loss of X silencing or gain of active X content in ovarian cancer cell lines and normal ovarian surface epithelium from BRCA1 mutation carriers. en
dc.format.extent 1058363 bytes
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher University of British Columbia
dc.subject genetics en
dc.subject breast and ovarian carcinoma en
dc.subject breast cancer en
dc.subject ovarian cancer en
dc.title X chromosome studies and breast and ovarian carcinoma en
dc.type Electronic Thesis or Dissertation
dc.degree.name Master of Science - MSc en
dc.degree.discipline Medical Genetics en
dc.degree.grantor University of British Columbia
dc.date.graduation 2008-05 en


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