Sarah Harbord
SARAH HARBORD- MSc DEFENSE
“X Chromosome Abnormalities in Breast and Ovarian Cancer”
BSc, Queen’s University, 2003
Tuesday, November 27, 2007, 9:00 am
, Room 3113, Child and Family Research Institute
Sarah Harbord-MSc Defense program-pdf
SUPERVISORY COMMITTEE
Dr. Wendy Robinson Dr. Carolyn Brown
Dr. Barb McGillivray
EXAMINING COMMITTEE
Chair: Dr. Angie Brooks-Wilson (Medical Genetics)Supervisory Committee: Dr. Carolyn Brown (Medical Genetics)
University Examiner: Dr. David Huntsman (Pathology)
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, we assayed two markers of X reactivation 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.PRESENTATIONS
S. Harbord, C.J. Brown, N. Auersperg, C. Salamanca, A. Cotton, W.P. Robinson. Genetic and epigenetic evidence for gain of active X-linked genes in both BRCA1 and non-BRCA1 ovarian cancers. American Society of Human Genetics 57th Annual Meeting, San Diego, Oct 23-27, 2007.
S. Harbord, C.J. Brown, D. Horsman, S. Young, W.P. Robinson. Androgen Receptor (AR) and Estrogen Receptor alpha (ESR1) Variants Have Minimal Impact upon Cancer Susceptibility in BRCA1 Mutation Carriers. American Society of Human Genetics 56th Annual Meeting, New Orleans, Oct 9-13, 2006.
S. Harbord, C.J. Brown, D. Horsman, WP Robinson. Skewed X Chromosome Inactivation is limited to BRCA1mutation negative Breast and Ovarian Cancer Patients American Society of Human Genetics 55th Annual Meeting, Salt Lake City, Oct 25-29, 2005.
AWARDS
2005-2007 Interdisciplinary Women's Health Research Scholarship (CIHR)
2004 UBC Medical Genetics Entrance Scholarship (UBC)
2003 Industrial Research Award (NSERC)
2003 The Queen's Golden Jubilee Medal of Canada (Government of Canada)
2002 Roberta and Bella Martin Award (Queens University)
COURSES
MEDG 520: Advanced Human Molecular Genetics, Dr. A. Brooks-WilsonMEDG 521: Molecular and Cell Biology of Cancer, Dr. P. Hoodless
MEDG 530: Human Genetics, Dr. L. Clarke
MEDG 545: Current Topics in Medical Genetics Research, Dr. W. Robinson