Ovarian cancer (OCa) remains the leading cause of death due to a gynecologic malignancy in North American women, and the pathogenesis of this disease is a consequence of the interplay between DNA, RNA and proteins. The genomes of these cancers are characterized by numerical and structural aberrations, resulting in copy number changes of the affected regions. The serine protease, Kallikrein 6 (KLK6), is a promising biomarker and is over-expressed in OCa. However, the mechanisms leading to the observed KLK6 overexpression are poorly understood; and to date, no study examining the chromosomal contributions to the overexpression have been conducted. Utilization of multi-colour Fluorescence in situ Hybridization (FISH)-based technologies to untreated primary serous OCa samples and cancer cell lines, showed that the KLK locus, on 19q13.3/4, is involved in both numerical and structural aberrations; was subject to high-level copy-number heterogeneity (p<0.001); and structural rearrangements of 19q were significantly co-related to grade (p<0.001). Patients with a loss of the KLK locus, or no structural rearrangement on 19q, experienced a trend towards longer disease free survival (DFS and better overall survival (OS), over those with a gain or amplification, or with breakage events on 19q. KLK6-specific immunohistochemistry (IHC) showed weak correlation with KLK6 copy-number, suggesting other mechanisms together with copy-number, drives its over-expression.
Among these mechanisms are microRNA (miRNAs), also shown to be affected by the copynumber changes in OCas. Therefore, we investigated the role of miRNAs in OCa and their role in KLK6 regulation. Specifically, we examined the copy-number status and miRNA expression in a representative OCa cell line, OVCAR-3. miRNA expression profiling of OCa cell lines and primary tumours showed their differential expression, including the decrease in expression of the let-7 family members, which are predicted to target KLK6. Indeed, when hsa-let-7a was transiently transfected into OVCAR-3, a reduction of secreted KLK6 protein was detected. Thus,
the contribution of numerical and structural aberrations of the OCa genome can directly affect the expression KLK6 through copy-number, but is also aided post-transcriptionally by miRNAs.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/35774 |
| Date | 02 August 2013 |
| Creators | Bayani, Jane Marie |
| Contributors | Diamandis, Eleftherios P., Squire, Jeremy A. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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