Despite improvements in treatment strategies for head and neck squamous cell carcinoma (HNSCC), clinical outcome has remained disappointing, with 5-year overall survival rates hovering around 40-50%, underscoring an urgent need to better understand the biological bases of this disease. We chose to address this challenge by studying the role of micro-RNAs (miRNAs), and iron in HNSCC.
We performed global profiling on 51 primary HNSCC compared to 4 normal laryngeal epithelial tissues, and identified 38 differentially expressed miRNAs between cancer vs. normal patient tissues. Functional validation confirmed a tumour promoting phenotype for miR-106b and miR-375. Integrating these findings with global miR profiling of HNSCC revealed two significantly over expressed miRNAs in HNSCC cell lines and patient samples: miR-193b and miR-205. Knockdown of miR-205 and miR-193b in HNSCC cell lines significantly decreased cell proliferation and colony formation. Moreover, NF1 was identified as a target of miR-193b. Downstream targets of NF1 including active-RAS and p-ERK were also suppressed after miR-193b knockdown. Finally, HNSCC patients with high levels of miR-193b experienced a lower disease-free survival than patients with low miR-193b expression.
The second approach we took to better understand the biology of HNSCC was to examine the involvement of iron in the disease. In a panel of HNSCC cell lines, hemochromatosis (HFE) was one of the most overexpressed genes involved in iron regulation. Knockdown of HFE in HNSCC cell lines significantly decreased intracellular iron levels, resulting in a significant decrease in HNSCC cell proliferation, DNA synthesis, and Wnt signalling. When iron was re-introduced back into the cell after HFE knockdown, these cellular changes were reversed, indicating that iron was mediating this phenotype. Concordantly, HNSCC cells treated with an iron chelator ciclopirox olamine (CPX) significantly reduced proliferation and clonogenic survival. Finally, patients with high HFE expression experienced a reduced survival compared to patients with low HFE expression, corroborating the oncogenic role of HFE in HNSCC.
In summary, using two independent methods, we have identified two potential prognostic biomarkers for HNSCC, namely miR-193b and HFE. Characterization of these two molecules, exposed critically dysregulated pathways driving disease progression. Specifically, the miR-193b~NF1 axis uncovered a novel mechanism of RAS and p-ERK activation in HNSCC; similarly, HFE exposed a novel tumour promotion role of iron in this disease.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/43629 |
| Date | 10 January 2014 |
| Creators | Lenarduzzi, Michelle |
| Contributors | Liu, Fei-Fei |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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