Colorectal cancer is the second leading cause of death from cancer (men and women combined) in the U.S. and Canada. The mainstay of treatment remains surgical resection and although new agents are constantly emerging to treat colorectal cancer, to date none of the agents have been successful at curing patients with advanced disease. In recent years there has been an increasing interest in the notion that cancers are organized as a hierarchy with the cancer-initiating cell (C-IC or cancer stem cell) existing at the apex. The C-ICs only represent a subset of the total tumour cells; however, research indicates that they are responsible for both the initiation and maintenance of tumour growth. In the studies presented here, we determined that human colon cancers are organized in a hierarchical manner. Furthermore, we prospectively isolated a subset of colon cancer-initiating cells (CC-ICs) based on the expression of the cell surface marker, CD133. The identification of CC-ICs has led to a number of questions concerning the molecular mechanisms driving these cells. Functionally all C-ICs are characterized by their ability to: i) generate a xenograft that histologically resembles the parent tumour from which it was derived, (ii) be serially transplanted in a xenograft assay thereby demonstrating the ability to self-renew and, (iii) generate daughter cells that possess some proliferative capacity but are unable to maintain the cancer because they lack intrinsic regenerative potential. It is becoming evident that cancer cells evolve as a result of their ability to hijack normal self-renewal pathways, a process that can drive malignant transformation. Studying self-renewal in the context of cancer and C-IC maintenance will lead to a better understanding of the mechanisms driving tumour growth. In this work we demonstrate that the inhibitors of differentiation genes (Id1 and Id3) play a central role in driving self-renewal in the CC-IC subset. Furthermore, we demonstrate that this effect is partially mediated through the cdk-inhibitor, p21cip1/waf1.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/32080 |
| Date | 19 January 2012 |
| Creators | O'Brien, Catherine Adell |
| Contributors | Gallinger, Steven |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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