Breast and pancreatic cancers are among the major causes of cancer mortality in our society. There has been a significant decline in mortality from breast cancer over the last two decades, while pancreatic cancer has an exceptionally poor prognosis. Although these malignancies have very different clinical outcomes they share the common feature that metastatic disease is almost uniformly fatal. The existence of cancer stem cells has been postulated as a major factor in tumour recurrence after traditional chemo- or radio-therapy. Addressing this important clinical question requires a deeper understanding of the biology of normal and cancer stem cells and the signalling pathways involved in their regulation. The identity of the pancreatic stem cell remains elusive. However, using a murine model of haematopoietic stem cell (HSC) transplantation I have demonstrated for the first time transdifferentiation of these bone marrow derived cells into mature pancreatic acinar cells, where they appear to contribute to cell turnover ultimately forming acini and lobules. These data show that HSC have surprising developmental plasticity and provide insight into a potential stem cell niche in the pancreas. The Hedgehog, Wnt and Notch signalling pathways play a critical role in early development and in the maintenance and self-renewal of stem cells. There is also increasing evidence that dysregulation of these pathways contributes to the development of many malignancies. There is relatively little information regarding their role in breast cancer development and progression. I used immunohistochemistry for key proteins in these pathways, sonic hedgehog, beta-catenin and Notch 1 in three substantial series of human breast lesions and determined that abnormal expression of these proteins is an early event in the development in breast cancer, and is associated with particular breast cancer subtypes, Shh and beta-catenin expression is associated predominantly with the basal-like phenotype and Notch 1 with the HER2 amplified phenotype. Overexpression of Shh in particular confers a worse clinical outcome in invasive ductal carcinoma. Furthermore, increased levels of Shh in a 3D culture model of non-transformed mammary epithelial cells resulted in disorganisation of acini and the development of an abnormal discohesive phenotype. Finally the role of Shh was investigated in a mammary epithelial transplantation model, where overexpression of Shh resulted in the development of hyperplasia of the mammary ductal epithelium. Together these data confirm that the Hedgehog, Wnt and Notch developmental pathways are dysregulated in breast cancer and represent viable targets for further investigation of potential novel therapies in breast cancer.
| Identifer | oai:union.ndltd.org:ADTP/215693 |
| Date | January 2008 |
| Creators | O'Toole, Sandra Alison, Garvan Institute of Medical Research, Faculty of Medicine, UNSW |
| Publisher | Publisher:University of New South Wales. Garvan Institute of Medical Research |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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