Under normal circumstances, the newly identified breast stem cell will produce healthy tissue. But it is believed that an accumulation of genetic errors, perhaps combined with external influences and a family predisposition, could cause the breast stem cell or a "daughter" cell to produce faulty cells. In effect, the errant breast cell can become a tumour factory.
For many years, scientists and clinicians have been puzzled by the fact that women whose breast cancer cells have been apparently eliminated by chemotherapy sometimes experience a recurrence of their cancer. A cancerous stem cell could provide one possible explanation for such a recurrence.
Chemotherapy works by targeting cells that are dividing rapidly, which is typical behaviour of cancer cells. But an errant stem-like cell may be more resistant to chemotherapy because it divides more slowly. So while chemotherapy can eliminate the bulk of cancer cells, the tumour factory itself - a breast cancer stem cell - may survive months or years later.
In the context of international breast cancer research, the discovery of the breast stem cell is quite profound and will most likely form the basis of research in the area for years to come.
The ultimate objective is to create a drug that will, in effect, switch off breast cancer cells. To do this, the exact makeup of genes expressed by normal and rogue stem cells will need to be determined. Then a drug will be designed to engage with and neutralize the faulty feature of the stem cell.
Further research is now under way on excised human breast tumours to confirm the findings derived from the mouse model. The research team is from the WEHI Group of the Victorian Breast Cancer Research Consortium, which is funded by the Victorian state government through the Cancer Council Victoria.
The team's work was carried out principally by Mark Shackleton and François Vaillant in the laboratory of Jane Visvader and Geoff Lindeman. The paper is published in the 5 January 2006 issue of the prestigious international journal, Nature.