Mice show crucial role of cancer stem-cells
Do cancers have their own stem-cells? The cancer research community have long debated their existence, but solid evidence has been lacking to support not only the existence of cancer stem-cells but also the controversial theory that they are the driving force behind tumour growth.
Now three different studies using mice provide fresh evidence for both the existence of cancer stem cells and their key role in tumour development.
The three groups have used different techniques to trace individual cells in tumours of the brain, the gut and the skin of mice. This means the findings are not just unique to one type of cancer and scientists believe the results could potentially apply to all cancers. Crucially, the experiments were performed in living mice, allowing the scientists to study the tumours in their natural environment over time. Cancer cells respond to many different external influences which are practically impossible to replicate outside of the body.
In the first experiment, cells suspected to be cancer stem cells were labelled and injected into mice. All the resulting intestinal tumours contained at least some of the labelled cells among many more unlabelled cells. The unlabelled cancer cells could be killed with chemotherapy but the tumours always grew back. It was only when the scientists specifically killed the labelled cells that the tumours shrank, showing that it was the cancer stem cells that were behind tumour re-growth and not all the cells found in the tumour.
In the second study researchers used a particular fluorescent marker to track tumour stem cells. The marker was passed on to all cells originating from the stem cells resulting in brain tumours that glowed under ultraviolet light. Non-stem cells labelled with a different fluorescent colour did not show up, demonstrating that most of the tumour arose from the stem cells.
In the third study, cells were randomly labelled in skin tumours to allow them and the cells they produced to be tracked. When the tumours were analysed the team found that most labelled cells produced a limited number of new cells before petering out, but there was a small population of cells dividing indefinitely to produce large parts of the tumours. This again shows that a few cells – cancer stem cells – are responsible for driving tumour growth.
This is fundamental research unlocking the secrets behind tumour growth is only made possible by the advanced genetic engineering techniques that mice provide scientists.
The reformation of tumours after they appear to have been totally removed or killed by chemotherapy is a sad but common story for cancer patients. Cancer stem cells offer an explanation for why tumours can be so difficult to eliminate and indicates that it is crucial collection to target cancer stem cells. And if these stem cells from different cancers share common features, the hope is that scientists may be able to find a 'one size fits all' therapy to destroy cancer stem cells in what could be a game-changing moment for cancer treatment.