From an article in the current Economist, a report on recent discoveries about the relationship between stem cells and tumour growth:
STEM cells have a controversial reputation, but in truth they are what makes human life possible. Each tissue in the body grows from a particular sort of stem cell. When it divides, one of its daughters remains a stem cell while the other eventually turns into whatever tissue its mother was designed to produce—be it blood, muscle, nerve or whatever. That is how healthy tissues are renewed, and it is now looking likely that it is how unhealthy tissues are renewed, too. Indeed, many researchers think that the underlying cause of cancer is the brakes coming off the regulatory system that stops normal stem cells from reproducing too much. For one of the most important medical discoveries made in recent years is that cancers, too, have stem cells and that these appear to be the source of the rest of the tumour.
This helps to explain why cancers are so hard to deal with. Treatments that kill the bulk of a tumour, but leave the stem cells alive, are only buying time. On the other hand, if all of a tumour's stem cells could be killed then it would torpedo the old wisdom that no patient is ever cured of cancer, but merely goes into remission. True cures for cancer would be possible.
The cancer-stem-cell theory, though plausible, was based on animal experiments and its relevance to humans was untested. But a series of studies reported this week at a meeting of the American Association for Cancer Research, in San Diego, has changed that. They suggest both that cancer stem cells are very relevant indeed to survival, and that going after them is an excellent idea.
