The body's deadly defector

More than 30 per cent of the population of Britain will develop cancer at some point in their lives. For many of these individuals the cancerous or pre-cancerous cells can be effectively removed by either chemical or surgical methods. This is thanks to cancer research, particularly that from the past 20 years.

Robert Weinberg leads us through a journey of discovery starting in 1909, when the first cancer-causing virus was discovered, through the confusion of the 1970s and into more recent times. The theories developed during this time have now been unified into what is a well accepted framework into which new pieces of the puzzle can fit.

It is generally understood that cancer is caused by some change in DNA that triggers an individual cell to embark on a frenzy of uncontrolled division, eventually resulting in a tumour.

If only cancer were so simple. Weinberg accessibly and expertly presents the incredible lengths to which a cell must go to become malignant. It is not enough for the DNA of a cell merely to change so that it can divide more frequently than its neighbours. The cell must also change the DNA that contains the blueprint for the mechanisms the body uses to stop tumour development.

The probability of an individual cell acquiring all of the required changes to specific parts of its DNA is incredibly small, but every day we roll the dice for each of our 50 million million cells. All it takes is for the losing combination to appear on the dice for one cell and it will have started on the road to a malignancy. The older you are, the more rolls of the dice you have had for each of your cells and so cancer is generally a disease associated with age. Genetic predisposition, diet and particularly smoking all weight the dice in favour of cancer, so that you are more likely to come up with the losing combination each time you roll.

Once we understand the causes of cancer, it would seem that avoiding them would be prudent if only to take away the unfavourable weighting of the dice. Yet millions of people continue to smoke despite the well-known risks and take their chances. In the 1990s, one-third of cancers in the United States were caused by tobacco. The increased incidence of breast cancer (by 10 per cent over the past 30 years) is another consequence of modern life, but this is much more difficult to avoid. Changes in nutrition and reproductive habits have led to an increase in the number of menstrual cycles that women now experience in their lifetimes. Each menstrual cycle involves more frequent rolling of the dice (as cells lining the milk ducts proliferate), increasing the risk of triggering cancer. The protective effect of early pregnancy is poorly understood, but it is clear that the trend towards starting a family at a later age is increasing the instances of breast cancer.

Weinberg reduces the complexity of the processes that must occur for a cell to turn cancerous into individual events and then deals with each in isolation. For instance, a cancerous cell must have the ability to ignore chemical messages telling it to stop dividing, to make itself immortal (most cells die after a certain number of divisions) and to pervert the surrounding tissue into making blood vessels to feed the tumour. There is a very small probability of all of these abilities being acquired by one cell, but Weinberg describes how a cell on the road to being cancerous uses certain tricks to raise its chances of becoming a fully fledged cancer cell.

The story ends by looking forward to where the cutting edge of research might lead us in terms of furthering our understanding of cancer. Given new insights into the mechanisms by which cancer develops, opportunities will become clear for intervention by new "cleaner" drugs free from the side-effects notorious in current chemotherapy. As the tools to diagnose cancer become more advanced, many more lives could be saved by removing the villainous cells before any real harm can be caused.

One Renegade Cell is a thoroughly engaging and fascinating account of what researchers have found to be an incredibly complex disease. That Weinberg has achieved this without presuming any advanced background in biology is remarkable. If only all researchers at the forefront of their science could explain their fields so admirably.

Martin Westwell is a junior research fellow, Lincoln College, Oxford.