Of cancer, genes and reporting

Q:When is a genetic genetic disease usually not an inherited disease? A:When the disease is cancer: uncontrolled cell growth caused by genetic damage acquired throughout a lifetime. Cancer, though rarely inherited, is most definitely genetic. Identifying the many genes involved (and the proteins they make) will almost certainly be the best way of gaining a detailed understanding of cancer, and the most effective approach for developing new therapies to treat it. So why were newspaper reports last week (both in the UK and US) claiming that a new study on the causes of cancer challenges the belief that the key to understanding cancer lies in understanding our genetic make-up?

Occasionally the genetic alterations involved in cancer are  inherited, so that some people are born with an increased risk of cancer because of a particular gene variant or, more likely, a combination of gene variants. But the vast majority of cancers are caused by lifestyle and environmental factors - smoking, diet, pollutants and radiation from the sun. All can damage genes, and if the gene is one that usually controls cell growth and division, then a normal cell may take the first step towards becoming a cancerous one. So cancer is genetic, but not usually inherited. An altered gene in a skin cell may lead to skin cancer, but it will not be passed on to the next generation.

All this was confirmed last week by a study, covered in this week's BioNews, of nearly 45,000 pairs of twins. It concluded that identical twins have a lifetime risk of around 10 per cent of developing the same type of cancer. The scientist who lead the team, Dr Paul Lichtenstein, was widely quoted as saying that the study meant that 'environmental factors were more important than gene factors' in studying the causes of cancer. This message rightly emphasises the important role of environmental factors in the understanding and prevention of cancer. But it was somewhat garbled by the time it reached the newspapers, which mostly saw the study as an antidote to the sometimes extravangent claims made for the importance of genetic explanations.

Part of the problem lay in the hype that surrounded the unveiling of first draft of the human genome last month. To enthuse that a stream of raw data is going to yield cures for cancer and the key to 120-year life, is an irresistible invitation to those waiting to prove otherwise. This is especially the case in the UK, where the media seem to specialise in trumpeting the Next Big Thing one week, for the sole purpose of tearing it apart the next. But the real problem may be the complexity cancer of itself. It is certainly quicker, to say that 'the key to cancer lies in our genes' than to explain the situation in full. Unfortunately, snappy, media-friendly sound-bites can sometimes backfire.