The gene, known as MSH2, serves normally to detect and correct small mutations that occur during cell division. The new studies show that when colon cells lack the protection the gene normally provides, they accumulate one mutation after another until they become cancerous. Roughly one American in 200 inherits a faulty version of MSH2–and people with those defects face a 70 to 90 percent chance of developing colon cancer during their lives. Carriers suffer elevated (but less dramatic) rates of uterine and ovarian cancer as well.
Until now, anyone with a family history of colon cancer has had to worry about being stricken. But thanks to last week’s discovery, simple blood tests could soon enable people from high-risk families to gauge their own prospects for $1,000 or less. The first such screening tests should be ready within six months.
