Study: Gene Flaw May Promote Cancer
by
Malcolm Ritter,
AP Science Writer

6:00 PM EST; November 14, 1999; New York (AP) -- Scientists have identified an inherited genetic mutation that may make people more vulnerable to colon cancer, possibly playing a role in up to 9 percent of cases diagnosed each year in the United States. If confirmed, the work might someday help doctors identify patients who should be tracked especially closely for early signs of the disease. The mutation apparently promotes cancer by hindering a process that keeps cell growth under control, said Dr. Kenneth Offit of the Memorial Sloan-Kettering Cancer Center in New York. He and colleagues present the work in Monday's issue of the journal Cancer Research.

Dr. Sanford Markowitz of the Case Western Reserve University School of Medicine in Cleveland, who did not participate in the work, said the result would be important if borne out by further work. "This is a provocative finding that is crying out to be confirmed by additional studies," Markowitz said in a telephone interview. The mutation affects the ability of a natural protein called transforming growth factor beta to control cell growth. The protein binds to a structure called a receptor on cells, and the mutation appears to hinder slightly the receptor's ability to respond properly.

People inherit two copies of the gene in which the mutation can appear, one copy from each parent. "The added cancer risk is more pronounced when both copies carry the mutation," Offit said. It's not yet clear how much of a risk the mutation produces. The researchers found that the mutation was more common in people with cancer than healthy people, which suggests the mutation plays a role in the disease.

Nine of 851 people with various types of cancer carried the mutation in both copies of the gene, compared to none of 735 healthy people. Four of the people with both copies mutated had colon cancer, two had testicular cancer, and each of the remaining three had a different cancer. In addition, about 15 percent of cancer patients versus 11 percent of healthy people carried the mutation in just one gene copy.