Theory of colorectal cancer risk revised

PHILADELPHIA, Sept. 25 (UPI) -- U.S. scientists say they've found failure to inherit a cancer-inhibiting gene from just one parent increases the risk of contracting colorectal cancer.

That discovery challenges the well-established, so-called "two-hit" theory that cancer only occurs in those who fail to inherit the gene from both parents.

The two-hit theory was advanced by Dr. Alfred Knudson more than 30 years ago. Now, Knudson and colleagues from the Fox Chase Cancer Center, the National Cancer Institute and Thomas Jefferson University say they've found evidence that "one hit" -- or failure to inherit a cancer-inhibiting gene from just one parent -- is enough to allow the growth of colorectal cancer cells.

Colorectal cancer is the second leading cause of cancer-related deaths in the United States.

"We hypothesized that an inherited one-hit gene mutation can, by itself, lead to changes in the proteins of normal-looking cells" said Anthony Yeung, a researcher from Fox Chase, and lead author of the paper. "The 'one-hit' event makes a second mutation that much more likely to push the cell over the edge into cancer," he added.

The research is reported in the Sept. 15 issue of the journal Cancer Research.