Four Genes That Cause Colorectal Cancer

Four Genes That Cause Colorectal Cancer

Johns Hopkins professor Ross C. Donehower, M.D., F.A.C.P. discusses four newly-identified genes for colorectal cancer.

Scientists are identifying specific genes that confer a high risk of developing some cancers, including colorectal cancer. If you happen to carry one of these specific genes, your risk of colorectal cancer is increased considerably. Your doctor may recommend genetic testing if cancer seems to run in your family or if a close relative has been found to carry one of these genes.

* Colorectal Cancer Gene 1: Hereditary Nonpolyposis Colorectal Cancer (HNPCC) -- Also called Lynch syndrome, this inherited tendency to develop colorectal cancer represents between 2% and 7% of all colorectal cancers. Not all people who inherit this genetic disorder will develop colorectal cancer, but they do inherit a significantly increased risk as well as a risk of developing other related cancers. Cancer tends to show up during puberty or the early twenties.

* Colorectal Cancer Gene 2: Familial Adenomatous Polyposis (FAP) -- This rare form of inherited cancer causes a massive overgrowth of polyps in the colon and rectum, often among people who are in their teens. Less than 1% of all colorectal cancers are due to FAP, which is also known as Gardner’s syndrome, familial polyposis, or hereditary polyposis of the colorectum.

* Colorectal Cancer Gene 3: APC I1307K Mutation -- This is a genetic variant of FAP found in about 6% of Ashkenazi Jews whose ancestors came from eastern Europe. The mutation increases the risk of developing colorectal cancer by as much as 30%. (The risk among the general population is about 5–6%.) Compared with FAP, the number of polyps in the colon is much lower, as is the risk of cancer.

* Colorectal Cancer Gene 4: MYH Polyposis Syndrome -- This form of colon cancer is a recently discovered recessive syndrome. Those who develop the disease must have inherited a particular mutated gene from both parents. Those who inherit only one affected gene are not at special risk for cancer but may pass the gene to their offspring. Affected individuals typically develop 10–100 polyps at around 40 years of age and are at high risk for developing colon cancer.