Researchers have found a link between an increased risk for colorectal cancer in young people and long telomeres, the pieces of DNA that protect the ends of chromosomes.
Short telomeres have long been associated with aging — they shorten over a person's life, and the shortening usually comes with an increased cancer risk. But the surprising new research suggests long telomeres may be associated with colorectal cancer in young people, Dr. Lisa A. Boardman, an associate professor of medicine at the Mayo Clinic in Rochester, Minn., said in a statement.
Boardman and her colleagues sought evidence of biological aging in people who develop colorectal cancer at a young age. They hoped to find what was causing the young patients to develop a disease that is typically associated with aging, she said.
They found individuals who had the longest telomeres — those whose telomeres were among the longest 5 percent — were 30 percent more likely to develop colorectal cancer than those whose telomeres had middle-of-the-group lengths, the results showed.
The people with the shortest and the longest telomere lengths were at an increased risk for colorectal cancer, Boardman said.
"We anticipated that we would see some people who had young-onset colon cancer and shorter telomeres, compared to people of the same age group who did not have cancer," said Boardman.
But instead, they found the young-onset colon cancer patients had longer telomeres than expected, even for healthy people.
Researchers measured the DNA telomere length in the white blood cells of 772 people who were diagnosed with colorectal cancer before age 60. They then compared this group's telomere length with 1,660 people of the same age who didn't have colorectal cancer.
Colorectal cancer can occur at any age, but more than 90 percent of the people who develop the tumors are older than 40, according to Pennsylvania State University. Most people who are diagnosed with colon or rectal cancer are in their 50s and 60s.
The finding suggests there could be two types of colorectal cancer in young-onset patients — one that involves telomere shortening, which may indicate accelerated aging, and one associated with longer telomeres.
That means there could be different mechanisms affecting telomere length and cancer susceptibility, she said.
Next, researchers will see if the patients with younger-onset colorectal cancer have tumors that are mechanically different. They are also in the process of comparing the lengths of telomeres in blood DNA with the telomeres in the cancer tumors.
The study was presented Oct. 28 at the American Association for Cancer Research’s special conference on colorectal cancer.