DNA strips that protect chromosome tips during cell division are influenced by aging, health status, and environmental factors.
Like the protective plastic cap at the ends of shoelaces that prevent them from unraveling, telomeres protect the ends of chromosomes. These small strips of DNA prevent chromosome tips from fraying during cell division. But as the cells divide, the telomeres shorten and the cells age. Shortened telomeres have been linked to an increased risk of cancer development. Researchers at the Mayo Clinic in Rochester, Minn., wanted to see if telomere shortening was linked to colon cancer development at a younger age.
“When we look at colorectal cancer, it’s typically a disease of the aging,” said lead investigator Lisa A. Boardman, MD, an associate professor of medicine. “In young-onset colon cancer, could telomere length relate to cancer? Are these patients biologically older based on their telomere length?”
Dr. Boardman’s group measured blood leukocyte DNA telomere length with quantitative polymerase chain reaction (PCR) in 772 people diagnosed with microsatellite stable colorectal cancer. The patients had been diagnosed at less than 60 years and had no history of chemoradiotherapy. These subjects’ telomere lengths were compared with telomere lengths from 1,660 nonrelated, healthy controls (2010 AACR Colorectal Cancer: Biology to Therapy abstract A26).
“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,” Dr. Boardman said.
Anil Rustgi, MD
Instead, the researchers found that in people under age 50, a longer telomere length correlated with a higher colorectal cancer risk. “If you were under the age of 50 and you had the longest telomere length, compared with the middle range, the odds in favor of developing colon cancer was 30%,” Dr. Boardman said. The reverse was true for people over 50, with a longer telomere lowering the cancer risk while a shorter telomere was associated with a 22% increased risk for cancer.
The group also found that the odds ratio (OR) for colorectal cancer in individuals with the shortest and longest telomere lengths was 1.14 (P = .01).
This OR remained high after adjusting for various environmental factors, such as fruit, vegetable, and red meat intake; folic acid(Drug information on folic acid) intake; and comorbidity of diabetes mellitus, Dr. Boardman’s group said.
|“In young-onset colon cancer, could telomere length relate to cancer? Are these patients biologically older based on their telomere length?” |
—Lisa A. Boardman, md