Colon Cancer Linked To Genes, Not Lifestyle

Colon cancer and many other geriatric diseases in primates appear to be natural outcomes of aging, rather than being caused by outside factors, a scientist at UW–Madison has found.

The findings, reported recently in Age and The American Journal of Primatology, adds to evidence that how we age may be linked more to our genes than our lifestyle.

“The simple lives of captive-born, aged rhesus monkeys result in minimal or no exposure to the varying environmental and lifestyle factors that affect humans,” said Hideo Uno, senior scientist at the Wisconsin Regional Primate Research Center and adjunct professor of pathology and laboratory medicine. “Yet the monkeys still get many of the same geriatric diseases people get.”

From 1980 to 1994, Uno compiled autopsy data from 175 monkeys, all aged 20 to 37 years, roughly the equivalent of people in their 50s to 80s. The animals, which were used for breeding rather than scientific experimentation during their lifetimes, either died spontaneously or were euthanized due to severe illness.

Autopsy data revealed that most of the diseases appeared to be brought on by old age and predisposing genetic factors, versus environmental or lifestyle factors. Colon cancer, coronary sclerosis, degenerative joint disorders, and cerebral amyloid plaque (a component of Alzheimer’s disease), were among the disorders, Uno said.

Despite a simple diet of high-fiber monkey chow and fruit, a relatively nonstressful environment, lack of exposure to known carcinogens, and good veterinary care-old monkeys often get colon cancer, Uno discovered. “As in humans, the incidence of colon cancer dramatically increases with aging,” he said.

Colon cancer is the third most common cancer in men, following prostate and lung cancer, and the third most common in women, following breast and lung cancer. In captive rhesus monkeys it appears to be the most common.

Uno’s data did show, however, that certain other geriatric diseases are much less common in monkeys than in humans. “Lung and prostate cancers in elderly people are extremely common, for example, but those two cancers are very rare in our monkeys.”

Rhesus monkeys share 93 percent of the human genome, which makes them the prime animal model for researchers seeking answers to human diseases like cancer, AIDS and diabetes.

“We have only now been able to study colon cancer and other aging-related diseases more closely in monkeys and compare it to that in humans,” said Uno. “Few populations of aged monkeys were in captivity up until about 15 years ago.”

Uno said the data will be valuable to scientists working on preventive or experimental studies related to geriatric diseases in humans.

The UW Primate Center is one of seven primate research centers in the U.S. supported by the National Center for Research Resources at the National Institutes of Health. It is a base for local, national and international research in biomedicine and conservation biology and has an annual operating budget of approximately $25 million.