Black raspberries alter genes, slow cancer

A mix of chemicals found in black raspberries may more effectively prevent cancer development than single agents aimed at shutting down single genes, a new study shows.

Led by Dr. Gary D. Stoner, a chemoprevention researcher at Ohio State University's Comprehensive Cancer Center, researchers examined the effect of freeze-dried black raspberries on genes altered by a chemical carcinogen in an animal model of esophageal cancer.

"We have clearly shown that berries, which contain a variety of anticancer compounds, have a genome-wide effect on the expression of genes involved in cancer development," Stoner said in a prepared statement. "This suggests to us that a mixture of preventative agents, which berries provide, may more effectively prevent cancer than a single agent that targets only one or a few genes."

In the study, Stoner and his colleagues fed rats either a normal diet or a diet containing 5 percent black-raspberry powder. During the third week, half the animals in each diet group were injected three times with a chemical carcinogen, N-nitrosomethylbenzylamine. The animals continued consuming the diets during the week of carcinogen treatment.

After the third week, the researchers examined the animals' esophageal tissue, thereby capturing gene changes that occur early during the exposure. Their analyses included measuring the activity, or expression levels of 41,000 genes. In the carcinogen-treated animals, 2,261 of these genes showed changes in activity levels of greater than 50 percent.

Among the rats given freeze-dried black raspberry powder as part of their diet during the exposure, however, 460 of those genes were restored to normal activity. The findings appear in the Aug. 1, 2008 journal Cancer Research.

Stoner said that most of these "normalized" genes are associated with cell proliferation and death, cell attachment and movement, the growth of new blood vessels and other processes that contribute to cancer development. The tissue also appeared more normal and healthy.

The study also helped identify 53 genes that may play a fundamental role in early cancer development and may therefore be important targets for therapeutic agents. Of the 462 genes restored to normal by the berries, 53 of them were also returned to normal by a second chemoprevention agent tested during a companion study.

"Because both berries and the second agent maintain near-normal levels of expression of these 53 genes, we believe their early deregulation may be especially important in the development of esophageal cancer," Stoner says.

Black raspberries have vitamins, minerals, phenols and phytosterols, many of which individually are known to prevent cancer in animals, according to Stoner.

"What's emerging from studies in cancer chemoprevention is that using single compounds alone is not enough," Stoner says. "And berries are not enough. We never get 100 percent tumor inhibition with berries. So we need to think about another food that we can add to them that will boost the chemopreventive activities of berries alone."

Source: cancerfacts.com

Publication date: 9/1/2008