New research strongly suggests that a mix of preventative
agents, such as those found in concentrated black raspberries,
may more effectively inhibit cancer development than single
agents aimed at shutting down a particular gene.
Researchers at the Ohio State University Comprehensive Cancer
Center examined the effect of freeze-dried black raspberries
on genes altered by a chemical carcinogen in an animal model
of esophageal cancer.
The carcinogen affected the activity of some 2,200 genes
in the animals’ esophagus in only one week, but 460
of those genes were restored to normal activity in animals
that consumed freeze-dried black raspberry powder as part
of their diet during the exposure.
These findings, published in recent issue of the journal
Cancer Research, also helped identify 53 genes that
may play a fundamental role in early cancer development and
may therefore be important targets for chemoprevention agents.
“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,”
says principal investigator Gary D. Stoner, a professor of
pathology, human nutrition and medicine who studies dietary
agents for the prevention of esophageal cancer.
“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
Stoner notes that black raspberries have vitamins, minerals,
many of which individually are known to prevent cancer in
“Freeze drying the berries concentrates these elements
about ten times, giving us a power pack of chemoprevention
agents that can influence the different signaling pathways
that are deregulated in cancer,” he says.
To conduct this 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 carcinogen 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 of 50 percent or higher.
“These changes in gene expression correlated with changes
in the tissue that included greater cell proliferation, marked
inflammation, and increased apoptosis,” Stoner says.
In the animals fed berry powder, however, a fifth of the
carcinogen affected genes – exactly 462 of them –
showed near-normal levels of activity, when compared with
controls. Most of these 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.
Lastly, 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.
“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.”