Researchers at the University of Illinois ( UIC ) at Chicago are unraveling the biochemical mechanism by which functional foods combat cancer.

" Compounds like sulforaphane in broccoli and resveratrol in wine have been shown to prevent cancer," said Andrew Mesecar, in the UIC. " They do that by signaling our bodies to ramp up the production of proteins capable of preventing damage to our DNA.

The findings are published in the Proceedings of the National Academy of Sciences ( PNAS ).

Two key proteins, Keap1 and Nrf2, are involved in spurring the defense against cancer when disease-preventing foods are ingested, according to Mesecar.

Keap1, the sensor protein, detects the presence of dietary compounds like sulforaphane when they link with its cysteine residues, one of the amino acids that make up proteins. Keap1 binds to Nrf2, the messenger that turns on the genes for the protective proteins, averting DNA damage.

"Earlier studies in mice suggested that natural cancer-preventing compounds worked by severing the tie between Keap1 and Nrf2, freeing Nrf2 to take action," Mesecar said. "But the signaling doesn't happen this way in humans."

The scientists found that in humans the connection between the two proteins is not broken.

What's important is the modification of cysteines in Keap1. They found that one particular cysteine was among the most likely to be altered in the interaction with cancer-preventing compounds.

That finding corresponded with results from other researchers. As a result, the scientists are proposing that the alteration of just this one amino acid in Keap1 is the critical step that spurs higher levels of the messenger Nrf2 and, consequently, increased production of the protective proteins.

Keap1 is a promising new target for drugs to fight many different kinds of cancer, Mesecar said.

The American Cancer Society estimates that there will be over 1.3 million new cases of cancer in 2005, and roughly half of these individuals will not survive their disease, Mesecar noted. "One way of preventing cancer may be to eat certain foods rich in cancer-preventing compounds. An alternative is identifying how these compounds work and replicating their modes of action with drugs."

The research was funded by the National Cancer Institute.

Source: University of Illinois at Chicago, 2005


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