Scientist in the Spotlight: Robert S. Chapkin Seeing Synergy to Prevent Colon Cancer
A body of laboratory research by Robert S. Chapkin, PhD, Regents Professor and University Faculty Fellow at Texas A & M University and a former AICR grantee, is unveiling how dietary omega-3 fats and other healthful food compounds may influence the colon's immune system. His recent studies investigating the dynamic relationships between diet and human biology are providing new insights into colon cancer prevention.
Omega 3s, Immune Cells and Rafts
In a recent review of the evidence surrounding omega-3s, published last month in Molecular Aspects of Medicine, Chapkin concludes that the fatty acids can alter the immune response by targeting specialized regions of the cell referred to as lipid rafts.
Lipid rafts are transient regions of cholesterol and fats that are interspersed among the layers of cell membranes. They serve as staging areas for a variety of cellular processes, such as the immune response.
Using a mouse model, Chapkin and his collaborators showed that when mice ate omega-3s, present in fatty fish such as salmon, the fatty acids were incorporated into the cell's lipid rafts. Once there, the omega-3s rearranged the molecules that participate in cell signaling, preventing the cells from initiating a pro-inflammatory cascade of events that may trigger disease.
"The lipid rafts are like rooms in a house that get larger when someone – like omega-3s – inhabits the rooms," said Chapkin. The extra space in the enlarged rooms enables the occupants – such as key signaling molecules – to communicate differently, says Chapkin, "This communication dampens the ability of certain immune cells to respond and this can suppress the immune response, which is beneficial in some circumstances."
In some cases, inflammation is necessary for good health, such as when the body is fighting an infection. But chronic inflammation, which brings a continuous stream of inflammatory compounds, is a risk factor for colon cancer.
"The inflammatory environment of the intestine can be tweaked, tipping the balance toward a more favorable one."
This research suggests, says Chapkin, "The inflammatory environment of the intestine can be tweaked, tipping the balance toward a more favorable one."
There is no established recommendation for omega-3 intake and, says Chapkin, there are insufficient data to conclusively identify the optimal amount. In fact, some studies show that the high amounts of omega 3s – found only in supplements – actually interfere with the white blood cells' ability to fend off foreign invaders.
The Synergy of Fiber and Fats
Chapkin's research extends to the health benefits of dietary fiber, as well. At the 2011 AICR Research Conference this month, Chapkin presented evidence that suggests omega-3s and fiber exert a powerful synergistic effect.
Dietary fiber is metabolized by the beneficial bacteria in the colon, a process referred to as fermentation. Butyrate is a product of the fermentation of pectin, a type of fiber present in many fruits and vegetables. When omega-3s and butyrate interact in animal models, there is a protective effect in the intestine. Levels of apoptosis, or programmed cell death, of pre-cancerous colon cells increase, offering protection against colon cancer.
These two dietary components – omega-3s and fiber – work together in a way that heightens or facilitates their chemoprotective properties, says Chapkin. He and his colleagues are now trying to determine how these whole food components promote the death of cancer cells that might be propagating in someone's intestine.
"The colon is the only tissue in the body that is impacted by this because the colon is the only place where fiber is fermented," says Chapkin. "This combination is targeting the colon."
Chapkin's next research will examine the effects of omega-3 fatty acids and fiber on intestinal stem cells, cells that have the potential to transform into different types of cells. Eventually, he hopes to conduct human studies to substantiate his findings.