The American Cancer Society estimate that in 2017, more than 95,500 people will develop cancer of the colon, almost 40,000 people will have rectal cancer, and more than 50,000 deaths will be caused by colorectal cancer.
A team of researchers led by Jairam K. P. Vanamala, associate professor of food sciences at the College of Agricultural Sciences at Pennsylvania State University in State College, set out to examine the effects of grape compounds on colon cancer stem cells.
More specifically, the researchers tested the effect of a combination of resveratrol - a polyphenolic compound found in grapes, red wine, peanuts, and some berries - and grape seed extract.
As the authors write, the study rests on the theory that "most, if not all, cancerous tumors are driven by [cancer stem cells]."
"Cancer stem cells are capable of self-renewal, cellular differentiation, and maintain their stem cell-like characteristics even after invasion and metastasis," explains lead researcher Prof. Vanamala.
The findings were published in the journal BMC Complementary and Alternative Medicine.
Grape extracts halved cancer tumors
Prof. Vanamala and colleagues examined 52 mice with colon cancer tumors. They divided the rodents into three groups: one group was fed the grape compound combination, another group was fed sulindac (an anti-inflammatory drug previously found to reduce tumors in humans), and one group was given a normal diet.
The researchers found that the number of tumors in the mice that had the grape compound diet decreased by 50 percent. This drop was similar to the one seen in the sulindac group, but unlike the anti-inflammatory drug, the grape compounds did not cause any gastrointestinal toxicity.
In vitro, the experiments yielded similar results, determining the "molecular basis for the beneficial effect" of the grape compounds on human cancer stem cells.
The study also found that resveratrol and grape seed extract did not suppress cancer stem cells as effectively when taken separately and in small doses. It seems to be the combined effect of the two that produces the best results.
"The combination of resveratrol and grape seed extract is very effective at killing colon cancer cells," says Prof. Vanamala. "And [...] the combination of these compounds is not toxic to healthy cells."
Colorful diet may prevent colon cancer
Prof. Vanamala suggests that the findings may bring us closer to understanding why cultures that traditionally eat more fruits and vegetables have lower colon cancer rates.
For instance, some studies have hypothesized that the West African diet may be the reason that Nigerians have a much lower rate of colon cancer compared with Caucasians.
Nigeria, along with other African countries, has been shown to have the lowest cancer rates in the world.
Plant-based diets may provide several key compounds that kill off cancer stem cells, says Prof. Vanamala. He also recommends consuming a large variety of colorful fruits and vegetables to prevent colon cancer and other chronic conditions such as type 2 diabetes.
"This also connects well with a plant-based diet that is structured so that the person is getting a little bit of different types of plants, of different parts of the plant, and different colors of the plant.
Prof. Jairam K. P. Vanamala
He adds, "This seems to be beneficial for not only promoting bacterial diversity, but also preventing chronic diseases and eliminating the colon cancer stem cells."
However, Prof. Vanamala also adds that more work is needed to fully understand the anti-cancer mechanism behind grape compounds and other extracts in fruit and vegetables.
The researchers hope that their findings will set the stage for human trials that could test the effects of the grape compounds on colon cancer.
If these trials are successful, the researchers hope that the combination of resveratrol and grape seed extract could be taken in the form of a pill; this may protect against colon cancer and prevent the disease from recurring in those who survived the condition.