Chemicals found in grape seeds significantly inhibited growth of colorectal tumors in both cell cultures and in mice, according to researchers who have already demonstrated the extract’s anti-cancer effects in other tumor types.

Their study, published in the October 18 issue of Clinical Cancer Research, documented a 44 percent reduction of advanced colorectal tumors in the animals, and also revealed, for the first time, the molecular mechanism by which grape seed extract works to inhibit cancer growth. The authors found that it increases availability of a critical protein, Cip1/p21, in tumors that effectively freezes the cell cycle, and often pushes a cancer cell to self destruct.

Rajesh Agarwal, Ph.D., professor in the Department of Pharmaceutical Sciences at the University of Colorado Health Sciences Center in Denver, said, “The value of this preclinical study is that it shows grape seed extract can attack cancer, and how it works, but much more investigation will be needed before these chemicals can be tested as a human cancer treatment and preventive.”

The skin and seeds of grapes are a rich source of proanthocyanidins, a class of antioxidant flavonoids that remove harmful free oxygen radicals from cells. Grape products (juice and red wine) are known for their heart healthy effects, especially in lowering levels of blood cholesterol, Agarwal said, and because grape seeds contain higher concentrations of these chemicals, they are widely marketed as a dietary supplement.

Agarwal and his team of investigators were first to report, in 1999, that grape seed extract also has chemopreventive activity against skin cancer. Their subsequent preclinical work has shown that the extract also retards growth of prostate cancer cells.

In this study, Agarwal tested the extract on colorectal cancer, the second most common malignancy in Americans as well as the second leading cause of cancer deaths in this country. They exposed two different human colon carcinoma cells to the extract, and found a dose- and time-dependent inhibition of cell growth.

“Beneficial effects were correlated with how much extract was used and how long it was used for,” Agarwal said. The number of live cells decreased by 92 percent in one cell line when the highest dose was given for the longest time period, which was two days, he said.

Source:

Department of Pharmaceutical Sciences at the University of Colorado Health Sciences Center in Denver

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