A pigmentation chemical that makes grape skins and wines red has been found to kill human leukemia and lymphoma cells cultured in a lab, according to research to be published May 4 in the Journal of Biological Chemistry. However, the compound, a type of anthocyanidin common in plants, left healthy blood cells alone.
"Current treatments for leukemia, such as chemotherapy and radiation, often damage healthy cells and tissues and can produce unwanted side effects for many years afterward," said coauthor Dr. Xiao-Ming Yin, an associate professor of pathology at the University of Pittsburgh School of Medicine. "So, there is an intensive search for more targeted therapies for leukemia worldwide."
There are several different types of leukemia, a cancer of the blood or bone marrow typically characterized by an uncontrolled increase in white blood cells (which, when functioning normally, help defend the body from disease). About 44,000 new leukemia cases will be diagnosed in the United States in 2007, and there will be about 22,000 leukemia-related deaths according to the National Cancer Institute.
Yin and his team focused on one of the most common anthocyanidins, which are forms of anthocyanin, water-soluble flavonoids that provide color to flowers, leaves, fruits and vegetables. In grapevines, anthocyanidin is believed to play a part in attracting honeybees to the vines' flowers, as well as serving as a natural sunscreen by protecting against high levels of ultraviolet radiation. Previous studies, the authors added, have shown that anthocyanidins work as antioxidants by helping to eliminate damaging rogue oxygen molecules, called free radicals.
For this latest experiment, Yin and his team studied the effects and the mechanisms of cyanidin-3-rutinoside (C-3-R), to see how it behaves in the presence of cancer. The C-3-R was extracted and purified from black raspberries, though it also abounds in red wine, and was used in much higher amounts than the typical red wine drinker would be able to consume.
The C-3-R was tested on several lines of human leukemia and repeated using cell cultures of lymphoma, another immune system—based cancer. The scientists observed that, at low doses of C-3-R, half of the cancer cells in all of the lines died within 18 hours of treatment. At higher doses, the C-3-R killed all of the cells by the end of the 18-hour period. The experiment was repeated several times, on different types of leukemia cancer cells, with similar results.
Yin's team found that C-3-R caused the cells to produce peroxides, a type of free radical that, in turn, activated a pathway within the cancer cells that caused them to die. In contrast, when the researchers treated normal human blood cells with C-3-R, they did not find any increased accumulation of free radicals and there were no apparent toxic effects on these cells.
"Therefore, if we can reproduce these anticancer effects in animal studies," Dr. Yin said, "this will present a very promising approach for treating a variety of human leukemias and, perhaps, lymphomas as well."