A Purple Sweet Potato with Antiangiogenic Components Shows Increased Anti-Cancer Activity

A Kansas State University researcher is studying the potential health benefits of a specially bred purple sweet potato with anti-cancer properties. Soyoung Lim, a doctoral student, and Dr. George Wang, Associate Professor of Human Nutrition at Kansas State, bred purple sweet potatoes to contain unusually high amounts of anthocyanin, a pigment that renders the purple hue in the vegetable. Anthocyanins can be red, blue or purple depending on the source’s chemical structure, and are also found in foods such as blueberries, black raspberries, red grapes and red cabbage. Anthocyanins are known to have antiangiogenic properties, and high intake of foods containing this family of molecules has been associated with a reduced cancer risk in epidemiology studies.

Lim used a sweet potato with pronounced purple flesh and skin that was originally developed by Kansas State’s Ted Carey, Professor of Horticulture, at the University’s John C. Pair Horticultural Center in Haysville. Three different varieties of purple sweet potatoes, including Kansas State’s, were tested. Each contained varying amounts of anthocyanin. To quantify the amount of anthocyanin in each potato, Lim extracted the pigments from the vegetables and analyzed them via HPLC-MS Analysis, a method that separates the individual components. The potatoes were then segregated by flesh pigmentation and fiber content.

The study showed that the Kansas-bred potato had significantly higher anthocyanin contents compared to the other potatoes, and found two derivatives of anthocyanin that were dominant: cyanidin and peonidin. The potatoes’ total phenolic content as also determined. Phenols are naturally occurring chemical compounds that have anti-aging and antioxidant components. The specially bred purple sweet potato had a much higher total phenolic content and antioxidant capacity than the other purple sweet potatoes, said Lim.

To observe the specific tumor-preventing effects of cyanidin and peonidin—compounds called anthocyanidins that are chemically similar to anthocyanins—Lim treated human colon cancer cells with low concentrations of the pigment derivatives and also studied their effects on the cancer cell cycles. Both cyanidin and peonidin showed significant cell growth inhibition for the cancer cells, but they did not significantly affect the cell cycle. Lim said a better understanding of the underlying mechanisms in the Kansas-bred potato could provide scientific evidence of its health benefits.

“This type of scientific study can lead to important advances in understanding how dietary strategies may impact on cancer and other diseases linked to angiogenesis,” said William W. Li, M.D., president and medical director of the Angiogenesis Foundation. “By comparing the different levels of anti-tumor activity in different strains of the same type of food, it may be possible to identify the specific strain that might confer the greatest health benefits in terms of disease modification.”

The Angiogenesis Foundation is actively studying the antiangiogenic activity of various dietary-derived natural compounds as part of its disease prevention research program.

By Roderick Smith, M.S.

Antiangiogenic component of broccoli inhibits growth of breast cancer cells

Numerous scientific studies have shown the cancer protective effects of increasing intake of cruciferous vegetables, including broccoli, cauliflower, Brussels sprouts, kale and cabbage. Among the beneficial chemical components of these vegetables is sulforaphane, a naturally occurring compound that suppresses both cancer cell growth and the growth of new tumor blood vessels (angiogenesis). The antiangiogenic properties of sulforaphane have been studied, and it downregulates the production by cancer cells of key angiogenesis-promoting factors, including vascular endothelial growth factor (VEGF), HIF-1α, matrix metalloproteinase-2 and matrix metalloproteinase-9.

Using an extract of sulforaphane, a group of researchers led by Yanyan Li and Duxin Sun at the Department of Pharmaceutical Sciences, University of Michigan, were able to inhibit the growth of breast cancer stem cells both in laboratory cultures and in mice. A growing body of research indicates that many types of cancer, including breast cancer, are initiated and maintained by a small fraction of tumor stem cells—characteristics that make them an attractive target for therapy.

Reporting their findings in the journal Clinical Cancer Research, the scientists found that sulforaphane reduced the size breast cancers in mice by more than 50%. Further, sulforaphane was able to reduce the numbers of breast cancer stem cells by 65-80% in mice implanted with human breast tumors. These findings provide rationale for future clinical evaluation of sulforaphane for breast cancer chemoprevention, and as an antiangiogenic intervention.

By Roderick Smith, M.S.