The findings prompt the researchers to suggest that adding 'nutraceuticals' to chemotherapy cycles may improve the effectiveness of conventional drugs, particularly in hard to treat cancers, such as pancreatic cancer.
They base their findings on the effectiveness of extract of chokeberry (Aronia melanocarpa) in killing off cancer cells--a process known as apoptosis.
Chokeberry is a wild berry that grows on the eastern side of North America in wetlands and swamp areas. The berry is high in vitamins and antioxidants, including various polyphenols--compounds that are believed to mop up the harmful by-products of normal cell activity.
The researchers chose to study the impact of the extract on pancreatic cancer, because of its persistently dismal prognosis: less than 5% of patients are alive five years after their diagnosis.
They therefore cultured a well known line of pancreatic cancer cells (AsPC-1) in the laboratory and assessed how well this grew when treated with either the chemotherapy drug gemcitabine, or different levels of commercially available chokeberry extract alone, and when treated with both.
The toxicity of chokeberry extract on other normal lining cells was tested and found to have no effects up to the highest levels used (50 ug/ml), suggesting that it may not be able to prevent the formation of new blood vessels (anti-angiogenic properties), a process that is important in cancer cell growth.
But the analysis indicated that 48 hours of chokeberry extract treatment of pancreatic cancer cells did induce some cell death (1 ug/ml).
And low doses of the extract greatly boosted the effectiveness of gemcitabine, when the two were combined, added to which lower doses of the conventional drug were needed.
This suggests either that the compounds work together synergistically, or that the extract exerts a "supra-additive" effect, say the researchers.
They go on to say that the potential of naturally occurring micronutrients in plants, such as those found in chokeberry, has not been adequately explored, at least in clinical trials.
And they point to similar experimental studies, indicating that chokeberry extract seems to induce cell death and curb invasiveness in brain cancer, as well as other research, highlighting the potential therapeutic effects of particular polyphenols found in green tea, soya beans, grapes, mulberries, peanuts and turmeric.
"This work, first adds reinforcement to the concept that therapy for intractable cancers might usefully be augmented by the inclusion of micronutrient supplementation into regimens," the researchers write.
"More specifically, it suggests that elements in chokeberry extract, while not intrinsically toxic, can have supra-additive effects in combination with at least one other conventional cytotoxic drug," they conclude.