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In laboratory experiments, pre-treating ovarian tumor cells with the juice bumped up the cancer-killing power of drugs sixfold, researchers say.
The study authors stressed that the finding is still experimental and preliminary, but it could offer a new option for patients whose ovarian cancer has become resistant to treatment.
"This was surprising and encouraging," noted study lead author Ajay P. Singh, a research associate and natural products chemist in the department of plant biology and plant pathology at Rutgers University in New Brunswick, N.J.
"We don't consider them to be a drug, but cranberries are already very well known to have antioxidants that boost the immune system and body strength, prevent urinary tract infection and help fight cardiovascular disease. So, we knew that cranberries would certainly not harm cancer patients. And now, we found that they actually increase sensitivity to chemo several-fold," he said.
The finding was to be presented Tuesday at the national meeting of the American Chemical Society being held this week in Boston.
Ovarian cancer is the seventh most common cancer in the United States and the fifth leading cause of cancer death among American women, according to the U.S. Centers for Disease Control (CDC).
Chemotherapy treatment commonly centers on so-called "platinum drugs", such as cisplatin and paraplatin. However, many women develop therapeutic resistance, necessitating the use of ever-higher doses that in turn raise the risk for both nerve damage and kidney failure.
To assess cranberries' ability to alleviate this problem, Singh and Rutgers colleagues Dr. Laurent Brard and Rakesh K. Singh teamed up with K.S. Satyan of the Molecular Therapeutics Laboratory at Brown Medical School's Women and Infants Hospital.
With funding from the U.S. National Institutes of Health, the authors collected ovarian cancer cells from patients experiencing platinum drug resistance. They then exposed some of the cells to a purified extract drawn from a store-bought cranberry drink that contained 27 percent pure juice. Doses varied, reaching a maximum of about one cup of juice.
All the cancer cells were subsequently treated with paraplatin chemotherapy.
The result: Cells pre-treated with the juice extract were killed at a rate that was equal to six times that of cells unexposed to cranberry components.
In addition, the juice appeared to slow both the growth and spread of some cancer cells.
It's not yet clear how cranberry juice might kill ovarian cancer cells, the researchers said, although an antioxidant unique to cranberries -- the "A-type" proanthocyanidins -- could be key.
This specific antioxidant is not present in other fruits and appears to bind with -- and block the activity of -- tumor proteins found in ovarian cancer cells, increasing their sensitivity to chemo.
Singh cautioned that it remains to be seen whether the cranberry-chemo effect can be repeated outside a lab setting. Testing in mice and rats is about to begin, followed by human trials, the scientist said.
However, even if the effect holds up, Singh stressed that cranberry compounds should not be considered any cure for cancer. They might have a role as adjunct treatment alongside existing drugs, he said.
Dr. Robert Morgan, Jr., section head of medical gynecologic oncology at the City of Hope Cancer Center in Duarte, Calif., agreed that the "cranberry effect" warrants further study.
"I think this is a very fertile and promising branch of research," he said. "But one needs to make sure this is proven in clinical trials, and you'd need to be sure about the levels of the compound needed and which active agent in the cranberry juice is actually causing this increase in sensitivity."
"Of course, cranberries are non-toxic, and the compounds they contain are part of the family of flavonoids found in grape seeds, which have been shown to be potentially beneficial in breast cancer," he added. "So, there's certainly no risk of harm here. There's just a lot more research that needs to be done."
SOURCES: Ajay P. Singh, Ph.D., research associate and natural products chemist, department of plant biology and plant pathology, Rutgers University; Robert Morgan Jr., M.D., section head of medical gynecologic oncology, City of Hope Cancer Center, Duarte, Calif.; Aug. 21, 2007, presentation, national meeting, American Chemical Society, Boston
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