Cranberry Juice Shows Promise for the Prevention of Bladder Cancer

Division of Cancer Prevention

Bladder cancer researchers are interested in certain chemicals in foods or dietary supplements that naturally concentrate in the urine and pass through the bladder that may help protect against bladder tumor formation. Dietary polyphenols are of high interest in recent years because of their promising efficacy with little or no toxicity in several pre-clinical cancer models. One naturally occurring source of these compounds is cranberries.

“Cranberry fruits are rich in dietary polyphenols and it is well known that cranberry juice is helpful in treating and preventing urinary tract infections (UTIs) caused by E. coli,” noted Jeevan K. Prasain, Ph.D., assistant professor of Pharmacology & Toxicology, University of Alabama at Birmingham. He and his colleagues have conducted previous studies* demonstrating that a commercially available cranberry juice concentrate can prevent urinary bladder cancers in chemically-induced bladder carcinogenesis in rats when compared to the control group of animals that did not receive the juice.

“Although our data suggest that the preventive ef­ficacy of cranberries is due to the inhibition of tumor cell proliferation, at least one report has demonstrated that cranberries can impair angiogenesis (blood vessel growth in tumors) and, therefore prevent tumor growth, suggesting another possible mechanism,” he explained.

With funding from NCI **, Dr. Prasain is now seeking to determine the bioavailability (i.e., absorption and retention in an unmetabolized form) of various phytochemicals present in cranberry juice, identify metabolites of these compounds, measure their concentrations in urine in the bladder of rats, and assess their ability to block bladder carcinogenesis.

A major focus is on quercetin and its glycosides, which are the major phytochemicals of cranberry juice concentrate. Their metabolism and bioavailability are complex, he noted. Although final results from the study are not expected until 2011, Dr. Prasain presented some preliminary data at the American Society of Mass Spectrometry annual conference in May 2010.

He and his colleagues are using liquid chromatography tandem mass spectrometry for profiling the constituents of cranberry. They reported that metabolites of quercetin and methyl quercetin were detected in the urine samples collected overnight after oral administration of cranberry powder to rats. “The presence of quercetin glycoside in the urine indicates that the intact glycoside may be absorbed,” Dr. Prasain commented. “This report identifying cranberry metabolites in plasma and urine may explain their beneficial effects against bladder cancer.”

If the final results from the study show further prom­se, Dr. Prasain will apply for an additional grant “to expand our investigation into the mechanics of activity at the molecular level.” Cranberries are “popular as a functional food and the juice is safe to drink,” he added. Cranberries are also unique in the sense that they contain a mixture of many types of different natural compounds. “Because of the blending of so many different compounds, cranberries may be more effective than a single purified compound because of synergistic and additive effects,” Dr. Prasain said. However, he added, the fruit “has not been very well investigated. For now, the major question is whether it is truly a preventive agent.”