Black Raspberries Studied To Prevent Oral Cancer

NCI CAM Annual Report-FY10

The Ohio State University (OSU) Com­prehensive Cancer Center and College of Public Health have a long and suc­cessful tradition of studying food for its health and anticancer properties. One of the well-studied components found in ripe black raspberries is anthocyanins, which give the berries their deep purple color. A number of studies in different animals (such as rats and hamsters) have shown that a liquid mixture of these fruits taken orally interferes with the growth of tumors in the oral cavity, esophagus, and colon.

“We think the primary reason that the berry mixture inhibits cancer is because it makes physical and biological contact with the precan­cerous tissue all along the digestive route of the animals,” noted Christopher Weghorst, Ph.D., a professor of Environmental Health Sciences and Otolaryngology at OSU. He said that many of the compounds found in black raspberries are not well absorbed through the digestive system into the bloodstream. “This certainly includes some of the components we think might be responsible for the protective effect we are finding,” he added. “We and others have also designed some novel delivery methods aimed at extending the period of time the berry compo­nents remain in contact with the target tissue.”

Many CAM researchers face a dilemma when trying to determine which ingredient in a food plant is responsible for the health effects they find in their studies, said Dr. Weghorst. While it is often possible to isolate just a single com­pound from the plant, test it for activity against a particular health problem, and then produce (and market) it as a supplement, “this may not be the best approach,” he commented. “In fact, there is a lot of evidence to the contrary.”

The study that NCI is funding* in Dr. Weg­horst’s lab is not intended to isolate and test the anthocyanins in black raspberries that many be­lieve are the “active ingredient.” Instead, he is testing the relative importance of anthocyanins by using green berries before they fully ripen into black raspberries. Anthocyanins are not developed in green berries because the fruit has not yet ripened. In hamsters, when the green berries were compared to the ripe raspberries, their inhibiting impact on oral cancer in the test animals was about the same, he reported.

One possible mode of action for the berries’ beneficial impact on cancer cells may involve gankyrin, a cancer-causing gene (or oncogene) “that produces a cell growth stimulus and is over-expressed in head and neck cancers,” said Dr. Weghorst. “Both the green and the ripe black raspberries reduced the expression of this oncogene to a more normal level. Thus, the an­thocyanins cannot logically be the sole cause.” On the other hand, the researchers found that the P16 tumor suppressor gene, which is often inactivated in oral cancers, was found in abun­dance in animals given the ripe black raspber­ries but not in those given the green berries. Thus, there are numerous helpful ingredients in the berries which can change gene expression patterns in a manner that might favor cancer prevention, Dr. Weghorst explained.

“All of this demonstrates there are multiple pathways involved in this type of cancer de­velopment and cancer prevention,” Dr. Weg­horst said. “We now know that that there are also bioactive components of the green forms of these plants that are effective against oral cancer.” This helps confirm the food-based ap­proach to cancer prevention, even using food at various stages of ripeness, he believes, and em­phasizes the capability of the complex mixtures of chemicals found in “whole” foods to inhibit multiple processes of cancer development.

These types of animal studies have set the stage for larger studies in humans, Dr. Weghorst stated. One such study already underway is evaluating the molecular effects of ripe black raspberries on “at risk” normal oral cells in post-surgical oral cancer patients. “Oral cancer has a strong connection with alcohol consump­tion and smoking,” he noted, “and reducing these behaviors would have a really dramatic impact.” But proving the preventive value of berries could enhance the options available to people, despite the consequences of their past behaviors or their personal risk of cancer recur­rence, he commented.