Prevention of Cancer with Freeze-Dried Berries

Gary D. Stoner, Ph.D., Department of Internal Medicine, Division of  Hematology and Oncology, College of Medicine and Public Health, The Ohio State University, Columbus, OH.  43210

For several years, our laboratory has been evaluating the ability of freeze-dried berries (black raspberries, blackberries and strawberries) to inhibit carcinogen-induced cancer in the rodent esophagus and colon. To assure a ‘standardized” berry preparation for study, all berries are of the same cultivar, obtained from a single Ohio farm, picked at about the same degree of ripeness, washed and frozen within an hour of the time of picking, and freeze-dried under conditions that preserve the components in the berries.  Some of the known chemopreventive agents in berries include vitamins A, C, E and folic acid; calcium and selenium; ß-carotene, α-carotene and lutein; polyphenols such as ellagic acid, ferulic acid, p-coumaric acid, quercetin and several anthocyanins; and, phytosterols such as ß-sitosterol, stigmasterol and kaempferol.  In initial bioassays, freeze-dried black raspberry, blackberry and strawberry powders were mixed into AIN-76A synthetic diet at concentrations of 5% and 10% and fed to Fischer 344 rats before, during and after treatment with the esophageal carcinogen, N-nitrosomethylbenzylamine (NMBA) (1-3).  At 25 weeks of the bioassay, all three berry types were found to inhibit the number of esophageal tumors (papillomas) in NMBA-treated animals by 40-60% relative to NMBA controls.  This inhibition correlated with reductions in the formation of the NMBA-induced O6-methylguanine adduct in esophageal DNA, indicating that the berries influenced the metabolism of NMBA leading to reduced DNA damage.  Studies are ongoing to determine the mechanisms by which berries influence NMBA metabolism and DNA adduct formation. Black raspberries and strawberries were also tested in a post-initiation scheme and were found to inhibit NMBA-induced esophageal tumorigenesis by 30-40% when administered in the diet after treatment of the animals with NMBA (1-3).  Berries, therefore, inhibit tumor promotion and progression events as well as tumor initiation. Mechanistic studies indicate that they reduce the growth rate of premalignant esophageal cells, in part, through down-regulation of cyclooxygenase-2 (COX-2) leading to reduced prostaglandin production and, c-Jun, one of the activator protein-1 (AP-1) family of transcription factors. Berries also inhibit the expression of other genes associated with tumor development in the rat esophagus such as inducible nitric oxide synthase (iNOS) and vascular endothelial growth factor (VEGF).

To date, only black raspberries have been evaluated for chemopreventive effects in the rodent colon. When administered in the diet at concentrations of 2.5, 5 and 10% after treatment of F-344 rats with azoxymethane, black raspberries prevented the development of all colon tumors by up-to 60% and of adenocarcinomas up-to 80% (4).  The berries markedly reduced oxidative DNA damage in the azoxymethane-treated animals, and lowered blood cholesterol levels by 10-15%.  Similarly, at 10% of the diet, freeze-dried black raspberries caused a 50% inhibition of intestinal tumor development in the Min mouse model of familial adenomatous polyposis. The mechanism(s) by which berries prevent colon cancer in rodents are under investigation.

Using biodirected fractionation techniques, studies are being conducted to identify the active inhibitory components in berries. Both organo- and water-soluble extracts of berries were shown to inhibit chemically-induced cell transformation in vitro and to down-regulate the transcription activator proteins, AP-1 and nuclear factor-kappa B (NF-кB), and their associated kinases (5).  Preliminary studies indicate that the anthocyanins in berries are amongst the most active inhibitory components

            Based upon the above-described preclinical data, we have initiated prevention trials in humans to determine if berries might exhibit chemopreventive effects in the esophagus, colon and oral cavity. In an initial Phase I clinical trial involving 10 normal subjects, freeze-dried black raspberries were administered orally for 7 days at a dose of 45 grams per day.  This is equivalent to rodents consuming a diet containing approximately 5% black raspberries. The berries were well tolerated with minimal side effects. Ellagic acid and the anthocyanins; cyanidin 3-glucoside, cyanidin 3-sambubioside, cyanidin 3-xylosylrutinoside and cyanidin 3 –rutinoside, were all absorbed into the blood with peak plasma levels occurring within 2-4 hours of oral berry consumption. The absorption of these polyphenols however, was minimal and represented less than 1% of the administered dose. Several Phase IIa clinical trials of freeze-dried black raspberries are underway in subjects with Barrett’s esophagus, oral leukoplakia and colonic polyps to determine if orally administered berries will modulate various histological and molecular biomarkers of esophageal, oral and colon tumor development. Supported by the Ohio Department of Agriculture, U.S. Department of Agriculture, and National Cancer Institute grants CA96130 and CA10318.


  1. Kresty, L.A., Morse, M.A., Morgan, C., Carlton, P.S., Lu, J., Gupta, A., Blackwood, M., and Stoner, G.D. (2001) Chemoprevention of esophageal tumorigenesis by dietary administration of lyophilized black raspberries. Cancer Res. 61:6112-6119.
  2. Carlton, P.S., Kresty, L.A., Siglin, J.C., Morgan, C., Lu, J., and Stoner, G.D. (2001) Inhibition of N-nitrosomethylbenzylamine-induced tumorigenesis in the rat esophagus by dietary freeze-dried strawberries. Carcinogenesis 22:441-446.
  3. Reinemann, T., Aziz, R., Nines, R., Gordon, M., and Stoner, G.D. (2004) The effect of lyophilized blackberries on N-nitrosomethylbenzylamine-induced tumorigenesis in the rat esophagus. Proc. Am. Assn. Cancer Res. 45/131.
  4. Harris, G.K., Gupta, A., Nines, R.G., Kresty, L.A., Habib, S.G., Frankel, W.L., LaPerle, K., Gallaher, D.D., Schwartz, S.J., and Stoner, G.D. (2001)  Effects of lyophilized black raspberries on azoxymethane-induced colon cancer and 8-hydroxy-2-deoxyguanosine levels in Fischer 344 rats. Nutrition and Cancer 40(2): 125-133.
  5. 5.   Huang, C., Huang, Y., Li, J., Hu, W., Aziz, R., Tang, M-s., Sun, N., Cassady, J., and Stoner, G.D. (2002) Inhibition of benzo(a)pyrene diol-epoxide-induced   transactivation of activated protein 1 and nuclear factor қB by black raspberry extracts. Cancer Res. 62:6857-6863.